Hydronephrosis: Why Your Kidney Is Swelling & Medically Approved Next Steps

Hydronephrosis is a condition where one or both kidneys become swollen due to a buildup of urine. This happens when urine cannot drain properly from the kidney to the bladder. While the word may sound alarming, hydronephrosis is a sign of an underlying problem—not a disease itself.

The key is understanding why it's happening and what to do next.

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What Is Hydronephrosis?

Your kidneys filter waste and extra fluid from your blood, producing urine. Normally, urine flows from the kidneys down thin tubes called ureters into the bladder, and then out of the body.

With hydronephrosis, that flow is blocked or slowed. As urine backs up, the kidney stretches and swells. If left untreated, prolonged swelling can reduce kidney function.

Hydronephrosis can affect:

• One kidney (unilateral)
• Both kidneys (bilateral) — which may be more serious
• People of any age, including infants (sometimes diagnosed before birth)

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Common Causes of Hydronephrosis

Hydronephrosis always has an underlying cause. Some are temporary and easily treated. Others require more urgent care.

In Adults

• Kidney stones (a very common cause)
• Enlarged prostate in men
• Urinary tract infections (UTIs)
• Tumors in the urinary tract or surrounding organs
• Scar tissue or narrowing of the ureter
• Blood clots
• Pregnancy (temporary pressure on ureters)

In Infants and Children

• Congenital blockages (present at birth)
• Vesicoureteral reflux (VUR) — urine flowing backward from the bladder
• Structural abnormalities in the urinary tract

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Symptoms of Hydronephrosis

Symptoms vary depending on how quickly the blockage develops.

Sudden (Acute) Hydronephrosis

• Severe side or back pain
• Nausea or vomiting
• Fever (if infection is present)
• Painful urination
• Urgent need to urinate

Gradual (Chronic) Hydronephrosis

• Mild or dull back pain
• Decreased urine output
• Swelling in the legs (if both kidneys are affected)
• Fatigue
• Sometimes no symptoms at all

If hydronephrosis is caused by infection, you may notice:

• Fever and chills
• Burning with urination
• Cloudy or foul-smelling urine

Seek urgent medical care if you have severe pain, high fever, vomiting, or difficulty urinating. These can signal a serious blockage or infection.

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How Serious Is Hydronephrosis?

Hydronephrosis ranges from mild to severe.

• Mild cases may resolve on their own.
• Moderate to severe cases can lead to kidney damage if not treated.
• Bilateral hydronephrosis (both kidneys) may affect overall kidney function more quickly.

The longer urine remains backed up, the greater the risk of:

• Permanent kidney damage
• Recurrent infections
• Sepsis (a life-threatening infection)

Early diagnosis and treatment greatly reduce these risks.

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How Is Hydronephrosis Diagnosed?

Doctors use imaging tests to confirm hydronephrosis and identify the cause.

Common tests include:

• Ultrasound (often first step, especially in pregnancy or children)
• CT scan (helps detect kidney stones or tumors)
• MRI (used in specific cases)
• Urine tests (to check for infection or blood)
• Blood tests (to assess kidney function)

In some cases, additional specialized imaging may be needed to evaluate how well urine flows.

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Medically Approved Treatment Options

Treatment focuses on relieving the blockage and protecting kidney function.

1. Relieving the Obstruction

Depending on the cause, options include:

• Kidney stone removal
• Catheter placement to drain the bladder
• Ureteral stent (a small tube placed inside the ureter)
• Nephrostomy tube (temporary drainage directly from the kidney)
• Surgery to correct structural problems

2. Treating Infection

If infection is present:

• Antibiotics are started promptly
• Hospital care may be needed for severe infections

3. Monitoring Mild Cases

In mild hydronephrosis:

• Regular imaging
• Follow-up kidney function tests
• Watchful waiting under medical supervision

In pregnancy-related hydronephrosis, the condition often improves after delivery.

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Can Hydronephrosis Be Prevented?

Not all cases are preventable, but you can reduce risk by:

• Staying well hydrated
• Treating urinary tract infections promptly
• Managing prostate health (for men)
• Getting evaluated quickly for persistent urinary symptoms
• Following up on kidney stone history

If you have recurring urinary issues, early evaluation can prevent complications.

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When Hydronephrosis May Signal Something More

In some cases, hydronephrosis can be related to chronic kidney conditions, including inherited disorders.

One example is a genetic condition that causes fluid-filled cysts to grow in the kidneys. These cysts can sometimes interfere with urine flow and kidney function.

If you have a family history of kidney disease, high blood pressure at a young age, enlarged kidneys, or recurrent kidney infections, you might consider using a free symptom checker for Polycystic Kidney Disease (PKD) to better understand your risk and what symptoms to watch for.

This is not a diagnosis, but it can help guide a conversation with your doctor.

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What Happens If Hydronephrosis Is Left Untreated?

Untreated hydronephrosis can lead to:

• Permanent kidney damage
• Chronic kidney disease
• Kidney failure
• Severe infection (pyelonephritis)
• Sepsis (life-threatening)

The good news: when treated early, most people recover without long-term damage.

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When to Speak to a Doctor Immediately

Do not delay medical care if you experience:

• Severe or worsening back/side pain
• Fever with urinary symptoms
• Vomiting and inability to keep fluids down
• Little or no urine output
• Blood in your urine
• Symptoms affecting both kidneys

These may signal a serious blockage or infection that requires urgent treatment.

If you suspect hydronephrosis, or you have ongoing urinary symptoms, speak to a doctor promptly. Kidney health is too important to ignore.

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The Bottom Line

Hydronephrosis means your kidney is swollen because urine is not draining properly. It is a warning sign—not a diagnosis by itself.

Most cases are treatable, especially when caught early. The key steps are:

• Identify the underlying cause
• Relieve any blockage
• Prevent infection
• Protect long-term kidney function

Do not panic—but do take it seriously.

If you are experiencing symptoms or have concerns about your kidney health, speak to a qualified healthcare professional. Early evaluation can prevent complications and protect your kidneys for the long term.