Small bowel obstruction: Difference between revisions
(Major update: CT transition point, strangulation signs, Gastrografin challenge evidence, closed-loop obstruction, nonoperative management criteria, classification, references with PMIDs) |
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==Background== | ==Background== | ||
*Mechanical obstruction of the small intestine preventing normal passage of intestinal contents | *Mechanical obstruction of the small intestine preventing normal passage of intestinal contents | ||
* | *Adhesions from prior surgery are the most common cause (60-75% of all SBO) | ||
*Second most common cause: | *Second most common cause: incarcerated [[hernia]] (~15%) | ||
*Other causes: malignancy, [[Crohn's disease]], [[intussusception]], volvulus, gallstone ileus, foreign body, stricture | *Other causes: malignancy, [[Crohn's disease]], [[intussusception]], volvulus, gallstone ileus, foreign body, stricture | ||
* | *Closed-loop obstruction: segment of bowel obstructed at two points → rapid progression to strangulation and ischemia | ||
*SBO accounts for ~15% of ED visits for acute abdominal pain | *SBO accounts for ~15% of ED visits for acute abdominal pain | ||
*Mortality: <5% for simple SBO; | *Mortality: <5% for simple SBO; up to 25% for strangulated SBO | ||
===Classification=== | ===Classification=== | ||
* | *Partial: some gas/fluid passes through → flatus may be present | ||
* | *Complete: no passage of gas or stool | ||
* | *Simple: obstruction without vascular compromise | ||
* | *Strangulated: obstruction with compromised blood supply → ischemia → necrosis → perforation | ||
==Clinical Features== | ==Clinical Features== | ||
* | *Crampy, intermittent abdominal pain (colicky; occurs in waves) | ||
* | *Nausea and vomiting (the more proximal the obstruction, the earlier and more prominent the vomiting) | ||
* | *Obstipation (absence of flatus and stool) — complete obstruction | ||
* | *Abdominal distension (more prominent with distal obstruction) | ||
* | *High-pitched, hyperactive bowel sounds → late: absent bowel sounds (ileus from ischemia) | ||
* | *Prior surgical history — ask about ALL prior abdominal/pelvic operations | ||
*Tachycardia, dehydration from third-spacing and vomiting | *Tachycardia, dehydration from third-spacing and vomiting | ||
===Signs of Strangulation (Surgical Emergency)=== | ===Signs of Strangulation (Surgical Emergency)=== | ||
* | *Constant, severe pain (no longer colicky) | ||
* | *Fever | ||
* | *Peritoneal signs (rebound, guarding) | ||
* | *Tachycardia, hypotension | ||
* | *Leukocytosis with left shift | ||
* | *Elevated lactate | ||
* | *No single clinical or lab finding reliably rules out strangulation | ||
==Differential Diagnosis== | ==Differential Diagnosis== | ||
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==Evaluation== | ==Evaluation== | ||
===Labs=== | ===Labs=== | ||
* | *BMP: electrolytes (hypokalemia, metabolic alkalosis from vomiting), BUN/Cr (dehydration), bicarbonate | ||
* | *CBC: leukocytosis (consider strangulation if WBC >15,000) | ||
* | *Lactate: elevated suggests bowel ischemia (but normal lactate does NOT exclude strangulation) | ||
* | *Lipase: rule out [[pancreatitis]] | ||
* | *Type and screen if surgery likely | ||
===Imaging=== | ===Imaging=== | ||
====Abdominal X-ray==== | ====Abdominal X-ray==== | ||
* | *Sensitivity ~60-70% for SBO | ||
*Findings: dilated small bowel loops ( | *Findings: dilated small bowel loops (> 3 cm), air-fluid levels on upright, absence of colonic gas | ||
* | *Three film series (supine, upright, CXR): may show free air if perforated | ||
* | *Normal X-ray does NOT exclude SBO | ||
====CT Abdomen/Pelvis with IV Contrast (Test of Choice)==== | ====CT Abdomen/Pelvis with IV Contrast (Test of Choice)==== | ||
* | *Sensitivity 90-95% for SBO | ||
*Identifies: | *Identifies: | ||
