Causes of bowel obstruction usually specific to the elderly include sigmoid volvulus, Ogilvie's Syndrome, colon carcinoma, and gallstone ileus. These conditions in the elderly patient can lead to gangrene with resulting perforation.
Sigmoid volvulus is 20 times more likely in the patient age 60 yr and greater (19). This age association may be due to acquired redundancy of the sigmoid colon. High-residue diets are believed to be the causative factor in developing a redundant sigmoid (20). Other factors associated with volvulus are Parkinson's disease, dementia including Alzheimer's disease, bedridden state, and prior abdominal operations, all of which increase in frequency in the elderly patient. Sigmoid volvulus usually presents as acute onset of colicky abdominal pain, distention, and obstipation. When strangulation has occurred, the patient can present with generalized abdominal pain, tenderness to palpation, fevers, leukocytosis, and hypotension. Plain abdominal radiographs characteristically show a dilated sigmoid loop with a "bird's beak" pointing to the site of obstruction. If the plain abdominal radiographs are equivocal, a barium enema may be used. However, this test is contraindicated if strangulation is suspected. Decompression with endoscopy and rectal tube placement should be performed in the absence of peritoneal signs. This is successful in 70-80% of patients. The risk of recurrence of sigmoid volvulus is high (approximately 55-90%), therefore the patient should be evaluated for elective sigmoid resection. If the sigmoid volvulus has progressed to gangrene, mortality approaches 50-70%. When peritoneal signs are present emergent laparotomy is indicated.
4.2. Ogilvie's Syndrome
Ogilvie's syndrome, also called colonic pseudo-obstruction, usually occurs in the elderly bedridden patient. When cecal distension approaches 12 cm, the risk of gangrene, infarction, and perforation increases. When perforation and gangrene occur, mortality is 50%. As in sigmoid volvulus, colonoscopic decompression is the treatment of choice. However, if endoscopy fails or the patient is unstable, cecostomy or laporatomy with resection may be indicated.
An interesting, yet rare, cause for small bowel obstruction in the elderly is gallstone ileus. This is caused by the passage of a large biliary calculus from the gallbladder to the distal iliem through a cholecystenteric fistula. This disorder carries an overall mortality rate of 15%. Rigler's triad, which includes small bowel obstruction, ectopic gallstones, and pneumobilia, characterizes this disorder. Enterolithotomy, which carries an operative mortality of 12%, is the procedure of choice (21). A one-stage procedure of enterolithotomy, cholecystectomy, and fistula repair carries a mortality of 17% (22).
Cancer of the colon and rectum is the second most common cancer in western countries with an incidence of 150,000 new cases per year. The incidence increases with age, with up to three-quarters of the cases occurring in patients 65 yr and older. Colorectal cancers may present with obstruction and/or peritonitis. The mortality from complicated obstruction from colorectal cancer is as high as 50%, and long-term survival after resection is greatly reduced. This is partially due to more advanced disease and metastasis in patients with this complication (23). In the critically ill elderly patient with perforation or obstruction, a bypass or diversionary procedure should be considered. Definitive treatment may then be performed on an elective basis.
5. ACUTE MESENTERIC INFARCTION 5.1. Epidemiology and Clinical Relevance
Acute mesenteric infarction can lead to a catastrophic intraabdominal infection in the elderly with mortality rates as high as 90%. Arterial emboli to the mesenteric vessels occur in 30% of patients with this disorder. These emboli originate most commonly from a mural thrombus in an infarcted left ventricle or a fibrillating left atrium. Thrombosis of a mesenteric vessel occurs in 25% of patients and is due to atherosclerotic stenosis. This is usually preceded by intestinal angina. Other less common causes of acute mesenteric infarction are thrombosis of mesenteric veins, dissecting aneurysms, fusiform aneurysms, and connective tissue disorders. Mesenteric vascular occlusion leads to necrosis of villi, mucosal sloughing, ulceration, and bleeding. Even without full-thickness necrosis, perforation, sepsis, multiorgan failure, and death may occur.
Pain out of proportion to the physical examination is one of the hallmarks of acute mesenteric ischemia. This pain is severe, poorly localized, and can be associated with nausea, vomiting, diarrhea, and/or constipation. When late in the presentation or when perforation occurs the patient may develop abdominal distention, tenderness to palpation, hypotension, and/or generalized peritonitis. Guaiac-positive stools are present in 75-95% of patients. Leukocytosis, hyperamylasemia, increased alkaline phosphatase, elevated serum lactate, hyperphosphatemia, and acidosis may be observed.
Acute abdominal radiographic series are commonly unremarkable early in ischemia. However, as the disease progresses the radiographs can show dilated loops of small intestine containing air-fluid levels, "thumbprinting" of the bowel wall, intramural gas, and/or free air (24). CT scans of the abdomen can be useful, especially to exclude other abdominal pathology. Findings on CT scan may show bowel wall thickening, intramural gas, dilatation of bowel loops, fluid-filled loops, increase attenuation of mesenteric fat, and/or mesenteric or portal venous gas. In evaluation of mesenteric venous thrombosis CT scan is the study of choice and may detect superior mesenteric artery thrombosis. Despite large numbers of negative studies angiography can be a precise method for diagnosing occlusive intestinal ischemia (25).
If peritoneal signs are present, exploratory laparotomy is warranted. Treatment will be focused on resection of nonviable bowel and restoration of intestinal blood flow. Transarterial embolectomy may be attempted in the stable patient. Thrombolytic therapy has yet to be proven an effective treatment, however, anticoagulant therapy may be used for prophylaxis against further emboli.
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