25. 1 Acute pancreatitis

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Содержание Colon Obstruction Diagnosis of intestinal obstruction Physical Examination Radiologic Examination

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Colon Obstruction

In general, obstruction of the colon produces less fluid and electrolyte disturbance than mechanical obstruction of the small bowel. If the patient has a competent ileocecal valve, there may be little or no small bowel distention, but in this instance, the colon behaves like a closed loop. The massively distended colon may perforate. Because of its spherical shape and large diameter, the cecum is a likely site for perforation. However, the most common cause of colon obstruction is cancer, and the usual site of perforation is adjacent to the cancer. In patients with incompetent ileocecal valves, signs of small bowel distention may accompany colon obstruction. The colon is also subject to strangulation when obstruction compromises the blood supply.

DIAGNOSIS OF INTESTINAL OBSTRUCTION

The questions to ask in evaluating a patient suspected of having intestinal obstruction are:

1. Does the patient have bowel obstruction?
   
2. If so, where is it?
   
3. What is the anatomic and pathologic nature of the obstructing lesions?
   
4. Has strangulation occurred?
   
5. What is the general condition of the patient (fluid-electrolyte balance and other systemic disease)?
   

Abdominal pain, vomiting, obstipation, abdominal distention, and failure to pass flatus characterize intestinal obstruction. The typical crampy pain in intestinal obstruction occurs in paroxysms at 4- to 5-minute intervals in proximal obstruction and less frequently in distal obstruction. After a long period of mechanical obstruction, the crampy pain may subside because bowel distention inhibits motility. One should suspect strangulation with peritonitis when continuous severe abdominal pain replaces crampy abdominal pain.

Proximal intestinal obstruction can produce profuse vomiting and little abdominal distention. In distal obstruction, the vomiting is less frequent but is feculent because of the large bacterial population of intestinal contents. Obstipation and failure to pass gas from the rectum characterize complete obstruction, after the bowel distal to the obstruction empties. Increase in abdominal girth because of fluid and gas accumulating in the intestine accompanies distal obstruction of the small bowel, obstruction of the colon, or paralytic ileus.

Physical Examination

The physical examination should note certain points. Tachycardia and hypotension may indicate severe dehydration, peritonitis, or both. Fever suggests the possibility of strangulation. Poor skin turgor and dry mucous membranes may reflect dehydration. The abdomen is usually distended. Occasionally the examiner must distinguish bowel distention from ascites. A fluid wave, shifting dullness, and fullness in the flanks characterize ascites. Peristaltic waves characteristic of small bowel obstruction are sometimes visible through the abdominal wall of thin patients with long-standing obstruction. Note surgical scars because of the etiologic implication of previous operation—for example, the presence of adhesions or cancer. Incarcerated hernias may be obscure, particularly in obese patients. Examine for abdominal masses (neoplasm, intussusception, abscess). Abdominal tenderness occurs in patients with intestinal obstruction; however, localized tenderness, rebound tenderness, and guarding suggest peritonitis and the likelihood of strangulation.

Abdominal auscultation in patients with mechanical intestinal obstruction usually reveals periods of increasing or crescendoing bowel sounds separated by relatively quiet periods. The bowel sounds in intestinal obstruction are usually high-pitched, tinkling, or musical in character.

A rectal examination should be done to seek luminal masses. The presence of feces should be noted, and they should be examined for occult blood. Blood in the feces suggests an alimentary mucosal lesion, as may occur with cancer, intussusception, or infarction. Sigmoidoscopic examination may help in the evaluation of suspected distal obstruction of the colon.

History and physical examination permit the diagnosis of intestinal obstruction. Any patient having crampy abdominal pain, vomiting, obstipation, abdominal distention, abdominal tenderness, and peristaltic rushes should be managed for intestinal obstruction until it can be confidently excluded.

Radiologic Examination

Radiographs usually confirm the clinical diagnosis and define more accurately the site of obstruction. Abdominal x-ray examination of patients with intestinal obstruction usually reveals abnormally large quantities of gas in the bowel. One can usually identify a distended small intestine or colon. Gas in the small bowel outlines the valvulae conniventes, which usually occupy the entire transverse diameter of the bowel image. Colonic haustral markings occupy only a portion of the transverse diameter of the bowel. Typically, the small bowel pattern occupies the more central portions of the abdomen, whereas the colon shadow is on the periphery of the abdominal film or in the pelvis. Patients with mechanical small intestinal obstruction usually have minimal or no colonic gas. Radiographs of patients who have obstruction of the colon with competent ileocecal valves show distention of the colon but little small bowel gas. Patients with obstruction of the colon and incompetent ileocecal valves usually have radiographic evidence of small bowel and colon distention. Films taken in the upright or lateral decubitus position in patients with mechanical obstruction of the small bowel usually show multiple gas-fluid levels, with distended bowel resembling an inverted U. Occasionally, ordinary x-ray films fail to distinguish colonic from small intestinal obstruction. In that circumstance, a carefully performed barium enema distinguishes the two.

Plain films may fail to distinguish paralytic ileus from mechanical obstruction. During paralytic ileus, gaseous distention occurs somewhat uniformly in the stomach, small bowel, and colon. Gas-fluid levels may occur in paralytic ileus. Examination after a barium meal may distinguish between paralytic ileus and mechanical obstruction. When clinical symptoms indicate intestinal obstruction, the clinical findings supersede x-rays, such films may appear normal in patients with strangulation obstruction.

When obstruction of the small bowel is suspected but remains in doubt, computed tomography (CT) may assist in the diagnosis. CT is sensitive for diagnosing complete obstruction of the small bowel and for determining the location and cause of obstruction. 11 Abdominal ultrasonography can help diagnose obstruction of the small bowel and its location and cause.