** | **Transition point (dilated proximal → decompressed distal bowel) | ||
**Cause of obstruction (adhesion, hernia, mass, volvulus) | **Cause of obstruction (adhesion, hernia, mass, volvulus) | ||
** | **Signs of strangulation: bowel wall thickening, mesenteric haziness/fluid, decreased/absent bowel wall enhancement, pneumatosis intestinalis, portal venous gas | ||
* | *Oral contrast NOT needed (pooled intraluminal fluid serves as natural contrast) | ||
* | *Small bowel feces sign: particulate material in dilated SB (distal/complete obstruction) | ||
==Management== | ==Management== | ||
===Initial Resuscitation=== | ===Initial Resuscitation=== | ||
* | *NPO | ||
* | *Aggressive IV fluid resuscitation (NS or LR) — patients are often significantly volume depleted | ||
* | *Electrolyte correction (K, Mg replacement) | ||
* | *NG tube decompression: for persistent vomiting, significant distension | ||
* | *Pain control: IV opioids as needed; ketorolac | ||
* | *Antiemetics: ondansetron 4 mg IV | ||
===Nonoperative Management (Adhesive SBO without Strangulation)=== | ===Nonoperative Management (Adhesive SBO without Strangulation)=== | ||
* | *Trial of nonoperative management for partial, adhesive SBO without signs of strangulation | ||
*NG decompression + IV fluids + bowel rest | *NG decompression + IV fluids + bowel rest | ||
* | *Water-soluble contrast challenge (Gastrografin): | ||
**100 mL PO/via NGT | **100 mL PO/via NGT | ||
**If contrast reaches | **If contrast reaches colon by 24 hours → predicts resolution with nonoperative management (sensitivity ~97%)<ref>Abbas S, et al. Water-soluble contrast in management of adhesive small bowel obstruction. ''Cochrane Database Syst Rev''. 2007;(3):CD005598. PMID 17636810</ref> | ||
**May also have therapeutic effect (osmotic — draws fluid into lumen, stimulates peristalsis) | **May also have therapeutic effect (osmotic — draws fluid into lumen, stimulates peristalsis) | ||
* | *~70-80% of adhesive SBO resolves with conservative management | ||
* | *Failure of nonoperative trial: no improvement in 24-72 hours → surgery | ||
===Surgical Management=== | ===Surgical Management=== | ||
* | *Indications for emergent surgery: | ||
** | **Complete obstruction | ||
** | **Signs of strangulation/peritonitis | ||
** | **Incarcerated/strangulated hernia | ||
** | **Closed-loop obstruction on CT | ||
** | **Hemodynamic instability not responding to resuscitation | ||
** | **Failure of nonoperative management | ||
*Surgical consult | *Surgical consult early for all cases (even if initially managed conservatively) | ||
==Disposition== | ==Disposition== | ||
* | *Admit all patients with SBO | ||
* | *Surgical consultation in ED for all patients | ||
* | *ICU if septic, hemodynamically unstable, or peritonitic | ||
*Serial abdominal exams every 4-8 hours | *Serial abdominal exams every 4-8 hours | ||
*Repeat imaging if clinical deterioration | *Repeat imaging if clinical deterioration | ||
Latest revision as of 09:30, 22 March 2026
Background
- Mechanical obstruction of the small intestine preventing normal passage of intestinal contents
- Adhesions from prior surgery are the most common cause (60-75% of all SBO)
- Second most common cause: incarcerated hernia (~15%)
- Other causes: malignancy, Crohn's disease, intussusception, volvulus, gallstone ileus, foreign body, stricture
- Closed-loop obstruction: segment of bowel obstructed at two points → rapid progression to strangulation and ischemia
- SBO accounts for ~15% of ED visits for acute abdominal pain
- Mortality: <5% for simple SBO; up to 25% for strangulated SBO
Classification
- Partial: some gas/fluid passes through → flatus may be present
- Complete: no passage of gas or stool
- Simple: obstruction without vascular compromise
- Strangulated: obstruction with compromised blood supply → ischemia → necrosis → perforation
Clinical Features
- Crampy, intermittent abdominal pain (colicky; occurs in waves)
- Nausea and vomiting (the more proximal the obstruction, the earlier and more prominent the vomiting)
- Obstipation (absence of flatus and stool) — complete obstruction
- Abdominal distension (more prominent with distal obstruction)
