Fever and Proximal Tubular Function in Acute Pyelonephritis

Abstract

The urinary excretion of α_1-microglobulin (α₁M), β₂-microglobulin (β₂M), retinol-binding protein (RBP) and N-acetyl-β- D-glucosaminidase (NAG) as markers of proximal tubular dysfunction was measured in various forms of urinary tract infections (UTI) and in fever due to non-renal infections. The urinary concentration of these proteins was significantly increased in acute pyelonephritis compared with acute cystitis and asymptomatic bacteriuria. Tubular proteinuria and enzymuria could also be demonstrated in subjects with fever of non-renal origin and corresponded to the findings in pyelonephritis. It is suggested that fever per se is the most likely cause of the tubular proteinuria seen in acute pyelonephritis. In localizing an acute UTI characterization of the urinary protein profile seems to have no advantage over a carefully measured body temperature. The urinary excretion of α₁M, β₂M and RBP were highly correlated, while urinary NAG activity was less correlated to these low-molecular weight proteins. Fibrin degradation product D (FDP-D) was detected in the urines in 60% of the patients with acute pyelonephritis and in one third of those with acute cystitis. The estimation of FDP in urine therefore seems to be of little value in the level diagnosis of UTI.