Hydronephrosis can lead to other health conditions called complications. Without treatment, some people who have severe hydronephrosis develop lasting kidney damage. Rarely, the condition can cause an affected kidney to lose its ability to filter blood, also called kidney failure.

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:

• Partial blockage in the urinary tract. Urinary tract blockages often form where the kidney meets the ureter. Less commonly, blockages may occur where the ureter meets the bladder.
• Vesicoureteral reflux. Vesicoureteral reflux happens when urine flows backward through the ureter from the bladder up into the kidney. Typically, urine flows only one way in the ureter. Urine flowing the wrong way makes it difficult for the kidney to empty properly and causes the kidney to swell.

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:

• A blood test to evaluate kidney function
• A urine test to check for signs of infection or urinary stones that could cause a blockage
• An ultrasound imaging exam, during which your doctor can view the kidneys, bladder and other urinary structures to identify potential problems
• A specialized X-ray of the urinary tract that uses a special dye to outline the kidneys, ureters, bladder and urethra, capturing images before and during urination

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.

You may start by seeing your main healthcare professional. Or you might be referred to a doctor called a urologist who finds and treats urinary tract conditions.

Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do in advance. For instance, you may need to stop eating for a certain number of hours before a test. Also, it helps to make a list of:

• Your symptoms, including any that don't seem related to the reason for your appointment.
• Key personal information, including major stresses, recent life changes and family medical history.
• All medicines, vitamins and other supplements you take, including the doses.
• Questions to ask your healthcare professional.

Take a family member or friend along if you can. This person can help you remember the information you're given.

For hydronephrosis, some basic questions to ask your healthcare professional include:

• What's likely causing my symptoms? Are there other possible causes?
• What tests do I need?
• Is my condition likely short-term or long lasting?
• What treatment is right for me? Are there other treatment choices as well?
• I have other health conditions. How can I best manage them together?
• Are there restrictions I need to follow?
• Should I see a specialist?
• Are there brochures or other printed material I can have? What websites do you recommend?

Feel free to ask other questions.

What to expect from your doctor

Your healthcare professional is likely to ask you questions such as:

• When did your symptoms start?
• Do your symptoms happen some of the time or all of the time?
• How bad are your symptoms?
• What, if anything, seems to make your symptoms better?
• What, if anything, appears to make your symptoms worse?

Hydronephrosis risk factors among adults ages 20 to 60 include being born female. The higher risk could be due to certain conditions that affect the uterus, such as pregnancy. It also could be due to conditions that affect the ovaries, such as cysts, buildups of pus and cancer. Risk factors for people older than age 60 include having an enlarged prostate or a urinary tract blockage from cancer.

Hydronephrosis often causes no symptoms. But when symptoms happen, they can include:

• Pain in the side and back that may travel to the lower stomach area or groin.
• Pain with urination, or feeling a need to urinate that is urgent or happens often.
• Upset stomach and vomiting.
• Fever.
• Failure to thrive in infants.
• Weight loss or loss of appetite.
• Blood in urine.

When to see a doctor

Call your healthcare professional if you have any symptoms of hydronephrosis. Babies with the condition often don't have symptoms. But get your baby a healthcare checkup right away for symptoms such as high fever.

Treatment for hydronephrosis depends on the underlying cause. Although surgery is sometimes needed, hydronephrosis often resolves on its own.

• Mild to moderate hydronephrosis. Your doctor may opt for a wait-and-see approach to see if you get better on your own. Even so, your doctor may recommend preventive antibiotic therapy to lower the risk of urinary tract infections.
• Severe hydronephrosis. When hydronephrosis makes it hard for the kidney to function — as can happen in more-severe hydronephrosis or in hydronephrosis that involves reflux — surgery may be recommended to fix a blockage or correct reflux.

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.