Comparison of Monoplanar and Biplanar Access Techniques for Percutaneous Nephrolithotomy

Abstract

Purpose:

The aim of this study was to compare the positive aspects and complications of monoplanar and biplanar access techniques used in percutaneous nephrolithotomy (PCNL) based on the modified Clavien complication grading system.

Patients and Methods:

The data from patients who underwent PCNL using either monoplanar access (group 1) or biplanar access (group 2) techniques were analyzed retrospectively. For the biplanar technique, puncture is adjusted based on different fluoroscopic projections, including vertical and 30 degree positions. For the monoplanar technique, a C-arm fluoroscope was brought into vertical position, the collecting system was visualized with a contrast agent, and the most appropriate calix was selected to extract the targeted stone.

Results:

The monoplanar technique was performed for renal access in 310 patients (group 1), and the biplanar technique was used for renal access in 351 patients (group 2). There were no statistically significant differences between the two groups with regard to demographic data. The mean puncture time was significantly lower in group 1 (monoplanar) when compared with that of group 2 (biplanar, P=0.04). The overall success rates of the monoplanar and biplanar groups were 88% and 89% (including clinically insignifican residual fragments in 9% and 7%), respectively (P>0.05), and the complication rates of both groups were similar.

Conclusion:

The monoplanar access technique, which is safe to use, decreases puncture time, minimizes the surgeon's direct exposure time to radiation, and has similar success rates as the biplanar access technique.

Introduction

Percutaneous nephrolithotomy (PCNL) is an essential technique in the management of various types of renal stone diseases that is commonly performed in daily urologic practice.¹ Although it is a minimally invasive surgical procedure, recent efforts have been made to modify PCNL to make it simpler, more profitable, and to have less potential complications.

During the PCNL procedure, successfully obtaining percutaneous renal access to the collecting system is the first step, because this is directly associated with surgical outcomes and complication rates. Several techniques have been used for guidance for entrance to the pelvicaliceal system, including fluoroscopy, CT, and ultrasonography (US); however, the most commonly used technique is antegrade fluoroscopy-guided percutaneous renal access.^2
–4 Biplanar access is based on the cephalad-caudad and mediolateral movements of the needle; the depth of the needle is adjusted with using fluoroscopic imaging, including 30 degree and vertical positions.^5,6

There are two well-defined techniques of fluoroscopic guidance for antegrade percutaneous access, including the “eye-of-the needle (i.e., bull's-eye)” technique and the “triangulation” technique.⁵ Recently, Hatipoglu and associates⁷ described a novel monoplanar access technique that is different from other methods in that it uses only fluoroscopic projections maintained on a vertical plane.

The eye-of-the needle technique and the triangulation technique were analyzed for many parameters such as outcomes and complications. It was found that neither has a clear advantage over the other, except that the triangulation technique results in lower blood loss.⁸ The current study aims to present the influence of the biplanar (eye-of-the needle) and monoplanar access techniques on operative outcomes. To our knowledge, there is no study in the literature that directly compares these methods; therefore, in this study, we intended to carefully examine the favorable and unfavorable aspects of each.

Patients and Methods

The local ethics committee approved this study, which included a total of 661 consecutive patients who underwent PCNL for stone diseases by the same surgical team at our institution between November 2012 and January 2014. The data were analyzed retrospectively. The patients underwent PCNL using either the monoplanar (group 1) access or biplanar (group 2) access techniques. The technique used was determined by the preferences of the surgeon.

The patient demographics and the perioperative and postoperative variables (e.g., operative time, puncture time, fluoroscopy screening time, hematocrit drop, complication rates, success rates, and duration of hospitalization) for both groups were recorded and compared. Patients with anomalous kidneys were excluded from the study. Informed consent was obtained from all patients before the start of the study.

All patients were evaluated according to their medical history, physical examination, complete blood cell count, plasma urea and creatinine values, coagulation profiles, urinalysis and urine cultures, and imaging methods (i.e., plain radiography, US. intravenous urography, and/or CT). Because a negative urine culture was required before surgery, positive urine cultures were adequately treated with appropriate antibiotics. Puncture time was defined as the time from the start of the fluoroscopic localization of the renal unit to the time when urine discharge came through the needle. The maximum diameter of the stone was defined as the stone size. Stone size was estimated as the sum of the longest axis of each stone if the patient had multiple calculi. US was used to assess the classification of hydronephrosis.

