Everything You Need To Know About Kidney Abscess

Kidneys are the primary filter of our bodies, cleaning approximately 150 quarts (142 liters) of blood every day. However, if you leave an infection untreated, it can damage your kidneys. Rarely, the infection may lead to an accumulation of pus within the kidney, which is a kidney abscess.

Read on to find out what it is, its symptoms, and how to treat the issue.

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What is a kidney abscess?

A kidney abscess is also referred to as a perirenal or renal abscess. Kidney abscesses account for 0.2%¹ of all intra-abdominal abscesses. An abscess is a pocket of pus building up in kidney tissues, resulting from bacteria moving from the infected area of the body to your kidneys.

More often than not, a perirenal abscess is due to complications with a urinary tract infection (UTI) that may worsen if there’s an obstruction to normal urine flow.

Symptoms of renal abscess

The symptoms of kidney abscesses vary, but they usually include one or several of the following:

  • Fever accompanied by chills or shakes

  • Abdominal pain spreading down your groin or leg

  • Unexpected weight loss

  • Pain when urinating

  • Blood or cloudiness in the urine

  • Night sweats

  • Back aches and tenderness

Causes and risk factors of renal abscess

Kidney abscesses primarily arise from UTIs that emanate from the bladder. From there, they radiate to the kidneys and the surrounding areas.

Kidney stones are the leading risk factor as they impede urine flow and have ideal conditions for bacteria growth. Pathogens attach themselves to the stone, and antibiotics cannot eradicate them there.

Risk factors

Around 20-60% of people with renal abscesses have kidney stones. Other risk factors include:

  • Diabetes mellitus (DM)

  • Vesicoureteral reflux: A condition where urine flows in the opposite direction and enters the kidney instead of being excreted        

  • Intravenous drug abuse (IVDA)

  • Skin abscesses

  • Kidney inflammation

  • Chronic kidney disease (CKD)

  • Having a compromised immune system

  • Abnormalities of the urinary tract, such as unilateral renal agenesis (URA), renal cysts

  • Trauma to the kidney area

Diagnosis

After the doctor has assessed your medical history and conducted a physical exam, they will administer some tests to determine if you have a kidney abscess. Signs of a renal abscess can be non-specific, so your doctor may conduct multiple investigations.

The two major ways to diagnose perirenal abscesses include:

Lab tests

A doctor may diagnose a renal abscess using several tests. These include:

Blood culture

To have a blood culture, you’ll need a blood draw from a hospital, specialized testing complex, or the emergency department. The medical professional will sterilize the draw site and take several blood samples from your arm using a needle. They will tap different veins to increase the chance of detecting foreign materials and avoid any false-positive samples. 

A blood culture detects the presence of foreign invaders in your blood, such as yeast, bacteria, and other pathogens. Carrying these microorganisms in your bloodstream may signal a blood infection and come back as a “positive blood culture.” 

Contact your doctor or emergency services immediately if you have any of these symptoms of a blood infection (septicemia):

  • Moderate or high fever

  • Shaking chills

  • Heart palpitations

  • Muscle aches

  • Headache

  • Extreme fatigue

Early medical attention is vital for blood infections as they can spread to other organs, including the kidneys. They can be life-threatening and cause sepsis or septic shock, where your blood pressure plummets.

Urinalysis

Urinalysis is a chemical, physical, and microscopic urine examination. It uses a couple of tests to check your urine sample. The two standard collection methods are the clean catch urine specimen and 24-hour urine collection. Your doctor will advise the process for your case. 

The laboratory will consider these aspects:

Chemical appearance

A lab technician uses a dipstick to detect local and foreign substances in the sample. Special chemical pads change color depending on which substances are present. 

Physical appearance

This is how your urine sample appears to the naked eye. The technician assesses the color and clarity of the sample.

Microscopic appearance

The technician puts your sample under a microscope's lens for evaluation. Using the microscope, they can identify urine crystals, cells, urinary casts, pus, bacteria, and parasites. 

Urine culture

A urine culture test determines if bacteria and other pathogens are present in a urine sample. It's a way to check for urinary tract infections in children and adults. Typical bladder or urinary tract infection symptoms include a burning sensation or pain when passing urine.

