SBO Management

• Risk factors for small bowel obstruction


  • Prior abdominal or pelvic surgery (risk for adhesion formation)
  • Abdominal wall or groin hernia
  • Intestinal inflammation (eg, Crohn disease)
  • History of or increased risk for neoplasm
  • Prior abdominopelvic irradiation
  • History of foreign body ingestion
• Symptoms of bowel obstruction

  • Vomiting
  • Pain
  • Constipation
• Vomiting in bowel obstruction

  • Occurs even if nothing is taken by mouth because saliva and other GI secretions continue to be produced and enter the stomach
  • Vomiting of semi digested food eaten a day or two earlier suggests gastric outlet obstruction
  • Copious vomiting of bile-stained fluid suggests upper small bowel obstruction
  • If the vomitus becomes thicker and foul-smelling (faeculent), more distal obstruction is likely and this change is often an indication for urgent operation
• Pain in bowel obstruction


  • Fluid and swallowed air proximal to an obstruction in combination with continuing peristalsis cause pain
  • Pain may not always be the most prominent symptom, but when it does occur, it is usually colicky, occurring in short-lived bouts as peristalsis attempts to overcome the obstruction
• Constipation in bowel obstruction

  Absolute constipation, that is, no faeces or flatus passed rectally, is pathognomonic of obstruction
• Physical signs of bowel obstruction

  • Dehydration
  • Abdominal distension
  • Visible peristalsis
  • Abdominal tenderness
  • Central resonance to percussion with dullness in the flanks
  • Abnormal bowel sounds
• Most common causes of mechanical small bowel obstruction

  • Adhesions
  • Tumors
  • Complicated hernias
• Less frequent causes of small bowel obstruction

  • Crohn disease
  • Gallstones
  • Volvulus
  • Intussusception
• Causes of mechanical small bowel obstruction

  • Extrinsic to the bowel (eg, adhesions, hernia, volvulus)
  • Within the wall of the bowel (eg, tumor, stricture, intramural hematoma)
  • Luminal defect that prevents the passage of gastrointestinal contents (eg, intussusception, gallstones, foreign body)
• Pathophysiology of mechanical bowel obstruction


  1. Obstruction leads to progressive dilation of the intestine proximal to the blockage

  2. Distal to the blockage, the bowel will decompress

  3. Swallowed air and gas from bacterial fermentation can accumulate, adding to bowel distention

  4. Bowel wall becomes edematous, normal absorptive function is lost, and fluid is sequestered into the bowel lumen

  5. There may also be transudative loss of fluid from the intestinal lumen into the peritoneal cavity

  6. Ischemic necrosis of the bowel is most commonly caused by twisting of the bowel and/or its mesentery around an adhesive band or intestinal attachments

  7. Incidence of ischemia is significantly increased with a closed loop obstruction

  8. If bowel dilation is excessive, the intramural vessels of the small intestine become compromised and perfusion to the wall of the intestine is reduced

  9. With proximal bowel obstruction, ongoing emesis leads to additional loss of fluid containing Na, K, H, and Cl; metabolic alkalosis; and, if ignored, paradoxical aciduria

  10. Fluid losses can result in hypovolemia

  11. Bacterial overgrowth can also occur in the proximal small bowel, which is normally nearly sterile, and emesis can become feculent
• Laboratory investigations for small bowel obstruction

  • Complete blood count with differential
  • Electrolytes, including blood urea nitrogen and creatinine
  • Arterial blood gas
  • Serum lactate
  • Blood cultures
  • Procalcitonin
• Abdominal X-ray findings in small bowel obstruction vs large bowel obstruction

  Small bowel obstruction:

  • Centrally located,
  • Dilated small bowel > 3 cm,
  • Paucity of colorectal gas,
  • Stretch sign,
  • Gasless abdomen,
  • Dilated stomach

  
  

  Large bowel obstruction:

  • Peripherally located,
  • Dilated colon>6 cm or cecum>9 cm,
  • Paucity of rectal gas,
  • +/− small bowel dilation,
  • Large bowel has haustral folds that do not span the entire diameter of the bowel
• Initial non-surgical management of small bowel obstruction

