The small bowel can get obstructed due to many causes. The most common causes are enumerated according to the site of pathology.
1. From outside the bowel
a. Bands and adhesions: due to previous surgery or inflammations and infections.
b. Volvulus: a loop of bowel gets twisted on its own or over a band.
c. Strangulations due to hernias: a loop of bowel gets out through a hernial orifice and the blood supply gets cut off leading to gangrene of the bowel.
d. Extension of malignant growths from neighboring organs: Late stages of carcinomas of pancreas, colon, uterus and ovary etc invade the bowel and cause obstruction of the intestines.
2. From the wall of bowel.
a. Strictures: Infection of the bowel with tuberculosis or an attack previously of ischemia lead to constriction of a segment of the intestines causing obstruction.
b. Tumors and Malignant growths: Carcinoma of colon is the most common cause of obstruction in large bowel .
c. Inflammatory bowel diseases and diverticulitis: Crohns disease, Ulcerative colitis and diverticulitis cause edema and strictures of the bowel causing obstruction.
e. Infarction of the bowel: Mesenteric thrombosis and embolism cause ischemia of the bowel and cause acute intestinal obstruction.
f. Congenital diseases: Duodenal and ileal atresia(non-development) and Hirschsprung's disease are the common causes of intestinal obstruction in infants and children.
3. From inside the lumen of bowel.
a. Round worm bolus: In untreated round worm infestation, a large number of round worms get to form a mass obstructing the bowel.
b. Gall stones: A large gall stone may get into the intestines and cause obstruction.
c. Fecal impaction: In chronic constipation the fecal matter gets hard and cause obstruction.
d. Intussusception: Telescoping of a segment of bowel into another segment is called intussusception.
e. Meconium in infants: New born infants may get intestinal obstruction due to meconium not getting passed.
Clinical features:Acute intestinal obstruction may occur at any age. The principal symptoms are the triad of pain, vomiting and constipation. The pain of obstruction occurs in bouts of colic . The frequency of colicky pain is dependent upon the location of the obstruction. Higher the obstruction, more frequent the pain. This is associated with severe projectile vomiting. There will be absolute constipation. Then appears distension of abdomen . Lower the obstruction, more the distension. Colonic obstructions cause the most prominent distension. Visible peristalsis may be apparent. Small bowel obstruction may give rise to tenderness over abdominal wall. Bowel sounds are heard loudly over the abdomen. In late stages, especially if a part of bowel gets gangrenous or gets perforated, symptoms and signs of peritonitis may supervene. Because of the loss of fluid into dilated loops of intestines and vomiting, dehydration will be mainifested. Untreated intestinal obstructions lead to shock, kidney failure and ultimately death.
Diagnosis:The typical triad of colicky pain, vomiting and absolute constipation point out to acute intestinal obstruction. X-rays of the abdomen in erect posture and lateral position show multiple fluid levels and dilated bowel loops with air shadows.
Management: The patient is hospitalized,Nasogastric suction is initiated. Intravenous fluids are given rapidly to replenish the fluid loss and electrolyte imbalance. Fluid balance sheet, serum electrolytes, blood urea, serum creatinine, pulmonary wedge pressure are monitored. Antibiotics are administered. Once the general condition improves, the patient is taken up for surgery. The actual surgical treatment depends on the cause of obstruction. Adhesions and bands are removed., volvulus is untwisted, strictures are either bypassed or removed, hernias are repaired. Any gangrenous segment of the bowel is resected and the bowel is reanastomosed. Bolus obstructions and intussusceptions are dealt with accordingly. If the obstruction is due to malignant growths, a definitive surgical treatment may be undertaken then itself or if the patient's general condition is poor-a temporary bypass to the exterior is made and the definitive treatment is deferred until later.
Post operatively, the nasogastric suction is continued till the bowel recovers completely. Oral fluids and food are introduced slowly. The prognosis depends on the cause of obstruction and time taken from onset of the problem and intervention. Later the treatment, poorer the prognosis.