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

Hydronephrosis is a condition where one or both kidneys become swollen because urine cannot drain properly. Instead of flowing smoothly from the kidneys to the bladder, urine backs up. This pressure causes the kidney to stretch and enlarge.

While the word may sound alarming, hydronephrosis is not a disease itself. It is a sign that something is blocking or interfering with urine flow. The key is identifying and treating the cause promptly to prevent kidney damage.

Below, you'll learn what hydronephrosis is, why it happens, common symptoms, how doctors diagnose it, and what medically approved next steps look like.

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What Is Hydronephrosis?

Your kidneys filter waste and excess fluid from your blood to make urine. Urine normally travels:

1. From the kidneys
2. Through thin tubes called ureters
3. Into the bladder
4. Out through the urethra

In hydronephrosis, this flow is blocked or slowed. As urine backs up, the kidney swells.

Hydronephrosis can affect:

• One kidney (unilateral hydronephrosis) – more common
• Both kidneys (bilateral hydronephrosis) – more serious and urgent

It can happen suddenly (acute) or develop slowly over time (chronic).

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Common Causes of Hydronephrosis

The most common reason for hydronephrosis is a blockage somewhere in the urinary tract.

1. Kidney Stones (Most Common Cause in Adults)

Stones can lodge in the ureter and block urine flow. Even a small stone can cause significant swelling.

If you're experiencing sharp flank pain, blood in your urine, or painful urination, you can use this free Nephrolithiasis (Kidney Stones) symptom checker to help determine if kidney stones might be causing your symptoms.

2. Enlarged Prostate (In Men)

An enlarged prostate can press against the urethra, slowing urine flow and causing backup into the kidneys.

3. Urinary Tract Infections (UTIs)

Severe or untreated infections can cause swelling and obstruction.

4. Pregnancy

The growing uterus can temporarily compress the ureters, especially in the second and third trimesters.

5. Scar Tissue or Strictures

Previous surgeries, infections, or inflammation may narrow parts of the urinary tract.

6. Tumors

Masses in the bladder, pelvis, abdomen, or urinary tract can block urine flow.

7. Congenital Conditions (In Babies)

Some babies are born with structural issues that affect urine drainage. Hydronephrosis is sometimes found during prenatal ultrasounds.

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Symptoms of Hydronephrosis

Symptoms depend on how quickly the blockage develops and how severe it is.

Common Symptoms

• Pain in the side (flank pain)
• Lower back pain
• Abdominal pain
• Nausea or vomiting
• Frequent urination
• Difficulty urinating
• Burning during urination
• Blood in the urine
• Fever (if infection is present)

Important Note

Chronic hydronephrosis may cause few or no symptoms at first. That's why imaging tests often detect it incidentally.

If you experience:

• Severe pain
• Fever with chills
• Inability to urinate
• Confusion
• Severe weakness

Seek urgent medical care. These can signal a serious infection or kidney injury.

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Is Hydronephrosis Dangerous?

Hydronephrosis can become serious if left untreated.

When urine remains backed up for too long, it increases pressure inside the kidney. Over time, this can:

• Reduce kidney function
• Cause permanent kidney damage
• Lead to kidney failure (in severe cases)

The good news:
When treated early, kidney function often returns to normal, especially if the blockage is relieved quickly.

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How Doctors Diagnose Hydronephrosis

If hydronephrosis is suspected, your doctor may use:

1. Ultrasound (Most Common First Test)

• Safe and painless
• Shows kidney swelling
• Often used in pregnancy and children

2. CT Scan

• Helps identify kidney stones
• Detects tumors or structural issues
• Provides detailed imaging

3. Urine Tests

• Checks for infection
• Looks for blood or crystals

4. Blood Tests

• Measures kidney function
• Checks creatinine and electrolyte levels

5. Additional Tests

In some cases, doctors may order:

• MRI
• Nuclear kidney scans
• Cystoscopy (camera inside bladder)

The goal is to determine what is causing the hydronephrosis, not just confirm the swelling.

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Medically Approved Next Steps for Hydronephrosis

Treatment focuses on removing the blockage and protecting kidney function.

If Caused by Kidney Stones

• Pain management
• Increased fluids (if appropriate)
• Medications to help pass the stone
• Shock wave therapy (lithotripsy)
• Ureteroscopy to remove the stone

Large or stuck stones may require a minor procedure.

If Caused by Infection

• Immediate antibiotics
• Drainage if obstruction is present

Infected hydronephrosis is considered a medical emergency because bacteria trapped in blocked urine can spread quickly.

If Caused by Enlarged Prostate

• Medications to shrink or relax the prostate
• Surgical procedures in some cases

If Caused by Tumors or Structural Issues

• Surgery
• Stents to open the ureter
• Nephrostomy tube (temporary drainage from the kidney)

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What Is a Ureteral Stent or Nephrostomy Tube?

If urine cannot drain naturally, doctors may:

• Insert a ureteral stent: a small tube placed inside the ureter
• Place a nephrostomy tube: drains urine directly from the kidney through the back

These are often temporary but can be lifesaving.

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Can Hydronephrosis Go Away on Its Own?

Sometimes, yes.

Examples include:

• Small kidney stones that pass naturally
• Mild swelling during pregnancy
• Temporary inflammation

However, you should never assume it will resolve without medical evaluation. Persistent obstruction can permanently damage the kidney.

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Who Is at Higher Risk?

You may be at higher risk for hydronephrosis if you:

• Have a history of kidney stones
• Have frequent UTIs
• Have an enlarged prostate
• Are pregnant
• Have had abdominal or pelvic surgery
• Have certain cancers

If you fall into one of these categories and develop urinary symptoms, speak to a healthcare provider promptly.

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Protecting Your Kidney Health

Here are general steps that support urinary health:

• Stay well hydrated (unless your doctor advises otherwise)
• Treat urinary infections quickly
• Follow up on persistent flank pain
• Manage chronic conditions like diabetes or high blood pressure
• Get recommended imaging when symptoms suggest obstruction

Remember, hydronephrosis is a warning sign, not a diagnosis. The cause determines the treatment and outcome.

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When to Speak to a Doctor

You should speak to a doctor if you experience:

• Persistent flank or back pain
• Blood in your urine
• Fever with urinary symptoms
• Difficulty urinating
• Reduced urine output
• Severe nausea and vomiting
• Any sudden, intense pain

If symptoms are severe or life-threatening, seek emergency care immediately.

Even mild symptoms deserve evaluation if they last more than a few days.

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The Bottom Line

Hydronephrosis means your kidney is swelling because urine cannot drain properly. The most common cause in adults is kidney stones, but infections, prostate enlargement, pregnancy, tumors, and structural problems can also be responsible.

The condition ranges from mild and temporary to serious and urgent. The key is early detection and treatment. When addressed promptly, kidney function often recovers fully.

If you are unsure whether your symptoms could be related to kidney stones, consider using a free online Nephrolithiasis (Kidney Stones) symptom checker to better understand your risk.

Most importantly, speak to a doctor about any symptoms that could be serious or life-threatening. Your kidneys are vital organs, and timely care can make all the difference.

Early action protects kidney function. Delays increase risk. If in doubt, get evaluated.