Hydronephrosis: Causes, Symptoms, and How It Is Diagnosed

Hydronephrosis is a condition in which one or both kidneys become swollen because urine cannot drain normally. It can affect people of any age, and early assessment helps identify the cause and protect kidney function.

Overview

Hydronephrosis is the medical term for swelling of a kidney caused by a backup of urine. Normally, urine flows from the kidneys through the ureters to the bladder and then leaves the body through the urethra. When this flow is blocked or slowed, pressure can build up in the urinary tract, causing the kidney to stretch and enlarge.

The condition can affect one kidney or both. It is not a disease by itself, but rather a sign that something is interfering with normal urine drainage. In some people, hydronephrosis is mild and found incidentally during imaging for another reason. In others, it can cause pain, infection, or reduced kidney function if it is not treated in time.

Hydronephrosis can occur suddenly or develop gradually. Acute hydronephrosis may cause more noticeable symptoms, especially if a stone or another blockage appears quickly. Chronic hydronephrosis can be quieter at first, sometimes producing few symptoms until pressure has been present for a longer period.

Symptoms of Hydronephrosis

Symptoms depend on how quickly the blockage develops, whether one or both kidneys are affected, and what is causing the problem. Some people have no symptoms at all, particularly when hydronephrosis is mild or develops slowly. Others may notice discomfort in the side, back, lower abdomen, or groin.

Common symptoms can include pain in the flank, nausea, vomiting, painful urination, frequent urination, a sudden urge to urinate, or difficulty emptying the bladder. If infection is present, fever and chills may occur. Blood in the urine is also possible, especially when kidney stones are involved.

In babies and young children, symptoms may be less specific. A child may be irritable, feed poorly, vomit, or develop a urinary tract infection. In adults, especially older men, urinary symptoms may also be linked to prostate enlargement, which can obstruct urine flow.

• Flank or back pain
• Nausea or vomiting
• Frequent or painful urination
• Blood in the urine
• Fever or chills if infection is present
• Reduced urine output or trouble urinating

Causes and Risk Factors

Hydronephrosis happens when urine cannot pass freely through part of the urinary tract. One of the most common causes is a kidney stone blocking the ureter. This is why evaluation for kidney stones is often part of the assessment, and in some cases the blockage can be treated with procedures such as laser lithotripsy.

Other causes include narrowing of the ureter, congenital abnormalities present from birth, scar tissue, blood clots, or pressure from nearby structures. In men, an enlarged prostate can slow or block urine outflow from the bladder. Tumors of the urinary tract or surrounding organs may also cause obstruction. Urinary tract infections can sometimes contribute to swelling, especially if they are recurrent or severe, and this may overlap with problems such as urinary infections.

Less commonly, hydronephrosis can be related to structural kidney conditions or diseases that affect the urinary tract over time. A person may also have a combination of causes, such as stones plus infection, or bladder emptying problems plus prostate enlargement. Risk factors include a personal history of stones, previous urinary tract surgery, repeated urinary infections, neurological conditions that affect bladder function, pregnancy, and certain anatomical abnormalities.

How Hydronephrosis Is Diagnosed

Diagnosis begins with a medical history and physical examination. The doctor asks about pain, urinary symptoms, fever, previous stones, infections, surgery, and any known prostate or kidney problems. A physical exam may check for tenderness in the abdomen or flank and signs of bladder distension.

Urine and blood tests help look for infection, blood in the urine, and changes in kidney function. A urine sample may show red blood cells, white blood cells, or bacteria. Blood tests can measure kidney function markers and help determine how urgently treatment may be needed.

Imaging is central to confirming hydronephrosis and finding the cause. Ultrasound is often the first test because it can show swelling of the kidney without radiation exposure; this is especially common in children and pregnancy. In many cases, detailed imaging such as renal ultrasonography or other forms of renal imaging helps define where the blockage is and how severe it is.

Depending on the situation, the doctor may also recommend a CT scan, MRI, or specialized bladder and urinary flow tests. These can help detect stones, tumors, strictures, or bladder outlet obstruction. The goal is not only to confirm hydronephrosis, but to identify the exact cause so the right treatment can be planned.

Treatment Options

Treatment depends on the cause, severity, symptoms, and whether kidney function is affected. The main priority is to relieve the obstruction and prevent lasting kidney damage. If infection is present at the same time as a blocked kidney, treatment is especially urgent because pressure and infection together can become serious.

