Illnesses that cause a distended abdomen, pressure and a feeling of fullness include irritable bowel syndrome, indigestion, inflammatory bowel disease and an intestinal parasite infection, according to Healthline. Pancreatitis, gallstones and an intestinal blockage can also cause fullness, pressure and a distended abdomen.
People who suffer from heartburn, a flux in hormones or an intolerance to lactose may experience a distended abdomen, explains Healthline. An overgrowth of bacteria in the small bowels, overeating, gas, weight gain and pregnancy can also cause the abdomen to distend. A distended stomach can cause a feeling of bloating, accompanied with swelling, tightness and pressure in the abdomen. Some patients experience pain, excessive gas and frequent burping when the abdomen is distended.