Atlas of Scoring Systems,Grading Tools,and Nomograms in Endourology: A Comprehensive Overview from the TOWER Endourological Society Research Group

Abstract

Introduction:

With an increase in the prevalence of kidney stone disease (KSD), there has been a universal drive to develop reliable and user-friendly tools such as grading systems and predictive nomograms. An atlas of scoring systems (SS), grading tools, and nomograms in Endourology is provided in this article.

Methods:

A comprehensive search of world literature was performed to identify nomograms, grading systems, and classification tools in endourology related to KSD. Each of these was reviewed by the authors and has been evaluated in a narrative format with details on those that are externally validated and their respective citation count on google scholar.

Results:

A total of 54 endourological tools have been described in our atlas of endourological SS, grading tools, and nomograms. Of the tools, 23 (43%) have been published in the past 3 years showing an increasing interest in this area. This includes five for percutaneous nephrolithotomy, six for flexible ureteroscopy, three for semi-rigid ureteroscopy (URS), nine for extracorporeal shockwave lithotripsy, two for stent encrustations, three for intraoperative appearance at the time of URS, and three to classify intraoperative ureteric injury. There were three tools for renal colic assessment, one each for prediction of future stone event, stone classification, and stone impaction and two for need of emergency intervention in ureteral stone. Two tools are related to stone recurrence, whereas six are related to postprocedural complications. There are now two tools for simulation in endourology and five for patient-reported outcome measures.

Conclusions:

A number of reliable and established tools currently exist in endourology. Each of these offers their own respective advantages and disadvantages. Although nomograms and SS can help in the decision making, these must be tailored to individual patients based on their specific clinical scenarios, expectations, and informed consent.

Introduction

In recent years, there has been a rise in the prevalence of kidney stone disease (KSD) as well as an expansion in the range of endourological interventions available.^1,2 Alongside modifications and advancements in equipment, for example, laser, digital systems, and miniaturization, there has been a universal drive to develop reliable and user-friendly tools such as grading systems and predictive nomograms.^3
–5 These can allow for more refined operative planning and improved procedural efficacy and safety. This befits better preoperative counseling and patient expectation and experience accordingly. It brings the clinician closer to providing a tailored approach as well as better resource allocation in a financially restricted environment.

Instruments such as the R.E.N.A.L. nephrometry scoring system (SS), which provides standardized reporting of renal tumor size, location, and depth, serve as an example of such a validated tool, and has achieved widespread dissemination.⁴ Within the subspecialty of endourology, there has been a plethora of new instruments that have been recently developed and are now available at the clinician's disposal. At the same time, review and awareness of these tools remains underreported. To date, there exists no reference that provides a summary of these in one document. This article serves to provide the clinician with such a resource. An atlas of SS, grading tools, and nomograms in Endourology is provided in this article.

Methods

A comprehensive search of world literature was performed to identify nomograms, grading systems, and classification tools in endourology related to KSD. Each of these was reviewed by all the authors and has been evaluated in a narrative format. A selection of the key instruments is outlined next. All the identified tools are listed in Table 1. Table 2 provides further information on those tools, which have been externally validated.

Table 1.

All Endourological Scoring Systems, Grading Tools, and Nomograms Included in the Paper