Surgical procedure

Rigid cystoscopy was performed to place a ureteral catheter while the patient was in the lithotomy position. After catheter insertion, the patient was placed in the prone position, and percutaneous access was achieved under the guidance of C-arm fluoroscopy. One of the two access techniques described previously (monoplanar or biplanar) was used for renal puncture.^5
–7

The collecting system in the biplanar technique was visualized with diluted contrast agent, and a fluoroscopy C-arm was used to determine the calix to be punctured with an 18-gauge needle. First, the arm of the fluoroscope was rotated to 30 degrees through to the desired calixes. This maneuver was targeted to the Brodel line that is accepted as a relatively avascular area. Once the eye of the needle (or bull's-eye appearance) was maintained, then the fluoroscopy device was retaken to the position of 90 degrees in a vertical position and the needle was inserted until the hemostat clamp to understand the depth of the needle. The obturator was removed when the tip of the needle reached the targeted calix. Proper positioning was confirmed by an efflux of urine.

The monoplanar technique, which was previously described by Hatipoglu and associates,⁷ relies on known anatomic landmarks. During the procedure, a C-arm fluoroscope was brought into vertical position to access the lower poles, the collecting system was visualized with contrast agent, and the stone location was marked with a clamp. The needle was placed with a 30-degree angle according to the sagittal plane. The angle of the needle, which was parallel to the ground, was defined as 90 degrees in the coronal plane. The needle was inserted into the targeted calixes without changing the angle in both the sagittal and horizontal planes. A curved renal appearance was observed during access into the kidney. If intervention failed, the needle was not drawn completely away from the skin, but was retracted approximately 1 cm intracorporeally, its angle of entry was adjusted on the same vertical plane, and the needle was reinserted.

Amplatz dilators was used for tract dilation (Microvasive, Natick, MA) up to 30F, and a 30F sheath (Amplatz) was accompanied by fluoroscopic image. A pneumatic lithotripter (Lithoclast; EMS, Nyon, Switzerland) and retrieval graspers were used to remove stone fragments through a rigid nephroscope (26F, Karl Storz^®). All patients had a nephrostomy tube placed at the end of the procedure. This nephrostomy tube was removed approximately day 1 post procedure, and the patient was discharged the following day.

Stone clearance was assessed with plain radiography or via US on day 1 post procedure and a spiral CT 3 months after surgery in an outpatient clinic setting. Asymptomatic stones smaller than 3 mm were considered as clinically insignificant residual fragments (CIRFs). Patients were classified as stone free, having CIRFs, or as unsuccessful (residual stones). Complications were classified according to the modified Clavien grading system.⁹ All statistical evaluations were performed with Statistical Package for Social Sciences (SPSS) for Windows 16.0. Variables were investigated using visual (histograms, probability plots) and analytical methods to determine if they were normally distributed. Data regarding normally distributed variables are presented as means±standard deviations (SD); categorical variables are shown as frequencies. The independent samples t test was used to compare parameters between the two groups, while the Pearson chi-square method was performed for categoric variables. Two-sided values of P<0.05 were considered statistically significant.

Results

The monoplanar technique was performed in 310 patients (group 1), and the biplanar technique was performed in 351 patients (group 2). The demographic values, preoperative and perioperative measures including presence of hydronephrosis, diagnostic imaging methods, laterality, operation type, number and type of access, and fluoroscopy time were prospectively recorded into a patient entry system. These two groups were compared in terms of age, stone location and size, and grade of hydronephrosis. The result of analysis of demographic data was found similar between the groups and summarized in Table 1.

Table 1.

Demographİc Data and Stone Characteristics

	Group 1 (monoplanar) (n=310)	Group 2 (biplanar) (n=351)	P value
Age (mean±SD) (years)	34.5±17.9	38.2±21.4	0.562
Sex	162/148	183/168	0.124
Male/female (n)
Mean BMI (kg/m2)	25.2±3.67	28.4±8.2	0.062
History of stone surgery, n (%)	48 (15%)	59 (17%)	0.423
History of SWL, n (%)	33 (10%)	54 (15%)	0.034
Solitary kidney, n (%)	21 (7%)	18 (5%)	0.048
Radiopacity of stone, n (%)	286 (91%)	317 (90%)	0.837
Nonopaque	24 (%7)	34 (9%)	0.743
Opaque	244 (78%)	291 (83%)	0.064
Semiopaque	42 (13%)	26 (7%)	0.026
Degree of hydronephrosis
Nil or mild	237 (76%)	256 (73%)	0.246
Moderate or severe	73 (24%)	94 (27%)	0.184
Stone laterality	148/162	166/185	0.743
Right/left (n)
Stone size (mean±SD) (mm²)	247.37±68.1	268.24±79.6	0.087
Stone location, n (%)
Renal pelvis	113 (36%)	119 (34%)	0.453
Lower calix	35 (11%)	57 (16%)	0.031
Middle calix	12 (3%)	24 (7%)	0.023
Upper calix	24 (7%)	18 (5%)	0.056
Multicaliceal	128 (41%)	133 (38%)	0.068

SD=standard deviation; BMI=body mass index; SWL=shockwave lithotripsy.

