Multicenter Review of Obstetric Management and Complications of Ureteroscopy During Pregnancy

Introduction

Nephrolithiasis afflicts pregnant patients with an incidence of up to 8 per 1000 pregnancies and is associated with both significant maternal and fetal risks. ¹ Management of nephrolithiasis during pregnancy represents a multidisciplinary challenge, involving anesthesiologists, obstetricians, and urologists. Efforts to aid providers in navigating this complex clinical scenario have yielded several guidelines with statements on choices of imaging modalities and risks of both conservative and operative management. ^2,3

When operative intervention is indicated, an established treatment is ureteroscopy (URS), which has been previously reported to be both safe and efficacious in pregnancy. Prior published series reported minimal urologic complications and ureteral stents or nephrostomy tubes require frequent exchanges and multiple anesthetic exposures, which has increased the utilization of URS during pregnancy. ^{4 –6} However, data surrounding obstetric (OB) risks of URS are limited. A prior multicenter study reported a 4.3% rate of OB complications from ureteroscopies performed prior to 2011, ⁷ while an insurance-claims database reported an 11.2% risk of preterm labor from urologic intervention for stones from 2008 to 2011. ⁸ Considering recent innovations in URS, we sought to examine OB risks of URS in a contemporary setting. Furthermore, data surrounding OB involvement and fetal monitoring (FM) with URS are unknown, and we sought to discover and present real-world multi-institutional practice patterns.

Materials and Methods

A retrospective descriptive review with Institutional Review Board approval (#STU00218796) of pregnant patients who underwent ureteroscopies with fellowship-trained endourologists at seven institutions was performed from 2015 to 2024. Ureteroscopies were performed at both community and tertiary care centers. Patient demographic data including age, gestational age, comorbidities (diabetes, hypertension, obesity, illicit drug use, mental health disorder), and a history of prior OB procedure were recorded. Indications for URS during pregnancy were obtained. Preoperative workup, including laboratory and imaging data such as creatinine, white blood cell count, urinalysis, urine culture, and imaging modality were collected. Perioperative OB management, including OB presence intraoperatively during URS and FM practice patterns, was collected. Intraoperative data, including anesthesia, operative time, laterality, ureteroscope type, ureteral access sheath utilization, and postoperative ureteral stent management, were recorded. Postoperative complications were recorded within 30 days after URS. Complications were noted to be either URS-specific or OB in nature.

Results

We identified 72 unique URS cases in 70 pregnant patients from 2015 to 2024 from seven different institutions. Average patient age at time of URS was 30 ± 5 years old. Average gestational age was 23.5 ± 7.5 weeks. URS during the first trimester occurred in 4 patients (5.6%), 44 were in their second trimester (61.1%), and 24 were in the third trimester (33.3%). Of the 70 patients, 24 had a prior history of nephrolithiasis. Two patients had URS performed in two distinct separate pregnancies.

Preoperative imaging was obtained in the form of ultrasound (US), magnetic resonance imaging (MRI), or computed tomography (CT) scan prior to URS. Imaging was performed prior to all cases. US was the most common imaging modality and was performed prior to 70/72 cases. Of these, 27 US identified hydronephrosis without nephrolithiasis, and 11/27 of these patients then went on to undergo a CT scan, which identified a stone. Of the US, 40 provided stone measurements, with stone size being an average of 9.5 mm (range = 4–15). CT scans were obtained in 20/72 cases, and 2/72 cases only underwent CT scans prior to URS. The average stone size measurement on CT was reported to be 8 mm (range = 3.5–15 mm). MRI was obtained prior to URS in 5/72 cases. MRI was preceded by US in 2/5 cases for further characterization after nondiagnostic US. MRI was obtained prior to US in three out of five cases and incidentally prompted further workup for nephrolithiasis. For one out of three of these cases, the patient initially underwent MRI, then US, which showed hydronephrosis without definitive evidence of an obstructing stone, and then finally CT scan, which identified an obstructing stone. MRI was nondiagnostic in one out of five cases, reported only hydronephrosis and hydroureter in three out of five cases, and stones were identified in two out of five cases with an average stone size of 5.25 mm (range = 5–5.5).

Prior to URS, 37 patients had some form of preoperative drainage: 13/37 had a nephrostomy tube, 23/37 had a ureteral stent, and 1/37 had both a nephrostomy tube and a ureteral stent. Indications for preoperative drainage included 17 patients who had preoperative infection, 18 patients due to intractable pain and hydronephrosis, and 2 patients due to history of stent encrustation or anatomical reasons. On average, preoperative drainage was performed 64.6 days (range = 9–127) prior to URS.

