Hydronephrosis

Hydronephrosis is the swelling of a kidney due to a build-up of urine. It happens when urine cannot drain out from the kidney to the bladder from a blockage or obstruction. Hydronephrosis can occur in one or both kidneys.

The main function of the urinary tract is to remove wastes and fluid from the body. The urinary tract has four parts: the kidneys, the ureters, the bladder and urethra. The urine is formed when the kidneys filter blood and remove excess waste materials and fluid. Urine collects into a part of the kidney called the renal pelvis. From the renal pelvis, the urine travels down a narrow tube called the ureter into the bladder. The bladder slowly fills up with urine, which empties from the body through another small tube called the urethra. Hydronephrosis occurs when there is either a blockage of the outflow of urine, or reverse flow of urine already in the bladder (called reflux) that can cause the renal pelvis to become enlarged.

Hydronephrosis may or may not cause symptoms. The main symptom is pain, either in the side and back (known as flank pain), abdomen or groin. Other symptoms can include pain during urination, other problems with urination (increased urge or frequency, incomplete urination, incontinence), nausea and fever. These symptoms depend on the cause and severity of urinary blockage.

How is Hydronephrosis Caused?
Hydronephrosis is usually caused by another underlying illness or risk factor. Causes of hydronephrosis include, but are not limited to, the following illnesses or risk factors:

  • Kidney stone
  • Congenital blockage (a defect that is present at birth)
  • Blood clot
  • Scarring of tissue (from injury or previous surgery)
  • Tumor or cancer (examples include bladder, cervical, colon, or prostate)
  • Enlarged prostate (noncancerous)
  • Pregnancy
  • Urinary tract infection (or other diseases that cause inflammation of the urinary tract)

How is Hydronephrosis Diagnosed?
An ultrasound is typically used to confirm a diagnosis. This procedure uses sound waves to create an image of your kidneys. A doctor can also confirm a diagnosis with x-rays, computerized tomography (CT) and magnetic resonance imaging (MRI). Diagnosis could also involve a cystoscopy, which uses a long tube with a light and camera at the end (cytoscope) that allows the doctor to look inside the bladder and urethra.

Blood and urine tests can also check kidney function. The doctor can also check for blood in the urine, which can be caused by a kidney stone, infection or other factor.

How is Hydronephrosis Treated?
Hyderonephrosis is usually treated by addressing the underlying disease or cause, such as a kidney stone or infection. Some cases can be resolved without surgery. Infections can be treated with antibiotics. A kidney stone can pass through by itself or might be severe enough to require removal with surgery.

In cases of severe blockage and hydronephrosis, excess urine may need to be removed using either a catheter to drain urine from the bladder or a special tube called a nephrostomy that drains urine from the kidney. The key to treatment is to get it addressed as soon as possible in order to avoid any permanent damage to the kidneys.

Severe cases of urinary blockage and hydronephrosis can damage the kidneys and lead to kidney failure. If kidney failure occurs, treatment will be needed with either dialysis or a kidney transplant. However, most people can recover from hydronephrosis if treated promptly.

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©2014 National Kidney Foundation. All rights reserved. This material does not constitute medical advice. It is intended for informational purposes only. Please consult a physician for specific treatment recommendations.