In addition, the mean operative times and hematocrit drop values were not different between the groups. The average length of hospital stay was 3.4±1.3 days for group 1 (monoplanar) and 3.2±1.3 days for group 2 (biplanar) (P=0.94). Further, there was no significant difference between the groups with regard to degree of hydronephrosis (P>0.05). The mean puncture time was significantly lower in group 1 (monoplanar) when compared with group 2 (biplanar) (P=0.04). The monoplanar and biplanar groups had similar success rates of 88% and 89%, respectively (P>0.05). The patients with residual stones (38 patients in group 1 [monoplanar] and 40 patients in group 2 [biplanar]) underwent shockwave lithotripsy (SWL) as an additional treatment modality.

The nephrostomy tube was removed after a mean of 2.1±0.5 days in group 1 (monoplanar) and after 2.1±0.42 days in group 2 (biplanar) (P=0.97). The perioperative and postoperative findings are summarized in Table 2. The complication rates of the two groups were similar; when the complications were re-evaluated by the modified Clavien system, there was no statistical difference between the groups (Table 3).

Table 2.

Perİoperatİve and Postoperatİve Data

	Group 1 (monoplanar) (n=310)	Group 2 (biplanar) (n=351)	P value
Operative time (min)	76.9±38.8	82.7±46.3	0.063
Puncture time (min)	1.09±0.27	2.03±0.46	0.042
Fluoroscopy screening time (min)	4.4±1.7	5.7±1.6	0.037
Hematocrit drop (%)	4.08±2.53	4.11±2.13	0.084
Entrance calix, n (%)
Lower	270 (87%)	312 (89%)	0.74
Middle	21 (7%)	18 (5%)	0.66
Upper	18 (6%)	18 (5%)	0.51
Stone-free status (%)
Stone free	244 (79%)	287 (82%)	0.541
CIRF	28 (9%)	24 (7%)	0.187
Rest	38 (12%)	40 (11%)	0.859
Nephrostomy removal time (mean±SD) (day)	2.1±1.4	2.2±1.4	0.971
Hospitalization time (mean±SD) (day)	3.4±1.3	3.2±1.3	0.940
Auxiliary procedure, n (%)	37 (12%)	56 (14%)	0.164
SWL	12 (4%)	12 (3%)	0.110
URS	8 (2%)	16 (4%)	0.09
Re-PCNL	28 (9%)	28 (7%)	0.212

CIRF=clinically insignificant residual fragment; URS=ureterorenoscopy; Re-PCNL=repeated percutaneous nephrolithotomy.

Table 3.

Complİcatİons of Percutaneous Nephrolİthotomy Classİfİed Accordİng to the Modİfİed Clavİen system

	Group 1 (monoplanar) (n=)	Group 2 (biplanar) (n=)	P value
Complications (n)
Grade I
Fever	34 (11%)	31 (9%)	0.312
Grade II
Blood transfusion	27 (9%)	24 (7%)	0.214
Urine leakage	27 (7%)	32 (9%)	0.226
Urinary tract infection	13 (4%)	14 (4%)	0.847
Grade III
Double-J placement for urine leakage	9 (2%)	11(3%)	0.410
Grade IV	-	-
Urosepsis	-	-
Neighboring organ injury (colon)	-	-

Discussion

For the past 35 years, PCNL has been used with proven reliability and effectiveness for various types of renal stone diseases.¹ There are some variables regarding the success and complications associated with percutaneous access, including the type of operator (radiologist vs urologist), imaging modality used for guidance (fluoroscopy vs US vs others), and access type.

The percutaneous renal access is performed by urologists or radiologists in different countries.^10
–12 Watterson and colleagues¹² retrospectively compared accesses obtained by urologists versus those obtained by radiologists and concluded that urologist-acquired percutaneous access resulted in fewer access-related complications and improvements in stone-free rates. Tomaszewski and coworkers¹¹ reported a significantly higher stone-free rates in patients whose access was performed by urologists, but complication rates were reported similar between urologists and radiologists. Another study reported no significant differences between urologists and radiologists in terms of success and complication rates.¹³

Although there is some controversy regarding the success and complications associated with percutaneous access obtained by urologists and radiologists, results indicate that urologists should direct the access for effective subsequent percutaneous procedures.

