Version July 2025
Please read the Disclaimer at the end of this page.
What is hydronephrosis? —
This is swelling of 1 or both kidneys. The kidneys are organs in the urinary tract that make urine (figure 1). Each kidney has 2 parts:
●A part that filters blood and removes waste and excess salt and water
●A part that collects urine
In hydronephrosis, the part of the kidney that collects urine gets too much urine in it. This makes it swell and get bigger than normal.
What causes hydronephrosis? —
It usually happens when the urinary tract gets blocked. Then, the urine can't drain, and it backs up into the kidney. Different conditions can cause a blockage in the urinary tract.
In adults, the most common causes of a blockage are:
●Benign prostatic hyperplasia ("BPH") – This is an enlarged prostate. The prostate is an organ that surrounds the urethra in males (figure 2). The urethra is the tube that urine goes through before leaving the body.
●Cancer of the prostate, or cancer of other organs in the lower belly – Cancer growths can push on the urinary tract and block the flow of urine.
●"Stones" in the urinary tract – Stones can form from the salts and minerals that are normally in the urine. The stones can block the urinary tract.
The problem can start suddenly or slowly over time. It can affect 1 or both kidneys.
What are the symptoms of hydronephrosis? —
Some people have no symptoms, especially if the problem started slowly over time. They might find out that they have hydronephrosis when their doctor does a test for another reason.
When people do have symptoms, they usually include:
●Pain – People can have pain in their lower belly, genital area, sides, or lower back.
●Changes in urination – Hydronephrosis usually makes people urinate less than usual. But this does not always happen.
People can have other symptoms, too, depending on what is causing the hydronephrosis. For example, if it is caused by BPH, symptoms might include:
●Needing to urinate often
●Trouble starting to urinate
●A weak urine stream
●Leaking or dribbling urine
●Feeling like the bladder is not empty after urinating
Will I need tests? —
Yes. Your doctor or nurse will ask about your symptoms and do an exam. They will also do tests to figure out why you have hydronephrosis and how serious it is.
Tests can include:
●Blood tests
●Urine tests
●Imaging tests – These create pictures of the inside of the body. Even if your doctor used imaging tests to diagnose hydronephrosis, they might order more to help them figure out what is causing it.
How is hydronephrosis treated? —
You might not need any treatment if you have no symptoms, your blood test results are normal, and your kidneys are working normally.
If you do need treatment, you might see a urinary tract surgeon (called a "urologist") or a kidney specialist (called a "nephrologist"). The kind of treatment you need depends on your situation:
●To help urine drain, your doctor might put tubes in different parts of your urinary tract.
●If you have an infection in your urinary tract, your doctor will prescribe antibiotics.
●If you have a blockage in your urinary tract, your doctor will usually remove it. How they do this will depend on what is causing the blockage. For example, BPH that causes hydronephrosis is usually treated with surgery to remove some of the prostate or shrink the prostate.
●If cancer is causing your hydronephrosis, your doctor will talk with you about your treatment options. Cancer can be treated in different ways, depending on the type of cancer.
●Stones in the urinary tract can be treated with:
•A machine that uses sound waves to break up the stones
•Surgery to remove the stones
•Ureteroscopy – A doctor puts a thin tube into your urethra. The tube has special tools on the end that can break up or remove the stones.
When should I call the doctor? —
Call your doctor or nurse if you have:
●Signs of an infection – These include a fever of 100.4°F (38°C) or higher, or chills.
●Problems urinating – These include pain when urinating, blood in your urine, or being unable to urinate.
●Pain or fullness in your lower belly
●Problems with your catheter (if you have one)
If you suddenly cannot urinate at all, get help right away.
Patient education: Benign prostatic hyperplasia (enlarged prostate) (The Basics)
Patient education: Prostate cancer (The Basics)
Patient education: Kidney stones in adults (The Basics)
Patient education: Urinary tract infections in adults (The Basics)
Patient education: Lithotripsy for kidney stones (The Basics)
Patient education: Ureteral stent placement (The Basics)
Patient education: Urinary catheter placement (The Basics)
Patient education: Benign prostatic hyperplasia (BPH) (Beyond the Basics)
Patient education: Treatment for advanced prostate cancer (Beyond the Basics)
Patient education: Kidney stones in adults (Beyond the Basics)
Patient education: Urinary tract infections in adults (Beyond the Basics)
