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

• Acute unilateral obstructive uropathy
• Chronic unilateral obstructive uropathy
• Vesicoureteric reflux (backflow of urine from bladder to kidney)
• Nephrolithiasis (kidney stones)
• Hydronephrosis that occurs without a known cause during pregnancy

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

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

• Abdominal MRI
• CT scan of the kidneys or abdomen
• Intravenous pyelogram (IVP)
• Isotope renography (special scan of the kidneys)
• Ultrasound of the kidneys or abdomen

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.

Prolonged hydronephrosis results in the eventual loss of kidney function.

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.

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

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

Wein AJ, et al. Campbell-Walsh Urology. 9th ed. St. Louis, Mo: WB Saunders; 2007.

Goldman L, Ausiello D, et al. Cecil Textbook of Medicine, 22nd ed. Philadelphia, Pa: WB Saunders; 2004.