Small bowel obstruction

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

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

Differential Diagnosis

Diffuse Abdominal pain

• Abdominal aortic aneurysm
  • Aortocaval fistula
• Acute gastroenteritis
• Aortoenteric fisulta
• Appendicitis (early)
• Bowel obstruction
  • Large bowel obstruction
    • Ogilvie's syndrome
  • Small bowel obstruction
• Bowel perforation
• Gastroparesis
• Diabetic ketoacidosis
• Inflammatory bowel disease
• Mesenteric ischemia
• Pancreatitis
• Peritonitis
• Sickle cell crisis
• Spontaneous bacterial peritonitis
• Volvulus

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
  • 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
  • Diagnostic and therapeutic
  • 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%
• Avoid barium as it becomes inspissated in bowel, causing complete obstruction
  • 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

Operative Management

• 25% of patients 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	Metronidazole 500mg IV q8hrs Plus one of the following: Ceftriaxone 1g IV once daily Ciprofloxacin 400mg IV q12hrs Cefazolin 1g (30mg/kg) IV q8hrs Levofloxacin 750mg IV once daily	Metronidazole 500mg IV q8h + Vancomycin 15mg/kg/dose IV q12h (Max dose = 1500mg) Plus one of the following: Piperacillin/tazobactam 4.5g IV q6h Ertapenem 1g IV q24h Ceftriaxone 1g IV q24h	One of the following: Piperacillin-tazobactam Ticarcillin-clavulanate 3.1 g IV every 6 hours Ertapenem 1 g every 24 hours Moxifloxacin 400 mg IV every 24 hours
Allergy or prior exposure	Piperacillin/Tazobactam 4.5g (80mg/kg) IV q8hrs OR Metronidazole 500mg IV q8hrs PLUS Cefepime 2g IV once daily OR Ciprofloxacin 400mg IV q12hrs OR Levofloxacin 750mg IV once daily Meropenem 1g (20mg/kg) IV q8hrs OR Doripenem 500mg IV q8hrs OR Aztreonam 2g (30mg/kg) IV q8hrs + Metronidazole 500mg IV q8hrs	aztreonam 2g IV q8h + metronidazole 500mg IV q8h +/- vancomycin 15mg/kg/dose IV q12h (Max dose = 1500mg)

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

• Malignant bowel obstruction
• Small Bowel Obstruction (SBO)
• Volvulus (Adults)
• Volvulus (Peds)

References

Authors

Ross Donaldson