Small bowel obstruction

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Background

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

Causes

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

Clinical Features

  • Abdominal pain
    • Colicky
    • Periumbilical or diffuse
    • Paroxysms of pain occur q5min
  • Vomiting
    • More common in proximal than distal obstruction
    • Bilious (proximal) or feculent (distal ileal)
      • Abdominal pain relieved with vomiting positively predictive +LR (4.50-2.82) -LR (0.78-0.35)
  • Abdominal distention
    • Seen more in distal than proximal obstruction
    • +LR (16.8-5.64) -LR (0.43-0.34)
  • Inability to pass flatus
    • Pts may pass flatus/stool initially
      • Takes 12-24hrs for colon to empty
      • History of constipation +LR 8.8 and -LR 0.59
  • Dehydration
  • Anorexia
  • Ischemia (increased intraluminal pressure initially leads to venous obstruction, progresses to frank arterial ischemia)
    • Fever
    • Leukocytosis
  • Abnormal Bowel sounds (+LR 6.33 -LR 0.27)

Differential Diagnosis

Diffuse Abdominal pain

Diagnosis

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

Treatment

Volume Resuscitation

  • IV fluid resuscitation with electrolyte repletion
  • Assessment of need for operative vs nonoperative management

Nonoperative Management

  • Sometimes successful in patients with partial SBO (must rule-out strangulation first)
  • If increasing pain, distention, or peristent high NGT output, consider surgery

NG tube

  • 14 French
    • Intermittent low wall suction
  • Nasogastric fluid losses can be replaced w/ NS + KCL (30-40 meq)

Contrast

  • Both diagnostic and therapeutic (draws water into the bowel stimulating peristalsis)
  • Associated with decreased hospital stay, more rapid resolution of symptoms
  • Repeat CT scan may be helpful to detect early signs of bowel ischemia
    • Repeat plain films are not helpful (only detect perforation)

Operative Management

  • 25% of pts admitted for SBO require surgery. Surgery is indicated for patients withh:
  • Complete SBO
  • Closed-loop obstruction (incarcerated hernia)
  • Fever, leukocytosis, peritonitis

Antibiotics

Indicated if evidence of ischemia or infection

Intra-Abdominal Sepsis/Peritonitis

Harbor-UCLA Santa Monica-UCLA Other
Primary
Allergy or prior exposure

In Pallatiave Medicine

In the context of advancing malignancy with widespread peritoneal metastases, bowel obstruction is common and often indicates a poor prognosis. A less interventional and more comfort based approach to treatment may be appropriate. See Malignant bowel obstruction for details.

References

  1. Maglinte DDT, Reyes BL, Harmon BH, et al. Reliability and role of plain film radiography and CT in the diagnosis of small-bowel obstruction. AJR 1996; 167:1451-1455