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
- Pts may pass flatus/stool initially
- 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
- Abdominal aortic aneurysm
- Acute gastroenteritis
- Aortoenteric fisulta
- Appendicitis (early)
- Bowel obstruction
- Bowel perforation
- Diabetic ketoacidosis
- Gastroparesis
- Hernia
- Hypercalcemia
- Inflammatory bowel disease
- Mesenteric ischemia
- Pancreatitis
- Peritonitis
- Sickle cell crisis
- Spontaneous bacterial peritonitis
- Volvulus
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
- CBC
- Imaging
- Acute Abdominal Series
- Films
- Upright chest film: r/o free air
- Upright abd film: air-fluid levels:
- 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
- Films
- 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
- Acute Abdominal Series
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 | |
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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
- ↑ 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