	Author, year	Nomogram name	Variables	Unique features	Pros	Cons	External validation^a
PCNL
1	Thomas, 2011⁵	GSS	Stone location, stone count, and staghorn calculi Severe comorbidity, e.g., spina bifida	The first of its kind Includes complex patient, e.g., spinal injury	Simple four-grade system Reproducible	Technical difficulty not described Stone density not included Variable imaging used	Yes
2	Smith, 2013⁷	CROES nomogram	Stone location, stone count Stone burden Case volume	Continuous scale and not discrete groups Only PCNL nomogram to include case volume	Generalizable—based on global data High- and low-volume centers included Data-driven and variables not determined by expert author panel	No stone density Developed from a database not specifically designed for this project SFS determined using KUB Variables, e.g., hydronephrosis and PCS abnormalities not included	Yes
3	Okhunov, 2013⁶	STONE nephrolithometry	Stone size, skin-to-stone distance (presence of hydronephrosis), number of involved calices, stone density	Inclusion of skin stone distance can act as surrogate for BMI and prompts access to calix to be considered	All information available from preoperative CT Available as online tool	Internally validation based on small cohort only and single surgeon experience Low incidence treatment failure in initial cohort Method for measuring hydronephrosis not clear Reproducibility dependent on expertise Complex anatomy not included Shares name with two other score systems	Yes
4	Jeong, 2013⁸	S-ReSC	Stone distribution	Based on a single variable only Based on using single tract	Can be scored at time of CT reporting Simple to use—based on one variable only Score available as continuous variable and also as categories	Retrospective Single center Developed on basis of expert opinion Relies on theory that stone distribution is most important factor for PCNL success Initial validation in single-center cohort only Only included single-tract cases and so possible more complex cases excluded Patients had lower average BMI than other studies	Yes
5	Mishra, 2012⁴⁸	Staghorn morphometry	Total stone volume with absolute volume and % volume in the pelvis, planned entry calix, favorable and unfavorable calix	Designed for staghorn calculi. Categorized into three types.	Predict number of tracts and sessions required.	Only applicable for staghorn calculi No prediction of SFS Requires CT scan volumetric software Not easily applied in clinical setting Requirement for CT with urographic phases incurs higher radiation dose.	No
fURS
1	Resorlu, 2012¹¹	RUSS	Stone size Lower pole location and IPA Stone number in different calices Abnormal renal anatomy	Includes abnormal renal anatomy	Includes complex anatomy Simple Quick to apply	Retrospective Only horseshoe kidney and pelvic kidney included as abnormalities in development	Yes
2	Ito, 2015¹²	Ito's score	Stone volume Lower pole calculi Operator experience at fURS Hydronephrosis Number of stones	Only tool in fURS group to include hydronephrosis	Includes operator experience Do not have to measure IPA, which is arguably cumbersome in daily practice	Retrospective Excluded cases that required more than two sessions Relatively high number presented	Yes
3	Jung, 2014¹⁰	Modified S-ReSC	Stone distribution	Based on a single variable only	Do not have to measure IPA Can be performed quickly	Only applies stone location Abnormal renal anatomy not included but authors argued this is rarely encountered and individualized approach warranted for such cases Not developed for use in large stones	Yes
4	Xiao, 2017⁴⁹	RIRS nomogram	Stone density Lower pole location and IPA Length of calix where stone located Stone burden	Includes length of calix where stone is located	Comprehensive—has already been externally validated	Retrospective Single center Longer learning curve—measurements difficult to make on CT scan	Yes
5	Hori, 2020⁵¹	T.O.HO	Stone size, stone density, and stone location	Designed to aid prediction of fURS success, including for large stones	Easy to apply—based on three variables only	Operator experience not included Single center Relatively high number presented	No
6	Kuroda, 2018⁵²	n/a	Stone volume, stone density, operator experience, gender, preoperative stenting, UAS diameter	Focus is prediction of length of operating time in fURS for renal stones	Includes size of UAS	Not applicable to predict SFS (NB same institution developed Ito score, which does this) Only used successful procedures in its development	No
Semi-rigid URS
1	Imamura, 2013⁵⁰	Imamura's score	Stone length, number of stones, stone location, pyruria	Designed for ureteral stones Includes pyruria as variable	User friendly and quick to apply	Operator experience is not included	Yes
2	Kim, 2014⁵³	n/a	Stone size Stone location Periureteral edema Stone density	Only semi-rigid URS tool to include periureteral edema	Can calculate at time of imaging	Difficult to accurately measure periureteral edema	No
3	Xun, 2020⁵⁴	n/a	Stone volume Operator experience Hydronephrosis Radiomics score	Additional stone features based on radiomics included	Includes operator experience	Not quick to apply in clinical practice Requires specialist software to produce radiomics score Solitary stones only Excluded lower pole stones	No
SWL
1	Tran, 2015¹³	Triple D score	Ellipsoid stone volume Skin-to-stone distance Stone density	Quick to apply tool for prediction of SWL success	Simple to calculate Simple score system Can calculate at time of imaging	Limited follow-up period	Yes
2	Toshioka, 2020¹⁴	S₃HoCKwave (acronym based on included variables)	Gender, skin-to-stone distance, size, HU, colic, and stone location	Risk of SWL failure (over 3 sessions)	Multi-center Included >2000 patients	Solely applicable to patients with CT imaging	No
3	Yamashita, 2017⁵⁵	n/a	Variation coefficient of stone density	Novel method to assess stone heterogeneity	Identifies limitations in reporting stone characteristics	Difficult to apply readily in clinical practice	No
4	Hirsch, 2020⁵⁶	n/a	Stone density, skin-to-stone distance, stone size, and presence of indwelling stent	Only assessment tool in group to include stent status as variable	Easy and quick to apply in clinical practice	SFR not determined by CT	No
5	Park, 2016⁵⁷	n/a	BMI. stone diameter and perinephric edema	Includes peri-nephric edema	Quick to apply	Limited to solitary proximal ureteral stones	No
6	Niwa, 2017⁵⁸	n/a	Stone size Stone density Skin-to-stone distance	Nil	Easy to apply in clinical practice	Only applicable for solitary proximal ureteral stones Imaging modality to assess SFS not consistent	No
7	Kim, 2016⁵⁹	Kim nomogram	Gender, stone location Skin-to-stone distance Stone size Hydronephrosis Stone density	Several nomograms made according to whether pre or post first treatment and whether CT available	Useful as different versions available depending on scenario Wide inclusion criteria	Possibly too detailed to achieve dissemination	No
8	Wiesenthal, 2011⁶⁰	n/a	Age Skin-to-stone distance Stone size	Based on single session of SWL Only tool in SWL group to include age	Quick to apply in clinical practice Can calculate using imaging only	Applicable for solitary stones only and single sessions only	No
9	Kanao, 2006⁶¹	n/a	Stone length Number of stones Stone location	One of first nomograms used in endourology—authors recognized need for such a tool early	First nomogram for SWL use	One type of machine at single institution Lack of clarity on size of largest stones treated in cohort Lack of skin-to-stone distance	No
Stent encrustation
1	Acosta-Miranda, 2009¹⁸	FECal Double-J stent score	Stone size Stone location Degree of encrustation	Novel tool for assessment of degree of stent encrustation	Simple Easy to follow accompanying algorithm	Retrospective Sample only included 9 patients	Yes
2	Arenas, 2016¹⁹	KUB grading system	Degree of calcification at three portions of stent: kidney, ureter, and bladder.	Includes prediction of whether surgery will be successful in only one session	Gives guidance to cases requiring multi-modal surgery, multiple surgeries, and long operating time (>180 minutes)	Retrospective Only rated by one urologist, therefore higher risk of inter-observer reliability	Yes
Intraoperative appearance at time of URS
1	Borofsky, 2016²⁰	PPLA	Plugging (with yellow plaque) Pitting (% surface involved) Loss of contour (e.g., flattened) Amount of Randall's plaques	Intra-renal collecting system appearances at time of fURS	Comprehensive methodology to map anatomic findings	Based on digital scope findings	Yes
2	Almeras, 2016²²	Classification of the papillary abnormalities described by endoscopy (acronym used is SPR based on included components)	Stone description (S) Number of abnormal papilla (n) and type (Px) Amount of Randall's plaque (R)	Based on format of TNM classification system	Once familiar can be applied easily Updated in 2020²³	Learning curve required Single surgeon established model with lack of inter-rater testing Based on <100 cases	Yes
3	Hamamoto, 2020⁶²	n/a	Edema, presence of polyps Mucosa stone adherence Distal ureteric tightness.	Emphasis is on application for impacted ureteral stones	Can aid selection of UAS size	Single ureteral stones only Not developed using any patients with stent in situ	No
Intraoperative ureteric injury
1	Schoenthaler, 2012²⁴	PULS	Lesion depth Mucosal edema Hematoma Perforation Transection %	Injury to ureter specifically as a result of URS	Easy to apply	Requires operator experience	Yes
2	Traxer, 2013²⁸	Injury secondary to ureteral access sheath (no shortened name)	Mucosal erosion Involvement smooth muscle Adventitia perforation Visible periureteral fat avulsion	Designed for UAS injuries Based on depth of injury	Easy to apply	Limited follow-up duration	Yes
3	Tepeler, 2014⁶³	Modified version of the Sativa classification system	Incidents without consequences Incidents treated inter-operatively with endoscopic surgery Incidents requiring endoscopic re-intervention Incidents requiring laparoscopic or conversion to open surgery	Focus is on intraoperative complications related to URS	Development included >1000 patients Comprehensive	Learning curve required	No
Stone classification
1	Daudon, 1993^64,65	Daudon classification	Stone surface and stone section	Thorough classification of stones based on microscopic examination	Comprehensive Covers 95% of known urinary stones Updated in 2020	Learning curve required More limited application in era of dusting	Yes
Stone impaction
1	Özbir, 2020⁶⁶	ISF	Ureteral wall thickness Stone density Grade of hydronephrosis	How to predict degree of stone impaction	Only tool of its kind Internal validation results show to be effective	Formula not quick to calculate May be more applicable for research than clinical practice	No
Recurrence
1	Rule, 2014²⁹	ROKS	Age, gender, race, family history, history uric acid stone, visible hematuria, location of stone when symptomatic, previous or concurrent asymptomatic stone, and previous suspected stone but not confirmed	Only tool of its kind to predict risk of recurrent kidney stone	Large cohort Available in online calculator Comprehensive analysis of medical records Available on a mobile app Modified version available applicable to people with more than one previous episode	Limited application in patients with rarer stone compositions or underlying genetic disorders Only predicts chance of developing stone that results in clinical care visit Sample analyzed largely in Caucasian population only Modified version pending external validation	Yes
2	Torricelli, 2015⁶⁷	n/a	Age BMI 24-Hour urine profile	Prediction of uric acid stones	Unique tool, which is tailored to a high-risk population group	Limited	No
Prediction of stone event
1	Okita, 2020⁶⁸	STEP tool	Age, gender, diabetes, renal function, serum albumin, and serum uric acid level.	Prediction of first-time formers based on metabolic factors	Could be used as screening tool Large sample	Previous stone history and family history not included	No
Complications
1	Hu, 2018⁶⁹	n/a	Gender, urine white cell count, hydronephrosis, and presence of nitrites Functional solitary kidney	Risk of patients with ureteral calculi developing sepsis	Applicable to inpatients and outpatients	Not the quickest tool to apply	No
2	Komeya, 2020⁷⁰	n/a	Age Gender Stone volume Stone density Narrow ureter	Perioperative complications in patients with overnight ureteral catheter post-fURS	Aids bed planning for hospitals	Many centers perform fURS as day case procedure, therefore relevance may be less Ureteral catheter not left in situ in many centers Short follow-up period	No
3	Gao, 2020⁷⁴	n/a	Preoperative serum creatinine value Multi-drug resistant bacteriuria	Sepsis after PCNL for struvite stones	Helps identify at-risk patients	Intraoperative stone analysis and urine culture from renal pelvis not performed in all cases Only applicable struvite stones	No
4	Lu, 2020³⁹	n/a	Albumin concentration Globulin concentration	Sepsis after fURS based on albumin-globulin ratio	Potentially an easy to obtain prediction tool to guide management	Only applicable to solitary, proximal ureteral stones Small cohort Limited imaging data available in some patients	No
5	Sugihara, 2013⁷²	n/a	Gender Age Charlson comorbidity index Type of anesthesia Operation time Hospital volume Type of admission	Adverse events after semi-rigid and fURS	Multi-center >12,000 patients Generalizable—based on global data High- and low-volume centers included Data-driven and variables not determined by expert author panel	Many variables included Developed from a database not specifically designed for this project Requires clinical caseload—information may not be readily available	No
6	Wang, 2020⁷³	n/a	Staghorn calculi (single/multiple) Midstream urine culture Preoperative renal fistula	Sepsis after PCNL in all stone types	Helps identify at-risk patients	Small sample Single center	No
Renal colic assessment
1	Moore, 2014³²	STONE (not an acronym)	Sex, duration of pain, race, nausea/vomiting, nonvisible hematuria	For suspected ureteral stone but normal kidney function	Aid triage in ED Avoid CT in low-risk patients Updated in 2018 Available as online tool	Shares name with two other score systems Not designed for patients with likely infection or very unwell Generalizability can vary depending on race	Yes
2	Fukuhara, 2017⁷⁴	CHOKAI (acronym based on included variables)	Age Nausea/vomiting History of ureteral stones Pain duration Nonvisible hematuria Hydronephrosis on ultrasound	Use of point-of-care ultrasound to aid prediction if likely ureteral stone present	Possibly more generalizable than other similar tools	Requires upfront ultrasound—likely not available in many smaller centers and extra time added to triage period Less than 80 patients in sample	Yes
3	Chen, 2018⁴⁰	DACA-KS	Charlson comorbidity index, adverse effects, hypertension, obesity, candidiasis, decreased libido, urine pH, urine protein, blood magnesium, blood chloride, red blood cell count, electrolyte imbalance, other bacterial infections, sleep disorder, chronic pulmonary heart disease, liver necrosis, neurotic disorders, blood CO₂, blood phosphate, urine bands, and urine red blood cell distribution width	Identifies patients with possible KSD based on post hoc analysis of large database of patients	Once integrated into electronic health system, can help triage process in hospitals	Complex system to calculate manually Many variables may not be available Possibly more suited as a research tool	No
Need for emergency intervention with confirmed ureteral stone
1	Al-Terki, 2020⁷⁵	ARC scoring system	Serum creatinine Leukocyte count Stone size Stone level/location	Decision guiding tool regarding need for emergency intervention if known uncomplicated ureteral stone	Can aid avoiding repeat visits to hospital with pain	Not applicable if solitary kidney, chronic renal failure, bilateral ureteral stones, and any signs of obstruction, e.g., sepsis Limited application if immunocompromised Recent kidney stone treatment	Yes
2	Bajaj, 2018⁷⁶	n/a	Symptom duration, use of alpha blocker therapy, use of opioid analgesia, renal function, history of previous KSD, stone size, stone location, stone density	Predictor of patients who will need surgical intervention after initial conservative management	Useful in aid given delays to treatment and waiting lists for URS	The retrospective design resulted in non-standardized decision making on those patients who had conservative treatment initially	No
Simulation
1	Biyani, 2020⁷⁷	GAUES	9 × endourology-specific items 2 × global skills items	Applicable for URS, cystoscopy, and TURP	Wide application in endourological surgery is possible	Inter-rated reliability was not repeatedly assessed Only been used in simulation setting Predictive validity not assessed	No
2	Quirke, 2020⁷⁸	n/a	PCNL broken down into 10 phases, 21 processes, and 43 sub-processes	Quantifies operator progress at PCNL	Allows for structured feedback and operator progress to be monitored Breakdown of surgery in phases allows area of operator weakness to be identified. Thorough methodological design based on HFMEA. Very useful in time where exposure to real-time surgery is more challenging.	Very detailed and may be difficult to easily apply in current format Difficult to apply in a poorer resource setting	No
PROMS
1	Joshi, 2003³⁶	USSQ	Domains include Urinary symptoms, pain, general health, quality of work, quality of sex, and additional problems	Only such tools applicable for ureteral stents	Applicable to ureteral stents not only inserted for KSD. Validated in many languages worldwide. Only tool of its kind.	Applicable only once stent in situ	Yes
2	Penniston, 2013³⁸	WISQoL	Domains include energy levels and fatigue, sleep disturbance, impact on daily life and work, diet, taking medication, general health, physical symptoms, libido, and emotional well-being	QoL in recurrent stone formers	Holistic—includes emotional health and libido Sample questionnaire available easily online	Designed for recurrent stone formers	Yes
3	Ragab, 2020⁷⁹	CReSP	Domains include pain, urinary symptoms, gastrointestinal symptoms, diet changes, anxiety, treatment side effects, travel, social life, and employment	Specific for renal stones	Holistic—covers many aspects of daily living Sample questionnaire in original article	Only for renal stones	No
4	Tran, 2018⁸⁰	CUSP	Domains include pain, fatigue, employment, daily life, sleep, and anxiety	Specific for ureteral stones	Holistic—covers many aspects of daily living Sample questionnaire in original article	Only for ureteral stones Small sample Does not include gastrointestinal symptoms	No
5	Joshi, 2021⁸¹	USIQoL measure	Domains include pain, urinary symptoms, appetite, energy levels, emotional well-being, sleep, travel, medication, water intake, and employment	Universal tool for urinary stones	Universal—applicable for renal and ureteral stones Sample questionnaire in original article.	Generalizability is yet to be determined at external validation	No

