Small bowel obstruction
Classic presentations of small bowel obstruction include:
_ crampy abdominal pain
_ nausea and vomiting
_ abdominal distension
Patients with a proximal small bowel obstruction are likely to present early (within a day) with pain and vomiting; abdominal distension and constipation are less likely. Patients with a distal obstruction frequently have a more prolonged symptom complex with a 2-3-day history of crampy abdominal pain prior to vomiting; distension and constipation are predominant features. The bowel sounds are initially hyperactive and high-pitched. In delayed presentation, the bowel sounds may be reduced, indicating onset of secondary ileus. The symptom complex also varies with the underlying aetiology. Small bowel obstruction due to hernia tends to present early and more acutely with a tense and irreducible external hernia, that associated with a neoplasm is more indolent and that due to adhesions intermediate in presentation. Recognition of strangulated obstruction with bowel ischaemia and impending perforation is important. Clinical features of bowel ischaemia include constant and severe abdominal pain associated with tenderness and guarding, tachycardia, fever and leucocytosis.
In adhesive obstruction, surgery is indicated where there are concerns of intestinal ischaemia or the patient fails to improve after a short period of non-operative management. Constant, rather than intermittent, pain suggests bowel ischaemia. Bowel obstruction due to hernia in the inguinal or femoral area requires prompt surgery, as the bowel entrapped within the hernia can develop irreversible ischaemia and gangrene. Pre-operative preparations include adequate fluid and electrolyte replacement, prophylaxis with broadspectrum antibiotics covering aerobes and anaerobes, anti-thrombotic prophylaxis with compressive stockings and subcutaneous heparin.
Avoidance of aspiration pneumonitis is ensured with adequate nasogastric decompression and a rapidsequence induction of anaesthesia with cricoid pressure until the endotracheal tube has been inserted. Surgery is sometimes easy when a single adhesive band or an external hernia is the cause of obstruction, and surgery may be complex where there are dense adhesions. Closed-loop obstruction, with occlusion at both ends of the loop of bowel, may arise from torsion or complex adhesions of the small bowel, and obstructed external hernia. The intraluminal pressure rapidly rises and the risk of perforation is accelerated. The object at surgery is to find the junction of the dilated and collapsed bowel. The viability of a segment of intestine is determined by observation. In doubtful cases, a warm pack is placed over the bowel in question and the bowel re-examined several minutes later. If the bowel is not viable, a simple resection and primary anastomosis is performed. Sometimes, as with carcinomatosis or extensive pelvic adhesions, a side-to-side bypass is the better choice. Obstruction due to external hernia is usually dealt with through the herniorrhaphy incision. The entrapped bowel is examined prior to returning it to the general peritoneal cavity. The hernia is then repaired. Local signs of inflammation at the hernia site may indicate strangulation of the entrapped bowel or omentum.