Often, your medical provider will use the clean catch urine sample method to collect the sample. You can take the sample at home or the doctor's office. If possible, hold urine in your bladder for two to three hours before collecting the specimen in the provided kit.

If you can’t provide a clean catch sample or urinate normally, your physician may insert a catheter into your bladder via the urethra. Your healthcare provider will handle this in the hospital or their offices. They will use a special gel to numb your urethra and remove discomfort. After taking the sample, they will send it to the lab for analysis.

The laboratory will detect any bacteria in the urine samples, and further tests will determine if the bacteria have any antibiotic resistance. This ensures your doctor prescribes antibiotics that will treat the infection. 

Blood tests may show an elevated white cell count, indicating an infection. In severe cases, blood cultures may return positive for the same pathogen. Staphylococcus aureus is the usual suspect. In recent times, the methicillin-resistant variant has been increasingly to blame.

Antibiotic resistance is a growing issue; your doctor will talk to you about this when they prescribe your antibiotics. 

Radiographical tests

These tests give physicians a clear picture of what's happening inside your body. They include:

X-rays

Findings from specialized x-rays can tell your doctor if there are any calcium-containing kidney stones. Kidney abscesses are not visible with this test.

Ultrasound

This imaging method uses sound waves that may bounce back or be absorbed by organs, muscles, and tissues. A kidney abscess will appear on an ultrasound, but blood and cysts show up similarly, so it’s not a diagnostic tool. Doctors use the ultrasound as additional information and likely request a CT scan to confirm an abscess.

CT scan

CT scans are currently the most accurate imaging technique for the proper diagnosis and follow-up of perirenal abscesses. A CT scan takes several x-rays that a computerized system assembles to display 'slices' of muscles, tissues, and organs. This imaging method can find a renal abscess around 96 out of 100 times.

Management and treatment

Doctors can treat the early stages of kidney abscesses with antibiotics. Depending on how quickly the abscess shrinks, you may be under this course of treatment for at least two months. Your physician can change your antibiotic dosage depending on what they see from regular ultrasounds.

If you have uncontrolled diabetes, your abscess may take longer to disappear as high blood sugar affects your immune system.

If you have a sizable kidney abscess, invasive surgery might be necessary. Your doctor may suggest percutaneous drainage of the pus using a catheter. They will also usually administer intravenous antibiotics until the infection goes away.

If you have an infection caused by a specific type of bacteria, Enterobacteriaceae, your doctor may transition you to oral antibiotics once they have removed your catheter.

Surgery is usually necessary to remove the pus if you have an exceptionally large abscess or kidney stones. Treating the cause reduces the likelihood of the perirenal abscess returning.

If left untreated, it is common for the infection to spread past the kidney region and into your bloodstream. This can be fatal.

Can a kidney abscess be prevented?

Kidney abscesses are preventable. If you suffer from kidney stones, speak with your healthcare provider to determine the best treatment regimen to avoid a kidney infection and an abscess. After undergoing urologic surgery, keep the operated-on area as sterile as possible. 

Treating urinary infections early will also prevent simple infections from becoming abscesses. It’s important to see a doctor if you have any symptoms of a UTI lasting longer than a couple of days. 

Complications of kidney abscess

The major complication of renal abscess is the rupture of the pus pocket. This may result in renal shrinkage due to obstruction or compression. If left untreated, it can also result in kidney failure, sepsis, or death. 

Sometimes the infection may persist if you have kidney stones. In extremely rare scenarios, you may need your kidney removed if the condition proves recurrent or stubborn to treat.

When to visit a doctor

It's advisable to contact your doctor if you have a history of kidney stones or UTIs and develop:

  • Fever

  • Chills

  • Urinary tract infections

  • Abdominal pain and discomfort

  • A burning feeling that accompanies urination

It’s vital to seek urgent care if you have symptoms of septicemia: 

  • Moderate or high fever

  • Shaking chills

  • Heart palpitations

  • Muscle aches

  • Headache

  • Extreme fatigue

The lowdown

A kidney abscess is a serious condition. You can prevent it by seeking early treatment for kidney stones and UTIs. Knowing the symptoms of a UTI might prevent you from developing a kidney abscess. A course of antibiotics today might mean avoiding an operating room visit tomorrow.

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