Lack of sensitivity and specificity of the renal clearance of amylase/clearance of inulin ratio in experimental acute rat pancreatitis with a study on the renal handling of amylase.

As there are controversies about the specificity and the sensitivity of the amylase clearance/inulin clearance ratio (Cam/Cin) in the diagnosis of pancreatitis, this ratio has been calculated: (a) in rats with induced pancreatitis with histologically proven lesions; (b) in toxic induced tubulopathy rats with lesions demonstrated histologically and biologically (enzymuria). Hyperamylasaemia was found in 86% of the pancreatitis rats at 24 h, 50% at 48 h and 25% at 60 h. The ratio Cam/Cin was elevated above 2 SD of the control values among 14% of the rats at 24 h, 50% at 48 h and 25% at 60 h. There were no changes in enzyme elimination rates in the urine as compared to control values. Renal histology remained normal. Histological scores expressing a severe haemorrhagic pancreatitis were identical at 24, 48 ad 60 h. In toxic induced tubulopathy rats, amylasaemia remained normal. but the Cam/Cin ratio only increased when the glomerular filtration rate was diminished by 90%. The diagnosis could only be made by hyperamylasaemia in 50% of the histologically proven pancreatitis in the rat. The use of the ratio Cam/Cin does not increase the frequency of a correct diagnosis. Finally, amylase must be only filtered by the kidney as no tubular enzymes appeared in the urine of pancreatitis rats. Furthermore, this ratio is not specific for pancreatitis as it could be elevated in other pathologic states such as severe renal failure.