Fever Duration in Hospitalized Acute Pyelonephritis Patients


Synopsis: Fever may persist beyond two days and up to four days in patients treated for acute pyelonephritis.

Source: Behr MA, et al. Am J Med 1996;101:277-280.

About one-quarter million cases of acute pyelonephritis are treated each year in the United States. Fever is present in almost three-fourths of the patients, and hospitalization may be required. The usual recommendation is that if there is continued fever after 2-3 days, investigations should be undertaken for complications, and consideration should be given to modifying antibiotic therapy.

The authors undertook a retrospective chart analysis at a 400-bed university-affiliated community hospital serving an urban population of mixed socio-economic status. All 234 charts listing urinary tract infection (UTI) as a principal or secondary diagnosis over a three-year period were reviewed. The criteria for acute pyelonephritis (APN) were fever (temperature > 100.4°F oral), a positive urine culture with a single organism 105 colonies/cm mm, and the absence of another possible source of infection on chart review. Seventy patients fit the inclusion criteria for APN. There were 52 females, and the mean age for all patients was 53.6 years. Significant clinical variables included diabetes (11%), previous UTI (43%), nosocomial infection (6%), known previous renal calculi (7%), and pregnancy (4%), and only one patient had a catheter-associated infection.

The mean duration of fever was 39 hours, with a median of 34 hours. Twenty-six percent continued to be febrile at 48 hours, and 13% still had not defervesced at 72 hours. Results of intravenous pyelography and sonography including radiologic abnormalities were not predictors of fever duration. There was no increase in duration of fever (38 hours) in the 16% of cases with evidence of radiological obstruction. No cases of intrarenal or perinephric abscess were found. Positive blood cultures were not associated with increased fever duration. The positive correlations of prolonged fever were with increasing creatinine (P = 0.0001) and increasing total leucocyte count (P = 0.027). Fever was prolonged in younger patients (P = 0.026) and in those with E. coli infection (P = 0.05).


What this study demonstrates clearly is that fever may persist beyond two days and up to four days in patients treated for acute pyelonephritis. There should not be a rush to reculture, change therapy, or conduct radiological or urological evaluation when fever persists after 2-3 days, unless there are other clinical features such as persistent flank pain, persistent hematuria, or azotemia.

The correlations with prolonged fever such as increased creatinine and younger age need corroboration. Further investigation of other correlates such as diabetes and pregnancy is also needed. Data on these correlations will be important in establishing guidelines for outpatient treatment of acute pyelonephritis given the increasing emphasis on reducing hospitalization.