  1. Admission and surgical consultation

  2. Fluid resuscitation with isotonic crystalloid

  3. Nil per os (NPO) diet

  4. Gastrointestinal decompression with nasogastric tube if significant distension, nausea, and/or vomiting

  5. Analgesia
• Paucity


  Lack or scarcity
• Small bowel obstruction


  • Obstruction prevents the passage of stool and gas through the distal ileum and rectum
  • Results in a paucity of gas in the rectum
• Initial management of small bowel obstruction (non-surgical)


  1. Admission and surgical consultation

  2. Fluid resuscitation

  3. Diet - Nil per os (NPO)

  4. Gastrointestinal decompression

  5. Analgesia and antiemetic management

  6. Antibiotics
• CT scan with IV contrast

  • Better visualize the extent and cause of the obstruction
  • Assess for any complications
• Laboratory studies


  • Repeated as indicated by clinical parameters
  • To ensure replacement therapy is effective for severe electrolyte or acid-base disturbances
  • Repeat white blood cell count may be helpful if there is concern for bowel ischemia and/or strangulation
• Indications for immediate surgery

  • Suspected bowel compromise (perforation, necrosis, or ischemia)
  • Closed loop obstruction
  • Acute incarcerated hernia
  • Intussusception
  • Gallstone ileus
  • Foreign body ingestion
  • Small bowel tumor
• Clinical signs of bowel ischemia

  • Fever
  • Leukocytosis
  • Tachycardia that does not respond to fluid resuscitation
  • Continuous or worsening abdominal pain, sometimes out of proportion to examination
  • Metabolic and lactic acidosis
  • Tachypnea
  • Peritonitis
  • Systemic inflammatory response syndrome (SIRS)
• Surgical management of bowel obstruction

  1. Remove the obstruction and restore normal bowel function

  2. Resecting the obstructed segment

  3. Repairing damaged tissues

  4. Bypassing the obstruction through the use of a colostomy or ileostomy
• Resection and anastomosis


  The obstructed segment of the intestine is surgically removed and the remaining healthy sections are anastomosed (sutured together) to create a new continuity of the intestinal tract
• Bypass (ileostomy or colostomy)


  The healthy intestine is rerouted around the obstruction, allowing the feces to pass through
• Colostomy


  Diverting the fecal stream from the colon (large intestine) to the abdominal wall
• Ileostomy


  Diverting the fecal stream from the terminal ileum (part of the small intestine)
• Stoma


  A surgically created opening on the abdominal wall that allows for the diversion of bodily waste outside the body
• A stoma is often temporary, serving as a way to divert the fecal stream and allow the intestines to heal from an obstruction or injury
• Adhesive small bowel obstruction

  Caused by intra-abdominal adhesions most commonly caused by prior abdominal surgeries or previous episodes of abdominal inflammation
• Non-adhesive small bowel obstruction


  Typically diagnosed by imaging studies (e.g., the presence of inflammation or abscess)
• In industrialized nations, adhesive small bowel obstruction is more prevalent than non-adhesive small bowel obstruction
• Water-soluble contrast


  Hypertonic water-soluble gastrointestinal contrast agents (e.g., Gastrografin) may be therapeutic for patients with adhesive small bowel obstruction
• Additional adjuncts in nonoperative management of adhesive small bowel obstruction

  • Magnesium oxide
  • Simethicone
• Serial monitoring of patients with small bowel obstruction

  1. Resolution of small bowel obstruction

  2. Patient remains stable but signs and symptoms persist

  3. Patient deteriorates and requires immediate surgical exploration
• Laboratory studies


  • Repeated as indicated by clinical parameters
  • To ensure replacement therapy is effective for severe electrolyte or acid-base disturbances
• Follow-up imaging


  Abdominal plain radiographs may be useful for assessing whether the obstruction has resolved by demonstrating that gas or oral contrast has passed from the small bowel into the colon
• Complete adhesive small bowel obstruction is associated with a higher failure rate of nonoperative management and a higher requirement for small bowel resection
• Postoperative small bowel obstruction

  • Small bowel obstruction that occurs within 4 to 6 weeks of an abdominal surgery
  • Adhesions associated with early postoperative bowel obstruction rarely lead to strangulation
  • After 10 to 14 days postoperatively, adhesions are dense and hypervascular, making reoperation difficult
• Postoperative small bowel obstruction should be treated nonoperatively and for a duration longer than non-postoperative small bowel obstruction, in the absence of clinical deterioration