In English Language.

ARC = acute renal colic; CReSP = Cambridge Renal Stone PROM; CROES = Clinical Research Office of the Endourologic Society; CUSP = Cambridge Ureteral Stone PROM; DACA-KS = diagnostic acute care algorithm–kidney stones; ED = emergency department; FECal = forgotten, encrusted, calcified; fURS = flexible ureteroscopy; GAUES = Global assessment tool for endourological skills; GSS = Guy's Stone Score; HFMEA = healthcare failure mode effects analysis; IPA = infundibulopelvic angle; ISF = impacted stone formula; KSD = kidney stone disease; KUB = kidney, ureter, and bladder radiograph; PCNL = percutaneous nephrolithotomy; PPLA = plugging, pitting, loss of contour, and amount of Randall's plaque; PROMS = patient-reported outcome measures; PULS = postureteroscopic lesion scale; QoL = quality of life; RIRS = retrograde intra-renal surgery; ROKS = recurrence of kidney stone; RUSS = Resorlu-Unsal stone score; SFR = stone-free rate; S-ReSC = Seoul National University renal stone complexity; STEP = Stone Episode Prediction; STONE = stone size, tract length, obstruction, number of involved calices, and essence/stone density; SWL = extracorporeal shockwave lithotripsy; TOHO = tallness, occupied lesion, hounsfield units; Triple D = density, distance, diameter; UAS = ureteral access sheath; URS = ureteroscopy; USIQoL = urinary stones and intervention quality of life; USSQ = ureteral stent symptom questionnaire; WISQoL = Wisconsin stone quality of life questionnaire.

Table 2.

Externally Validated Tools with Citation Count

Author/name (if present)	Grade/score	Description	Citation count^a
PCNL
Thomas/GSS⁵	1–4	For grading complexity of PCNL procedures and predicting SFR	279
Smith/CROES⁷	0–350	Prediction of PCNL success (SFR) using preclinical and radiological information	194
Okhunov/STONE⁶	5–13	Prediction of SFR at PCNL using standardized parameters from imaging	201
Jeong/S-ReSC⁸	1–9	Prediction of SFR after single-tract PCNL based on number of involved sites	86
fURS
Resorlu/RUSS¹¹	0–4	Prediction of SFR	107
Ito/Ito's score¹²	0–13	Prediction of SFR	50
Jung/Modified S-ReSC¹⁰	1–12	Modification of previously established PCNL nomogram for use in URS to predict SFR	34
Xiao/RIRS⁴⁹	4–10	Prediction of SFR	13
Semi-rigid URS
Imamura/Imamura's score⁵⁰	0–200	Prediction of SFR	23
SWL
Tran/Triple D score¹³	0–3	Prediction of SFR	58
Kim/Kim⁵⁹	0–100	Prediction of SFR	19
Stent encrustation
Acosta-Miranda/FECal¹⁸	1–5	Grading system to classify encrusted ureteral stent and algorithm for management	55
Arenas/KUB¹⁹	3–15	Grading system to identify encrusted ureteral stents requiring multiple surgeries, combined treatments, and long operative times	13
Intraoperative appearance at time of URS
Borofsky/PPLA²⁰	0–9 a–c	Standardized reporting system of renal papilla appearance in patients with KSD	18
Almeras/SPR²²	S_0–c3P_0–c3R_a–c	Classification of papillary abnormalities at time of fURS	13
Stone classification
Daudon/Daudon's classification^64,65	1–7	Morphological classification of urinary calculi	321
Intraoperative complications during URS
Schoenthaler/PULS²⁴	0–5	Injury assessment tool post-URS principally to guide need for stent placement	51
Traxer/n/a²⁸	0–4	Assessment of ureteral wall injury to ureteral access sheath use during fURS	358
Recurrence
Rule/ROKS²⁹	0–400	Prediction of second symptomatic stone episode	133
Renal colic assessment
Moore/STONE³²	0–13	Prediction of uncomplicated ureteral stones in patients under consideration for CT imaging	111
Fukuhara/CHOKAI⁷⁴	0–13	Prediction of uncomplicated ureteral stones in patients under consideration for CT imaging. Incorporates point of care ultrasound to determine hydronephrosis	13
Need for emergency intervention with confirmed ureteral stone
Al-Terki/ARC⁷⁵	4–8	Tool for those who need emergency intervention for uncomplicated ureteral stone	2
PROMS
Joshi/USSQ³⁶	38 items (6 sections)	Assessment of symptoms and impact on QoL caused by ureteral stents	371
Penniston/WISQoL³⁸	28–140	Disease-specific tool to assess QoL in patients with KSD	73

According to Google Scholar (as of January 18, 2021).

