Large Bowel Obstruction

LARGE BOWEL OBSTRUCTION

Pathophysiology

As in small bowel obstruction, large bowel obstruction results in an accumulation of intestinal contents, fluid, and gas proximal to the obstruction. Obstruction in the large bowel can lead to severe dis-tention and perforation unless some gas and fluid can flow back through the ileal valve. Large bowel obstruction, even if complete, may be undramatic if the blood supply to the colon is not disturbed. If the blood supply is cut off, however, intestinal strangulation and necrosis (ie, tissue death) occur; this condition is life threatening. In the large intestine, dehydration occurs more slowly than in the small intestine because the colon can absorb its fluid contents and can dis-tend to a size considerably beyond its normal full capacity.

Clinical Manifestations

Large bowel obstruction differs clinically from small bowel ob-struction in that the symptoms develop and progress relatively slowly. In patients with obstruction in the sigmoid colon or the rectum, constipation may be the only symptom for days. Even-tually, the abdomen becomes markedly distended, loops of large bowel become visibly outlined through the abdominal wall, and the patient has crampy lower abdominal pain. Finally, fecal vom-iting develops. Symptoms of shock may occur.

Assessment and Diagnostic Findings

Diagnosis is based on symptoms and on x-ray studies. Abdominal x-ray studies (flat and upright) show a distended colon. Barium studies are contraindicated.

Medical Management

A colonoscopy may be performed to untwist and decompress the bowel. A cecostomy, in which a surgical opening is made into the cecum, may be performed for patients who are poor surgical risks and urgently need relief from the obstruction. The proce-dure provides an outlet for releasing gas and a small amount of drainage. A rectal tube may be used to decompress an area that is lower in the bowel. The usual treatment, however, is surgical resection to remove the obstructing lesion. A temporary or per-manent colostomy may be necessary. An ileoanal anastomosis may be performed if it is necessary to remove the entire large colon.

Nursing Management

The nurse’s role is to monitor the patient for symptoms that in-dicate that the intestinal obstruction is worsening and to provide emotional support and comfort. The nurse administers intra-venous fluids and electrolytes as prescribed. If the patient’s con-dition does not respond to nonsurgical treatment, the nurse prepares the patient for surgery. This preparation includes pre-operative teaching as the patient’s condition indicates. After surgery, general abdominal wound care and routine postopera-tive nursing care are provided.