Acute pyelonephritis in US hospitals in 1997: hospitalization and in-hospital mortality.

PURPOSE: To describe the 1997 incidence of hospitalization for acute pyelonephritis in the US and the risk factors for in-hospital mortality associated with acute pyelonephritis.
METHODS: Cases were defined as those with ICD9-CM codes corresponding to acute pyelonephritis in the 1997 Health Care Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS). Frequencies and calculations were weighted to produce either national or state estimates. Hospitalization rates were calculated using 1997 US Census Bureau population projections for the denominator.
RESULTS: Females were almost five times as likely as males to be hospitalized for acute pyelonephritis (11.7/10,000 vs. 2.4/10,000), but males had higher mortality rates (16.5/1000 vs. 7.3/1000); 30% greater after adjustment. Hospitalization and in-hospital mortality rates increased with age, but not with diabetes. Mortality rates increased with number of procedures, diagnoses and having a major diagnostic category other than disorders of the kidney and urinary tract. Persons living in zip codes with lower median incomes were also at higher risk of mortality. There was little variation in mortality by hospital size, ownership, location or teaching status.
CONCLUSION: In hospital mortality for pyelonephritis was associated with patient rather than hospital characteristics suggesting uniform application of standard care across hospitals and populations.