Results

A total of 54 endourological tools have been described in our atlas of endourological SS, grading tools, and nomograms (Fig. 1). Of the tools, 23 (43%) have been published in the past 3 years, showing an increasing interest in this area. This includes five for percutaneous nephrolithotomy (PCNL), six for flexible ureteroscopy (fURS), three for semi-rigid URS, nine for extracorporeal shockwave lithotripsy (SWL), two for stent encrustations, three for intraoperative appearance at the time of URS, and three to classify intraoperative ureteric injury. There were three tools for renal colic assessment, one each for prediction of future stone event, stone classification, and stone impaction, and two for need of emergency intervention in ureteral stone. Two tools are related to stone recurrence, whereas six are related to postprocedural complications. There are now two tools for simulation in endourology and five for patient-reported outcome measures (PROMS).

FIG 1.

Infographics of all included studies. Color images are available online.

Discussion

Predictive tools in stone surgery

Percutaneous nephrolithotomy

There are multiple quantitative SS in use for PCNL that have been externally validated. Four main tools of this kind exist, which are the most commonly used in clinical practice as well as in the research setting.^5

–8 The principal goal of this particular tool is prediction of outcomes after PCNL.

Guys Stone Score

Developed in 2011, this was the first of its kind for use in PCNL.⁵ The need for such a tool was triggered at the time of national audit of PCNL in the United Kingdom, where it became evident that stratifying procedural complexity was difficult. The initial form comprised five grades, but the final version consolidated this to four. It was devised based on expert opinion and published reports. At the time of conception, it was based on CT, plain X-ray, or intravenous urography. The two key parameters are stone location and renal anatomy.⁹ The assessment incorporates all stones identified at imaging and, therefore, not just the stone targeted for treatment. Reproducibility was determined through evaluation of preoperative images of 40 cases by a panel of 3 clinicians. Internal validation was then carried out over 100 consecutive cases at their tertiary referral center.

STONE nephrolithometry score

This SS is based on the five variables that give its name: stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E).⁶ The assessment is made based on noncontrast CT imaging. Each variable is graded and allocated a score. The total score can range from 5 to 13. The latter indicates the most complex scenario. It was devised based on a literature review of outcome variables affecting PCNL and then tested on a cohort of 117 adult patients. The overall accuracy of this SS to predict stone-free rate (SFR) was 83.1% at the time of its conception.

Clinical Research Office of the Endourologic Society nephrolithometric nomogram

This was developed by using data from the Clinical Research Office of the Endourologic Society (CROES) prospective patient registry from 97 centers globally.⁷ A total of 2806 patients were included in the multiple logistic regression analysis, and exclusions had been made where patients were <14 years of age, in centers performing <10 PCNL cases per annum, and where plain X Ray had not been used to evaluate treatment success. It has been externally validated by a number of studies confirming the suitability of applying CT scans.

Seoul National University renal stone complexity

This tool is quite different in that the system is wholly based on the complexity of stone distribution.⁸ In this respect, it is unique because it does not evaluate parameters such as size and number of stones. It is also, therefore, arguably the simplest tool. The authors determined this was the most important outcome to determine PCNL outcomes and derived a schematic diagram of nine areas that the stone can occupy, and a point given for each area. A cumulative score is calculated by the user out of a maximum score of 9. Of note, this system was designed for single-tract PCNL. Patients can be then categorized into three groups based on complexity: low (1 and 2), medium (3 and 4), and high (≥5). The risk of complications was 18.7%, 28.6%, and 34.2% for low, medium, and high Seoul National University renal stone complexity (S-ReSC) score groups, respectively. The SFRs were 96.0%, 69.0%, and 28.9% in these groups. A modified version has been successfully designed for application in URS and has since also been externally validated.¹⁰

Ureteroscopy

Resorlu-Unsal stone score

Developed in 2012, it was the first tool specifically designed for prediction of SFR after URS.¹¹ It was achieved after a retrospective evaluation of 207 cases at their institution. Variables that were significantly associated with SFR were stone size, stone composition, number of stones, lower infundibulopelvic angle (IPA), and anatomical abnormalities, for example, horseshoe kidney. These were all incorporated into the SS with the exception of stone composition, as this is not known preoperatively. The clinician scores the case based on each of these four variables. It is a simple system, as each variable is either scored zero or one based on a yes or no answer. Scoring points are given for abnormal anatomy, IPA <45°, stone positioned in more than one calix, and if the stone size is >2 cm. Additional points can also be given in this variable. One extra point can be given for every centimeter in size where the stone is larger than 2 cm. There was a significant correlation between final RUS score and final SFR. For example, SFR was 84.4% and 27.2% for RUS score 1 and ≥3, respectively.

Ito's score

In 2015, Ito and colleagues developed a tool for fURS based on five independent predictors for the stone-free status that they identified.¹² These were stone volume (SV), lower pole calculi, hydronephrosis, stone number, and operator experience (>50 fURS). In contrast to other SS, a higher score correlates with high treatment success where the maximum possible score is 25.

Shockwave lithotripsy

Triple D score

Tran and colleagues carried out a retrospective analysis of 235 patients undergoing SWL and used this evaluation to create a CT-based, 3-metric system, incorporating stone density in HU, ellipsoid SV, and skin-to-stone distance.¹³ Cutoff values for each of these parameters were generated from receiver operator characteristic curves. If a stone under evaluation has a value less than the cutoff for one of the parameters, they are given a score of 1. The Triple D scores of 0, 1, 2, and 3 are consistent with successful stone clearance rates of 21.4%, 41.3%, 78.7%, and 96.1%, respectively. An advantage is that it can be calculated by the radiologist even at time of reporting, which could provide early assistance in clinical decision making.

S₃HoCKwave score system

This new tool is the result of a multi-center retrospective cohort study carried out over a 10-year period.¹⁴ Analysis of 2271 patients allowed for eventual creation of a clinical prediction model based on six variables. These are sex, skin-to-stone distance, size, HU, colic, and location (kidney or ureter). This tool primarily addresses the risk of SWL failure. This was the primary outcome of interest for this study and was defined as a lack of stone clearance after three SWL sessions. It has yet to be externally validated.

Stent encrustation

Stents represent an integral tool in the endourologist's toolkit, and the global market is estimated to exceed $560 million by 2025.¹⁵ Despite advances related to design since first described in a urological setting in 1967, adverse effects related to them include pain, infection, and stent encrustation.¹⁶ Kawahara and colleagues, reported stent encrustation to occur to some extent in up to 47% of cases, and length of indwelling time is regarded as the greatest risk factor for encrustation.¹⁷ Careful surgical planning is required to achieve clearance and minimize morbidity. Two validated tools now exist to assist the clinician in achieving this.

