Hydronephrosis is a condition of the urinary tract where one or both kidneys swell. This happens because pee (urine) doesn’t fully empty from your body. Symptoms may include sudden or intense pain in your back or side, vomiting, painful urination, blood in your pee, or weakness and fever due to a urinary tract infection. There are several approaches to treating the condition, depending on the underlying cause.


Urinary tract anatomy showing an enlarged kidney with pee backing up into it.
Hydronephrosis causes your kidney to swell because pee isn't flowing from your kidney to your bladder.

What is hydronephrosis?

Hydronephrosis (upper urinary tract dilation) is a condition where something keeps pee (urine) from flowing from your kidney to your bladder. When that happens, one or both of your kidneys swell.

It can be sudden or chronic, partial or complete, one-sided or bilateral (both sides). If only one kidney is affected, the condition is called unilateral hydronephrosis. If both kidneys are affected, it’s called bilateral hydronephrosis. It can also vary in severity from mild swelling to severe swelling.

Hydronephrosis may lead to loss of kidney function or kidney failure. However, prompt treatment reduces the risk of long-term complications.

How your urinary tract works

The main job of your urinary tract is to remove waste and fluid from your body. Your urinary tract consists of the following:

  • Two kidneys. Kidneys clean toxins and waste out of your blood.
  • Two ureters. Ureters are ducts that carry pee from your kidney to your bladder.
  • A bladder. Your bladder is an organ that stores your pee.
  • A urethra. Your urethra is a tube that lets pee leave your body.

Often, a blockage or obstruction between your kidney and ureter is the cause of hydronephrosis.

How common is hydronephrosis?

Hydronephrosis can occur in people of all ages. It occurs in about 1 in 100 adults at some point in their life.

In infants, it’s often due to an obstruction (blockage) that happens during fetal development (antenatal hydronephrosis). This occurs in up to 1% of all pregnancies. It usually resolves on its own before birth.


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Symptoms and Causes

What are the symptoms of hydronephrosis?

Symptoms of hydronephrosis usually depend on the cause. Often, there aren’t any symptoms. Antenatal hydronephrosis in babies doesn’t usually cause symptoms after birth.

When symptoms occur, they can include:

Your chances of getting a UTI increase if you have hydronephrosis because pee is trapped in your body. This can lead to bacteria growing in your urinary tract. Symptoms of UTI include:

  • Fever, chills and feeling tired.
  • Painful or burning feeling when you pee.
  • Pee that’s cloudy (not clear).

What causes hydronephrosis?

The most common cause of hydronephrosis is a blockage or obstruction in one of the parts of your urinary tract. Many conditions can cause this.

In adults, the conditions that most often cause hydronephrosis include:

  • Kidney stones: Stones (hard deposits made of calcium and oxalate) that may become lodged in your kidneys or urinary tract.
  • Ureteral obstruction: An obstruction in your ureters.
  • Tumors: Tumors in your bladder, prostate gland, uterus or other organs that are part of or near your urinary tract may keep pee from flowing.
  • Benign prostatic hyperplasia (BPH): Enlargement of your prostate gland can cause pressure on your urethra.
  • Narrowing of your urinary tract: This narrowing can be due to injury, infection, birth disorders or surgery.
  • Nerve or muscle problems: These issues can affect your kidneys or ureters.
  • Urinary retention: You can’t empty your pee from your bladder.
  • Vesicoureteral reflux: Your pee flows backward from your bladder to your kidneys.
  • Ureterocele: This is a condition where the lower part of your ureter may protrude into your bladder.

In people with a uterus, hydronephrosis may occur as a result of:

  • Pregnancy: As your uterus expands, it can press on your ureters and block the flow of pee.
  • Uterine prolapse:A condition in which your uterus sags or slips out of its normal position.
  • Cystocele (fallen bladder): A condition that occurs when the wall between your bladder and vagina weakens and allows your bladder to droop into your vagina.

In babies, antenatal hydronephrosis may occur due to:

  • An increase in the amount of pee the fetus produces.
  • A blockage in the flow of pee at some point in their urinary tract.
  • A backflow of pee from their bladder to their kidneys.


What are the complications of hydronephrosis?

Severe cases of hydronephrosis can damage your kidneys and lead to kidney failure. If this happens, you may need treatment with dialysis or a kidney transplant. Most people recover from hydronephrosis and don’t cause permanent damage to their kidneys.

Diagnosis and Tests

How is hydronephrosis diagnosed?

