Most common cause of gas under diaphragm is

Ans) a (DU perforation) Ref: http://en.wikipedia.orgPerforation of the stomach or duodenum can occur as a result of peptic ulceration. Gastric cancers can also erode through the wall of the stomach and perforate. Perforation of the small intestine is much less common, and is typically casued by either an inflammatory bowel disease such as Crohn's, or by cancers - although primary cancer arising in the small bowel is very rare. Adjacent cancers in the colon or in the small bowel mesentery (cancers such as lymphoma or "GIST", gastrointestinal stromal tumor) are more common reasons for small bowel perforation, but are still unlikely to cause perforated small bowel rather than colon, except in AIDS patients where it becomes more common.Colonic perforation is relatively common. The most common lesion of the colon to perforate is diverticulitis, and this will most likely occur in the sigmoid colon or at least on the left side. There are occasional cases of right colon diverticular inflammation and infection, however, and the right colon is thinner than the left. If this perforates, it leads to disasterous leakage of liquid stool. Colon cancers sometimes perforate too, and because of that, any questionable perforated lesion of the colon at the time of emergency surgery needs to be treated like a cancer, and be fully removed with appropriate margins of normal tissue along with it.Perforation of the esophagus can happen but rarely leads to abdominal air, because it will more likely leak into the chest. Perforation of the bile system can happen, but even though this is connected to the gastrointestinal tract, gas does not typically climb out of the leak - just fluid (bile).Another source of free air is abdominal trauma such as stabs, gunshot wounds, or even blunt force injury from things like car accidents. In these cases, anything and everything must be suspected of leaking.Differential diagnosis1) Boerhaave's syndrome (esophageal tear) - rare cause2) Perforated peptic ulcer (stomach or duodenum) - common3) Perforated gastric cancer - less common4) Spontaneous perforation of the small intestine - rare5) Perforated diverticulitis of the colon - common6) Perforated colon cancer - common7) Abdominal trauma