The signs and symptoms of hydronephrosis depends upon whether the obstruction is acute or chronic. Unilateral hydronephrosis may even occur without symptoms.

Blood tests can show elevated creatinine and electrolyte imbalance. Urinalysis may show an elevated pH due to the secondary destruction of nephrons within the affected kidney.

Symptoms that occur regardless of where the obstruction lies include loin or flank pain. An enlarged kidney may be palpable on examination.

Where to obstruction occurs in the lower urinary tract, suprapubic tenderness (with or without a history of bladder outflow obstruction) along with a palpable bladder are strongly suggestive of acute urinary retention, which left untreated is highly likely to cause hydronephrosis.

Upper urinary tract obstruction is characterised by pain in the flank, often radiating to either the abdomen or the groin. Where the obstruction is chronic renal failure may also be present. If the obstruction is complete, an enlarged kidney is often palpable on examination.

Aetiology

The obstruction may be either partial or complete and can occur anywhere from the urethral meatus to the calyces of the renal pelvis.

The obstruction may arise from either inside or outside the urinary tract. Intrinsic obstructions (those that occur within the tract) include blood clots, stones, along with tumours of the kidney, ureter and bladder. Extrinsic obstructions (those that are caused by factors outside of the urinary tract) include pelvic tumours, strictures of the ureters, and neurological defecits.

Complications

Left untreated bilateral obstruction (obstruction occurring to both kidneys rather than one) has a poor prognosis.

Treatment

Treatment of hydronephrosis focusses upon the removal of the obstruction and drainage of the urine that has accumulated behind the obstruction. Therefore, the specific tretment depends upon where the obstruction lies, and whether it is acute or chronic.

Acute obstruction of the upper urinary tract is usually treated by the insertion of a nephrostomy tube. Chronic upper urinary tract obstruction is treated by the insertion of a ureteric stent or a pyeloplasty.

Lower urinary tract obstruction (such as that caused by bladder outflow obstruction secondary to prostatic hypertrophy) is usually treated by insertion of a urinary catheter or a suprapubic catheter.

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Hydronephrosis of pregnancy
From American Family Physician, 6/1/91 by 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)

Evaluation

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.

Treatment

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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