Serum lactic dehydrogenase and irreversible renal allograft rejection.

The relationship between serum lactic dehydrogenase (SLDH) values and renal allograft rejection was examined in the dog and in man. Nine dogs with renal allografts and four with autografts had similar maximal elevations of SLDH during the first five postoperative days (mean, 420 +/- 213 and 433 +/- 80 I.U. per liter, respectively). During rejection of the allografts between days 7 and 14 the maximum SLDH was 810 +/- 285 I.U. per liter, and in autografts the peak SLDH was 233 +/- 22 I.U. per liter (p less than 0.01). The isoenzyme pattern of maximum SLDH during rejection was prominent in LDH5 and corresponded with renal tissue LDH isoenzyme composition. In 93 episodes of initial acute human renal allograft rejection reactions, the SLDH peaked above 500 I.U. per liter in 23 cases and remained below 500 I.U. per liter in 70 cases. SLDH levels above 500 I.U. per liter were associated with complete rejection of the kidney in 91 percent of patients and SLDH levels persistently below 500 I.U. per liter corresponded with reversal of rejection reaction in 99 percent of patients (p less than 0.01). Marked SLDH elevation is associated with severe, usually complete renal allograft rejection and may be useful in identifying patients with irreversible rejection reactions.