Epidemiological studies on pancreatic pseudocysts are retrospective analyse
s on alcoholic patients. The aims of this study were to investigate the inc
idence, natural history, and predictors of the appearance and disappearance
of pancreatic fluid collections and pseudocysts after nonalcoholic acute p
ancreatitis. We carried out a prospective cohort study in a series of 926 p
atients with acute pancreatitis. Pancreatic fluid collections or pseudocyst
s were treated only after complications. We studied pancreatic fluid collec
tions from 83 patients (8.9%): 48 of whom developed pseudocysts (5.1%). Bot
h were less frequent after biliary pancreatitis (P < 0.0001). In the first
60 days of follow-up, patients with fluid collections or pseudocysts showed
more complications than spontaneous disappearance; two of them died. After
the 60th day, spontaneous disappearance was more frequent, and at one year
the cumulative incidence of complications and spontaneous disappearance wa
s 36% and 56%, respectively. A total of 33 patients with fluid collection n
eeded interventional treatment (surgery or percutaneous or endoscopic drain
age). Pseudocysts that were small (<5 cm) or developed in the tail had a hi
gher incidence of spontaneous disappearance: 22/24 (91.7%) and 11/12 (91.7%
), respectively. In conclusion, fluid collections and pseudocysts after non
alcoholic pancreatitis have a low incidence of complications and mortality
with a high rate of spontaneous disappearance. We suggest treating them onl
y after complications.