A 24-yrs-old male, who has been having fever for 15 days, starts having acute pain and distension of abdomen. Abdominal examination reveals generalized tenderness with guarding. The most likely diagnosis is:

The clinical picture described is classical of enteric perforation and peritonitis. In enteric fever ulcers occur in intestine, which may perforate if not treated properly. This complication is seen in third or fourth week of fever. It is a life threatening complication and urgent medical and surgical intervention is required; GIT haemorrhage is another life threatening complication of enteric fever that occurs in third or fourth week of fever. In acute appendicitis and acute pancreatitis abdominal pain is the main feature rather than fever of 15 days duration. In DU perforation fever is absent.