A 24-year-old woman, gravida 1 para 0, at 26 weeks gestation comes to the office due to increased urinary frequency and back pain. For the past 2 weeks, the patient has had to urinate almost hourly during the day and has awakened multiple times each night to void. She has also developed back pain and occasionally has a sharp, pulling pain in the right groin. The patient has no nausea, vomiting, dysuria, or hematuria. She has had no vaginal bleeding, leakage of fluid, or contractions. Fetal movement is normal. The patient has had recurrent nephrolithiasis outside of pregnancy. Temperature is 37.2 C (99 F), blood pressure is 130/80 mm Hg, and pulse is 72/min. There is tenderness to palpation throughout the lower back and along the paravertebral muscles. Laboratory results are as follows:
| Serum chemistry | |
| Creatinine | 0.6 mg/dL |
| Urinalysis | |
| Specific gravity | 1.001 |
| Protein | trace |
| Leukocyte esterase | negative |
| White blood cells | 1-2/hpf |
| Red blood cells | negative |
Renal and pelvic ultrasound of the mother reveals bilateral enlargement of the kidneys. The right kidney is larger than the left; there is dilation of the renal pelvis and proximal ureter on both sides. Which of the following is the best next step in management of this patient's condition?
Show Explanatory Sources
This patient has nonspecific, common symptoms of pregnancy including urinary frequency, nocturia, back pain, and round ligament pain (ie, sharp groin pain). Although her examination is benign and her laboratory results are normal for pregnancy, a renal ultrasound can be performed due to her recurrent nephrolithiasis. The renal ultrasound findings of bilateral kidney enlargement and bilateral dilation of the renal pelvises and proximal ureters are consistent with physiologic hydronephrosis of pregnancy.
During pregnancy, kidney enlargement occurs because there is an increase in maternal blood volume that requires increased renal filtration, resulting in greater renal vasculature and interstitial tissue. Hydronephrosis begins during the first trimester as high progesterone levels cause ureteral dilation and decreased peristalsis. Hydronephrosis becomes more pronounced in the second and third trimesters as uterine enlargement compresses the ureters at the pelvic brim, which results in dilation of the proximal ureters and bilateral hydronephrosis. Right hydronephrosis is often more pronounced due to dextrorotation of the uterus, which causes increased compression of the right ureter. Unlike pathologic hydronephrosis (eg, secondary to obstruction or infection), physiologic hydronephrosis of pregnancy requires no additional management.
(Choices A and C) Ureteral stents and nephrostomy tubes are inserted when the etiology of hydronephrosis is ureteral blockage (eg, nephrolithiasis). Obstruction usually presents with microscopic hematuria and unilateral imaging findings (eg, visible stone, unilateral hydronephrosis). This patient's urinalysis is negative for blood, and she has bilateral findings on ultrasound.
(Choice B) Disorders of bladder outlet obstruction are treated with Foley catheter placement. In contrast to this patient, those with bladder outlet obstruction have decreased urination (rather than frequency) and have both distal and proximal ureteral dilation.
(Choice E) Urodynamic testing is performed to evaluate mixed urinary incontinence (eg, urgency and stress) outside of pregnancy. Urinary frequency and nocturia are normal in pregnancy due to bladder compression by the uterus and nighttime shifting of edema back into circulation.
Educational objective:
Hydronephrosis in pregnancy occurs due to ureteral compression from uterine enlargement and decreased ureteral peristalsis due to increased progesterone. Ultrasound findings include bilateral renal enlargement (right > left) with dilated renal pelvises and proximal ureters. Physiologic hydronephrosis of pregnancy requires no additional management.