What is a kidney infection?

You'll know you have a kidney infection if you have discomfort or pain when urinating, frequent urination, high fever and chills, lower torso pain, nausea and vomiting, and/or blood in urine.
You'll know you have a kidney infection if you have discomfort or pain when urinating, frequent urination, high fever and chills, lower torso pain, nausea and vomiting, and/or blood in urine.

Your kidneys remove waste and excess fluids from your body, but sometimes they can get infected. Kidney infection, or pyelonephritis, is a type of urinary tract infection (UTI).

It's estimated that kidney infections account for about 200,000 hospital admissions each year in the United States.

Anyone can get a kidney infection, but some people are more at risk, including:

  • Women, whose urethra (the tube from the bladder to where your urine passes out of your body) is shorter than men’s, making it easier for bacteria to enter the bladder
  • Those with lower immune system function due to diabetes, HIV, or medications such as immunosuppressants, which are taken after an organ transplant
  • People with a blockage of the urinary tract such as kidney stones or an enlarged prostate
  • People who use a catheter to drain urine, such as during or after surgery or if confined to a bed
  • Those with structural problems of the urinary tract such as vesicoureteral reflux, which causes urine to flow back up to the kidneys and cause infections.

It's important to recognize the symptoms of a kidney infection, as it requires prompt medical attention and can lead to serious problems if not treated.

Signs and symptoms of kidney infections

The symptoms of kidney infections depend on age, but in general, it starts with symptoms of a lower urinary tract infection, such as discomfort when urinating and frequent urination. Then, once the infection reaches the kidneys, there will be more serious symptoms, such as:

  • High fever and chills
  • Back, side, and groin pain
  • Nausea and vomiting
  • Painful and frequent urination: The infection can cause irritation and swelling in the urinary tract which makes urination painful and makes you think you need to urinate more.
  • Blood in urine: Red blood cells in your urine might only be seen when checked under a microscope, but in some cases, the urine is visibly pink, red, or brown. This means that the filters in the kidneys or other parts of the urinary tract are allowing blood to leak into the urine.

Young children under two may only have a high fever without any other symptoms. People above the age of 65 may not have typical symptoms but may seem confused, have muddled speech, or hallucinate.

If left untreated, kidney infections can result in serious complications. Kidney failure can result from the infection. A kidney infection can also cause sepsis, an adverse reaction to infection in your bloodstream, which can lead to organ failure and death.

QUESTION

How much urine does the average adult pass each day? See Answer

Causes of kidney infections

Bacteria or viruses

Most kidney infections are caused by bacteria or viruses. The urinary system is designed in a way to keep bacteria out. Most of the time, the urinary tract flushes out bacteria before it reaches the bladder. However, sometimes your body is unable to fight the bacteria.

Experts say this usually begins as a bladder infection most often caused by bacteria that lives in your bowel, called E. coli. The bacteria then travels upstream to one or both of your kidneys. About one in 30 urinary tract infection cases leads to a kidney infection.

Surgery

In some cases, a kidney infection can result if bacteria enters the body during surgery and then travels to the kidneys through the blood.

Diagnosis of kidney infections

Besides discussing your medical history and symptoms, your doctor will do a physical exam and order some tests.

Lab tests

Your doctor will order a urinalysis (urine test) to look for infection signs, such as high white blood cell count and bacteria. Your doctor may do a urine culture. Bacteria in urine is grown on a culture dish for about one to three days, and an expert can then see which type of bacteria is causing the infection.

Imaging tests

Your doctor may order imaging tests to help diagnose a kidney infection. These can include:

Treatments for kidney infections

Your doctor may first prescribe a general antibiotic. When the lab results come in, they may switch to a specific antibiotic that treats the type of infection you have. It's common to have antibiotics prescribed for at least two weeks. It's important to complete the antibiotic course so that the infection doesn't return.

If your infection is severe, you may have to be hospitalized. Antibiotics, as well as fluids, may be given through an IV (intravenous therapy) in your arm to ensure the drug will reach the kidneys.

If your infection is due to an underlying medical problem such as kidney stones or an enlarged prostate, you might have to be referred to a specialist for treatment.

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Medically Reviewed on 12/14/2020
References
American Academy of Family Physicians: "Painful Urination."

American Family Physician: "Diagnosis and Treatment of Acute Pyelonephritis in Women."

American Kidney Fund: "Blood in urine."

American Kidney Fund: "Kidney infection."

Centers for Disease Control and Prevention: "What is sepsis?"

National Institute of Diabetes and Digestive and Kidney Diseases: "Definition & Facts of Kidney Infection (Pyelonephritis)."

National Institute of Diabetes and Digestive and Kidney Diseases: "Symptoms & Causes of Kidney Infection (Pyelonephritis)."

National Kidney Foundation: "Hematuria in Adults."

UCLA Health: "Urinary Tract Infection."

Urology Care Foundation: "What is Kidney (Renal) Infection - Pyelonephritis?"