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Pronounced: high-drow nef-row-sis


Hydronephrosis a build-up of urine in the kidneys. The kidneys swell from the excess urine which cannot drain into the bladder. The condition may affect one or both kidneys. Hydronephrosis is not a disease, but a symptom of a problem with the urinary system.

Kidney, Ureter, Bladder, and Kidney Stone

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Hydronephrosis is caused by one of two problems in the urinary system:

Risk Factors

Factors that may increase your chance of hydronephrosis include:

  • Defect in the urinary system that is present at birth
  • Scarring of the ureters, the tubes that carry urine from the kidneys to the bladder
  • Cancers in the pelvic area (bladder, cervix, colon, or prostate)
  • Persistent kidney or urinary tract infections
  • Blood-clotting disorders
  • Benign prostatic hyperplasia
  • Neurogenic bladder
  • Injury to structures in the urinary system, such as from surgery or trauma
  • Enlarged uterus during pregnancy

Hydronephrosis may or may not cause any symptoms. If symptoms occur, they may include:

  • Pain in the back, waist, lower abdomen, or groin
  • Persistent pain with urination or urinary frequency from urinary tract infections
  • Increased urge to urinate or urinary incontinence
  • Incomplete urination
  • Fever
  • Nausea and vomiting
  • Unexplained itching

Your doctor will ask about your symptoms and medical history. A physical exam will be done. It may include a pelvic or rectal exam to feel for blockages. You may be referred to a urologist and/or nephrologist for further diagnosis and treatment.

Tests may include:

  • Blood tests
  • Urine tests

Imaging tests evaluate the urinary system. This can be done with:


A catheter may be inserted into the bladder to drain excess urine from the kidney. Some causes of hydronephrosis resolve without treatment, such as pregnancy and kidney stones.

Treatment options include:


Depending on the cause, hydronephrosis may be treated with:

  • Antibiotics for infection
  • Medications for neurogenic bladder or to reduce excess uric acid excretion

Surgery is usually not needed, but it may be necessary in some cases. Procedures may include:

  • Removing a blockage or correcting a defect in the urinary system
  • Nephrostomy—A catheter is placed into the kidney. The catheter is attached to a urine collection bag.
  • Nephrectomy—Removal of part or all of the kidney (rare).

In general, the causes of hydronephrosis cannot be prevented. Prompt treatment of conditions that cause hydronephrosis reduces the risk of complications, such as kidney failure.


National Institute of Diabetes and Digestive and Kidney Diseases

National Kidney Foundation


Health Canada

Kidney Foundation of Canada


Hydronephrosis. National Kidney Foundation website. Available at: Accessed July 12, 2013.

Kidney disease and kidney failure. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: Updated November 15, 2012. Accessed July 12, 2013.

Last reviewed May 2015 by Adrienne Carmack, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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