Hydronephrosis

Overview

Hydronephrosis is a condition in which one or both kidneys become swollen because urine cannot drain normally from the kidney to the bladder. Urine is made in the kidneys, travels through narrow tubes called ureters, and is stored in the bladder before leaving the body. If this flow is blocked or if urine moves backward, pressure can build up inside the kidney.

Hydronephrosis is not a disease by itself, but a sign that there is an underlying problem affecting urine drainage. It can occur at any age, including before birth, in children, and in adults. The condition may be mild and temporary, or it may be more serious if the blockage is severe or lasts for a long time. Early evaluation is important because ongoing pressure can affect kidney function.

Symptoms

Symptoms of hydronephrosis can vary depending on the cause, how quickly it develops, and whether one or both kidneys are affected. Some people, especially babies or those with mild cases, may have no symptoms and the condition may be found during imaging for another reason.

• Pain in the side, back, lower abdomen, or groin
• Pain that comes in waves, especially if related to a kidney stone
• Frequent or urgent need to urinate
• Pain or burning during urination
• Blood in the urine
• Fever or chills if an infection is present
• Nausea or vomiting, particularly with severe pain
• Reduced urine output in some cases
• Poor feeding, irritability, or failure to thrive in infants

In some situations, hydronephrosis develops slowly and causes only vague discomfort or no symptoms until kidney function is affected.

Causes and Risk Factors

Hydronephrosis occurs when urine flow is blocked, slowed, or reversed. The obstruction may be located anywhere along the urinary tract, from the kidney to the urethra.

• Kidney stones blocking the ureter
• Narrowing of the ureter due to scarring, previous surgery, inflammation, or congenital differences
• Enlargement of the prostate in men, which can affect bladder emptying
• Tumors or growths pressing on the urinary tract
• Pregnancy, where the enlarged uterus may temporarily compress the ureters
• Urinary tract infections causing swelling or inflammation
• Vesicoureteral reflux, a condition in which urine flows backward from the bladder toward the kidneys
• Nerve or muscle problems affecting bladder function
• Congenital urinary tract abnormalities found during pregnancy or early childhood

Risk factors depend on the underlying cause. A history of kidney stones, urinary tract infections, pelvic surgery, prostate problems, or congenital urinary tract conditions may increase the likelihood of hydronephrosis.

Diagnosis

Diagnosis usually begins with a medical history and physical examination. The doctor may ask about pain, urinary symptoms, infections, previous kidney stones, surgeries, pregnancy, and other health conditions.

Imaging tests are commonly used to confirm hydronephrosis and identify the possible cause. Ultrasound is often the first test because it can show swelling of the kidneys and does not use radiation. Other imaging methods may be recommended when more detail is needed, such as scans that show the urinary tract, stones, or surrounding organs.

Urine tests may be performed to look for signs of infection, blood, or other abnormalities. Blood tests can help assess kidney function and check for signs of infection or inflammation. In some cases, specialized tests may be used to evaluate how well urine drains from the kidneys or how the bladder is working.

The aim of diagnosis is not only to detect hydronephrosis, but also to understand what is causing it and whether kidney function is at risk.

Treatment Options

Treatment depends on the cause, severity, symptoms, and whether one or both kidneys are affected. Mild cases, especially in infants or during pregnancy, may be monitored with follow-up imaging if kidney function is stable and there are no concerning symptoms.

If hydronephrosis is caused by a blockage, treatment focuses on relieving the obstruction and protecting kidney function. This may involve procedures to allow urine to drain, removal or management of stones, treatment of narrowing in the urinary tract, or addressing prostate-related or bladder-emptying problems. If infection is present, medical treatment is needed because infection with blocked urine flow can become serious.

In some patients, temporary drainage may be required to reduce pressure in the kidney. Depending on the situation, this can be done through internal or external drainage methods performed by specialists. Surgery may be considered when there is a structural problem, persistent blockage, recurrent infections, or risk of kidney damage.

For children with hydronephrosis detected before birth, care may involve observation with regular imaging after delivery. Many cases are monitored closely, while others require further evaluation or treatment by pediatric specialists.

The best approach is individualized. The healthcare team may include nephrologists, urologists, radiologists, obstetric specialists, or pediatric specialists, depending on the patient’s age and the cause of the condition.

When to See a Doctor

Medical evaluation is important if you have symptoms that may suggest a urinary blockage or kidney infection. Seek prompt medical care for severe side or back pain, fever, chills, vomiting, blood in the urine, or difficulty passing urine.

Urgent care is especially important if pain is severe, if there is fever with urinary symptoms, if urine output is greatly reduced, or if hydronephrosis is known and symptoms suddenly worsen. People with a single functioning kidney, pregnancy, existing kidney disease, or a child with urinary symptoms should also be assessed without delay.

If hydronephrosis is found on an ultrasound or other imaging test, follow-up with a healthcare professional is recommended even if there are no symptoms. Timely diagnosis and appropriate management can help reduce pressure on the kidney and address the underlying cause.