Hydronephrosis of pregnancy

Hydronephrosis of pregnancy

Tim Ferguson

Hydronephrosis of pregnancy is thought to be the result of obstruction by the gravid uterus and hormonal effects that produce ureteral atony. It occurs three times as often in the right kidney than in the left, possibly because the right ureter crosses the iliac vessels more proximally and, therefore, tends to lie on the less distensible proximal iliac artery. The cushioning of the left ureter by the sigmoid colon may also contribute to this difference.’

Acute hydronephrosis is one of the most common causes of severe flank pain in pregnancy.(2) The clinical picture, however, can be misleading. Symptoms may be attributed to acute appendicitis, cholecystitis, acute hydramnios or nephrolithiasis.(3) Urinary tract calculi, another cause of flank pain, have an incidence of 0.1 percent.(3) Ureteral obstruction is a rare cause of renal failure in pregnancy, with a calculated incidence of less than 0.01 percent.(4)

Illustrative Case

A 19-year-old woman in the 26th week of her first pregnancy came to the emergency department following the acute onset of right flank pain, nausea and vomiting. She denied fever or urinary tract symptoms and had had an unremarkable prenatal course.

On presentation she was afebrile. On physical examination, right costovertebral angle tenderness was noted, as well as diminished bowel sounds. Complete blood count, liver function studies, urinalysis, and blood urea nitrogen and creatinine levels were within normal limits. Urine culture showed no growth. Ultrasound study of the gallbladder revealed no abnormalities, but right hydronephrosis was noted and thought to represent hydronephrosis of pregnancy.

On the second hospital day, the pain localized to the right lower quadrant, and guarding and rebound tenderness were noted on abdominal examination. Surgical consultation was obtained, and an emergency appendectomy was performed. Pathologic evaluation revealed a normal appendix.

The patient was discharged on the fourth hospital day in improved condition, but returned two weeks later because of increasing right flank pain. Examination at that time revealed marked right costovertebral angle tenderness. Urinalysis revealed only two to five white blood cells per high-powered field. A single-view excretory urogram performed 30 minutes after injection of the contrast agent revealed marked dilatation of the right intrarenal collecting system, with extravasation of the contrast material into the retroperitoneum from the fomix of a lower pole calyx Figure 1).

Antibiotic therapy was started. The patient subsequently underwent a right percutaneous nephrostomy Figure 2). Within 24 hours, pain and flank tenderness subsided. The patient required nephrostomy drainage throughout the remainder of the pregnancy, which ended with an uneventful cesarean section at 35 weeks. Two weeks postpartum, an antegrade nephrostomogram showed no residual hydronephrosis and rapid drainage of injected contrast material into the bladder Figure 3). The nephrostomy tube was removed.

Although extravasation of urine in pregnancy has been reported in association with kidney rupture or a tear in the renal pelvis, only one other case of forniceal extravasation caused by hydronephrosis of pregnancy has been reported.(1) Severe complications of hydronephrosis of pregnancy, such as pain that is unresponsive to conservative measures, renal failure or a ruptured collecting system, occur rarely, but may lead to complications such as urinoma, perinephric abscess and sepsis.(1)


Hydronephrosis seen on renal ultrasonography is a normal, nonspecific finding and, thus, is of little diagnostic use.(2) In a prospective study(5) that utilized ultrasound examination of the urinary tract in normal pregnancies, the absence of excessive hydronephrosis was thought to speak against pathologic obstruction. This seems to us a rather nebulous criterion to apply and, in addition, is dependent on technical factors and the skills of the sonographer. An intravenous pyelogram (IVP) often can confirm the diagnosis and delineate the site and cause of obstruction.(2) Excretory urography, with a single film 30 to 60 minutes after contrast injection, should be adequate to delineate delayed drainage.

A single radiograph of the abdomen delivers 0.2 rad to mother and fetus; a standard IVP delivers 0.4 to 1.6 rad.(3) As few films as possible should be used to evaluate a pregnant woman, thereby limiting radiation exposure to the unborn child.


To preserve renal function and relieve discomfort, prompt urinary tract drainage is required in ureteral obstruction from any cause. Weiss and colleagues(6) recommend retrograde ureteral catheterization as a first choice for relieving obstruction, with nephrostomy tube placement if this fails. Kinn,(7)on the other hand, used percutaneous nephrostomy as a primary modality in two patients with pathologic pregnancy-induced ureteral obstruction. Which strategy is used depends on the available expertise or standard of practice in a particular community. Nephrostomy was chosen in the illustrative case because ureteral stenting requires spinal or general anesthesia, requires fluoroscopy and can be technically difficult in pregnant women. Percutaneous nephrostomy, which uses local anesthesia, can often be performed under ultrasonographic guidance, which reduces fetal radiation exposure.


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JC. Acute renal failure and acute hydronephrosis

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COPYRIGHT 1991 American Academy of Family Physicians

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