Pyelonephritis: Why Your Kidney Is Infected & Vital Medical Next Steps

Pyelonephritis is a serious kidney infection that requires prompt medical attention. While many urinary tract infections (UTIs) stay in the bladder, pyelonephritis occurs when bacteria travel upward into one or both kidneys. Because your kidneys play a critical role in filtering waste and balancing fluids, an infection here is more than just uncomfortable—it can become dangerous if left untreated.

This guide explains what pyelonephritis is, why it happens, common symptoms, treatment options, and what you should do next.

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What Is Pyelonephritis?

Pyelonephritis is a type of urinary tract infection (UTI) that affects the kidneys. It is often referred to as a "kidney infection."

Most cases begin as a lower urinary tract infection (involving the bladder or urethra). If bacteria are not eliminated, they can travel up the ureters (the tubes connecting the bladder to the kidneys) and infect the kidney tissue itself.

There are two main types:

• Acute pyelonephritis – A sudden, severe kidney infection.
• Chronic pyelonephritis – Repeated or ongoing kidney infections that can lead to kidney damage over time.

Acute pyelonephritis is far more common and is considered a medical urgency.

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Why Does Pyelonephritis Happen?

The most common cause of pyelonephritis is bacteria, especially Escherichia coli (E. coli), which normally live in the intestines.

Infection usually happens when:

• Bacteria enter through the urethra.
• They multiply in the bladder.
• They travel upward to one or both kidneys.

Less commonly, bacteria can spread to the kidneys through the bloodstream from another infected area in the body.

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Risk Factors for Pyelonephritis

Some people are more likely to develop pyelonephritis, including:

• Women, due to a shorter urethra
• People with frequent UTIs
• Pregnant women
• Individuals with kidney stones
• People with diabetes
• Those with a weakened immune system
• Individuals with urinary tract blockages
• People who use urinary catheters
• Anyone with structural abnormalities in the urinary tract

Children and older adults may also be at higher risk, especially if symptoms of bladder infection are overlooked.

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Symptoms of Pyelonephritis

Symptoms of pyelonephritis are usually more severe than a simple bladder infection. They may include:

Common Symptoms

• Fever (often high)
• Chills or shaking
• Pain in the back, side, or flank (often on one side)
• Nausea and vomiting
• Fatigue or weakness

Urinary Symptoms

• Pain or burning when urinating
• Frequent urination
• Urgent need to urinate
• Cloudy or foul-smelling urine
• Blood in the urine

In older adults, symptoms may be less typical and could include:

• Confusion
• Changes in mental alertness
• General weakness

If symptoms are severe, especially with high fever and shaking chills, it may signal a spreading infection that requires urgent care.

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How Serious Is Pyelonephritis?

Pyelonephritis is treatable, but it is not something to ignore.

If left untreated, it can lead to:

• Permanent kidney damage
• Kidney scarring
• Sepsis (a life-threatening blood infection)
• Kidney failure (in severe cases)
• Complications during pregnancy

The good news: with prompt antibiotic treatment, most people recover fully without long-term problems.

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How Is Pyelonephritis Diagnosed?

A doctor will evaluate your symptoms and perform tests to confirm the infection.

Common diagnostic steps include:

• Urine test (urinalysis) – Checks for bacteria, white blood cells, and blood.
• Urine culture – Identifies the specific bacteria causing the infection.
• Blood tests – May be done to check for infection in the bloodstream.
• Imaging tests (CT scan or ultrasound) – Used if symptoms are severe, not improving, or if a blockage is suspected.

Because pyelonephritis can progress quickly, testing and treatment often begin right away.

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Treatment for Pyelonephritis

1. Antibiotics

Antibiotics are the main treatment. Depending on severity:

• Mild cases may be treated with oral antibiotics at home
• More severe cases may require hospitalization and IV antibiotics

Treatment typically lasts 7–14 days, depending on the medication and individual case.

It's critical to:

• Take the full course of antibiotics
• Not stop early, even if you feel better

Stopping too soon can allow bacteria to survive and return.

2. Hospital Care (If Needed)

Hospital treatment may be necessary if you:

• Cannot keep fluids down
• Have severe symptoms
• Are pregnant
• Have other serious medical conditions
• Show signs of sepsis

In the hospital, you may receive:

• IV fluids
• IV antibiotics
• Pain control medication

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When to Seek Immediate Medical Care

Seek urgent medical attention if you have:

• High fever with chills
• Severe back or side pain
• Vomiting that prevents keeping fluids down
• Confusion
• Signs of low blood pressure (dizziness, fainting)
• Symptoms that are rapidly worsening

Pyelonephritis can become life-threatening if it spreads to the bloodstream. Early treatment greatly reduces this risk.

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Can Pyelonephritis Be Prevented?

While not all cases can be prevented, you can lower your risk by:

• Drinking plenty of fluids
• Urinating when you feel the urge (don't hold it)
• Wiping front to back (for women)
• Urinating after sexual activity
• Managing blood sugar if you have diabetes
• Seeking treatment quickly for bladder infections

If you experience frequent UTIs, speak with a doctor about preventive strategies.

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Should You Do a Symptom Check?

If you're experiencing symptoms like fever, back pain, or painful urination and want to understand whether they could indicate a kidney infection, you can use a free Acute Pyelonephritis symptom checker to assess your symptoms in minutes.

A symptom checker can help you:

• Understand whether your symptoms match pyelonephritis
• Determine how urgently you should seek care
• Prepare for a conversation with your doctor

However, a symptom checker is not a diagnosis. It should never replace professional medical evaluation—especially if symptoms are severe.

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What Happens If Pyelonephritis Is Treated Early?

When treated promptly:

• Fever often improves within 48–72 hours
• Pain gradually decreases
• Long-term kidney damage is unlikely
• Most people recover fully

Follow-up may include a repeat urine test to ensure the infection has cleared, especially in complicated cases.

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Key Takeaways About Pyelonephritis

• Pyelonephritis is a serious kidney infection.
• It usually starts as a bladder infection that spreads upward.
• Symptoms often include fever, back pain, nausea, and urinary discomfort.
• Antibiotics are essential and highly effective when started early.
• Untreated pyelonephritis can lead to kidney damage or sepsis.
• Prompt medical care dramatically reduces risks.

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Final Word: Don't Delay Care

Pyelonephritis is treatable—but it requires medical attention. If you suspect a kidney infection, especially if you have fever and back pain, speak to a doctor promptly.

If symptoms are severe, worsening, or include confusion, high fever, or vomiting, seek emergency medical care immediately.

When it comes to kidney infections, early treatment protects your kidneys, your overall health, and in some cases, your life.

If you're unsure, start by evaluating your symptoms carefully—and most importantly, speak to a qualified healthcare professional about anything that could be serious or life-threatening.