Small bowel obstruction

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Background

  • Small bowel obstruction without history of surgery or hernia is malignancy until proven otherwise
  • "Never let the sun rise or set on a small bowel obstruction"

Causes

  • Adhesions (history of previous abdominal surgeries +LR 3.86 and -LR 0.19)
  • Hernia
    • Port hernias can occur after laparoscopic surgery
  • 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
  • Small bowel volvulus (3-6% of causes of SBO)[1]

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
    • 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
    • Studies suggest that auscultating bowel sounds is not clinically useful to differentiate between normal and pathologic[2]

Differential Diagnosis

Diffuse Abdominal pain

Evaluation

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 - sensitive (90-100%), though not specific marker of strangulation

Imaging

  • Xray
    • Acute Abdominal Series
    • Upright chest film: rule out free air
    • Upright abdominal film: air-fluid levels:
      Peds SBO
    • Supine abdominal 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[3]
    • Small bowel diameter ≥3cm is associated with obstruction
      • 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 patient does not tolerate upright position left lateral decub abdominal 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

Management

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 with 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)

Gastrografin PO

  • Alternative to operative management if early obstructive process
  • Gastrografin through NG or OG decreases bowel wall edema and increases bowel motility[4]
    • Diagnostic and therapeutic[5]
    • 100 cc of gastrografin through NG tube
    • Transit may be observed through serial radiographs
      • Contrast within the large bowel within 24 hrs suggest partial SBO
      • Contrast failing to reach large bowel within 24-48 hrs suggests complete obstruction, requiring laparotomy
    • Therapeutic, may reduce necessary operative rate by ~75%[6]
  • Avoid barium as it becomes inspissated in bowel, causing complete obstruction[7]
    • If perforation occurs with barium, leakage can be lethal
    • Gastrografin is water-soluble and relatively safer if perforation occurs
    • Be aware that anaphylactoid reactions and serious aspirations have occurred rarely with Gastrografin, however[8]

Operative Management

  • 25% of patients admitted for SBO require surgery. Surgery is indicated for patients withh:
  • Complete SBO
  • Closed-loop obstruction (incarcerated hernia, small bowel volvulus)
  • 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

Disposition

  • Admit

Prognosis

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

See Also

References

  1. Roline CE and Reardon RF. Disorders of the Small Intestine. Rosen's. Edition 8. Chapter 92. 2014. 1216-1224.
  2. Felder S, Margel D, Murrell Z, et al. Usefulness of Bowel Sound Auscultation: A Prospective Evaluation. J Surg. 2014; 71(5):768–773.
  3. 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
  4. Assalia A, Schein M, Kopelman D, et al. Therapeutic effect of oral Gastrografin in adhesive, partial small-bowel obstruction: A prospective randomized trial. Surgery 1994; 115: 433-437.
  5. Chen SC, Lin FY, Lee PH, et al. Water-soluble contrast study predicts the need for early surgery in adhesive small bowel obstruction. Br J Surg 1998; 85: 1692-1694.
  6. Choi HK et al. Therapeutic Value of Gastrografin in Adhesive Small Bowel Obstruction After Unsuccessful Conservative Treatment: A Prospective Randomized Trial. Annals of Surgery. 2002;236(1).
  7. Choi HK et al. Therapeutic Value of Gastrografin in Adhesive Small Bowel Obstruction After Unsuccessful Conservative Treatment: A Prospective Randomized Trial. Annals of Surgery. 2002;236(1).
  8. Skucas J. Anaphylactoid reactions with gastrointestinal contrast media. AJR Am J Roentgenol 1997; 168: 962-964.