Kidney infection is an infection located in the upper urinary system that is caused by bacteria. The infection usually starts when bacteria entering the lower urinary tract cause a urinary tract infection (UTI). From there the bacteria can spread to the kidneys.

The kidneys are a pair of organs located on either side of the abdomen that remove waste products from the blood and produce urine. Among other functions, the kidneys:

• Remove toxins from the blood and send the cleansed blood back to the bloodstream
  
  
• Regulate concentration of acids
  
  
• Help maintain water balance in the body
  
  
• Create substances that regulate blood pressure and formation of red blood cells

In some cases, the infection begins in the kidneys because of an obstruction or blockage (e.g., enlarged prostate in men, kidney stones, tumors). This blockage prevents urine from flowing, allowing bacteria to grow instead of being flushed out of the body.

Kidney (renal) diseases, diabetes mellitus or renal abnormalities that interfere with normal kidney function can contribute to infection. In some instances, the bladder and ureters do not work normally and urine flows back into the kidneys instead of on through the urethra. This is known as vesicoureteral reflux.

Symptoms of kidney infection include pain in the back and side as well as tenderness in the abdomen and groin. Most patients develop a fever. Urination may be painful, burning, frequent or the urine may contain blood or pus. Patients can also have nausea and vomiting.

Patients who suspect a kidney infection should consult a physician for proper diagnosis and treatment. Diagnosing a kidney infection includes a physical examination and a urine test to detect the presence of bacteria and white blood cells.

Treating the infection requires antibiotics to kill the bacteria. In rare instances, surgery may be needed. Kidney infections caused by obstructions or other problems inside the kidney must receive treatment for the infection along with treatment for the underlying cause.

The best way to prevent kidney infections is to prevent urinary tract infections. Methods to help include wiping from front to back after using the toilet to decrease the chances of bacteria from the rectum migrating to the urinary tract. Drinking plenty of water and other fluids to prevent dehydration and increase urination is helpful.

For those who develop a urinary tract infection, appropriate treatment with antibiotics is important to prevent spreading the infection to the kidneys.