Small Bowel Obstruction

SMALL BOWEL OBSTRUCTION

Pathophysiology

Intestinal contents, fluid, and gas accumulate above the intesti-nal obstruction. The abdominal distention and retention of fluid reduce the absorption of fluids and stimulate more gastric secre-tion. With increasing distention, pressure within the intestinal lumen increases, causing a decrease in venous and arteriolar cap-illary pressure. This causes edema, congestion, necrosis, and even-tual rupture or perforation of the intestinal wall, with resultant peritonitis.

Reflux vomiting may be caused by abdominal distention. Vomiting results in a loss of hydrogen ions and potassium from the stomach, leading to a reduction of chlorides and potassium in the blood and to metabolic alkalosis. Dehydration and acidosis develop from loss of water and sodium. With acute fluid losses, hypovolemic shock may occur.

Clinical Manifestations

The initial symptom is usually crampy pain that is wavelike and colicky. The patient may pass blood and mucus, but no fecal matter and no flatus. Vomiting occurs. If the obstruction is com-plete, the peristaltic waves initially become extremely vigorous and eventually assume a reverse direction, with the intestinal contents propelled toward the mouth instead of toward the rectum. 

If the obstruction is in the ileum, fecal vomiting takes place. First, the patient vomits the stomach contents, then the bile-stained con-tents of the duodenum and the jejunum, and finally, with each paroxysm of pain, the darker, fecal-like contents of the ileum. The unmistakable signs of dehydration become evident: intense thirst, drowsiness, generalized malaise, aching, and a parched tongue and mucous membranes. The abdomen becomes distended. The lower the obstruction is in the GI tract, the more marked the abdominal distention. If the obstruction continues uncorrected, hypovolemic shock occurs from dehydration and loss of plasma volume.

Assessment and Diagnostic Findings

Diagnosis is based on the symptoms described previously and on x-ray findings. Abdominal x-ray studies show abnormal quantities of gas, fluid, or both in the bowel. Laboratory studies (ie, elec-trolyte studies and a complete blood cell count) reveal a picture of dehydration, loss of plasma volume, and possible infection.

Medical Management

Decompression of the bowel through a nasogastric or small bowel tube is successful in most cases. When the bowel is completely obstructed, the possibility of strangulation warrants sur-gical intervention. Before surgery, intravenous therapy is necessary to replace the depleted water, sodium, chloride, and potassium.

The surgical treatment of intestinal obstruction depends largely on the cause of the obstruction. In the most common causes of obstruction, such as hernia and adhesions, the surgical procedure involves repairing the hernia or dividing the adhesion to which the intestine is attached. In some instances, the portion of affected bowel may be removed and an anastomosis per-formed. The complexity of the surgical procedure for intestinal obstruction depends on the duration of the obstruction and the condition of the intestine.

Nursing Management

Nursing management of the nonsurgical patient with a small bowel obstruction includes maintaining the function of the na-sogastric tube, assessing and measuring the nasogastric output, assessing for fluid and electrolyte imbalance, monitoring nutri-tional status, and assessing improvement (eg, return of normal bowel sounds, decreased abdominal distention, subjective im-provement in abdominal pain and tenderness, passage of flatus or stool). The nurse reports discrepancies in intake and output, worsening of pain or abdominal distention, and increased naso-gastric output. If the patient’s condition does not improve, the nurse prepares him or her for surgery. The exact nature of the surgery depends on the cause of the obstruction. Nursing care of the patient after surgical repair of a small bowel obstruction is similar to that for other abdominal surgeries.