Hydronephrosis is a condition that typically occurs when a kidney swells due to urine failing to properly drain from the kidney to the bladder. This swelling most commonly affects only one kidney, but it can involve both kidneys.

Hydronephrosis isn’t a primary disease. It’s a secondary condition that results from some other underlying disease. It’s structural and is the result of a blockage or obstruction in the urinary tract. Hydronephrosis is said to affect about .

Normally, urine flows through the urinary tract with minimal pressure. Pressure can build up if there’s an obstruction in the urinary tract. After urine builds up for an extended period, your kidney can enlarge.

Your kidney may become so engorged with urine that it starts to press on nearby organs. If it’s left untreated for too long, this pressure can cause your kidneys to lose function permanently.

Mild symptoms of hydronephrosis include urinating more frequently and an increased urge to urinate. Other potentially severe symptoms you may experience are:

Interrupting the flow of urine increases your chances of getting a urinary tract infection (UTI). This is why UTIs are one of the most common complications of hydronephrosis. Some signs of a UTI include:

  • cloudy urine
  • painful urination
  • burning with urination
  • a weak urine stream
  • back pain
  • bladder pain
  • a fever
  • chills

If you see signs of hydronephrosis, schedule an appointment with your doctor to talk about your symptoms. Untreated UTIs may lead to more serious conditions such as pyelonephritis, an infection of the kidney, and sepsis, an infection in the bloodstream or blood poisoning.

Hydronephrosis isn’t a disease. Instead, it can be due to internal and external conditions that affect the kidney and the urinary collecting system.

One of the most common causes of hydronephrosis is acute unilateral obstructive uropathy. This is the sudden development of an obstruction in one of your ureters, which are the tubes that connect your kidneys to your bladder.

The most common cause for this blockage is a kidney stone, but scarring and blood clots can also cause acute unilateral obstructive uropathy.

A blocked ureter can cause urine to go back up into the kidney, which causes swelling. This backflow of urine is known as vesicoureteral reflux (VUR).

Other potential causes of a blockage include:

  • a kink in the ureteropelvic junction, which is where the ureter meets the pelvis of the kidney
  • an enlarged prostate gland in men, which can be due to benign prostatic hyperplasia (BPH) or prostatitis
  • pregnancy, which causes a compression due to a growing fetus
  • tumors in or near the ureter
  • a narrowing of the ureter from an injury or birth defect

Getting a diagnosis as early as possible is extremely important. Your kidneys could be permanently damaged if your condition is left untreated for too long.

Your doctor will likely begin by getting an overall assessment of your health status and then focus on any urinary symptoms you might have. They may also be able to feel your enlarged kidney by gently massaging the abdomen and flank area.

Your doctor may use a catheter to drain some of the urine from your bladder.

If they’re unable to release a large amount of urine this way, it could mean that your obstruction is in your bladder or your urethra. The urethra is a tube that carries urine from your bladder to the outside of your body.

Your doctor may also want to perform a renal ultrasound or CT scan to get a closer look at the extent of the swelling and to possibly locate the area of the blockage.

Both of these procedures let your doctor view an image of the inside of your body, but the renal ultrasound is generally considered the gold standard for the diagnosis of hydronephrosis. It allows your doctor to get a closer look at your kidney.

Treatment for hydronephrosis primarily focuses on getting rid of whatever is blocking the flow of urine. The treatment option your doctor chooses for you will depend on the cause of your obstruction.

If a blocked ureter is causing your condition, your doctor might need to do any of the following:

  • insert a ureteral stent, which is a tube that allows the ureter to drain into the bladder
  • insert a nephrostomy tube, which allows the blocked urine to drain through the back
  • prescribe antibiotics to control infection

Your doctor might have to remove the obstruction with surgery. If something like scar tissue or a blood clot is causing the blockage, your doctor might remove the affected area completely. They can then reconnect the healthy ends of your ureter to restore normal urine flow.

If the cause of your hydronephrosis is a kidney stone, you may need surgery to remove it. To do this, your doctor might perform endoscopic surgery, which involves using tiny instruments to perform the procedure. This drastically reduces your healing and recovery time.

Your doctor might also prescribe you antibiotics. This will help ensure you don’t develop a kidney infection.

If you receive treatment early, your outlook is good. Removal of the obstruction is essential for your kidney to return to normal functioning. If your hydronephrosis requires surgery, the success rate to having a full recovery is estimated at .

Q:

Who’s at risk for hydronephrosis?

A:

There are several demographic groups that are considered to have an increased risk of hydronephrosis. These groups include:

  • pregnant women, due to an enlarging womb that may compress the ureters
  • men over the age of 50, due to enlargement of the prostate or prostate cancer
  • sexually active women, due to their risk for recurrent urinary tract infections
  • people who are predisposed to recurrent kidney stones
Steve Kim, MDAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.