268 - Metabolic Acidosis In Pediatric Patients With E. Coli Pyelonephritis

Pyelonephritis is the most common serious bacterial infection in the pediatric population, with the majority of cases caused by E. coli. Animal model research demonstrated that an E. coli cell membrane component inhibits bicarbonate reabsorption in the renal collecting duct, contributing to the development of metabolic acidosis. Several electrolyte abnormalities have been described in pediatric patients with pyelonephritis, including metabolic acidosis.

Objective:

We sought to describe the frequency and clinical significance of normal anion gap (AG) metabolic acidosis in pediatric patients with acute pyelonephritis.

Design/Methods:

This was a single center, retrospective study of pediatric patients 2-18 years old admitted for initial pyelonephritis episode. The nadir serum bicarbonate (HCO3) was collected, defined as the lowest serum HCO3 during admission, along with corresponding AG. Available baseline and recovery HCO3 and AG values were collected. These data were also collected for pediatric patients with initial lobar pneumonia admission to serve as an illness control. Nadir lab values were collected for 94 pyelonephritis subjects, with 25 baseline and 40 recovery lab sets. Nadir lab values were collected for 95 pneumonia subjects, with 27 baseline and 28 recovery lab sets. Results are expressed as mean (std dev). Changes in serum HCO3 from baseline to nadir were compared between groups using t tests. Multiple regression analyses were performed to evaluate the association between nadir HCO3 and infection severity measures.

Results:

The mean age of pyelonephritis patients was 8.8 (5.6) years, and 6.4% were male. The mean age of pneumonia patients was 7.6 (4.8) years, and 51.6% were male. Baseline HCO3 in pyelonephritis patients was 23.5 (1.7), and in pneumonia patients was 24.7 (1.9). Decrease in HCO3 from baseline to nadir was 4.4 (2.0) in pyelonephritis, significantly greater than 2.7 (2.7) in pneumonia. Pyelonephritis nadir HCO3 was 20.0 (2.6), significantly lower than 20.9 (2.9) in pneumonia. Corresponding AG was 16.0 (3.6) in pyelonephritis, significantly lower than 17.3 (3.2) in pneumonia. There was a significant correlation between nadir HCO3 and number of fever days (each 0.78 mmol/L decrease in HCO3 was associated with 1 additional fever day) in the pyelonephritis group, which was not significant in the pneumonia group.

Conclusion(s):

This study provides substantiation for development of a metabolic acidosis in pediatric patients with acute pyelonephritis. There is potential for the concomitant treatment of acidosis in reducing pyelonephritis infection severity and limiting clinical course.