Acute pyelonephritis

Acute pyelonephritis in adults commonly presents as acute-onset fever, chills, severe back or flank pain, nausea and vomiting, and costovertebral angle tenderness.

Urinalysis and urine culture confirm the diagnosis of pyelonephritis. Urine cultures, obtained prior to treatment, demonstrate bacteria, most often Escherichia coli.

The route and choice of empiric antibiotics depend on the severity of illness and the presumed bacterial sensitivities pending culture results.

Complications most often result from inappropriate (wrong drug or wrong dose) antibiotic use or antibiotic resistance, leading to recurrent or progressive infection.

Other common causes of complications are inadequate treatment of anatomic abnormalities (e.g., kidney stones or obstruction), preventing bacterial clearance.

Pyelonephritis, from the Greek "pyelo" (pelvis), "nephros" (kidney), and "-itis" (inflammation), describes a severe infectious inflammatory disease of the renal parenchyma, calices, and pelvis that can be acute, recurrent, or chronic. Acute infections may be caused by enteric bacteria (e.g., Escherichia coli) that ascend from the lower urinary tract or that spread hematogenously to the kidney. Most episodes are uncomplicated and are cured with no residual renal damage. Complicated infections can result from underlying medical problems (e.g., diabetes mellitus, HIV), genitourinary anatomic abnormalities, obstruction (e.g., benign prostatic hypertrophy, calculi), and/or multidrug-resistant pathogens. Urinary tract infection, or UTI, is a nonspecific term that refers to infection anywhere in the urinary tract from the urethra to the kidneys. Pyelonephritis refers specifically to infections in the kidney. 

Urinary tract infections in children is a specialized topic that is not covered here. See Urinary tract infections in children.