Forgotten, encrusted, calcified Double-J ureteral stents

The authors devised a five-level grading system based on stone size, location, and degree of encrustation.¹⁸ Grade 1 refers to minimal encrustation at one of the stent's coils, grade 2 encrustation completely encompasses one of the stent coils, grade 3 involves complete encrustation of one of the coils as well as the linear portion of the stent along the course of the ureter, grade 4 refers to complete encrustation of coils at both ends of the stent, and grade 5 involves diffuse encrustation affecting the entirety of the stent. Each grade of encrustation is accompanied by a pictorial schematic to show clinicians the morphology to expect. It was developed by using a retrospective analysis of cases presenting with this clinical problem between 2000 and 2007. It is accompanied by a useful algorithm to help guide potential management based on imaging gained with the CT stone protocol. This allows for recommendation for a single or multimodality treatment. It has already achieved widespread dissemination owing to its ease of application and novelty in addressing a challenging scenario. However, it was established on a review of only nine patients, which is acknowledged as a limitation.

Kidney, ureter, and bladder radiograph system

This tool holds an overlap with forgotten, encrusted, calcified (FECal); however, it was designed more with the aim of aiding the clinician determine the nature of patients with stent encrustation that may require multimodal surgery, multiple surgeries, and a prolonged operative time.¹⁹ A retrospective review of 110 cases was carried out to find associations with these variables as well as SFR. The final system created gives a separate score for each third of the stent affected by encrustation: proximal coil in the kidney (K), portion of the stent in the ureter (U), and distal coil in the bladder (B). Each portion is attributed a score (1–5) based on the degree of calcification present. These can be summated to provide an overall score (3–15). The authors were able to correlate scores to likelihood of different operative outcomes. For example, K score ≥3 was determined to be matched to longer operative time (>180 minutes), need for multi-modal surgery, and poorer stone-free status. This study was only devised based on retrospective observations of a single surgeon, and, therefore, inter-rater reliability was not measured at time.

Renal papillary appearance

Plugging, pitting, loss of contour, and amount of Randall's plaques

This novel grading scale was developed to aid surgeons in describing the appearance of renal papilla at the time of endoscopy.²⁰ This research was borne out of the finding that at a histological level, different stone-forming pathologies render varying papillary morphologies, for example, calcium oxalate stones do not result in intratubular crystals or interstitial fibrosis. Further, a macroscopic view of papilla at time of surgery can also be indicative of stone type. For example, calcium phosphate stones result in greater flattening and erosion of papilla compared with idiopathic calcium stone formers.²¹

It contains four domains and includes: plugging, pitting, loss of contour, and amount of Randall's plaque (mild, moderate or severe). Assessment can be made once an overlying stone has been cleared. A completely healthy appearance receives a final score of 0(a) in contrast to the most diseased appearance, which is given the maximum score of 6(a). Each renal papilla is given a separate score and at the end of the procedure a mean score can be calculated. This was developed in a cohort of 342 patients who had been prospectively enrolled in the project and had undergone digital video mapping at the time of surgery. This tool was made possible as a result of the high-definition scopes, which are available nowadays. This is the first study of its kind to create a standardized assessment method for this purpose.

Endoscopic description of renal papillary abnormalities in stone disease by fURS

Almeras et al. developed a tool to describe and classify papillary abnormalities seen at fURS.²² Findings were formulated by using 164 sequential cases. The result is a system, inspired by the oncological TNM classification, which allows the surgeon to outline findings according to a stone description (Sx), for example, anchored, subepithelial, or intraductal, the number of abnormal papilla (n), and description of its abnormality (Px), for example, tip erosion or extrophic papilla and the amount of Randall's plaque (Rx). The authors also generated a simple algorithm, which groups the most important abnormalities. After systematic use, the authors gave an update in 2020, which provides improvements to address previous limitations such as for mixed stones.²³

Intraoperative ureteric injury (iatrogenic)

Postureteroscopic lesion scale

This tool was developed in 2012 with the principle aim of creating a way for surgeons to intraoperatively grade injury due to URS to determine whether a Double-J stent should be inserted at the end of the procedure and establish standardized recommendations accordingly.²⁴ The authors highlighted ambiguity in the definition of studies referring to URS as “complicated” or “uncomplicated.” The only existing tool prior to this was the generic American Association for the Surgery of Trauma (AAST) classification of ureteric injuries, which holds limited value in its application for endourological scenarios.²⁵ The Clavien-Dindo classification also exists, but this is intended for use postoperatively.²⁶ This new tool was developed through use on 435 patients before evaluation on a further 112 patients to confirm inter-rater reliability. The result is a 0 to 5 level grading system, which is assessed by the surgeon at the time of the final endoscopic passage in the ureter. Postureteroscopic lesion scale (PULS) grade 0 indicates no lesions and therefore an uncomplicated URS, which does not warrant stent insertion. Grade 5 refers to a complete transection with formal reconstruction indicated. Grade 1 to 4 ranges from a superficial mucosal lesion only to a >50% partial transection, which required stent insertion. The authors then provide recommendations for duration of stent insertion. This ranged from 2 days for a grade 1 injury to 6 to 8 weeks for a grade 4 injury.

Although the follow-up period in this study was <1 year only, in 2014 the authors published findings from a multi-center international study, which further supported the high inter-rater reliability (Kendall's W = 0.69, p < 0.001) among urologists.²⁷ This involved participant viewing video sequences from the final endoscopic passage of URS procedures in 100 cases and grading them accordingly.

Injury secondary to ureteral access sheath

Although the PULS grading system has been validated for use in the assessment of ureteral access sheath (UAS) injuries as well, Traxer and Thomas designed a tool specifically for this purpose rather than after a generic URS.²⁸ Again, limitations of the AAST scale were cited as the key reasons for the clinical need for such a tool. Advantages related to UAS are numerous and include facilitation of access of the collecting system, lowering intra-renal pressures, and scope protection.²⁸ However, ureteric injuries can occur and systematic evaluation of ureteral integrity at the end of the procedure is therefore of paramount importance. This classification system was made through an iterative process carried out prospectively over 359 consecutive patients. A five-level grading system (0–4) was the end result. Overall, 46.5% of the study group was identified to have had some degree of ureteric injury. Grade 0 refers to no identifiable lesion, and grade 4 corresponds with total avulsion. High-grade injuries (≥2) were recommended by the authors to have a ureteral stent left in for 3 to 6 weeks followed by ultrasound follow-up 1 to 3 months after stent removal.

KSD recurrence

Up to 50% of patients with KSD are estimated to experience recurrence within 10 years after their first episode.¹ Any means of identifying patients who will go on to experience a further symptomatic stone episode holds immeasurable value and offers the ability to tailor prevention measures accordingly.

Recurrence of kidney stone

The recurrence of kidney stone (ROKS) tool aimed at achieving this.²⁹ It was developed through the identification of first-time symptomatic stone formers in a longitudinal study based in Olmsted County, USA which had been led by the Rochester Epidemiology Project. Between 1984 and 2003, a total of 2239 patients had follow-up carried out until 2012. The end result is a tool including variables such as gender, race, visible hematuria, stone location, and nature of presentation. A revised version was developed in 2019 and was made by using a longer follow-up.³⁰ This model is applicable to patients with any previous episode(s) and not just after their first episode.

Renal colic assessment tools

Real-world studies have shown that more than 50% of patients with acute flank pain and suspected renal/ureteral stone who have a CT are found to have an alternative diagnosis.³¹ Largely driven by need, therefore, of clinicians in the emergency department to help identify and triage those patients most in need of up-front CT imaging based on the likelihood of having a ureteral stone, nomograms have been developed to help this process.

STONE

This is the most well-known tool of its kind.³² The nomenclature can be confusing, as it shares its name with one of the nomograms used to predict PCNL success. The name of this nomogram is not based on an acronym. Released in 2014, it was derived by using the medical records from ∼1000 patients who had been managed under the CT “renal colic pathway.” The advantage of such an objective SS is that it relies less on clinician experience during the triage process. The tool is based on five prognostic factors: gender, race, nausea/vomiting, timing of onset, and nonvisible hematuria. Patients are attributed a total score (0–13 point scale) and can be categorized into three groups of risk, which correlates with the probability of having a ureteral stone. In the internal validation phase, low (0–5), moderate (6–9), and high (10–13) correspond to 9.2%, 51.3%, and 88.6% risk, respectively. Two separate revisions to this STONE nomogram now exist.