Mean preoperative serum creatinine was 0.68 mg/dL, and mean white blood cell count was 12.0 × 10⁹/L. Urinalysis data were available in 63/72 cases, with pyuria, defined as white blood cell >10/high-power field, present in 41/63, microscopic hematuria in 55/63, and nitrite positivity in 9/63. Preoperative urine culture was positive in 19/72 cases, with the most common organisms being Escherichia coli in 6/19, Klebsiella in 2/19, and Streptococcus in 2/19. Multiple bacteria considered mixed urogenital flora were noted in 2/19 positive cultures, 3/19 positive cultures with >10⁵ colony-forming unit were not speciated, and the remaining positive cultures were single cases of Enterococcus, Proteus, Pseudomonas, and Staphylococcus aureus.

Operative details are provided in Table 1. The most common indication for URS during pregnancy was renal colic alone in 50/72 cases, followed by recurrent infections in 9/72 cases. No intraoperative complications were noted. Negative URS without stone identified was noted in 13/72 cases. Of these negative URS, preoperatively 3/13 had an US followed by a CT scan on average 6.5 days prior to URS (range = 0.5–12 days), which showed distal ureteral stones; 1/13 had an US with hydronephrosis alone followed by a nondiagnostic MRI; and 9/13 had an US only with no stones seen but hydronephrosis was present.

Perioperative and intraoperative obstetrician involvement varied from site to site. One site required pre- and postoperative nonstress tests (NST). Five sites performed FM on a case-to-case basis. One site required obstetrician’s presence and availability during the URS, independent of gestational age, and this represented 13/72 cases. Pre- and postoperative fetal heart rates were performed in 11/72 cases. Intraoperative FM was performed in 16/72 cases—8/16 were intermittent FM and 8/16 were continuous FM. The remaining 45 cases did not have any OB evaluation reported.

Of the 72 cases, 8 patients experienced URS-specific complications within 30 days of procedure. All complications were Clavien-Dindo grade I/II. Two patients had stent intolerance with pain and discomfort. Two patients (2 out of 39 patients with a dangle) had premature accidental stent removal. Three patients had an emergency department (ED) visit or readmission for pain. One patient had an ED visit for fever. One patient had urinary incontinence that resolved after stent removal, and one patient had postoperative hypotension after spinal anesthesia requiring phenylephrine that spontaneously resolved.

Of the 72 cases, 8 cases (11.1%) had OB complications within 30 days of procedure, which are noted in Table 2. Preterm delivery requiring C-section at 27 weeks was noted in two cases (2.78%) for pre-eclampsia (postpartum day [POD] 4) and intrauterine fetal growth restriction (POD 21). One patient who was 5 weeks pregnant had a miscarriage after URS on POD12, but was noted to not have a viable pregnancy, with ultimately no finding of intrauterine pregnancy. There were no cases of preterm labor in the immediate postoperative period. Of note, for patients requiring postoperative admission for self-resolving nonreactive NST and uterine contractions, an obstetrician was present in the operating room. Continuous intraoperative FM was performed in two out of three cases with an OB complication on POD 0. An obstetrician was not present, and intraoperative FM was not performed in the patients who required C-section at 27 weeks.

Discussion

URS during pregnancy is uncommonly performed. From a national database over a 5-year period between 2011 and 2016, only 180 cases of URS were performed for nephrolithiasis during pregnancy out of more than 14,000 pregnant women with stones. ⁹ Our current series captured 72 cases across 7 institutions from 2015 to 2024, representing a significant portion of cases occurring in North America. Our goal was not only to evaluate urologic and OB outcomes but also to identify OB monitoring practice patterns for URS during pregnancy.

Herein, we collected granular details on preoperative workup and intraoperative details for URS cases during pregnancy (Table 1). Our series had no major urologic complications, further contributing to the evidence that URS is safe in pregnancy with surgeons who specialize in stone disease at tertiary medical centers. ^4,5,7 General anesthesia was used in 68.0% of cases, and regional anesthesia was used in 30.6% of cases without any associated complications. There was a URS-specific postoperative minor complication rate of 11.1% and no intraoperative complications. Comparatively, a Norwegian series of 96 URS over 3 decades had a complication rate of 11% postoperatively and 2% intraoperatively. ⁴ Furthermore, a systematic analysis in 2012 revealed a complication rate of 7.8% over 116 procedures, with one complication being intraoperative ureteral perforation. ⁵ Our minor complication rate was slightly higher but is likely related to our utilization rate of stents, with the bulk of our complications being related to stent colic and malfunction. Postoperative ureteral stents were deployed in 74% of our cases, with more than 50% being placed on dangle extraction strings, vs a stent-deployment rate of 42% and 55% in the other series, respectively.

