Small bowel obstruction: Difference between revisions
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==Diagnosis== | ==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=== | ||
*'''Xray''' | |||
**[[Acute Abdominal Series]] | **[[Acute Abdominal Series]] | ||
**Upright chest film: rule out free air | |||
**Upright abd film: air-fluid levels: [[File:Peds_SBO.JPG|thumb|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<ref>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</ref> | |||
*** Sen 75% Spec 66% +LR 1.6 -LR 0.43 | |||
***Air in colon or rectum makes complete obstruction less likely (esp if symptoms >24hr) | ***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 | ***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<ref | |||
*** Modern CT Scanner (0.75mm slices): Sen 96%, Spec 100%, +LR infinity -LR 0.04 | *** 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 | *** Historical CT scanner meta-analysis: Sen 87% Spec 81%, +LR 3.6 -LR 0.18 | ||
*[[Ultrasound: Abdomen|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 | *** Sen 92%, Spec 89% +LR 6.7 -LR 0.11 | ||
Revision as of 19:26, 23 October 2015
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
- Studies suggest that auscultating bowel sounds is not clinically useful to differentiate between normal and pathologic[1]
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
Imaging
- Xray
- Acute Abdominal Series
- Upright chest film: rule out 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[2]
- 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 indicatedCite error: Invalid
<ref>tag; invalid names, e.g. too many
- ↑ Felder S, Margel D, Murrell Z, et al. Usefulness of Bowel Sound Auscultation: A Prospective Evaluation. J Surg. 2014; 71(5):768–773.
- ↑ 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