Table Of Contents
Small Bowel Obstruction (SBO)
Small bowel obstruction (SBO) is obstruction of the gastrointestinal tract at the level of the small intestine. It is a common surgical condition. It is mostly caused by mechanical obstruction of the bowel (intraluminal or extraluminal). Aetiology varies from region to region. The most common being adhesions from prior abdominal surgery (accounts for 75% in the west and 25% in sub-Saharan Africa). Other common causes include small bowel volvulus, ileal knotting (compound volvulus) and intestinal parasites e.g. Ascariasis. Small bowel volvulus, though uncommon, can obstruct the bowel, block mesenteric vessels and result in bowel ischemia. Symptoms that are progressive and chronic may point to a neoplasm. Obstruction due to adhesions and volvulus tends to be more acute. It is important to find out whether the patient has intestinal ischemia due to bowel strangulation (persistent tachycardia, writhing pain and focal tenderness).
Classification of Small Bowel Obstruction
| Classification | Description |
|---|---|
| Complete bowel obstruction | Obstruction with vomiting or distension, but with no passage of any flatus or stool (obstipation). More surgically urgent |
| Partial bowel obstruction | Obstruction with vomiting or distention, but continues to pass flatus and liquid stool |
Causes of Small Bowel Obstruction
| Classification | Examples of causes |
|---|---|
| Intrinsic | Neoplasm (benign or malignant, primary or metastatic), hematoma, inflammatory disease (Crohn’s), infectious disease (tuberculosis), intussusception, ischemia (stricture), congenital (webs, malrotation, Meckel’s diverticulum) |
| Extrinsic | Adhesions, hernias, small bowel volvulus, ileal knotting, ileosigmoid knotting, endometrioma, hematoma, abdominal or pelvic tumor |
| Intraluminal | Parasites (ascariasis), foreign bodies, bezoars, gallstone (gallstone ileus) |
Forms of Small Bowel Volvulus
| Forms of volvulus | Description |
|---|---|
| Malrotation | The small intestine twists about its mesentery |
| Knotting | One portion of the intestine wraps around the others as ileo-ileal knots (ileal knotting) or ileo-sigmoid knots (compound volvulus) |
Clinical features of SBO
| Clinical feature | Signs and symptoms |
|---|---|
| Cardinal signs and symptoms | Crampy abdominal pain, distention, vomiting, diarrhoea followed by obstipation |
| Signs of proximal obstruction | More acute and severe pain, bilious vomiting |
| Signs of distal obstruciton | Longer lasting subacute pain, severe abdominal distention |
- Common causes of SBO
- Surgical adhesions (MCC)
- Small bowel tumor
- Hernia
- IBD
- Volvulus
- Causes of SBO in Paediatrics
- Congenital atresia
- Pyloric stenosis
- Intussusception (can be deadly)
- Signs and symptoms
- Abdominal pain
- Periumbilical (Visceral small bowel is midgut in origin)
- Diffuse pain
- Localized pain (may point to ischemic bowel or a different cause)
- Colicky in nature (early – reflects contractions and peristalsis against the obstruction)
- Constant (may indicate bowel ischemia)
- Vomiting
- Abdominal distention (varies based on the level of obstruction – proximal obstruction may have little or no distention)
- Obstipation or decreased passage of flatus or stool
- Abdominal pain
- Physical examination
- Abdominal wall for surgical scars or hernias
- Signs of peritonitis (indicates immediate operation after fluid resuscitations)
- Hemodynamic instability (hypotension and tachycardia may be due to hypovolemia, poor oral intake or fluid sequestration in the bowel wall. If hemodynamic instability does not improve with fluid resuscitation the patient may have septic shock from ischemia or perforation)
- Distension with tympanic percussion (uncomplicated obstruction)
- Minimal tenderness (uncomplicated obstruction)
- Investigations
- Abdominal X-ray (upright): 67% sensitivity and 83% specificity (proximal obstruction and fluid-filled bowel may mask the presence of small bowel obstruction
- Distended loops of small bowel (> 3 cm)
- Air-fluid levels
- Lack of gas in the colon (if there is gas in the colon the cause could be large bowel obstruction or ileus)
- CT scan abdomen: better sensitivity and specificity than X-ray. Can give better insight into the cause e.g. adhesion vs neoplasm. May help operative planning. Can detect ischemia.
- Small bowel follow-through (SBFT) contrast study: Using Gastrograffin to evaluate the progression of contrast through the small bowel. Enables early identification of patients who need surgery and predicts those who will respond to non-operative treatment
- Contrast within the colon by 24 hours: no obstruction or resolved obstruction (97% sensitivity and 96% specificity for adhesive small bowel obstruction)
- CBC
- U/E/Cs
- Amylase
- Urinalysis
- B-hCG
- Occult stool test: blood raises suspicion for strangulation
- Abdominal X-ray (upright): 67% sensitivity and 83% specificity (proximal obstruction and fluid-filled bowel may mask the presence of small bowel obstruction
- Initial treatment
- Admit for observation (mechanical obstruction usually resolves in 3 days)
- Correct fluid and electrolyte losses (replace volume deficits): Normal saline is fluid of choice
- Vasopressor support, antibiotics and plan for surgery in patients with septic shock
- Indication for non-operative management
- Partial small bowel obstruction due to adhesions, or other aetiologies amenable to medical treatment e.g. Ascariasis, Crohns, with no evidence of bowel ischemia
- Indications for operative management
- Obstructive process that will not resolve spontaneously: obstructing masses, volvulus, hernia
- Non-operative treatment
- Nil per oral
- Nasogastric tube (decompress proximal GI tract and relive vomiting)
- IV fluids to replace losses and maintenance
- Monitor electrolytes (if there are specific derangements or their is high NGT output)
- Serial abdominal examination (ideally by the same clinician to detect evolving bowel ischemia)
- Serial CBC for WBC count
- SBFT may be used
- Should resolve within 3 days (complications rates rise when non-operative therapy is extended beyond 72 hours)
- Signs of resolution in non-operative treatment
- Improvement in symptoms with passage of gas and decreasing abdominal distention
- Reduced NGT output and transition from bilious to non-bilious
- Operative treatment
- Fluid resuscitation and correct electrolyte abnormalities
- NGT to decompress stomach (reduces risk of aspiration at induction. RSI is used)
- Pre-operative antibiotics (broad-spectrum and cover GP, GN and anaerobes)
- Laparoscopic approach
- Open approach (laparotomy): midline incision provides good access to the length of the small intestine
- Adhesiolysis
- Resection and anastomosis of non-viable bowl
- Ileostomy can be performed if there is instability or gross intraperitoneal contamination
- Inspect the bowel from ligament of treitz to the cecum for points of obstruction and iatrogenic injury
- Post-operative (admission) notes
- Nasogastric tube
- Bowel rest (prolonged bowel rest is rarely needed unless the patient develops ileus)
- Remove NGT if output is minimal
- Advance diet as tolerated
- Complications
- Intestinal ischemia: suggested by elevated WBC, lactic acidosis (anion gap on ABG), and CRP > 75 mg/dL
- Hypovolemic shock
- Hypokalemic, hypochloremic, metabolic alkalosis due to persistent vomiting
- CT-scan findings indicative of intestinal ischemia
- 500ml of free fluid or dense fluid (> 10 HU)
- Oedema in the mesentery
- Decreased contrast enhancement of the bowel wall
- Thickened loops of small bowel
- Pneumatosis intestinalis (air within the bowel wall)
- Free air
- Portal venous gas
Visible peristalsis
**https://youtu.be/M8v9ZLnNHnU**
