Our long-term goal is to alter the clinical course of AP in patients who are at high risk for the development of organ failure (OF) and death. The objective of this randomized, double-blind, placebo-controlled pilot trial is to evaluate the efficacy of rectal indomethacin on attenuating systemic inflammation in patients with AP who also have SIRS. The investigators hypothesize that the treatment of patients with AP and SIRS with therapeutic doses of rectal indomethacin will mitigate the inflammatory response through the inhibition of inflammatory mediators. The investigators will also test the hypothesis by enrolling 42 patients randomized to receive either rectal indomethacin or placebo for 48 hours and pursuing the following specific aims: