A kidney infection, medically known as pyelonephritis, is a type of urinary tract infection (UTI) that affects one or both kidneys.

It often develops when bacteria enter the urinary tract and travel upward from the bladder toward the kidneys. Without appropriate treatment, a kidney infection can become serious and, in some cases, lead to complications such as bloodstream infection or impaired kidney function.

Recognizing the signs and symptoms of kidney infection early can help patients seek appropriate medical care without unnecessary delay.

At Prabhakar Bhurke Clinic, Dr. Sandip Prabhakar Bhurke, super specialist nephrologist and transplant physician, provides specialized evaluation and management of kidney and urinary-related conditions.

Common Signs and Symptoms of Kidney Infection

Kidney infection symptoms can develop relatively quickly. The intensity varies from person to person.

1. Fever and Chills

A fever is one of the common symptoms of an upper urinary tract infection.

Some patients may also experience:

• Chills

• Shivering

• Sweating

• Feeling unusually cold

Fever accompanied by urinary symptoms or flank pain should be medically evaluated.

2. Pain in the Side or Back

Kidney infection may cause pain in the flank, typically around the side of the back beneath the ribs.

The pain may occur on:

• The right side

• The left side

• Both sides in some cases

It can sometimes be confused with muscular back pain.

3. Burning or Painful Urination

A person may experience a burning sensation while passing urine.

This symptom is often associated with infection involving the lower urinary tract but may also occur when an infection has reached the kidneys.

4. Frequent Urination

A kidney infection can be accompanied by an increased need to urinate.

Some people may feel an urgent need to pass urine even when only a small amount is produced.

5. Cloudy or Strong-Smelling Urine

Changes in urine appearance or odor can occur with a urinary infection.

However, urine odor alone does not confirm a kidney infection and can be influenced by hydration, diet and other factors.

6. Blood in the Urine

Some people may notice pink, red or dark-colored urine.

Blood in urine can have several causes, including infection, kidney stones and other urinary conditions, so it should not automatically be attributed to infection.

7. Nausea and Vomiting

Kidney infections can cause nausea and, in more significant infections, vomiting.

Persistent vomiting can also contribute to dehydration, making medical assessment more important.

8. Feeling Weak or Unwell

Patients may experience:

• Fatigue

• Weakness

• Loss of appetite

• General discomfort

• Body aches

These symptoms can accompany the body's response to infection.

Kidney Infection Symptoms vs Bladder Infection

A bladder infection and kidney infection are both urinary tract infections, but they can present differently.

Bladder Infection	Kidney Infection
Burning during urination	Fever may be prominent
Frequent urination	Flank or back pain
Urgent need to urinate	Chills may occur
Lower abdominal discomfort	Nausea or vomiting
Usually no significant systemic illness	Can cause marked weakness and illness

A bladder infection can sometimes spread upward and involve the kidneys.

What Causes a Kidney Infection?

Most kidney infections are caused by bacteria.

A common pathway is:

Bacteria enter the urinary tract → bladder infection develops → bacteria travel upward through the ureters → kidney infection occurs.

Risk can increase in certain situations, including:

• Previous urinary tract infections

• Kidney stones

• Urinary obstruction

• Enlarged prostate

• Structural urinary abnormalities

• Pregnancy

• Use of urinary catheters

• Certain medical conditions affecting immunity

• Conditions that interfere with normal urine flow

Can Kidney Stones Cause a Kidney Infection?

Kidney stones do not always cause infection, but they can increase the risk when they obstruct urine flow.

An infected obstructed urinary system can become a serious medical emergency.

A person with a suspected kidney stone who develops fever, chills, severe pain or difficulty passing urine should seek urgent medical evaluation.

How Is a Kidney Infection Diagnosed?

Diagnosis usually involves a combination of symptoms, physical examination and laboratory tests.

Urine Routine Examination

A urine test can identify findings suggestive of infection, such as:

• White blood cells

• Red blood cells

• Bacteria

• Other abnormalities

Urine Culture

A urine culture can help identify the responsible bacteria and determine which antibiotics may be effective.

Blood Tests

Depending on the patient's condition, testing may include:

• Complete blood count

• Serum creatinine

• eGFR

• Electrolytes

• Other infection-related tests

Blood tests become particularly important when a patient appears significantly unwell or kidney function may be affected.

Imaging Tests

Ultrasound or other imaging may be recommended when there is concern about:

• Kidney stones

• Urinary obstruction

• Recurrent infections

• Structural abnormalities

• Complications

Imaging is not necessarily required for every uncomplicated kidney infection.

Kidney Infection Treatment

Treatment depends on the severity of infection and the patient's overall health.

Antibiotics

Bacterial kidney infections are generally treated with antibiotics selected according to the clinical situation and, when available, urine culture results.

The choice of antibiotic, dose and duration should be determined by a qualified healthcare professional.

Patients should not use leftover antibiotics or stop prescribed treatment without medical advice.

Fluids

Adequate hydration can be helpful for many patients, but fluid intake must be individualized.

People with advanced kidney disease, heart failure or prescribed fluid restrictions should follow their healthcare professional's recommendations rather than forcing excessive fluids.

Pain and Fever Management

Appropriate medicines may be recommended to control fever and discomfort.

Patients with kidney disease should consult a healthcare professional before using certain pain medicines because some can adversely affect kidney function.

Treatment of the Underlying Problem

If infection occurs because of an obstruction, stone or another urinary abnormality, treating the underlying problem may be necessary.

An obstructed and infected urinary system can require urgent drainage.

How Long Does a Kidney Infection Take to Improve?

Improvement depends on:

• Severity of infection

• The bacteria involved

• Antibiotic sensitivity

• Presence of obstruction

• Kidney function

• Other medical conditions

Some patients begin feeling better after appropriate treatment, while more serious infections may require hospital-based care.

If symptoms are not improving or are getting worse after treatment begins, medical reassessment may be necessary.

Warning Signs That Need Urgent Medical Attention

A kidney infection can become serious if it progresses beyond the urinary tract.

Seek urgent medical care if you experience:

• High or persistent fever

• Severe chills

• Severe flank or back pain

• Repeated vomiting

• Confusion

• Extreme weakness

• Difficulty passing urine

• Very little or no urine

• Rapid deterioration

• Symptoms of severe infection

Extra caution is needed when a suspected urinary infection occurs alongside a kidney stone or urinary obstruction.

Kidney Infection During Pregnancy

Pregnancy can increase the risk of urinary tract infections progressing to the kidneys.

Symptoms such as fever, flank pain, burning urination or significant urinary changes during pregnancy should be evaluated promptly.

Pregnant patients should not self-medicate with antibiotics or other medicines without medical advice.

Kidney Infection in Older Adults

Older adults may sometimes develop less typical symptoms.

Instead of obvious urinary symptoms, they may experience:

• Weakness

• Reduced appetite

• Fever

• Confusion

• Functional decline

Because symptoms can be less specific, medical assessment is important when infection is suspected.

Can a Kidney Infection Damage the Kidneys?

A properly treated uncomplicated kidney infection often responds well to treatment.

However, severe, recurrent or untreated infections can cause complications, particularly when associated with obstruction or other kidney problems.

People with recurrent infections may need evaluation to identify contributing factors such as stones, urinary obstruction or structural abnormalities.

Can Kidney Infection Lead to Kidney Failure?

A single uncomplicated kidney infection does not usually cause kidney failure in an otherwise healthy person.

However, severe infection, recurrent infections, urinary obstruction or pre-existing kidney disease can increase the risk of complications.

Patients with existing CKD require particularly careful assessment when they develop an infection.

How Can Kidney Infections Be Prevented?

Not every kidney infection can be prevented, but some measures may reduce the risk of urinary infections and complications.

Depending on individual circumstances:

• Stay appropriately hydrated.

• Do not routinely hold urine for prolonged periods.

• Seek evaluation for recurring urinary symptoms.

• Complete prescribed treatment for UTIs.

• Address recurrent kidney stones or urinary obstruction.

• Follow appropriate hygiene practices.

• Discuss recurrent UTIs with a healthcare professional.

There is no single prevention strategy that works for everyone.

Kidney Infection vs Kidney Stone

Kidney infections and kidney stones can sometimes cause similar flank pain, but they are different conditions.

Kidney infection is usually associated with infection-related symptoms such as fever, chills, urinary burning and feeling unwell.

Kidney stones more commonly produce severe, wave-like pain that may travel toward the groin and may be associated with blood in urine.

Both conditions can occur together, and an obstructed infected urinary system requires urgent attention.

When Should You See a Nephrologist?

A nephrologist may be appropriate when a kidney infection is associated with:

• Reduced kidney function

• Recurrent kidney infections

• Chronic kidney disease

• Significant electrolyte abnormalities

• Complex medical conditions

• Recurrent urinary problems affecting kidney health

A urologist may be involved when stones, obstruction or structural urinary abnormalities require procedural treatment.

Kidney Infection Care at Prabhakar Bhurke Clinic

At Prabhakar Bhurke Clinic, Dr. Sandip Prabhakar Bhurke, super specialist nephrologist and transplant physician, provides individualized evaluation for patients with kidney-related concerns.

Depending on the clinical situation, assessment may include:

• Urine testing

• Urine culture

• Kidney-function testing

• Electrolyte evaluation

• Blood tests

• Kidney imaging when indicated

• Assessment for recurrent infection

• Evaluation of associated kidney disease

Treatment recommendations are based on the patient's symptoms, test results, medical history and overall health.

Frequently Asked Questions

What are the main signs of a kidney infection?

Common signs include fever, chills, flank or back pain, burning urination, frequent urination, cloudy urine, nausea and feeling generally unwell.

Where does kidney infection pain occur?

Kidney infection pain commonly occurs in the flank or side of the back, usually beneath the ribs. It may occur on one side or both sides.

Can a kidney infection occur without burning urination?

Yes. Not everyone experiences the same symptoms. Some patients may primarily have fever, flank pain or generalized illness.

Can a kidney infection go away without antibiotics?

A bacterial kidney infection should not be assumed to resolve without appropriate medical treatment. Delaying treatment can allow the infection to become more serious.

Is fever with kidney pain an emergency?

Fever accompanied by significant flank pain can indicate a kidney infection and warrants prompt medical assessment. If there is severe illness, vomiting, confusion, very low urine output or suspected obstruction, urgent care is particularly important.

Can kidney infection cause kidney failure?

A routine uncomplicated infection does not usually cause kidney failure, but severe or complicated infections can affect kidney function, particularly in people with existing kidney disease or urinary obstruction.

Conclusion

Knowing the signs and symptoms of kidney infection can help people recognize when urinary symptoms may represent a more serious upper urinary tract infection.

Fever, chills, flank pain, painful urination, frequent urination, nausea and changes in urine can all occur. However, symptoms overlap with kidney stones and other urinary conditions, so proper medical evaluation is important.

Early diagnosis and appropriate treatment can reduce the risk of complications. Particular caution is needed when infection occurs alongside a kidney stone, urinary obstruction or pre-existing kidney disease.

For specialized kidney evaluation and management, Dr. Sandip Prabhakar Bhurke at Prabhakar Bhurke Clinic provides super specialist nephrology and transplant-related care.

Medical Disclaimer

This article is intended for general educational purposes only and does not constitute medical advice, diagnosis or treatment. Symptoms of kidney infection can overlap with kidney stones, bladder infections and other medical conditions. Antibiotics and other treatments should be prescribed by a qualified healthcare professional based on the patient's clinical condition and, when appropriate, test results. Do not self-medicate with leftover antibiotics. Seek urgent medical attention for severe flank pain with fever or chills, repeated vomiting, confusion, difficulty passing urine, very little or no urine, or rapidly worsening symptoms. Patients with known kidney disease, pregnancy or significant medical conditions should seek prompt professional evaluation.