The resultant small-bowel distension may mimic a distal SBO. An incompetent ileocecal valve will decompress the LBO into the small bowel. It is important to note that the exact size of the cecum is less important than the duration and rapidity of cecal distension ( 12– 13). In intermittent or chronic obstruction, however, the cecal wall may become hypertrophied and the colon may greatly exceed 10 cm in diameter without perforation ( 11). The exact size of the cecum at risk for perforation ranges in the literature from 9 to 12 cm ( 5). Cecal distension will lead to increased wall tension and without intervention, will progress to ischemia and necrosis. Because the cecum is the largest diameter of the colon, it requires the least amount of pressure to distend ( 9, 10). According to the La Place law, the intraluminal pressure needed to stretch the wall of a hollow tube is inversely proportional to the radius of the tube. If the ileocecal valve is competent, which occurs in about 75% of patients, an LBO will result in a closed -loop obstruction, which cannot decompress into the small bowel ( 4). The competence of the ileocecal valve influences the response of the colon. In the setting of vascular compromise and ischemia, patients often demonstrate substantial abdominal tenderness. Bowel sounds are usually hypoactive in patients with LBO this is caused by the cessation of peristalsis ( 8). At the time of the acute volvulus, these patients rapidly develop acute pain and distension. Colonic volvulus, especially in the setting of chronically distended colon, may include symptoms of chronic abdominal distension and abdominal pain.
Obstruction from sigmoid diverticulitis may manifest with symptoms of left lower quadrant pain, fever, and a palpable mass. LBO caused by obstruction in the left colon manifests earlier than that caused by obstruction in the right colon because the lumen of the sigmoid and descending colon is smaller and the stool is more inspissated in the distal colon ( 3). The etiology of the LBO may be suggested by the specific symptoms and presentation of the patient. LBO occurs more frequently within the left colon ( 5). The major sites of obstruction include the cecum, hepatic and splenic flexures, and recto-sigmoid colon. Patients with LBO are usually elderly and the signs and symptoms of LBO are often insidious in contrast to the abrupt onset of symptoms seen in most SBOs these symptoms include abdominal pain, constipation or obstipation, and abdominal distension ( 3, 5). Both the clinical findings and the pathophysiology of LBO differ substantially from SBO. Of note, the etiology of LBO worldwide varies substantially as does the patient population affected in Africa and India, volvulus is the primary cause of LBO (50%), and patients in these areas are usually young and healthy ( 7).Īn LBO occurs when there is occlusion of the lumen of the colon anywhere along its course and dilatation of the large bowel proximal to the site of obstruction. Colonic obstruction is most often seen in elderly individuals, as the aforementioned causes of obstruction are more common in advanced age groups. Additional causes of LBO include entities such as diverticulitis, colonic volvulus, and adhesions. Colonic malignancy remains the most common cause of LBO (> 60%) ( 4, 6). LBO is four to five times less frequent than SBO and the causes of LBO and SBO differ substantially ( 5) ( Table 1). While the same principles of initial management of small-bowel obstruction (SBO) (attention to strangulation, hydration, and nasogastric suction) are used in LBOs, emergency surgery or colonoscopy is usually required to relieve the obstruction ( 4). The marked distension of colon proximal to the level of obstruction leads to mucosal edema, bowel ischemia, and, if not treated, bowel infarction and perforation.
While LBO may develop over a protracted period of time, the clinical presentation is often acute and includes abdominal pain, constipation or obstipation, and abdominal distension ( 3). Acute complete large-bowel obstruction (LBO) is an abdominal emergency, with high morbidity and mortality rates if left untreated ( 1, 2).