Urinary enzymes excretion in pancreatic diseases. Clinical role and pathophysiological considerations

The amylase-creatinine clearance ratio was first proposed as a useful tool in the diagnosis of acute pancreatitis, and later it was claimed that trypsin creatinine clearance ratio was a sensitive and accurate test of pancreatic cancer. More recent observations have undermined the role of both clearances in the diagnosis of acute pancreatitis, and their utility in patients with chronic pancreatic diseases has largely been ignored. Three orders of factors, (a) the physicochemical characteristics of the protein, (b) the glomerular filtration rate variations, and (c) renal tubular damage, may have a role in determining the changes in the plasma-urine transfer of enzymes such as amylase and trypsin. Amylase urinary output is related both to variations in amylase serum levels (since this enzyme probably is not intensively reabsorbed by the tubule) and to the presence of renal tubular damage. Trypsin plasma-urine transfer changes depend greatly on the presence of tubular alterations. Elastase 1 and phospholipase A2 urinary outputs can also be predicted on the basis of the presence of tubular damage. Renal tubular alteration in pancreatic diseases may depend on the damaging effect of toxic substances (proteolytic enzymes, for example) released by the inflamed pancreas; the role of liver damage and of extrahepatic jaundice, which are frequent findings in chronic pancreatic diseases, should also be considered. However, toxic compounds such as ethanol, which can alter the pancreas and possibly the kidney, could also have a key role in the genesis of urinary findings in pancreatic diseases.