US, CT, and antegrade fluoroscopy guidance have all been described for percutaneous access, with the latter being the most commonly used; the method of choice is based on patient characteristics and physician preference.^2,4 Compared with fluoroscopy, US has the advantages of portability, real-time appreciation of topographic anatomy, the ability to rapidly evaluate different aspects of the kidney, the ability to avoid puncture of adjacent organs, and has a reduction in radiation exposure.¹⁴

The widespread use of US, however, is restricted by a limited field of view and difficulty in monitoring the subsequent steps of the procedure. Recently reported articles indicate that the use of color Doppler US for guidance during PCNL reveals significantly decreased complications related with percutaneous access such as bleeding and transfusion rates.¹⁵

US-guided access to the kidney is the first choice when retrograde access cannot be obtained or is difficult to obtain, such as in cases with urinary diversions, anatomic abnormalities, transplanted kidneys, or when radiation exposure is a concern, such as in pregnant patients and in children. In some complex cases, CT-guided percutaneous access may be an alternative; this approach is especially useful in patients with anatomic abnormalities or when other techniques are not feasible or have failed.⁴

While a literature review indicates that several alternative access techniques have been used safely and efficiently, the eye of the needle and triangulation techniques are the two primary procedures used to achieve proper percutaneous renal access under fluoroscopic guidance.^2,4 In both of these techniques, multiplanar fluoroscopic imaging is essential and repeated rotation of the C-arm is needed during the procedure.^5,6 Furthermore, it may be difficult to maintain the needle's orientation, especially in situations of prolonged access time and radiation exposure. In addition, gaining access sometimes requires multiple attempts. It should be emphasized that the ionizing radiation presents a small but very real risk.

Mues and colleagues¹⁶ used fluoroscopic projections directed at an angle of 30 degrees to the head of the patient for lower pole entries and at 20 degrees toward the opposite side of the surgeon for middle and upper pole entries. They described a modification that did not require rotation of the C-arm, which diminished radiation exposure. Radiation exposure is a major limitation of the access techniques performed under fluoroscopic guidance. This is especially true in biplanar accesses, where fluoroscopic projections are directed from both the vertical plane and at an angle of 30 degrees to the horizontal plane.

When images are taken from an angle of 30 degrees, the surgeon is directly exposed to high doses of radiation, particularly to the upper part of his/her body. Studies comparing anteroposterior or posteroanterior projections with lateral fluoroscopic projections indicate that the latter exposes the patient and the operating room staff to three to seven times higher radiation doses than do the other techniques.^17,18

In our current study, monopolar fluoroscopy was used during the creation of an access tract, and therefore fluoroscopic projections at an angle of 30 degrees were not needed. When using the monoplanar technique, our average fluoroscopy screening time and puncture times were comparatively shorter than those when we used the biplanar technique; we believe that the fluoroscopic exposure time in the monoplanar technique is relatively decreased during the puncture procedure. Even if the surgeon works under fluoroscopy with short puncture times, however, his/her fingers must be adequately protected from excessive radiation.

In a study comparing access obtained by triangulation and eye of the needle procedures in an animal model, the authors observed that both procedures had similar learning curves, but that the triangulation technique had higher fluoroscopy time.^19,20 Tepeler and associates⁸ analyzed and compared these two access techniques with regard to outcomes and complications in a clinical study and reported that both access techniques had similar hospitalization times, operative times, success and complication rates; the only difference was decrease in hemoglobin with the triangulation technique. The authors hypothesized that this difference may be because of better alignment of the access tract with the infundibulum, which decreases the necessity for exerting excessive force.

There are some limitations to the current study, because it was not a prospective study and patients were not selected randomly. In addition, our results suggest that monoplanar access exposes the patient and operating room staff to less radiation exposure, but we did not measure the radiation level.

Conclusion

The monoplanar access technique is a newly described method. To our knowledge, the current study is the first to compare the monoplanar and biplanar methods. Monoplanar access is safe to use, decreases puncture time, and minimizes the surgeon's direct exposure to radiation. Our data support that monoplanar access is safe and effective for the management of renal stones with PCNL and has similar complication rates to those seen with biplanar access.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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