Atlas of pathophysiology, 2 Edition

Part II - Disorders


Acute pyelonephritis (also known as acute infective tubulointerstitial nephritis) is a sudden inflammation caused by bacterial infection; it primarily affects the interstitial area and the renal pelvis or, less often, the renal tubules. It's one of the most common renal diseases. Symptoms characteristically develop rapidly over a few hours or days and may disappear within days, even without treatment. However, residual bacterial infection is likely and may cause symptoms to recur later. With treatment and continued follow-up care, the prognosis is good and extensive permanent damage is rare.


Acute pyelonephritis results from bacterial infection of the kidneys. Infecting bacteria usually are normal intestinal and fecal flora that grow readily in urine. The most common causative organism is Escherichia coli, but Proteus or Pseudomonas species, Staphylococcus aureus, or Enterococcus faecalis (formerly Streptococcus faecalis) may also cause this infection.

Clinical Tip

Emphysematous pyelonephritis is an uncommon disorder seen in patients with diabetes or those who are immunocompromised. It's caused by a gas-forming organism such as E. coli, which produces gas that forms in the renal parenchyma or perirenal space. This life-threatening condition requires aggressive medical management or nephrectomy.

Clinical Tip

Pyelonephritis occurs more commonly in females, probably because bacteria reach the bladder more easily through the short female urethra; the urinary meatus is in close proximity to the vagina and the rectum, and women lack the male's antibacterial prostatic secretions.


Typically, the infection spreads from the bladder to the ureters, then to the kidneys, as in vesicoureteral reflux. Vesicoureteral reflux may result from congenital weakness at the junction of the ureter and the bladder. Bacteria refluxed to intrarenal tissues may create colonies of infection within 24 to 48 hours. Infection may also result from instrumentation (such as catheterization, cystoscopy, or urologic surgery), a hematogenic infection (as in septicemia or endocarditis), or possibly lymphatic infection.

Pyelonephritis may also result from an inability to empty the bladder (for example, in patients with neurogenic bladder), urinary stasis, or urinary obstruction due to tumors, strictures, or benign prostatic hyperplasia.

Signs and symptoms

·   Urgency, frequency, nocturia

·   Burning during urination, dysuria

·   Hematuria, usually microscopic but may be gross

·   Cloudy urine, ammonia-like or fishy odor

·   Fever of 102 F (38.9 C) or higher, shaking chills

·   Flank pain

·   Anorexia

·   General fatigue

Age Alert

Elderly patients may exhibit GI or pulmonary symptoms rather than the usual febrile responses to pyelonephritis.

In children younger than age 2, fever, vomiting, nonspecific abdominal complaints, or failure to thrive may be the only signs of acute pyelonephritis.

Diagnostic test results

·   Urine sediment reveals the presence of leukocytes singly, in clumps, and in casts and, possibly, a few red blood cells.

·   Urine culture reveals more than 100,000 organisms/l of urine.

·   Urinalysis reveals low specific gravity and osmolality, proteinuria, glycosuria, and ketonuria.

·   Urine pH testing shows a slightly alkaline pH.

·   Computed tomography scan of the kidneys, ureters, and bladder reveals calculi, tumors, or cysts in the kidneys and the urinary tract.

·   Excretory urography shows asymmetrical kidneys.


Antibiotic therapy appropriate to the specific infecting organism after identification by urine culture and sensitivity studies:

·   Enterococcus—ampicillin, penicillin G, vancomycin

·   Staphylococcus—penicillin G; if resistance develops, a semisynthetic penicillin, such as nafcillin, or a cephalosporin

·   E. coli—sulfisoxazole, nalidixic acid, nitrofurantoin

·   Proteus—ampicillin, sulfisoxazole, nalidixic acid, a cephalosporin

·   Pseudomonas—gentamicin, tobramycin, carbenicillin

·   Not identified—broad-spectrum antibiotic, such as ampicillin or cephalexin

·   Pregnancy or renal insufficiency—antibiotics prescribed cautiously


·   Urine culture repeated 1 week after drug therapy stops, then periodically for the next year

Infection from obstruction or vesicoureteral reflux

·   Antibiotics possibly less effective

·   Surgery to relieve the obstruction or correct the anomaly

Patients at high risk for recurring urinary tract and kidney infections

·   Prolonged use of an indwelling catheter or maintenance antibiotic therapy

·   Long-term follow-up to prevent chronic pyelonephritis





If you find an error or have any questions, please email us at Thank you!