Pyelonephritis, acute
Pyelonephritis, acute: Excerpt from Handbook of Diseases
One of the most common renal diseases, 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. With treatment and continued follow-up, the prognosis is good and extensive permanent damage is rare. (See Chronic pyelonephritis.)
Causes
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 Streptococcus faecalis may also cause such infections.
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), 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 rectum (both of which allow bacteria to reach the bladder more easily) and a lack of the antibacterial prostatic secretions produced in the male.
Risk factors
Incidence increases with age and is higher in the following groups:
❑ sexually active women — increased risk of bacterial contamination from intercourse.
❑ pregnant women — about 5% develop asymptomatic bacteriuria; if untreated, about 40% develop pyelo-nephritis.
❑ diabetics — neurogenic bladder causes incomplete emptying and urinary stasis; glycosuria may support bacterial growth in the urine.
❑ people with other renal diseases — increased susceptibility resulting from compromised renal function.
CLINICAL TIP: Acute pyelo-nephritis is more likely to occur in patients who have undergone urinary tract manipulation — such as for the placement of a urinary catheter. Caution is advised in selecting patients for urinary catheter placement.
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 ammoniacal 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 signs and 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 later recurrence of symptoms.
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 — more than 100,000 organisms/µl of urine revealed in urine culture
❑ low specific gravity and osmolality, resulting from a temporarily decreased ability to concentrate urine
❑ slightly alkaline urine pH
❑ proteinuria, glycosuria, and keto-nuria — less common.
X-rays also help in the evaluation of acute pyelonephritis. X-ray films of the kidneys, ureters, and bladder may reveal calculi, tumors, or cysts in the kidneys and urinary tract. Excretory urography may show asymmetrical kidneys.
Treatment
Effective treatment centers on antibiotic therapy appropriate to the specific infecting organism after identification by urine culture and sensitivity studies.
Antibiotic therapy
I.V. antibiotics are used initially to control bacterial infection. Chronic pyelonephritis may require long-term antibiotic therapy. Commonly used antibiotics include sulfa drugs, amoxicillin, cephalosporins, levofloxacin, and ciprofloxacin. If the patient is pregnant, antibiotics must be prescribed cautiously. Urinary analgesics such as phenazopyridine are also appropriate.
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
Follow-up treatment includes reculturing urine after drug therapy stops. Most patients with uncomplicated infections respond well to therapy and don’t suffer reinfection.
CLINICAL TIP: 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 for recurring urinary tract and kidney infections — such as those with prolonged use of an indwelling urinary catheter or maintenance antibiotic therapy — require long-term follow-up.
Special considerations
❑ Administer antipyretics for fever.
❑ Make sure the patient receives plenty of fluids so that he achieves urine output of more than 2,000 ml/day. This helps to empty the bladder of contaminated urine. Don’t encourage the intake of more than 3 qt (3 L) of fluids, because this may decrease the effectiveness of the antibiotics.
❑ 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.
❑ For patient-teaching information on disease prevention, see Preventing acute pyelonephritis.
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Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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