Biochemical studies in peritoneal fluid from patients with acute pancreatitis.  Relationship to etiology. 
The levels of pancreatic digestive enzymes, lysosomal hydrolases, and protease inhibitors were evaluated in ascites fluid from 24 patients with acute pancreatitis diagnosed as alcoholic, gallstone-induced, or idiopathic.  In this group the concentrations of amylase (354 +/- 98 ng/ml), immunoreactive cationic trypsinogen (1840 +/- 238 ng/ml), and immunoreactive elastase 2 (1492 +/- 262 ng/ml) were greatly elevated in comparison to the corresponding serum values.  Enzyme levels in ascites from the idiopathic pancreatitis group tended to be higher than the levels from the other two groups.  Activity of acid phosphatase and beta-glucuronidase was significantly higher in ascites compared to serum in all groups.  On the other hand, levels of immunoreactive alpha 1-protease inhibitor and alpha 2-macroglobulin in ascites fluid were about half the average concentrations reported for normal serum.  Significant amounts of tryptic amidase activity (61.7 +/- 13.7 micrograms/ml) were observed, indicating a trypsin-alpha 2-macroglobulin complex.  These data indicate an imbalance in the protease-to-inhibitor ratio in ascites fluid from patients with acute pancreatitis.  Coupled with elevated ribonuclease activity (27.4 +/- 3.4 units), a positive methemalbumin test in 23 of 24 patients (1.1 +/- 0.4 mg hematin/100 ml), and an average protein concentration of 4.0 +/- 0.2 g/100 ml, these observations demonstrate that abdominal paracentesis and the biochemical analyses of ascites fluid provide useful information related to the biochemical events in acute pancreatitis and may be useful in the diagnosis of difficult cases, but their predictive value of severity remains to be established.