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What is hydronephrosis?

Hydronephrosis is a condition that typically occurs when the kidney swells due to the failure of normal drainage of urine 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 a structural condition that’s the result of a blockage or obstruction in the urinary tract. According to the Boston Children’s Hospital, hydronephrosis affects about one in every 100 babies.

What are the symptoms of hydronephrosis?

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.

The length of time you have the obstruction affects your symptoms. Mild symptoms of hydronephrosis include urinating more frequently and an increase in the 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, or infection of the kidney, and sepsis, which is an infection in the bloodstream or blood poisoning.

What causes hydronephrosis?

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 of causes of hydronephrosis is acute unilateral obstructive uropathy. This is a 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 vesicoureteric reflux (VUR).

Other causes of blockage may 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 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 

How is hydronephrosis diagnosed?

Getting as early a diagnosis 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. Your doctor may 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 as the gold standard for the diagnosis of hydronephrosis. It allows your doctor to get a closer look at your kidney.

What are the treatment options for hydronephrosis?

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 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 allows your doctor to make smaller incisions, drastically reducing your healing and recovery time. Your doctor might also prescribe you antibiotics. This will help ensure you don’t develop a kidney infection.

What is the long-term outlook?

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, you have a 95 percent chance of having a full recovery, according to the Boston Children’s Hospital.

Content licensed from:

Written by: Carmella Wint
Medically reviewed on: Feb 11, 2016: Steve Kim, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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