Pyelonephritis

Alternative names

Urinary tract infection - complicated; Infection - kidney; Complicated urinary tract infection; Kidney infection

Definition

Pyelonephritis is an infection of the kidney and the ducts that carry urine away from the kidney (ureters).

Causes, incidence, and risk factors

Pyelonephritis most often occurs as a result of urinary tract infection, particularly in the presence of occasional or persistent backflow of urine from the bladder into the ureters or kidney pelvis (vesicoureteric reflux).

Pyelonephritis can be further classified as follows:

• Acute uncomplicated pyelonephritis (sudden development of kidney inflammation)
  
• Chronic pyelonephritis (a long-standing infection that does not clear)
  
• Reflux nephropathy (an infection that occurs in the presence of an obstruction)
  

Although cystitis (bladder infection) is common, pyelonephritis occurs much less often. The risk is increased if there is a history of cystitis, renal papillary necrosis, kidney stones, vesicoureteric reflux, or obstructive uropathy.

The risk is also increased when there is a history of chronic or recurrent urinary tract infection and when the infection is caused by a particularly aggressive type of bacteria.

Acute pyelonephritis can be severe in the elderly and in people who are immunosuppressed (for example, those with cancer or AIDS).

Symptoms

• Flank pain or back pain
  
• Severe abdominal pain (occurs occasionally)
  
• Fever
  o Higher than 102 degrees Fahrenheit
  o Persists for more than 2 days
  
• Chills with shaking
  
• Warm skin
  
• Flushed or reddened skin
  
• Moist skin (diaphoresis)
  
• Vomiting, nausea
  
• Fatigue
  
• General ill feeling
  
• Urination, painful
  
• Increased urinary frequency or urgency
  
• Need to urinate at night (nocturia)
  
• Cloudy or abnormal urine color
  
• Blood in the urine
  
• Foul or strong urine odor
  
• Mental changes or confusion *
  

* Sometimes in the elderly, mental changes or confusion are the only signs of a urinary tract infection.