548 UNIT VIII RENAL AND UROLOGICAL DISORDERS
Instruments can introduce pathogens into the bladder during procedures. Lastly, pregnancy increases the risk of pyelonephritis, partly because of obstruction by the enlarged uterus and partly because of ureteral relax- ation secondary to elevated progesterone levels. Pathophysiology The pathophysiology of pyelonephritis varies based upon whether the condition is acute or chronic. With acute pyelonephritis, an inflammatory process devel- ops, usually secondary to infection. Most often the infection ascends from the lower urinary tract and is associated with gram-negative bacteria. Less fre- quently, the infection is from the bloodstream and is most often secondary to a Staphylococcus aureus infection. Chronic pyelonephritis occurs because of repeated kidney infection. Because of recurrent infections and inflammatory processes, permanent changes develop in the renal tissue that increase susceptibility to infec- tion. Any deformity, scar, or fibrotic tissue can cause reflux of urine or stagnant urine that leads to growth of microorganisms and an infectious process. Clinical Presentation The clinical presentation of acute pyelonephritis includes fever, chills, flank or groin pain, CVA ten- derness, urinary frequency, and dysuria. Flank or CVA pain can be mild or severe, but the patient usually feels a general malaise. Nausea and vomiting commonly accompany this disorder. Hematuria is present in 30% to 40% of patients. The patient may or may not present with signs of lower UTI such as dysuria, urgency, and frequency. Symptoms can develop gradually and can be present for weeks before the patient seeks health care. In patients with chronic pyelonephritis, the clinical manifestations may be more subtle; patients present with urinary frequency, dysuria, and flank pain, with HTN possibly accompanying these symptoms. Chronic pyelonephritis may present more insidiously, partic- ularly with unilateral involvement. As renal function declines because of this disorder, polyuria, nocturia, and proteinuria are common.
have significant pyuria, which is defined as more than 20 WBCs per high power field [hpf]. A positive leukocyte esterase test is found with presence of WBCs in the urine. The nitrite test can be used for bacteriuria and is usually positive, though it may be falsely negative in the presence of diuretic use, low dietary nitrate, or organisms that do not produce nitrate reductase, such as Enterococcus, Pseudomonas, or Staphylococcus. The cardinal confirmatory test is the urine culture, which typically yields 10,000 or more colony-forming units of a uropathogen per milliliter of urine. Gross hematuria usually does not occur in pyelonephritis but is more common with cystitis, cal- culi, cancer, glomerulonephritis, tuberculosis, trauma, and vasculitis. Microscopic hematuria may be present in patients with uncomplicated acute pyelonephritis, but other causes also should be considered, particu- larly calculi. Proteinuria is expected (up to 2 g/day). When it exceeds 3 g/day, glomerulonephritis should be considered. Blood cultures to rule out sepsis may be neces- sary in ambiguous cases (e.g., in populations with a high prevalence of asymptomatic bacteriuria or in patients who have received previous antimicrobial therapy). Imaging studies are reserved for patients with suspected obstruction or a new decrease in the glomerular filtration rate to 40 mL/minute or lower (which is suggestive of obstruction). Noncontrast, helical CT scan or renal ultrasound are recommended. Treatment Acute pyelonephritis is usually treated with antibiotic therapy; antibiotic selection depends on the specific microorganism identified by urine culture. Antipyretic medications and analgesics may be necessary. The patient is advised to drink large amounts of water (e.g., 3 L per day). If symptoms recur, repeat urine cultures are recommended at 1 and 4 weeks after completion of the antibiotic regimen. For patients with hypovolemia, extended care in the emergency department or obser- vation unit for more extensive resuscitation and initial intravenous antimicrobial therapy may be necessary. Hospital admission is warranted for patients who have severe illness, unstable coexisting medical conditions, an unreliable psychosocial situation, or no acceptable oral therapy option. Treatment of chronic pyelonephritis includes man- agement of an infectious process and prevention of further renal function deterioration. During exacerba- tions of chronic pyelonephritis, antibiotics are admin- istered. If an obstruction is found to be the underlying cause of the recurrent infections, the obstruction must be relieved for cure. Complications With appropriate treatment of acute pyelonephritis, long-term complications are infrequent. Bactere- mia can occur in 20% to 30% cases of pyelonephri- tis. Emphysematous pyelonephritis can occur if there
CLINICAL CONCEPT Costovertebral tenderness, fever, chills, and pyuria are classic signs of pyelonephritis.
Diagnosis In both acute and chronic processes, urine cultures are important diagnostic tools. The most common bacte- ria that cause acute pyelonephritis are uropathogenic Escherichia coli. Others include S. saprophyticus, Proteus mirabilis, and Klebsiella pneumoniae. On dipstick uri- nalysis, almost all patients with acute pyelonephritis
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