- High-pitched, hyperactive bowel sounds → late: absent bowel sounds (ileus from ischemia)
- Prior surgical history — ask about ALL prior abdominal/pelvic operations
- Tachycardia, dehydration from third-spacing and vomiting
Signs of Strangulation (Surgical Emergency)
- Constant, severe pain (no longer colicky)
- Fever
- Peritoneal signs (rebound, guarding)
- Tachycardia, hypotension
- Leukocytosis with left shift
- Elevated lactate
- No single clinical or lab finding reliably rules out strangulation
Differential Diagnosis
- Large bowel obstruction
- Paralytic ileus (postoperative, metabolic, medication-related)
- Mesenteric ischemia
- Volvulus
- Incarcerated hernia
- Appendicitis
- Pancreatitis
- Pseudo-obstruction (Ogilvie syndrome — large bowel)
- Crohn's disease flare
Evaluation
Labs
- BMP: electrolytes (hypokalemia, metabolic alkalosis from vomiting), BUN/Cr (dehydration), bicarbonate
- CBC: leukocytosis (consider strangulation if WBC >15,000)
- Lactate: elevated suggests bowel ischemia (but normal lactate does NOT exclude strangulation)
- Lipase: rule out pancreatitis
- Type and screen if surgery likely
Imaging
Abdominal X-ray
- Sensitivity ~60-70% for SBO
- Findings: dilated small bowel loops (> 3 cm), air-fluid levels on upright, absence of colonic gas
- Three film series (supine, upright, CXR): may show free air if perforated
- Normal X-ray does NOT exclude SBO
CT Abdomen/Pelvis with IV Contrast (Test of Choice)
- Sensitivity 90-95% for SBO
- Identifies:
- Transition point (dilated proximal → decompressed distal bowel)
- Cause of obstruction (adhesion, hernia, mass, volvulus)
- Signs of strangulation: bowel wall thickening, mesenteric haziness/fluid, decreased/absent bowel wall enhancement, pneumatosis intestinalis, portal venous gas
- Oral contrast NOT needed (pooled intraluminal fluid serves as natural contrast)
- Small bowel feces sign: particulate material in dilated SB (distal/complete obstruction)
Management
Initial Resuscitation
- NPO
- Aggressive IV fluid resuscitation (NS or LR) — patients are often significantly volume depleted
- Electrolyte correction (K, Mg replacement)
- NG tube decompression: for persistent vomiting, significant distension
- Pain control: IV opioids as needed; ketorolac
- Antiemetics: ondansetron 4 mg IV
Nonoperative Management (Adhesive SBO without Strangulation)
- Trial of nonoperative management for partial, adhesive SBO without signs of strangulation
- NG decompression + IV fluids + bowel rest
- Water-soluble contrast challenge (Gastrografin):
- 100 mL PO/via NGT
- If contrast reaches colon by 24 hours → predicts resolution with nonoperative management (sensitivity ~97%)[1]
- May also have therapeutic effect (osmotic — draws fluid into lumen, stimulates peristalsis)
- ~70-80% of adhesive SBO resolves with conservative management
- Failure of nonoperative trial: no improvement in 24-72 hours → surgery
Surgical Management
- Indications for emergent surgery:
- Complete obstruction
- Signs of strangulation/peritonitis
- Incarcerated/strangulated hernia
- Closed-loop obstruction on CT
- Hemodynamic instability not responding to resuscitation
- Failure of nonoperative management
- Surgical consult early for all cases (even if initially managed conservatively)
Disposition
- Admit all patients with SBO
- Surgical consultation in ED for all patients
- ICU if septic, hemodynamically unstable, or peritonitic
- Serial abdominal exams every 4-8 hours
- Repeat imaging if clinical deterioration
See Also
References
- ↑ Abbas S, et al. Water-soluble contrast in management of adhesive small bowel obstruction. Cochrane Database Syst Rev. 2007;(3):CD005598. PMID 17636810
- Maung AA, et al. Evaluation and management of small-bowel obstruction: an Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012;73(5 Suppl 4):S362-369. PMID 23114494
- Defined by ten Broek RP, et al. Bologna guidelines for diagnosis and management of adhesive small bowel obstruction. World J Emerg Surg. 2018;13:24. PMID 29946347
- Taylor MR, Lalani N. Adult small bowel obstruction. Acad Emerg Med. 2013;20(6):528-544. PMID 23758299