Learn about this condition that occurs when urine doesn't drain properly from the upper urinary tract, leading to kidney swelling.
Hydronephrosis is swelling of one or both kidneys. Kidney swelling happens when urine can't drain from a kidney and builds up in the kidney as a result. This can occur from a blockage in the tubes that drain urine from the kidneys (ureters) or from an anatomical defect that doesn't allow urine to drain properly.
Hydronephrosis can happen at any age. Hydronephrosis in children may be diagnosed during infancy or sometimes during a prenatal ultrasound before the baby is born.
Hydronephrosis doesn't always cause symptoms. When they occur, signs and symptoms of hydronephrosis might include:
Hydronephrosis occurs when a kidney has an excess of fluid due to a backup of urine, often caused by an obstruction in the upper part of the urinary tract. Kidney swelling can result, causing the part of the kidney called the renal pelvis to bulge (distend), leading to possible kidney scarring and impaired kidney function.
Typically, urine passes from the kidney through a tube called a ureter that drains into the bladder, and then out of the body. But, sometimes urine backs up or remains inside the kidney or in the ureter. That's when hydronephrosis can develop.
Some common causes of hydronephrosis include:
Less-common causes of hydronephrosis include kidney stones, a tumor in the abdomen or pelvis, and problems with nerves that lead to the bladder.
Your health care provider may refer you to a doctor who specializes in conditions affecting the urinary system (urologist) for your diagnosis.
Tests for diagnosing hydronephrosis may include:
If necessary, your doctor may recommend additional imaging exams, such as a CT scan or MRI. Another possibility is a test called a MAG3 scan that evaluates function and drainage in the kidney.
Treatment for hydronephrosis depends on the underlying cause. Although surgery is sometimes needed, hydronephrosis often resolves on its own.
Left untreated, severe hydronephrosis can lead to permanent kidney damage. Rarely, it can cause kidney failure. But hydronephrosis typically affects only one kidney and the other kidney can do the work for both.