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Hydronephrosis is an abnormal dilation of the renal pelvis and the calyces of one or both kidneys. It's caused by an obstruction of urine flow in the genitourinary tract. A partial obstruction and hydronephrosis may not produce symptoms initially, but pressure that builds up behind the area of obstruction eventually results in symptoms of renal dysfunction.


Hydronephrosis is a condition that occurs with a disease and is not a disease itself. Treatment and prognosis for unilateral hydronephrosis depend what is causing the kidney swelling.

Conditions that are often associated with unilateral hydronephrosis include:

  • Acute unilateral obstructive uropathy
  • Chronic unilateral obstructive uropathy
  • Vesicoureteric reflux
  • Nephrolithiasis
  • Hydronephrosis that occurs without a known cause during pregnancy

Signs and Symptoms

Hydronephrosis usually develops over just a few hours when a blockage forms quickly - from a kidney stone for example. But it can develop gradually over a period of weeks or months if the blockage is due to something like a slow-growing tumour.

The severity of your symptoms will depend on the extent of the blockage and the amount your kidney is stretched. The type of symptoms you experience will depend on the location of the blockage and the length of time the flow of urine remains blocked.

When the blockage begins quickly (acute hydronephrosis), you will usually experience a severe pain (renal colic) in your back or side between your ribs and hip. The pain will be on the side of the affected kidney, or if both kidneys are affected, on both sides.

Other symptoms can include:

  • swelling in your abdomen,
  • nausea,
  • vomiting,
  • fever,
  • needing to go to the toilet more often than normal, and
  • pain when you pass urine.

Diagnostic tests

Excretory urography, retrograde pyelography, renal ultrasonography, and renal function studies confirm the diagnosis. Visualization tests show concave (early stage) or convex (later stage) calyces as dilation progresses. If the disease is extensive, tests show atrophied distal and proximal tubules and obstructions.

Urine studies confirm the inability to concentrate urine, a decreased glomerular filtration rate and, possibly, pyuria if infection is present.


The goals of treatment are to preserve renal function and prevent infection through surgical removal of the obstruction. Surgery includes dilatation for a urethral stricture or prostatectomy for benign prostatic hyperplasia.

If renal function has already been affected, therapy may include a diet low in protein, sodium, and potassium. This diet is designed to stop the progression of renal failure before surgery.

Inoperable obstructions may necessitate decompression and drainage of the kidney, using a nephrostomy tube placed temporarily or permanently in the renal pelvis. Concurrent infection requires appropriate antibiotic therapy.


Prevention of the disorders associated with unilateral hydronephrosis will prevent this condition.

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