The influence of disease progression and pancreatic surgery on the appearance of diabetes mellitus in patients with chronic pancreatitis is unknown.

A prospective cohort study of 500 consecutive patients with chronic pancreatitis (alcoholics, 85%) followed up over a mean period of 7.0 ± 6.8 years in a medical-surgical institution between 1973 and 1996 was performed. Multivariate analysis of risk factors for diabetes mellitus was performed after exclusion of 47 patients. Patients who underwent elective pancreatic surgery (n = 231, 51%) were compared with patients who never underwent surgery (n = 222, 49%).

The cumulative rate of diabetes mellitus was 83% ± 4% 25 years after the clinical onset of chronic pancreatitis (insulin requirement, 54% ± 6%). The prevalence of diabetes mellitus did not increase in the surgical group overall but was higher 5 years after distal pancreatectomy (57% ± 8%) than after pancreaticoduodenectomy (36% ± 18%), pancreatic drainage (36% ± 13%), or cystic, biliary, or digestive drainage (24% ± 7%) (P = 0.005), without difference in the latter ones. Pancreatic drainage did not prevent the onset of diabetes mellitus. Distal pancreatectomy (risk ratio, 2.4; 95% confidence interval [CI], 1.6–3.8; P < 0.0001) and early onset of pancreatic calcifications (risk ratio, 3.2; CI, 2.2–4.7;P < 0.0001) were the only independent risk factors for diabetes mellitus.

The risk of diabetes mellitus is not influenced by elective pancreatic surgical procedures other than distal pancreatectomy in patients with chronic pancreatitis. This risk seems to be largely caused by progression of the disease because it increased by more than 3-fold after the onset of pancreatic calcifications.