A small bowel obstruction is a blockage in the small intestine. Small bowel obstructions are usually caused by scar tissue, hernia, or cancer. In the United States, most obstructions occur as a result of prior surgeries. The bowel often forms bands of scar (called adhesions) after being handled during an operation. The more surgeries that involve the bowel, the more scars are likely to form. If the bowel becomes trapped in adhesions, it may lead to a small bowel obstruction. In severe cases, the blood supply might be compromised, and the bowel tissues might die. This is a life-threatening situation. A small bowel obstruction caused by adhesions may occur as early as a few weeks and as late as several years after a surgery without any obvious inciting event. An obstruction can cause the material inside the bowel to back up into the stomach. This causes nausea and vomiting of dark green bile (bilious vomiting). The bowel preceding the obstruction becomes large, dilated, and filled with the fluid and air that would otherwise move forward. This causes bloating (abdominal distention).