Serum alkaline phosphatase and γ-glutamyl transferase in acute pyelonephritis

Elevated serum alkaline phosphatase (AP) and γ-glutamyl transferase (γ-GT) are commonly observed in patients with acute pyelonephritis. The goal of this study was to examine the clinical significance of elevated serum AP and γ-GT levels and to explore the mechanisms underlying these changes.

We examined serum AP and γ-GT levels in 438 patients with acute pyelonephritis. Urine AP/creatinine (Cr), urine γ-GT/Cr, fractional excretion of AP, and fractional excretion of γ-GT (FE_γ-GT) were evaluated in patients with elevated and normal serum levels. AP isoenzymes were also examined.

We identified 77 patients (17.6%) with elevated serum AP and 134 patients (30.6%) with elevated serum γ-GT. Among them, both enzymes were elevated in 64 patients (14.6%). Older age, longer hospital stay, elevated baseline serum Cr, and complicated pyelonephritis were associated with increases in serum AP and γ-GT. Multivariate analysis showed that high serum AP levels were significantly correlated with renal impairment (odds ratio, 2.13; 95% confidence interval, 1.08-4.19; P = 0.029). FE_γ-GT was significantly lower in patients with elevated serum enzyme levels. The liver fraction for AP isoenzyme profile did not increase in patients with elevated serum AP.

Our results demonstrated that elevated serum AP and γ-GT levels are associated with complicated pyelonephritis and renal impairment. Lower FE_γ-GT levels in patients with elevated serum enzymes may be the result of decreased urinary excretion of these enzymes.