REVIEW Urological issues in pregnancy: A review for urologists Joshua White, MD1; Jesse Ory, MD1; Andrea G. Lantz Powers, MD1; Michael Ordon, MD2; Jamie Kroft, MD3; Ashley Cox, MD1 1Department of Urology, Dalhousie University, Halifax, NS, Canada; 2Division of Urology, University of Toronto, Toronto, ON, Canada; 3Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON, Canada Cite as: White J, Ory J, Lantz Powers AG, et al. Urological issues in pregnancy: A review for urologists. stalsis and contraction pressure.6 Right-sided hydronephro- Can Urol Assoc J 2020;14(10):352-7. http://dx.doi.org/10.5489/cuaj.6526 sis is more commonly observed as compared to left-sided as a result of several factors. First, the ovarian vein on the right crosses over the ureter before entering the inferior vena Published online May 12, 2020 cava, whereas the left ovarian vein runs parallel to the ure- ter before entering the renal vein;7 second, the uterus is dextrorotated; and lastly, the left ureter is protected by the Abstract gas-filled sigmoid colon.8 Physiological changes may also influence stone forma- Urological issues in the pregnant patient present a unique clinical tion. The capacity of the collecting system increases by dilemma. These patients may be challenging to treat due to risks an estimated 200–300 mL, leading to urinary stasis.9 An associated with medications and surgical procedures. This review increased excretion of sodium, calcium, and uric acid due aims to provide an update on the physiological changes and surgi- 9 cal risks in pregnancy. In addition, we review the approach for man- to increased glomerular filtration rate is observed. These fac- 10 agement of urolithiasis and urinary tract infections in pregnancy. tors may increase the patient’s propensity to form stones. Lastly, we highlight the importance of a multidisciplinary approach Conversely, increased urine alkalinity, renal blood flow, and to placenta percreta, a condition not commonly addressed in uro- excretion of urinary citrate, magnesium, and nephrocalcin logical education. may inhibit stone formation.10-12 This leads to no overall change in the incidence of nephrolithiasis in pregnancy compared to the general population; yet, the rate of stent Introduction and nephrostomy tube encrustation is higher in pregnancy, possibly due to urinary stasis and the increase in urinary Pregnant patients presenting with urological complaints can calcium excretion.13 often be a challenging population to treat. There is a paucity of high-quality literature to guide management and the risks Surgical risk in pregnancy of inappropriate treatment may have serious consequences for both the fetus and mother. We reviewed the literature for The most common indication for urological surgery in common urological presentations in pregnancy and present a the pregnant patient is symptomatic urolithiasis.13,14 The review of the literature to help guide clinical decision-making. American College of Obstetricians and Gynecologists (ACOG), in conjunction with the American Society of Physiology in pregnancy Anesthesiologists (ASA), published recommendations for non-obstetrical surgery during pregnancy.15 Important for the There are important physiological changes in pregnancy that urologist to consider are the following points: 1) a pregnant urologists must consider. Physiologic hydronephrosis is com- woman should never be denied medically necessary sur- monly observed, particularly on the right side; 50–90% of gery or have that surgery delayed, regardless of trimester, patients may have hydronephrosis by the third trimester.1,2 because this can adversely affect the pregnant woman and Dilatation develops primarily in the second and third tri- her fetus and; 2) elective surgery should be postponed until mester, where the ureters cross the pelvic brim, and so the after delivery.15 A third recommendation, present in the 2017 dilatation tends to be seen proximal to this.3 This is par- ACOG guideline, is absent in the 2019 opinion: to perform tially due to hypertrophy of Waldeyer’s sheath, the external non-urgent surgery in the second trimester. This recommen- longitudinal muscle layer in the distal ureter.4,5 In addition, dation was largely based on poor-quality data and has since progesterone reduces ureteric tone, thereby reducing peri- been removed.16 352 CUAJ • October 2020 • Volume 14, Issue 10 © 2020 Canadian Urological Association Urological issues in pregnancy The urologist should approach surgery in the obstetri- include patients with refractory pain, bilateral obstruction, cal patient in a multidisciplinary fashion. When possible, obstruction in a solitary kidney, and obstruction with urinary surgery should be performed in a center with neonatal and tract infection (UTI) or sepsis.13 pediatric services15 if the fetus is beyond viability (22 weeks The use of alpha-blockers for medical expulsive thera- gestational age).17 Obstetrics should be notified if surgery py (MET) for ureteric stones is controversial, even in non- is planned, and peri/intraoperative monitoring coordinated pregnant patients. In appropriately selected, non-pregnant when appropriate.15 patients, (i.e., distal stones >5 mm), MET may be advocated for the passage of ureteric stones.38 Use of alpha-blockers Urolithiasis in pregnancy for MET is “off-label,” with the proposed benefit of smooth muscle relaxation of the ureters to facilitate stone passage.39 The incidence of symptomatic urolithiasis in pregnant Urologists must question the utility of such medications in patients is equal to non-pregnant women of childbearing pregnancy given that increased progesterone in pregnancy age, estimated to be 0.03–0.53%.18-21 The largest and most has an effect of smooth muscle relaxation.6,32 A number recent population-based study from Ontario, Canada, dem- of small retrospective studies evaluating MET in pregnant onstrated an incidence of 0.2% for symptomatic stones in women have found that MET is not associated with statisti- pregnancy from 2004–2014.22 Kidney stones in pregnancy cally significant maternal or fetal outcomes.40,41 One of these have been associated with an increased risk of preterm birth, studies identified two cases of sudden infant death syndrome low birth weight, pre-eclampsia, caesarian section, prema- in the MET group compared with none in the conservative ture rupture of membranes, and preterm delivery in vari- management group, though this failed to reach statistical ous studies.22-24 Diagnosis of urolithiasis in pregnancy can significance.40 There is a paucity of high-quality evidence to be challenging, as common symptoms and findings often support the efficacy of MET in pregnant patients. One meta- occur in the setting of pregnancy independent of urolithia- analysis of the effects of alpha-blockers and antimuscarinics sis. One retrospective review found that most clinical signs used alone or in combination therapy to relieve stent-related and symptoms were not helpful in distinguishing urolithiasis symptoms found that the efficacy and appropriateness in and physiological hydronephrosis.25 Left-sided flank pain, pregnant patients is unclear.42 microscopic hematuria, and a prior history of stones were Temporization with ureteric stents and/or percutane- reported as statistically significant predictors of urolithiasis.25 ous nephrostomy tubes has been widely used in pregnant The American Urological Association (AUA), European patients with obstructing stones. This may be performed Association of Urology (EAU), and American College of under local anesthetic or sedation. Indwelling stents may be Radiology (ACR) recommend ultrasound as the first-line poorly tolerated, however, and are at a high risk of bacterial imaging study in pregnant patients.26-28 Unfortunately, ultra- colonization and encrustation.43 Stent encrustation can result sound is only 34% sensitive for ureteric stones in this popu- in obstruction requiring further surgical management, and as lation.25 Adjuncts, such as a reduced or absent ureteric jet such, stents require exchange every 4–6 weeks in pregnant coupled with an elevated renal resistive index (RI) or an patients.31,43,44 Placement of nephrostomy tubes has been elevated RI alone have been shown to improve ultrasound shown to be safe in numerous studies, though they come accuracy 71.9–77%.25,29 The RI is defined as the peak dia- with similar limitations as stents.45,46 stolic velocity subtracted from the peak systolic velocity, Advances in endourology have improved the safety and divided by the peak systolic velocity.29 False positives may efficacy of ureteroscopic management of stones in pregnan- occur due to compression of the ureter by the uterus when cy.14 Spinal anesthetic may be used for the treatment of distal assessing ureteric jets with color Doppler. Therefore, the test stones.47 Ureteroscopy is a safe form of treatment in the preg- should be repeated in the contralateral decubitus position.30 nant patient, as demonstrated in a 2012 systematic review. Urolithiasis is one of the most common causes of non- Eight-six percent (100/116) of procedures resulted in stone obstetrical admission in the gravid patient.31 Conservative clearance, with a serious complication rate of only 1.6% (one management with intravenous fluids and analgesia is rec- ureteric perforation, one case of premature uterine contrac- ommended as a first step for suitable patients.32 Likely as a tions that resolved without progressing to preterm labor).48 result of the increased ureteric dilation,