The role of preoperative CT scans in pregnant women is controversial because of theoretical risks of ionizing radiation to the fetus. Indeed, two institutions in our series have hospital policies to never perform CT imaging in pregnant women despite American College of Obstetricians and Gynecologists (ACOG) and ACR recommendations. Correspondingly, according to the IBM MarketScan national database, from 2011 to 2016, over 14,000 pregnant women were found to have urolithiasis, and CT scans were not used in any of the cases for diagnosis. ⁹ In contrast, some assert that preoperative CT is beneficial and reduces the risk of negative URS. Indeed, the ACOG endorses the use of low-dose CT scans to diagnose and manage stone disease in pregnant women when US is not diagnostic. ^2,10 From our series, 20/72 cases had preoperative CT imaging, demonstrating that CT imaging is used in real-world practice for pregnant patients with stones.

Moreover, White et al reported an overall negative URS rate of 7/51 (14%) in pregnant women, but this decreased to 4.2% of cases if examining women who had both a preoperative CT and US compared to 23% rate of negative URS in women who had a preoperative US alone. ¹¹ For our series, we had a comparable rate of negative URS of 13/72 cases (18.1%), with 9/13 negative URS cases having an US alone, 3/13 having both a CT and US, and 1/13 having both an US and MRI. Interestingly, we did not have as stark a difference in negative URS rates when examining specific preoperative imaging modalities, with a rate of 19.5% (9/46) in women who had a preoperative US alone, and 15% (3/20) in women who had a preoperative CT.

A major goal of our study was to update the literature on the OB complication rate from URS. Limited existing literature, from prior to 2011, reported a preterm labor rate of 0.86%–11.2% after urologic intervention for stone disease. ^4,5,7,8 For our series, there were no cases of preterm labor, and our OB complication rate was 11.1% (Table 2). There were two cases of preterm C-section within 30 days of URS during pregnancy, but these cases were likely secondary to OB factors as the C-sections were performed more than 24 hours after the URS. Our finding of a 0.0% rate of URS-induced preterm labor is lower than the 4.3% rate previously reported in a multicenter study, ⁷ likely reflecting advancements in contemporary equipment, technique in URS, and OB management.

The benefit of FM and obstetrician presence during URS is largely unknown. Of note, although many guidelines have been published regarding the management of nephrolithiasis during pregnancy, only a minority of institutions have hospital policies in place, and these policies are significantly variable. A recent worldwide survey study of 355 institutions showed that 66.2% of institutions have no hospital policy for management of nephrolithiasis in pregnancy. ¹² ACOG recommends FM at a minimum before and after non-OB surgeries per a 2019 opinion, ¹³ but when asked whether fetal heart rate monitoring is performed during urologic intervention, only 42.2% of institutions answered yes. ¹² For our current study, OB management policies surrounding URS in pregnancy are similarly heterogeneous, with most performing FM on a case-to-case basis. Intraoperative FM was performed in 16/72 cases, but according to OB literature, FM intraoperatively for non-OB procedure is based on low-quality evidence and is not regularly supported or endorsed. ¹⁴ In our opinion, obtaining FM prior to and after anesthesia and procedure is important to show the viability of the pregnancy was not directly affected by the procedure and can be important medicolegally if loss of pregnancy was to occur.

In our series, only one site required obstetrician’s presence and availability during URS. Interestingly, there were three cases of admission less than 24 hours after URS for OB monitoring, and all three of these cases occurred when an obstetrician was present during URS. It is unclear whether requiring the obstetrician to be present prompted an unnecessary admission or perhaps due to obstetrician involvement, preterm labor was prevented. For all three cases, the indications for admission self-resolved spontaneously without active intervention. However, the two cases of post-URS C-section occurred at institutions that did not require intraoperative FM nor an obstetrician to be present in the operating room (what about pre and post FM for these patients who required C-section). Therefore, the potential benefits of obstetrician presence for non-OB surgeries and implications for the obstetrician workforce require further research to discern and could perhaps be integrated into future guideline development. An OB team being present during URS may be most useful in the third trimester, especially during interventions late in pregnancy where onset of labor may require delivery. ¹⁵

Our study is limited by its retrospective nature and heterogeneity in data collection due to its multi-institutional involvement. There was similar heterogeneity in practice patterns for preoperative imaging workup and OB involvement. However, including multiple centers is also a strength as we collected a large series of patients for this rare condition and provided an update to the literature regarding contemporary outcomes and practice patterns.

Conclusions

URS is safe in pregnancy in the care of urologists who are experienced in stone disease. Our contemporary multicenter series of 72 cases of URS in pregnant patients revealed a 0% rate of preterm labor in the immediate postoperative period. Across our seven centers, there was no consensus on perioperative and intraoperative obstetrician involvement and FM during URS. It is unclear whether obstetrician presence or FM is beneficial to reduce complication rates of URS during pregnancy.