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Unilateral hydronephrosis



Unilateral hydronephrosis is swelling of one kidney due to a backup of urine.

See also:  Bilateral hydronephrosis

Alternative Names



Hydronephrosis is a condition that occurs with a disease. It is not a disease itself. Conditions that are often associated with unilateral hydronephrosis include:

Unilateral hydronephrosis occurs in approximately 1 in 100 people.

  • Flank pain
  • Abdominal mass
  • Nausea and vomiting
  • Urinary tract infection
  • Fever
  • Painful urination (dysuria)
  • Increased urinary frequency
  • Increased urinary urgency

Note: Sometimes unilateral hydronephrosis does not have symptoms.

Signs and tests

Unilateral hydronephrosis is usually identified with tests such as the following:

Support Groups

Expectations (prognosis)

Prolonged hydronephrosis results in the eventual loss of kidney function.

Calling your health care provider

Call your health care provider if you have prolonged or severe flank pain, or if you suspect hydronephrosis.


If hydronephrosis is left untreated, the affected kidney may be permanently damaged. Kidney insufficiency or kidney failure is rare with unilateral hydronephrosis because the other kidney usually functions normally. However, if the patient has only one functioning kidney, kidney failure will occur.


Treatment and prognosis for unilateral hydronephrosis depend on what is causing the kidney swelling. Treatment may include:

  • A ureteral stent (tube that allows the ureter to drain into the bladder)
  • A nephrostomy tube (allows the blocked urine to drain through the back)
  • Antibiotics for infections

Patients who have only one kidney, who have immune-compromising disorders such as diabetes or HIV, or who have received a transplant should be treated promptly.

Preventative antibiotics may be prescribed to decrease the risk of urinary tract infections in patients who have long-term hydronephrosis.


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


Frøkiaer J, Zeidel ML. Urinary tract obstruction. In: Brenner BM, ed. Brenner and Rector's The Kidney. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 35.

Review Date: 3/22/2010
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Scott Miller, MD, Urologist in private practice in Atlanta, Georgia. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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