Health Library

Hydronephrosis occurs when urine builds up in the kidneys and cannot drain out to the bladder. The kidneys swell from the excess urine. Swelling can lead to damage. One or both kidneys may be affected.

This is not a condition. It is a sign of another condition that is affecting the kidneys. Swelling of the kidneys can lead to kidney damage.

Urinary Tract System

Copyright © Nucleus Medical Media, Inc.

Hydronephrosis is caused by urinary tract problems, like a blockage that prevents urine from draining out of the kidneys. Blockage can be due to:

• A birth defect that causes a narrowing where the ureter (tube that leads from the kidney to the bladder) connects with the bladder
• Kidney stones
• Blood clots
• Tumors
• Scar tissue or injury to the urinary tract

Kidney, Ureter, Bladder, and Kidney Stone

Copyright © Nucleus Medical Media, Inc.

Other causes include:

• A condition called reflux that causes urine to flow back into the kidneys from the bladder
• Abnormal bladder function due to problems with the nerves

In most cases, the child is born with one of these conditions that affect the urinary tract. For some, the condition develops later on.

Being male is a risk factor for this condition.

In mild cases, there may not be any symptoms. If the condition is more severe, symptoms may include:

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

The doctor will ask about your child’s symptoms and medical history. A physical exam will be done. The doctor will examine the pelvis or rectum to feel for any blockages. Tests may include:

• Urine tests—to check for blood, protein, bacteria, or other evidence of damage to the kidneys
• Blood tests—to check for evidence of damage to the kidneys
• Voiding cystourethrogram—x-rays of the bladder and urethra taken during urination after contrast dye is placed in the bladder
• Ultrasound —a test that uses sound waves to examine the kidneys, ureters, and bladder
• Intravenous urogram (or pyelogram)—an x-ray test that uses contrast dye to assess the structure and function of the kidneys, bladder, and ureters
• MRI —a test that uses magnetic waves to make pictures of the kidneys, bladder, and ureters
• CT scan —a type of x-ray that uses a computer to make pictures of structures inside the body
• Cystoscopy —a thin, lighted tube inserted through the urethra and into the bladder to examine the lining

When an infant is born with a condition that causes hydronephrosis, the doctor will monitor him to see if he will need treatment. In some cases, antibiotics are given to prevent infections. If the condition is mild, further treatment may not be needed, and it may resolve on its own. In severe cases, the doctor will have to do surgery to treat the condition causing the urinary blockage or reflux.

In many cases, hydronephrosis cannot be prevented. However, if your child has nerve problems preventing the bladder from functioning normally, regular bladder emptying and medicines may be able to help prevent this problem.