SERUM HIPPURIC-ACID CONCENTRATION IN RENAL-ALLOGRAFT REJECTION, URETER OBSTRUCTION, AND TUBULAR-NECROSIS

Plasma from 35 renal allograft recipients (21 males and 14 females) wa s sampled daily and analyzed for hippuric acid (HA) by highperformance liquid chromatography (HPLC) and serum creatinine. Twelve of these pa tients experienced an acute renal allograft rejection or a ureter obst ruction as proven by clinical signs and biopsy, as well as by radiogra phy or ultrasound, respectively. Two patients suffered from tubular ne crosis followed by rejection during the postoperative period. Mean ser um HA increased by 39.9 mu mol/l from baseline (range 20.4-115.5 mu mo l/l) in patients with acute rejection 3 days after an initial increase that was observed 24 h before the mean serum creatinine increased by 107.1 mu mol/l (range 21-193 mu mol/l). In cases of ureter obstruction , HA rose by 1.6 mu mol/l (range 1-8.2 mu mol/l), significantly less t han elevations due to rejection. The increase in creatinine, however, amounted to 65.3 mu mol/l (range 22-140 mu mol/l) and was not differen t from the change in rejecting patients. Successful antirejection trea tment coincided with a decrease in serum HA starting 24 h earlier than the decrease in the serum creatinine concentration. Of special intere st was the observation of a parallel decrease in HA with creatinine co ncentration in patients with tubular necrosis after allotransplantatio n; HA increased in cases of an additional rejection. Our data suggest that HA, which is excreted by tubular secretion and glomerular filtrat ion, could be a sensitive and early marker of acute allograft rejectio n. Furthermore, it seems to discriminate between acute renal allograft rejection and ureter obstruction. It might, therefore, be of value in the diagnosis of rejection complicating tubular necrosis after transp lantation.