The “modified STONE” nomogram was created in 2016 to improve the diagnostic performance.³³ The main adjustment is the replacement of nausea/vomiting and racial origin with C reactive protein and previous stone history, respectively. The other revision to this nomogram is called “STONE point of care limited ultrasonography,” which uses ultrasound imaging to check for hydronephrosis.³⁴ Interestingly, the authors of that study did not find the addition of hydronephrosis to increase the detection of ureteral stones in high-risk patients, but they put forward that it holds relevance and application in deciding the patients who require urgent surgical intervention.

Quality-of-life instruments

Another development within endourology over the past two decades has been the development of multiple PROMS to assess the impact on quality of life (QoL) as a result of KSD and treatment related to it.³⁵

Ureteral stent symptom questionnaire

In 2003, Joshi and colleagues developed this tool to assess symptoms and impact on QoL caused by ureteral stents.³⁶ With six domains covering urinary symptoms, body pain, general health, work performance, sexual matters, and any additional problems, it has become well used and now established in endourology. It is the most commonly used validated stent symptom questionnaire in the literature.³⁷

Wisconsin stone quality-of-life questionnaire

Penniston and Nakada established the first PROM specific for use in patients with KSD.³⁸ It has since achieved validation in many different languages worldwide.³⁹ It comprises 28 question items, which cover multiple domains, including fatigue, sleep disturbance, urinary symptoms, pain, employment, and emotional well-being. Although other QoL questionnaires have been applied in the setting of KSD, at present it serves as the only stone-specific tool for QoL that has achieved external validation.

Other resources and future directions

There exists a range of other tools in addition to those mentioned earlier (Table 1). The majority have been published recently and have therefore yet to gain recognition and external validation. Many have not achieved dissemination, and this is most likely through a lack of simple application. The latter is one explanation for why multiple nomograms appear to exist on the same topic. Another possible reason why there have been challenges in producing a universally agreeable tool is that they are constructed by using different patient populations and, therefore, the results are less generalizable to a worldwide population. For example, the ROKS tool was developed by using a predominantly Caucasian sample. On a similar note, one of the reasons for generation of the CHOKAI tool was to deliver a tool more specific for their patient population in Japan, in contrast to the STONE nomogram, which was made in the United States. The “ideal” nomogram should be easy to utilize in daily clinical practice and achieve reproducible results with minimal subjectivity or inter-observer variability. Newly published tools should be followed by external validation and head-to-head comparison with any previous similar tools, with standardized outcome measures. Findings from this review would suggest that the most widely disseminated tools use simple systems that do not rely on special software, for example, for radiomics, and where parameters can be easily obtained. For example, albumin-globulin ratio may not be readily available as a part of routine work-up.⁴⁰ Limiting the tool to only a few parameters is also likely to make it more user-friendly and promote its uptake. The maximum number of parameters in one study included was 25.⁴¹

Currently, machine-learning software applications exist, which represent advancements in artificial intelligence (AI) within endourology.⁴² Aminsharifi et al. reported validation of outputs from a software, which is an intelligible interface for predicting PCNL outcomes.⁴³ It is anticipated that such research will expand in the future. Development of a nomogram specific for miniaturized PCNL is still awaited. Given the expanded role of URS, for example, a nomogram, which could highlight chances of success through different interventions could be of great clinical use to aid decision making for stone cases. Similarly, a nomogram to give clinicians information regarding whether a case is better suited to miniaturized PCNL or standard PCNL would also be valuable.⁴⁴ Penniston and colleagues are currently developing a stone dietary assessment tool.⁴⁷ More recent advancements in endourology include simultaneous bilateral endoscopic surgery and endoscopic combined intra-renal surgery.^45,46 Nomograms for use within these surgeries is also eagerly anticipated, including to help predict patients most suited for these particular interventions. An ideal nomogram would take into account patient demographics and stone factors, cost, and equipment availability balanced with morbidity and outcomes. Perhaps, AI with big data should be able to help with this dilemma and make the predictive tools better.

Limitations

Although we have covered the most commonly used SS and nomograms in the article, there are others that are either relatively new or that have not been clinically used or externally validated; we have included them in Table 1.^{39,40,47

–81} Of the included tools, 23 (43%) have been published in the past 3 years. We presume that the use of these helpful clinical tools is going to increase in the future. A limitation of many of the available nomograms in stone surgery is that they only provide predictions related to a limited number of outcomes such as stone clearance. They do not, therefore, necessarily aid the tailored intervention as much as one might hope. Future tools should also aim at guiding the surgeon on themes such as the context of URS, for example, whether a UAS or postoperative ureteral stent is recommended and the cost comparison of these interventions.^82,83 A further limitation of this review is the lack of appraisal beyond description of advantages and disadvantages. There are a number of studies that do this for a particular surgery, for example, for PCNL.⁸⁴ However, to our knowledge, this review is the first to provide an overview of all those available collectively. Although images could have been used for the explanation of SS, we would need copyright permission for individual studies, and this was beyond the scope of our review.

Conclusions

A number of reliable and established tools already exist in endourology. Each of these offers their own respective advantages and disadvantages. Although nomograms and SS can help in the decision making, these must be tailored to individual patients based on their specific clinical scenarios, expectations, and informed consent.

Footnotes

Acknowledgment

The authors acknowledge the Team of Worldwide Endourological Researchers (TOWER) Endourological society research group.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received.

Abbreviations Used

References

Scales

Jr ., Smith

, Hanley

, et al. Urologic Diseases in America Project. Eur Urol, 2012; 62:160–165.

Geraghty

, Jones

, Somani

. Worldwide trends of urinary stone disease treatment over the last two decades: A systematic review. J Endourol, 2017; 31:547–556.

Shariat

, Karakiewicz

, Godoy

, et al. Use of nomograms for predictions of outcome in patients with advanced bladder cancer. Ther Adv Urol, 2009; 1:13–26.

Kutikov

, Uzzo

. The R.E.N.A.L. nephrometry score: a comprehensive standardized system for quantitating renal tumor size, location and depth. J Urol, 2009; 182:844–853.

Thomas

, Smith

, Hegarty

, et al. The Guy's stone score—Grading the complexity of percutaneous nephrolithotomy procedures. Urology, 2011; 78:277–281.

Okhunov

, Friedlander

, George

, et al. S.T.O.N.E. nephrolithometry: Novel surgical classification system for kidney calculi. Urology, 2013; 81:1154–1159.

Smith

, Averch

, Shahrour

, et al. CROES PCNL Study Group. A nephrolithometric nomogram to predict treatment success of percutaneous nephrolithotomy. J Urol, 2013; 190:149–156.

Jeong

, Jung

, Cha

, et al. Seoul National University Renal Stone Complexity Score for predicting stone-free rate after percutaneous nephrolithotomy. PLoS One, 2013; 8:e65888.

, Okeke

. Current clinical scoring systems of percutaneous nephrolithotomy outcomes. Nat Rev Urol, 2017; 14:459–469.

10.

Jung

, Lee

, Park

, et al. Modified Seoul National University Renal Stone Complexity score for retrograde intrarenal surgery. Urolithiasis, 2014; 42:335–340.

11.

Resorlu

, Unsal

, Gulec

, et al. A new scoring system for predicting stone-free rate after retrograde intrarenal surgery: the “resorlu-unsal stone score”. Urology, 2012; 80:512–518.

12.

Ito

, Sakamaki

, Kawahara

, et al. Development and internal validation of a nomogram for predicting stone-free status after flexible ureteroscopy for renal stones. BJU Int, 2015; 115:446–451.

13.

Tran

, McGillen

, Cone

, et al. Triple D Score is a reportable predictor of shockwave lithotripsy stone-free rates. J Endourol, 2015; 29:226–230.

14.

Toshioka

, Ikenoue

, Hashimoto

, et al. Development and validation of a prediction model for failed shockwave lithotripsy of upper urinary tract calculi using computed tomography information: The S₃HoCKwave score. World J Urol 2020. [Epub ahead of print]; DOI: 10.1007/s00345-020-03125-y.

15.

Tomer

, Garden

, Small

, et al. Ureteral stent encrustation: epidemiology, pathophysiology, management and current technology. J Urol, 2021; 205:68–77.