Getting a diagnosis from your healthcare provider quickly is important because hydronephrosis can cause long-term kidney damage.

Your provider will diagnose hydronephrosis with:

  • Physical examination: Your provider will ask you about any symptoms you’re having and examine the area near your kidneys and bladder for tenderness or swelling. They may ask about your medical history and your family’s medical history. People with a penis may need a rectal exam to determine whether their prostate is enlarged. People with a vagina might require a pelvic exam to evaluate whether there are any problems with their uterus or ovaries.
  • Urine tests: Your healthcare provider will collect a sample of your pee and analyze it for blood, stone crystals, bacteria or infection. They may need to use a catheter to drain the pee.
  • Blood tests: A complete blood count (CBC) may determine whether an infection is present. Tests of kidney function, including creatinine, estimated GFR (eGFR) and blood urea nitrogen (BUN), may also occur.
  • Imaging procedures: The main imaging test is ultrasound. A CT scan or MRI may be necessary.

A healthcare provider can detect hydronephrosis in a fetus as early as the first trimester on an ultrasound. It’s typically discovered during a 20-week ultrasound. A diagnosis at this time usually means the birth parent needs additional ultrasounds to monitor the fetus. However, most cases resolve on their own.


Management and Treatment

What will my healthcare provider do to treat hydronephrosis?

The goal of treatment is to restore the flow of pee from your kidney and decrease the swelling and pressure. Treatment depends on the underlying condition, as that is the primary issue.

Sometimes, mild cases resolve on their own without treatment. Other times, your provider may recommend a “wait and see” approach. Surgery is another option that your provider may consider. You should discuss all possible treatment options with your healthcare provider.

If hydronephrosis is sudden and due to a blockage, your provider may place a nephrostomy tube through your skin into your kidney to drain excess pee. They may also use a soft plastic tube called a ureteral stent to hold your ureters open, which allows your pee to flow as it should.

If stones in your kidneys or ureters are the cause, treatment options may include:

  • Shock wave lithotripsy: This is the most common method for treating kidney stones. High-energy shock waves break up the stones into dust or smaller fragments so they can pass out of your body.
  • Ureteroscopy: Your provider places a thin tube into your urethra to break up and remove the stones. Providers use this method for stones in your bladder or the lower part of your ureters. It can be used in combination with other techniques to break up stones.
  • Surgery: When kidney stones are very large or difficult to remove, your provider may need to remove them with surgery. Also, you might need surgery in the case of tumors, scar tissue or other types of blockages.

If you experience a UTI or your urinary tract is narrow due to infection, your provider will prescribe antibiotics to treat the infection.


How can I prevent hydronephrosis?

As an underlying condition causes hydronephrosis, prevention depends on avoiding or promptly treating that cause. Recognizing factors that put you at risk is also helpful in prevention.

Conditions that put you at risk for hydronephrosis are:

  • Kidney stones.
  • History of cancer in your urinary tract.
  • Past surgeries on your urinary tract.
  • Past infections in your urinary tract, like UTIs.
  • Blood clots.
  • Enlarged prostate.
  • Pregnancy, due to your uterus putting pressure on your pelvis.

Outlook / Prognosis

Is hydronephrosis a serious problem?

Yes, it can become a serious issue without prompt treatment. However, most cases are mild to moderate and don’t cause serious health problems.

Living With

Should I worry about hydronephrosis?

Try not to worry about a hydronephrosis diagnosis. In most cases, treatment will allow you to continue on with your life as usual without any long-term complications. Discuss any questions you have about hydronephrosis and your recovery with your healthcare provider. They can let you know if there are lifestyle modifications you should make or how long you can expect until a complete recovery.

When should I see my healthcare provider?

Contact your provider if you have symptoms such as:

  • Sudden or intense pain in your side or back.
  • Vomiting.
  • Changes in your pee, like peeing more or less than usual, pain when you pee or blood in your pee.
  • Fever above 100.5 degrees Fahrenheit (38 degrees Celsius).

A note from Cleveland Clinic

Hydronephrosis — a condition where your kidneys become swollen due to pee building up — can affect anyone. Luckily, getting a diagnosis and starting treatment can prevent complications from the condition. Talk to a healthcare provider if you have any unusual symptoms like pain in your side or abdomen, nausea or vomiting, and changes in how much or how often you pee. Your provider can discuss the many treatment options available for hydronephrosis after diagnosing the underlying cause.

Medically Reviewed

Last reviewed on 08/25/2023.

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