Timing of surgical drainage for pancreatic pseudocyst. Clinical and chemical criteria.

Traditional concepts of managing pancreatic pseudocysts have changed with the advent of computerized tomography (CT) and ultrasound scanning, but new misconceptions related to spontaneous resolution have replaced some old ones. This report shows a difference in natural history and treatment requirements when pseudocysts are associated with acute versus chronic pancreatitis. There were 42 consecutive patients with pseudocysts treated over 5 years. Thirty-one were known alcoholics, two had gallstone pancreatitis, and nine had idiopathic pancreatitis. An attack of acute pancreatitis was identifiable within 2 months preceding in 22 patients, but there were only chronic symptoms in 20. Spontaneous resolution of the pseudocyst occurred in three patients (7%), all of whom had recent acute idiopathic pancreatitis, normal serum amylase levels, and pancreatograms showing normal pancreatic ducts freely communicating with the pseudocyst. Factors associated with failure to resolve included known chronic pancreatitis, pancreatic duct changes of chronic pancreatitis, persistence greater than 6 weeks, and thick walls (when seen) on scan. Nearly all (18/19) patients with known chronic pancreatitis had successful internal drainage of the pseudocysts immediately upon admission, whereas 6/20 patients with antecedent acute pancreatitis were found to require external drainage at the time surgery was eventually elected. Isoamylase analysis, performed on serum from 19 patients by means of polyacrylamide gel electrophoresis, detected the abnormal pancreatic isoamylase pattern described as "old amylase" in 15. When old amylase was present in the serum, internal drainage was always possible (14/14). In four of five patients whose serum contained no detectable old amylase, internal drainage was not possible regardless of the length of prior observation. There were four nonfatal complications arising from an acute pseudocyst during the wait for maturity. It is concluded that prolonged waiting is expensive and unnecessary for pseudocysts in chronic pancreatitis when there has been no recent acute attack. However, pseudocysts developing after identifiable acute pancreatitis should be observed in the safety of a hospital for up to 6 weeks to allow for either spontaneous resolution or maturation of the cyst wall. The appearance of old amylase in the serum suggests that the pseudocyst wall has achieved sufficient maturity to allow safe internal anastomosis.