16.

Zimskind

, Fetter

, Wilkerson

. Clinical use of long-term indwelling silicone rubber ureteral splints inserted cystoscopically. J Urol, 1967; 97:840–844.

17.

Kawahara

, Ito

, Terao

, Yoshida

, Matsuzaki

. Ureteral stent encrustation, and colouring: Morbidity related to indwelling times. J Endourol, 212; 26:178–182.

18.

Acosta-Miranda

, Milner

, Turk

. The FECal Double-J: a simplified approach in the management of encrusted and retained ureteral stents. J Endourol, 2009; 23:409–415.

19.

Arenas

, Shen

, Keheila

, et al. Kidney, ureter, and bladder (KUB): A novel grading system for encrusted ureteral stents. Urology, 2016; 97:51–55.

20.

Borofsky

, Paonessa

, Evan

, et al. A proposed grading system to standardize the description of renal papillary appearance at the time of endoscopy in patients with nephrolithiasis. J Endourol, 2016; 30:122–127.

21.

Evan

, Lingeman

, Worcester

, et al. Contrasting histopathology and crystal deposits in kidneys of idiopathic stone formers who produce hydroxy apatite, brushite, or calcium oxalate stones. Anat Rec (Hoboken), 2014; 297:731–748.

22.

Almeras

, Daudon

, Ploussard

, et al. Endoscopic description of renal papillary abnormalities in stone disease by flexible ureteroscopy: a proposed classification of severity and type. World J Urol, 2016; 34:1575–1582.

23.

Almeras

, Daudon

, Estrade

, Gautier

, Traxer

, Meria

. Classification of the renal papillary abnormalities by flexible ureteroscopy: evaluation of the 2016 version and update. World J Urol, 2021; 39:177–185.

24.

Schoenthaler

, Wilhelm

, Kuehhas

, et al. Postureteroscopic lesion scale: A new management modified organ injury scale—Evaluation in 435 ureteroscopic patients. J Endourol, 2012; 26:1425–1430.

25.

Coccolini

, Moore

, Kluger

, et al. WSES-AAST Expert Panel. Kidney and uro-trauma: WSES-AAST guidelines. World J Emerg Surg, 2019; 14:54.

26.

Clavien

, Barkun

, de Oliveira

, et al. The Clavien-Dindo classification of surgical complications: Five-year experience. Ann Surg, 2009; 250:187–196.

27.

Schoenthaler

, Buchholz

, Farin

, et al. The Post-Ureteroscopic Lesion Scale (PULS): A multicenter video-based evaluation of inter-rater reliability. World J Urol, 2014; 32:1033–1040.

28.

Traxer

, Thomas

. Prospective evaluation and classification of ureteral wall injuries resulting from insertion of a ureteral access sheath during retrograde intrarenal surgery. J Urol, 2013; 189:580–584.

29.

Rule

, Lieske

, Li

, et al. The ROKS nomogram for predicting a second symptomatic stone episode. J Am Soc Nephrol, 2014; 25:2878–2886.

30.

Vaughan

, Enders

, Lieske

, et al. Predictors of symptomatic kidney stone recurrence after the first and subsequent episodes. Mayo Clin Proc, 2019; 94:202–210.

31.

Nachmann

, Harkaway

, Summerton

, et al. Helical CT scanning: The primary imaging modality for acute flank pain. Am J Emerg Med, 2000; 18:649–652.

32.

Moore

, Bomann

, Daniels

, et al. Derivation and validation of a clinical prediction rule for uncomplicated ureteral stone—The STONE score: Retrospective and prospective observational cohort studies. BMJ, 2014; 348:g2191.

33.

Kim

, Kim

, et al. External validation of the STONE score and derivation of the modified STONE score. Am J Emerg Med, 2016; 34:1567–1572.

34.

Daniels

, Gross

, Molinaro

, et al. STONE PLUS: Evaluation of emergency department patients with suspected renal colic, using a clinical prediction tool combined with point-of-care limited ultrasonography. Ann Emerg Med, 2016; 67:439–448.

35.

Mehmi

, Jones

, Somani

. Current status and role of Patient-reported Outcome Measures (PROMs) in endourology. Urology, 2021; 148:26–31.

36.

Joshi

, Newns

, Stainthorpe

, et al. Ureteral stent symptom questionnaire: Development and validation of a multidimensional quality of life measure. J Urol, 2003; 169:1060–1064.

37.

El-Nahas

, Elsaadany

, Tharwat

, Mosbah

, Metwally

, Hawary

, Keeley

Jr ., Sheir

. Validation of the Arabic linguistic version of the Ureteral Stent Symptoms Questionnaire. Arab J Urol, 2014; 12:290–293.

38.

Penniston

, Nakada

. Development of an instrument to assess the health related quality of life of kidney stone formers. J Urol, 2013; 189:921–930.

39.

Gottstein

, Pratsinis

, Güsewell

, et al. The German linguistic validation of the Wisconsin Stone Quality of Life questionnaire (WisQoL). World J Urol 2020. [Epub ahead of print]; DOI: 10.1007/s00345-020-03405-7.

40.

, Xun

, Yu

, et al. Albumin-globulin ratio: A novel predictor of sepsis after flexible ureteroscopy in patients with solitary proximal ureteral stones. Transl Androl Urol, 2020; 9:1980–1989.

41.

Chen

, Bird

, Ruchi

, et al. Development of a personalized diagnostic model for kidney stone disease tailored to acute care by integrating large clinical, demographics and laboratory data: The diagnostic acute care algorithm–kidney stones (DACA-KS). BMC Med Inform Decis Mak, 2018; 18:72.

42.

Shah

, Naik

, Somani

, Hameed

BMZ

. Advancements in artificial intelligence (AI) within endourology-Current use and future directions: An iTRUE study. Turk J Urol, 2020; 46(Suppl 1):S27–S39.

43.

Aminsharifi

, Irani

, Tayebi

, et al. Predicting the postoperative outcome of percutaneous nephrolithotomy with machine learning system: Software validation and comparative analysis with Guy's Stone Score and the CROES Nomogram. J Endourol, 2020; 34:692–699.

44.

Jones

, Elmussareh

, Aboumarzouk

, et al. Role of minimally invasive (micro and ultra-mini) PCNL or standard PCNL would also be valuable for adult urinary stone disease in the modern era: Evidence from a systematic review. Curr Urol Rep, 2018; 19:27.

45.

Giusti

, Proietti

, Rodríguez-Socarrás

, et al. Simultaneous Bilateral Endoscopic Surgery (SBES) for patients with bilateral upper tract urolithiasis: Technique and outcomes. Eur Urol, 2018; 74:810–815.

46.

Cracco

, Scoffone

. Endoscopic combined intrarenal surgery (ECIRS)—Tips and tricks to improve outcomes: A systematic review. Turk J Urol, 2020; 46(Suppl 1):S46–S57.

47.

Penniston

. Diet and kidney stones: The Ideal Questionnaire. Eur Urol Focus, 2021; 7:9–12.

48.

Mishra

, Sabnis

, Desai

. Staghorn morphometry: a new tool for clinical classification and prediction model for percutaneous nephrolithotomy monotherapy. J Endourol, 2012; 26:6–14.

49.

Xiao

, Li

, Chen

, et al. The R.I.R.S. scoring system: An innovative scoring system for predicting stone-free rate following retrograde intrarenal surgery. BMC Urol, 2017; 17:105.

50.

Imamura

, Kawamura

, Sazuka

, et al. Development of a nomogram for predicting the stone-free rate after transurethral ureterolithotripsy using semi-rigid ureteroscope. Int J Urol, 2013; 20:616–621.

51.

Hori

, Otsuki

, Fujio

, et al. Novel prediction scoring system for simple assessment of stone-free status after flexible ureteroscopy lithotripsy: T.O.HO. score. Int J Urol, 2020; 27:742–747.

52.

Kuroda

, Ito

, Sakamaki

, et al. A new prediction model for operative time of flexible ureteroscopy with lithotripsy for the treatment of renal stones. PLoS One, 2018; 13:e0192597.

53.

