Hydronephrosis occurs when urine builds up in the kidneys and cannot drain out to the bladder. The kidneys swell from the excess urine. The condition may affect one kidney or both. Hydronephrosis is not a disease itself. It is a sign of another disease or condition affecting the kidneys.

Kidney, Ureter, Bladder, and Kidney Stone

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Causes

Hydronephrosis is caused by one of two problems in the urinary system. A blockage may prevent urine from draining out of the kidneys. Or, a condition called reflux may cause urine to flow back into the kidneys from the bladder.

Conditions that may cause hydronephrosis include:

  • A blockage or defect in the urinary system that is present at birth
  • Kidney stones
  • A blood clot
  • Scarring of the ureters, which are the tubes that connect the kidneys to the bladder
  • A tumor in the pelvic area such as the bladder, cervix, colon, or prostate
  • Enlarged prostate
  • Enlarged uterus during pregnancy
  • Persistent urinary infection in the kidneys
  • Neurogenic bladder
  • Injury to structures in the urinary system, such as from surgery or trauma
Risk Factors

The following factors increase your chances of developing hydronephrosis:

  • Defect in the urinary system that is present at birth
  • Cancers in the pelvic area
  • Pelvic surgery
  • Blood-clotting disorders
  • Recurrent urinary tract infections
  • Enlarged prostate
  • Neurogenic bladder
  • Pregnancy
Symptoms

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
Diagnosis

Your doctor will ask about your symptoms and medical history. A physical exam will be done. It may involve examination of the pelvis or rectum to feel for blockages. You will likely be referred to an urologist and/or nephrologist for further diagnosis and treatment.

Your bodily fluids may be tested. This can be done with:

  • Urine tests
  • Blood tests
  • Bladder catheterization

Your internal structures may need to be viewed. This can be done with:

Treatment

Treatment involves:

  • Draining excess urine from the kidney
  • Removing the blockage
  • Treating conditions that cause blockage or reflux
  • Treating infections in the urinary system

Some causes of hydronephrosis resolve without treatment, such as pregnancy and kidney stones.

Treatment options include:

  • Antibiotics to treat urinary tract infections
  • Medications to treat neurogenic bladder or to reduce excess uric acid excretion
  • Catheter inserted into the bladder to drain the urine
  • Nephrostomy—a tube inserted into an opening in the midsection to drain urine from the kidney
  • Surgery to remove a blockage or correct a defect in the urinary system
  • Surgery to remove part or all of the kidney—rare
Prevention

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.