The human small bowel is about 20 to 25 feet long and about one inch in diameter. The taller a person is, the longer his/her small bowel will be. The small bowel consists of three sections. The first and shortest segment is the duodenum, which is about eight to 10 inches long. The top of the duodenum connects to the stomach. The common bile duct, which starts in the liver and passes by the gallbladder and through the pancreas, empties into the mid duodenum via the sphincter of Oddo. The common bile duct supplies bile and digestive enzymes to the duodenum. The duodenum absorbs nutrients from food including iron. The next section of the small bowel is the jejunum, which is about eight to 10 feet long. The jejunum absorbs products of digestion including sugars, amino acids, and fatty acids. The last section is the ileum, which is about 10 to 12 feet long. It absorbs more nutrients including vitamin B12 and bile acids. It connects to the large bowel, or colon, via the ileocecal valve.
A small bowel obstruction (SBO) is a blockage in the small intestine. The most common causes of SBO are abdominal scar tissue, hernias, strictures (internal narrowing caused by scar tissue), and cancers. In severe cases of SBO, the blood supply to the intestine may be compromised, causing bowel tissue to die. This is a life-threatening situation. Any abdominal surgery causes scar tissue to form. The scar tissues are called adhesions. The more abdominal surgeries a person has, the more adhesions form. An SBO caused by adhesions may occur as early as a few weeks after the surgery to as late as several years after without any obvious inciting event. The obstruction can cause the digestive materials in the intestines to back up, causing pain and vomiting of dark green bile or darker stool. The obstructed bowel becomes large, or dilated, with air and fluid that would normally move forward. This dilation and air/fluid may be seen on an abdominal X-Ray.
Most obstructions will resolve by allowing the bowel to rest and shrink back to normal size. This is accomplished by passing a nasogastric, or NG, tube into the stomach to remove the backed-up intestinal contents. The tube is connected to a vacuum. The patient will not be allowed to have anything by mouth (NPO, or nothing per oral) and will be kept hydrated via intravenous fluids. By this method, the obstruction will usually resolve in a few days. If the patient does not improve, then surgical correction will become necessary. The surgeon will cut the adhesions that are blocking the bowel. This is called lysis of adhesions. As mentioned above, hernias may also cause an SBO by entrapping a loop of bowel. Strictures, or narrowing of the bowel, may be caused by inflammatory bowel diseases like Crohn’s disease. Cancers originating in the small bowel are quite rare. An SBO caused by cancer is usually caused by a cancer that originated outside of the small bowel.
For more information, go to: www.mayoclinic.org/diseases-conditions/intestinal-obstruction/symptoms-causes/syc-20351460
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