Kim

, Chae

, Kim

, et al. Computed tomography-based novel prediction model for the stone-free rate of ureteroscopic lithotripsy. Urolithiasis, 2014; 42:75–79.

54.

Xun

, Chen

, Liang

, et al. A novel clinical-radiomics model pre-operatively predicted the stone-free rate of flexible ureteroscopy strategy in kidney stone patients. Front Med (Lausanne), 2020; 7:576925.

55.

Yamashita

, Kohjimoto

, Iguchi

, et al. Variation coefficient of stone density: A novel predictor of the outcome of extracorporeal shockwave lithotripsy. J Endourol, 2017; 31:384–390.

56.

Hirsch

, Abt

, Güsewell

, et al. Outcome groups and a practical tool to predict success of shock wave lithotripsy in daily clinical routine. World J Urol, 2021; 39:943–951.

57.

Park

, Gong

, Yoon

, et al. Computed tomography-based novel prediction model for the outcome of shockwave lithotripsy in proximal ureteral stones. J Endourol, 2016; 30:810–816.

58.

Niwa

, Matsumoto

, Miyahara

, et al. Simple and practical nomograms for predicting the stone-free rate after shock wave lithotripsy in patients with a solitary upper ureteral stone. World J Urol, 2017; 35:1455–1461.

59.

Kim

, Ha

, Jeon

, et al. Clinical nomograms to predict stone-free rates after shock-wave lithotripsy: Development and internal-validation. PLoS One, 2016; 11:e0149333.

60.

Wiesenthal

, Ghiculete

, Ray

, et al. A clinical nomogram to predict the successful shock wave lithotripsy of renal and ureteral calculi. J Urol, 2011; 186:556–562.

61.

Kanao

, Nakashima

, Nakagawa

, et al. Preoperative nomograms for predicting stone-free rate after extracorporeal shock wave lithotripsy. J Urol, 2006; 176(Pt 1):1453–1456; discussion 1456–1457.

62.

Hamamoto

, Okada

, Inoue

, et al. Prospective evaluation and classification of endoscopic findings for ureteral calculi. Sci Rep, 2020; 10:12292.

63.

Tepeler

, Resorlu

, Sahin

, et al. Categorization of intraoperative ureteroscopy complications using modified Satava classification system. World J Urol, 2014; 32:131–136.

64.

Daudon

, Bader

, Jungers

. Urinary calculi: Review of classification methods and correlations with etiology. Scanning Microsc, 1993; 7:1081–1104; discussion 1104–1106.

65.

Corrales

, Doizi

, Barghouthy

, et al. Classification of stones according to Michel Daudon: A narrative review. Eur Urol Focus, 2021; 7:13–21.

66.

Özbir

, Can

, Atalay

, et al. Formula for predicting the impaction of ureteral stones. Urolithiasis, 2020; 48:353–360.

67.

Torricelli

, Brown

, Berto

, et al. Nomogram to predict uric acid kidney stones based on patient's age, BMI and 24-hour urine profiles: A multicentre validation. Can Urol Assoc J, 2015; 9:E178–E182.

68.

Okita

, Hatakeyama

, Imai

, et al. STone Episode Prediction: Development and validation of the prediction nomogram for urolithiasis. Int J Urol, 2020; 27:344–349.

69.

, Zhong

, Cui

, et al. Development and validation of a risk-prediction nomogram for patients with ureteral calculi associated with urosepsis: A retrospective analysis. PLoS One, 2018; 13:e0201515.

70.

Komeya

, Odaka

, Asano

, et al. Development and internal validation of a nomogram to predict perioperative complications after flexible ureteroscopy for renal stones in overnight ureteral catheterization cases. World J Urol, 2020; 38:2307–2312.

71.

Gao

, Lu

, Xie

, et al. Risk factors for sepsis in patients with struvite stones following percutaneous nephrolithotomy. World J Urol, 2020; 38:219–229.

72.

Sugihara

, Yasunaga

, Horiguchi

, et al. A nomogram predicting severe adverse events after ureteroscopic lithotripsy: 12 372 patients in a Japanese national series. BJU Int, 2013; 111:459–466.

73.

Wang

, Mi

, Wu

, et al. Impact factors and an efficient nomogram for predicting the occurrence of sepsis after percutaneous nephrolithotomy. Biomed Res Int, 2020; 2020:6081768.

74.

Fukuhara

, Ichiyanagi

, Midorikawa

, Kakizaki

, Kaneko

, Tsuchiya

. Internal validation of a scoring system to evaluate the probability of ureteral stones: The CHOKAI score. Am J Emerg Med, 2017; 35:1859–1866.

75.

Al-Terki

, El-Nahas

, Abdelhamid

, et al. Development and validation of a score for emergency intervention in patients with acute renal colic secondary to ureteric stones. Arab J Urol, 2020; 18:236–240.

76.

Bajaj

, Yuan

, Holmes

, et al. Predictors of surgical intervention following initial surveillance for acute ureteric colic. World J Urol, 2018; 36:1477–1483.

77.

Biyani

, Kailavasan

, Rukin

, et al. Global Assessment of Urological Endoscopic Skills (GAUES): Development and validation of a novel assessment tool to evaluate endourological skills. BJU Int 2020. [Epub ahead of print]; DOI: 10.1111/bju.15255.

78.

Quirke

, Aydın

, Bultitude

, et al. Development and content validation of the percutaneous nephrolithotomy assessment score. Int J Urol, 2020; 27:960–964.

79.

Ragab

, Baldin

, Collie

, et al. Qualitative exploration of the renal stone patients' experience and development of the renal stone-specific patient-reported outcome measure. BJU Int, 2020; 125:123–132.

80.

Tran

MGB

, Sut

, Collie

, et al. Development of a disease-specific ureteral calculus patient reported outcome measurement instrument. J Endourol, 2018; 32:548–558.

81.

Joshi

, Johnson

, Pietropaolo

, et al. Urinary Stones and Intervention Quality of Life (USIQoL): Development and validation of a new core universal patient-reported outcome measure for urinary calculi. Eur Urol Focus 2021. [Epub ahead of print]; DOI: 10.1016/j.euf.2020.12.011.

82.

Geraghty

, Jones

, Herrmann

TRW

, et al. Ureteroscopy is more cost effective than shock wave lithotripsy for stone treatment: Systematic review and meta-analysis. World J Urol, 2018; 36:1783–1793.

83.

Somani

, Robertson

, Kata

. Decreasing the cost of flexible ureterorenoscopic procedures. Urology, 2011; 78:528–530.

84.

Al Adl

, Mohey

, Abdel Aal

, et al. Percutaneous nephrolithotomy outcomes based on S.T.O.N.E., GUY, CROES, and S-ReSC Scoring Systems: The first prospective study. J Endourol, 2020; 34:1223–1228.

Atlas of Scoring Systems,Grading Tools,and Nomograms in Endourology: A Comprehensive Overview from the TOWER Endourological Society Research Group

Abstract

Introduction:

Methods:

Results:

Conclusions:

Introduction

Methods

Results

Discussion

Predictive tools in stone surgery

Percutaneous nephrolithotomy

Guys Stone Score

STONE nephrolithometry score

Clinical Research Office of the Endourologic Society nephrolithometric nomogram

Seoul National University renal stone complexity

Ureteroscopy

Resorlu-Unsal stone score

Ito's score

Shockwave lithotripsy

Triple D score

S3HoCKwave score system

Stent encrustation

Forgotten, encrusted, calcified Double-J ureteral stents

Kidney, ureter, and bladder radiograph system

Renal papillary appearance

Plugging, pitting, loss of contour, and amount of Randall's plaques

Endoscopic description of renal papillary abnormalities in stone disease by fURS

Intraoperative ureteric injury (iatrogenic)

Postureteroscopic lesion scale

Injury secondary to ureteral access sheath

KSD recurrence

Recurrence of kidney stone

Renal colic assessment tools

STONE

Quality-of-life instruments

Ureteral stent symptom questionnaire

Wisconsin stone quality-of-life questionnaire

Other resources and future directions

Limitations

Conclusions

Footnotes

Acknowledgment

Author Disclosure Statement

Funding Information

Abbreviations Used

References

S₃HoCKwave score system