For some people, treatment may include pain relief, fluids, antibiotics for infection, or close monitoring if the swelling is mild and expected to improve. When a stone is the cause, the treatment plan may range from waiting for a small stone to pass to procedures that break up or remove the stone. If the blockage is due to enlarged prostate, scarring, or another structural problem, targeted treatment is needed.

In more significant cases, urine may need to be drained temporarily with a stent placed in the ureter or a tube placed into the kidney. Surgery may be recommended to correct a narrowing, remove an obstruction, or repair part of the urinary tract. Minimally invasive approaches, including laparoscopic urology, may be suitable in selected patients.

Follow-up is important even after symptoms improve. Repeat imaging and kidney function tests may be needed to confirm that swelling has gone down and urine is flowing normally again. In some cases, ongoing care is needed for the underlying condition, including specialist review for disorders of the urinary tract or kidneys such as hydronephrosis treatment and follow-up.

Prevention and Self-care

Not all cases of hydronephrosis can be prevented, but some steps may reduce the risk of common causes. Staying well hydrated may help lower the chance of certain kidney stones, though fluid needs vary from person to person. Seeking treatment early for urinary symptoms can also reduce the risk of complications from infection or obstruction.

People who have had kidney stones before may be advised to make dietary changes based on the stone type, such as adjusting salt intake or discussing calcium and oxalate balance with a doctor. Good bladder habits, such as not delaying urination for long periods and managing constipation, may also support urinary tract health. Men with symptoms of prostate enlargement should have a medical evaluation rather than trying to manage persistent symptoms alone.

Self-care is not a substitute for medical treatment when there is significant pain, fever, vomiting, or difficulty urinating. Home measures cannot remove many blockages, and delaying care may allow kidney pressure to increase. It is safest to follow a clinician’s guidance and attend follow-up appointments if hydronephrosis has been diagnosed.

When to See a Doctor

A person should seek medical attention if they develop ongoing flank pain, painful urination, visible blood in the urine, repeated urinary infections, or changes in urination such as weak flow or trouble emptying the bladder. These symptoms do not always mean hydronephrosis, but they should be assessed to find the cause.

Urgent care is needed if symptoms are severe or if there are warning signs such as fever, chills, vomiting, severe pain, or inability to pass urine. These can suggest infection, acute blockage, or worsening pressure on the kidneys. Quick treatment may help protect kidney function and prevent complications.

For international patients who need evaluation, Acibadem International’s multidisciplinary specialists in JCI-accredited hospitals diagnose and treat urinary tract conditions, including hydronephrosis, with individualized assessment and imaging-based care. A timely medical review is the best way to understand the cause and decide on the most appropriate treatment plan.

Frequently asked questions

Is hydronephrosis the same as kidney disease?

No. Hydronephrosis is a description of kidney swelling caused by impaired urine drainage, not a single disease by itself. However, if it is prolonged or severe, it can affect kidney function and may lead to kidney damage.

Can hydronephrosis go away on its own?

Sometimes it can, especially if the cause is temporary or mild. For example, a small stone may pass on its own, or mild swelling may resolve after the underlying problem improves. Even so, a doctor should decide whether monitoring is safe.

Is hydronephrosis painful?

It can be, but not always. Some people have sudden, strong flank pain, while others have only mild discomfort or no symptoms at all. Pain often depends on how quickly the blockage develops and what is causing it.

What tests are usually used to diagnose hydronephrosis?

Doctors typically use a combination of medical history, physical examination, urine tests, blood tests, and imaging. Ultrasound is often the first imaging test, and CT or MRI may be used when more detail is needed.

Can an enlarged prostate cause hydronephrosis?

Yes. In men, an enlarged prostate can block urine flow from the bladder, causing pressure to build up farther back in the urinary tract. If this obstruction is significant, it may lead to hydronephrosis.

Is hydronephrosis an emergency?

It can be urgent in some situations, especially when there is fever, severe pain, vomiting, or inability to pass urine. A blocked kidney with infection needs prompt treatment. Mild cases without complications may be managed less urgently, but they still need medical assessment.

References

• National Institute of Diabetes and Digestive and Kidney Diseases
• American Urological Association
• National Kidney Foundation
• Mayo Clinic
• European Association of Urology

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.