Kidney Infections: Symptoms and Treatments

Most urinary tract infections (UTIs) involve only the bladder and urethra (the lower urinary system). Pyelonephritis results when a UTI progresses to involve the upper urinary system (the kidneys and ureters).

The kidneys filter the blood to produce urine. Two tubes called the ureters carry urine from the kidneys down to the bladder. Urine travels from the bladder out of the body through the urethra.

Most cases of pyelonephritis are complications of common bladder infections. Bacteria enter the body from the skin around the urethra. They then travel up the urethra to the bladder.

Sometimes, bacteria escape the bladder and urethra, traveling up the ureters to one or both kidneys.

Pyelonephritis is a potentially serious kidney infection that can spread to the blood, causing severe illness. Fortunately, pyelonephritis is almost always curable with antibiotics.

The urethra is much shorter in women than in men, which is one reason why women are more vulnerable to UTIs and pyelonephritis.

Symptoms of Pyelonephritis

At least half of women have experienced the discomfort with urination caused by a urinary tract infection: painful, urgent, or frequent urination.

Pyelonephritis may start with similar symptoms. However, once the infection has spread to the kidney, signs of more severe illness usually result. They include:

  • Back pain or flank pain
  • Fever (usually present) or chills
  • Feeling sick (malaise)
  • Nausea and vomiting
  • Confusion (especially in the elderly)

Pyelonephritis may cause noticeable changes in the urine, such as:

  • Blood in the urine (hematuria)
  • Cloudy or foul-smelling urine
  • Pain when urinating
  • Increased frequency or urgency of urination


Causes of Pyelonephritis

Most often, the bacteria that cause pyelonephritis are the same as those that cause ordinary urinary tract infections. Bacteria found in stool (such as E. coli or klebsiella) are most common. Uncommonly, bacteria from the skin or the environment cause pyelonephritis.

Conditions that create reduced urine flow make pyelonephritis more likely. When urine flow slows or stops, bacteria can more easily travel up the ureters. Some causes of urine obstruction include:

  • Benign prostatic hypertrophy (BPH)
  • Abdominal or pelvic masses (as from cancer)
  • Stones in the bladder, ureters, or kidneys

Kidney stones contribute to pyelonephritis by providing a place for bacteria to grow while evading the body's defenses.

People with diabetes or conditions that impair the immune system are more likely to get pyelonephritis.

How Pyelonephritis Is Diagnosed

Doctors may rely on various tests to diagnose pyelonephritis:

History. Telling the story of your illness and specific symptoms helps a doctor make the diagnosis of pyelonephritis.

Physical examination. A doctor notes a person's general appearance, vital signs, and presses over the kidneys to check for tenderness.

Urinalysis . In pyelonephritis, microscopic analysis of the urine virtually always shows signs of infection. This can include an excess of white blood cells and bacteria.

Urine culture . Within days, bacteria in urine may grow on a culture dish, allowing the best antibiotic to be chosen.

Blood cultures. If pyelonephritis has spread to the blood, blood cultures can detect this and guide treatment.

Computed tomography (CT scan). A scanner takes a rapid series of X-rays, and a computer creates detailed images of the abdomen and kidneys. A CT scan is not necessary to diagnose pyelonephritis, but sometimes helps.

Kidney ultrasound. A probe directs high-frequency sound waves through the skin, creating images of the kidneys and ureters. Ultrasound can help identify abscesses, stones, and blockages.

In addition to diagnosing pyelonephritis itself, doctors look for any conditions that make pyelonephritis more likely. For example, kidney stones or birth defects of the urinary tract can increase the chance of an infection. Both are potentially correctable, which will reduce the chances of future kidney infections.


Treatment of Pyelonephritis

Pyelonephritis is a serious infection that always requires treatment with antibiotics. Home remedies alone aren't effective or recommended for pyelonephritis.

For most cases of pyelonephritis, hospitalization isn't required. Home treatment is appropriate if a person is able to get around and can consistently take oral antibiotics. For example, they must not be confined to bed or regularly vomiting.

Hospitalization is required to treat more severe pyelonephritis, however. Delivering antibiotics intravenously in the hospital ensures that the medicine is reaching the kidneys.

Antibiotics are generally prescribed for a total of at least seven days. Part of this course of treatment may be given in the hospital intravenously; the remainder of the treatment may be taken at home in the form of pills.

In rare cases, pyelonephritis may progress to form a pocket of infection (abscess). Abscesses are difficult or impossible to cure with antibiotics alone and must be drained. Most often, this is done with a tube inserted through the skin on the back into the kidney abscess (a procedure called a nephrostomy).

Acute and Chronic Pyelonephritis

Most cases of pyelonephritis are acute, meaning sudden and self-limited. After cure with antibiotics, there is rarely any lasting damage to the kidneys. Most people do not develop pyelonephritis again.

Chronic (long-lasting) pyelonephritis is a rare condition, usually caused by birth defects in the kidney. Repeated UTIs (usually in children) result in progressive damage and scarring in the kidney. This can eventually cause kidney failure. Usually, chronic pyelonephritis is discovered in childhood.

WebMD Medical Reference Reviewed by Carol DerSarkissian on May 28, 2016



Ramakrishnan K. American Family Physician, 2005.

National Kidney and Urologic Diseases Information Clearinghouse: "Pyelonephritis (Kidney Infection) in Adults."

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