Small bowel obstruction

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)

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
      • 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	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)