Small bowel obstruction

Background

1. SBO without hx of surgery, no hernia is malignancy until proven otherwise
2. "Never let the sun rise or set on a small bowel obstruction"

Causes

1. Adhesions (Hx of previous abdominal surgeries +LR 3.86 and -LR 0.19)
2. Hernia
3. Malignancy
4. Intraluminal strictures
   1. Crohn's disease
   2. Radiation therapy
   3. Mesenteric ischemia
5. Intussusception (due to lymphoma as lead point)
6. Foreign body (bezoars)
7. Trauma (duodenal hematoma)
8. Gallstone ileus

Clinical Manifestations

1. Abdominal pain
   1. Crampy
   2. Periumbilical or diffuse
   3. Paroxysms of pain occur q5min
2. Vomiting
   1. More common in proximal than distal obstruction
   2. Bilious (proximal) or feculent (distal ileal)
      1. Abdominal pain relieved with vomiting positively predictive +LR (4.50-2.82) -LR (0.78-0.35)
3. Abdominal distention
   1. Seen more in distal than proximal obstruction
   2. +LR (16.8-5.64) -LR (0.43-0.34)
4. Inability to pass flatus
   1. Pts may pass flatus/stool initially
      1. Takes 12-24hrs for colon to empty
      2. History of constipation +LR 8.8 and -LR 0.59
5. Dehydration
6. Anorexia
7. Ischemia (when intraluminal pressure exceeds venous pressure in bowel wall)
   1. Fever
   2. Leukocytosis
8. Abnormal Bowel sounds
   1. 1. +LR 6.33 -LR 0.27

Diagnosis

1. Labs
   1. CBC
      1. WBC >20K suggests bowel gangrene, abscess, or peritonitis
      2. WBC >40K suggests mesenteric vascular occlusion
   2. Chemistry - degree of dehydration, evidence of ischemia (acidosis)
   3. Lactate - Sn (90-100%), though not Sp marker of strangulation
2. Imaging
   1. Acute Abdominal Series
      1. Films
         1. Upright chest film: r/o free air
         2. Upright abd film: air-fluid levels
         3. Supine abd film: width of bowel loops most visible (estimate of amount of distention)
         4. Sen 75% Spec 66% +LR 1.6 -LR 0.43
      2. Air in colon or rectum makes complete obstruction less likely (esp if symptoms >24hr)
      3. If pt does not tolerate upright position left lateral decub abd film can substitute
   2. CT A/P with IV contrast
      1. Consider if plain films are non-diagnostic
      2. Can show closed-loop obstruction, evidence of ischemia
      3. Per American College of Radiology PO contrast is no longer indicated
      4. Modern CT Scanner (0.75mm slices): Sen 96%, Spec 100%, +LR infinity -LR 0.04
      5. Historical CT scanner metanalysis: Sen 87% Spec 81%, +LR 3.6 -LR 0.18
   3. Ultrasound for SBO
      1. Sen 97%, Spec 90%, +LR 9.5, -LR 0.04 (four studies, 2 done by EM residents and 2 by radiology residents)
   4. MRI for SBO
      1. Sen 92%, Spec 89% +LR 6.7 -LR 0.11

Treatment

1. IV fluid resuscitation with electrolyte repletion
2. Assessment of need for operative vs nonoperative management
   1. Nonoperative Management
      1. Sometimes successful in patients with partial SBO (must rule-out strangulation first)
      2. NG tube
         1. 14 French
         2. Intermittent low wall suction
         3. Nasogastric fluid losses can be replaced w/ NS + KCL (30-40 meq)
      3. Contrast
         1. Both diagnostic and therapeutic (draws water into the bowel stimulating peristalsis)
         2. Associated with decreased hospital stay, more rapid resolution of symptoms
      4. If increasing pain, distention, or peristent high NGT output, consider sx
      5. Repeat CT scan may be helpful to detect early signs of bowel ischemia
         1. Repeat plain films are not helpful (only detect perforation)
   2. Operative Management
      1. 25% of pts admitted for SBO require surgery
      2. Indicated for pts with:
         1. Complete SBO
         2. Closed-loop obstruction
            1. E.g. incarcerated hernia
         3. Fever, leukocytosis, peritonitis
3. Abx
   1. Indicated if e/o ischemia or infection
      1. Piperacillin-tazobactam 3.375gm IV q6hr OR
      2. Ampicillin-sulbactam 3gm IV q6hr

Source

• UpToDate
• Tintinalli
• ACR Appropriateness Criteria for suspected SBO (guidelines.gov/content.aspx?id=32636)
• Academic Emergency Medicine June 2013, Vol. 20, No. 6 Evidence-Based Diagnostics Series "Adult Small Bowel Obstructions" Taylor and Lalani