Hydronephrosis

Hydronephrosis is a condition in which your urine (pee) can't drain from the kidney to the bladder due to a blockage or obstruction. Often, the obstruction causes kidney swelling, which may affect one or both kidneys.

If left untreated, hydronephrosis can lead to decreased kidney function and possible permanent kidney damage.

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On this page:  

• What Is Hydronephrosis?  
• What Are the Symptoms of Hydronephrosis?  
• How Do You Diagnose Hydronephrosis? 
• How Do You Treat Hydronephrosis?  

What Is Hydronephrosis?  

Hydronephrosis occurs when a kidney swells and can't drain urine (pee) to the bladder as it normally does. This swelling is usually from a blockage or obstruction.

Over time, if left untreated, the backup of urine can affect kidney function and even cause permanent kidney damage in extreme cases.

Hydronephrosis usually affects only one kidney but may involve both.

How common is hydronephrosis? 

Hydronephrosis affects about 1% of babies and 1% of adults.

What causes hydronephrosis?  

Hydronephrosis isn't a primary disease. It's considered a secondary condition because it results from an underlying structural condition. Its cause can be internal and external conditions that affect the kidney and the urinary collecting system (UCS).

A common cause of hydronephrosis is acute unilateral obstructive uropathy, the sudden onset of an obstruction in one of the ureters — the tubes that connect your kidneys to your bladder. Kidney stones commonly cause this blockage, but scar tissue and blood clots can also cause it.

A ureter blockage may cause urine to backflow into the kidney, causing swelling. This condition is known as vesicoureteral reflux (VUR).

Additional causes of an obstruction include:

• A twist in the ureteropelvic junction, which is where the ureter attaches to the kidney.
• A narrowing of the ureter from an injury or birth abnormality.
• Pregnancy, which may compress a ureter as the developing baby grows.
• Tumors in or near the ureter.

What are hydronephrosis risk factors and complications?  

Hydronephrosis risk factors

You may be at risk of hydronephrosis if you have certain underlying conditions.

These conditions may include:

• Blood clots.
• Congenital blockages, or defects present at birth.
• Enlarged prostate (noncancerous).
• Kidney stones.
• Pregnancy.
• Scar tissue from a prior injury or surgery.
• Tumors or certain kinds of cancer, including bladder, cervical, colon, or prostate cancer.
• Urinary tract infection (UTI) or other inflammation diseases of the urinary tract.

Complications of hydronephrosis

A urinary tract infection (UTI) is the most common complication of hydronephrosis.

Signs of a UTI include:

• Back pain.
• Bladder pain.
• Chills.
• Pee that looks cloudy.
• Pain or burning sensation when you pee.
• Weak urine stream.

When should I see a doctor about my hydronephrosis symptoms?

If you have signs of a UTI, schedule an appointment with your doctor to talk about your symptoms.

If you don't treat a UTI, it can lead to more serious conditions, including:

• Pyelonephritis, a kidney infection.
• Sepsis, a serious and possibly life-threatening infection in the bloodstream.
• Blood poisoning.

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What Are the Signs and Symptoms of Hydronephrosis? 

In the urinary tract, urine normally flows through with little pressure. But if a ureter is blocked, urine can build up pressure and cause the kidney to enlarge. The engorged kidney may become so large that it presses on other organs.

At first, hydronephrosis may cause only mild symptoms like:

• An increased urge to urinate.
• Needing to pee more often.      

Other potentially severe symptoms are:

• Fever.
• Frequent urination.
• Incomplete voiding or bladder emptying.
• Nausea or vomiting.
• Pain in your lower back, belly, or side.
• Pain when you pee.
• An urge to pee but being unable to produce any urine.

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How Do You Diagnose Hydronephrosis?  

Your doctor will take your medical history and do a physical exam, but they'll need to order tests to diagnose hydronephrosis.

Tests to diagnose hydronephrosis

Tests used to diagnose hydronephrosis include:

• Blood tests.
• Urine tests.
• Imaging tests, such as an ultrasound, CT scan, MRI, or cystoscope to see your kidneys and bladder and find the blockage.

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How Do You Treat Hydronephrosis?

It’s important to get treatment as soon as possible to avoid any permanent damage to the kidneys. Severe hydronephrosis can lead to kidney failure, which may then require dialysis or a kidney transplant.

Most people recover from hydronephrosis with prompt treatment.

The key goal of treatment for hydronephrosis is to prevent any further swelling of the kidney.

Common treatment options include:

• Prescription medication to ease pain and/or fight infection.
• A surgery called pyeloplasty to remove the blockage.

In severe cases of hydronephrosis due to a blockage, extra urine may need to be drained using either a catheter or a special tube called a nephrostomy.

By UPMC Editorial Staff. Last reviewed on 2024-09-05.