Acute pyelonephritis
Acute pyelonephritis: Excerpt from Professional Guide to Diseases (Eighth Edition)
Acute pyelonephritis (also known as acute infective tubulointerstitial nephritis) is a sudden inflammation caused by bacteria that primarily affects the interstitial area and the renal pelvis or, less often, the renal tubules. It’s one of the most common renal diseases. With treatment and continued follow-up care, the prognosis is good, and extensive permanent damage is rare.
Causes and incidence
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, Pseudomonas, Staphylococcus aureus, and Enterococcus faecalis (formerly Streptococcus faecalis) may also cause this infection.
Typically, the infection spreads from the bladder to the ureters, then to the kidneys, as in vesicoureteral reflux due to 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), from a hematogenic infection (as in septicemia or endocarditis), or possibly from 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.
Pyelonephritis occurs more commonly in females, probably because of a shorter urethra and the proximity of the urinary meatus to the vagina and the rectum — both conditions allow bacteria to reach the bladder more easily — and a lack of the antibacterial prostatic secretions produced in the male. Incidence increases with age and is higher in the following groups:
❑ Sexually active females: Intercourse increases the risk of bacterial contamination.
❑ Pregnant females: About 5% develop asymptomatic bacteriuria; if untreated, about 40% develop pyelonephritis.
❑ Diabetics: Neurogenic bladder causes incomplete emptying and urinary stasis; glycosuria may support bacterial growth in the urine.
❑ Persons with other renal diseases: Compromised renal function aggravates susceptibility.
Signs and symptoms
Typical clinical features include urgency, frequency, burning during urination, dysuria, nocturia, and hematuria (usually microscopic but may be gross). Urine may appear cloudy and have an ammonia-like or fishy odor. Other common symptoms include a temperature of 102° F (38.9° C) or higher, shaking chills, flank pain, anorexia, and general fatigue.
These symptoms characteristically develop rapidly over a few hours or a few days. Although these symptoms may disappear within days, even without treatment, residual bacterial infection is likely and may cause symptoms to recur later.
ELDER TIP Elderly patients may exhibit altered mental status or GI or pulmonary symptoms rather than the usual febrile responses to pyelonephritis.
PEDIATRIC TIP In children younger than age 2, fever, vomiting, nonspecific abdominal complaints, or failure to thrive may be the only signs of acute pyelonephritis.
Diagnosis
Diagnosis requires urinalysis and culture. Typical findings include:
❑ Pyuria (pus in urine): Urine sediment reveals the presence of leukocytes singly, in clumps, and in casts; and, possibly, a few red blood cells.
❑ Significant bacteriuria: Urine culture reveals more than 100,000 organisms/µl of urine.
❑ Low specific gravity and osmolality: These findings result from a temporarily decreased ability to concentrate urine.
❑ Slightly alkaline urine pH.
❑ Proteinuria, glycosuria, and ketonuria: These conditions are less common.
Excretory urography or computed tomography (CT) scan of the kidneys, ureters, and bladder also help in the evaluation of acute pyelonephritis by revealing calculi, tumors, or cysts in the kidneys and the urinary tract. In addition, excretory urography may show asymmetrical kidneys.
Treatment
Treatment centers on antibiotic therapy appropriate to the specific infecting organism after identification by urine culture and sensitivity studies. When the infecting organism can’t be identified, therapy usually consists of a broad-spectrum antibiotic. Urinary analgesics are also appropriate.
Alert If the patient is pregnant, antibiotics must be prescribed cautiously.
Symptoms may disappear after several days of antibiotic therapy. Although urine usually becomes sterile within 48 to 72 hours, the course of such therapy is 10 to 14 days. Follow-up treatment may include reculturing urine 1 week after drug therapy stops, then periodically for the next year to detect residual or recurring infection. Most patients with uncomplicated infections respond well to therapy and don’t suffer reinfection.
In infection from obstruction or vesicoureteral reflux, antibiotics may be less effective; treatment may then necessitate surgery to relieve the obstruction or correct the anomaly. Patients at high risk of recurring urinary tract and kidney infections, such as those with prolonged use of an indwelling catheter or maintenance antibiotic therapy, require long-term follow-up. Recurrent episodes of acute pyelonephritis can eventually result in chronic pyelonephritis. (See Chronic pyelonephritis.)
Special considerations
Patient care is supportive during antibiotic treatment of the underlying infection.
❑ Administer antipyretics for fever.
❑ Encourage fluids to achieve urine output of more than 2,000 ml/day. This helps to empty the bladder of contaminated urine. Don’t encourage intake of more than 2 to 3 qt (2 to 3 L) because this may decrease the effectiveness of the antibiotics.
❑ Provide an acid-ash diet to prevent stone formation.
❑ Teach proper technique for collecting a clean-catch urine specimen. Be sure to refrigerate or culture a urine specimen within 30 minutes of collection to prevent overgrowth of bacteria.
❑ Stress the need to complete prescribed antibiotic therapy, even after symptoms subside. Encourage long-term follow-up care for high-risk patients.
To prevent acute pyelonephritis:
❑ Observe strict sterile technique during catheter insertion and care.
❑ Instruct females to prevent bacterial contamination by wiping the perineum from front to back after defecation.
❑ Advise routine checkups for patients with a history of urinary tract infections. Teach them to recognize signs of infection, such as cloudy urine, burning on urination, urgency, and frequency, especially when accompanied by a low-grade fever.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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