Small bowel obstruction: Difference between revisions

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==Background==
==Background==
#SBO without hx of surgery, no hernia is malignancy until proven otherwise
[[File:Blausen 0817 SmallIntestine Anatomy.png|thumb|Small bowel anatomy with surrounding structures.]]
#"Never let the sun rise or set on a small bowel obstruction"
*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==
===Causes===
#Adhesions (Hx of previous abdominal surgeries +LR 3.86 and -LR 0.19)
*Adhesions (history of previous abdominal surgeries +LR 3.86 and -LR 0.19)
#Hernia
**Most common cause in developed countries
#Malignancy
*Hernia
#Intraluminal strictures
**Port hernias can occur after laparoscopic surgery
##Crohn's disease
*Malignancy
##Radiation therapy
*Intraluminal strictures
##Mesenteric ischemia
**[[Crohn's disease]]
#Intussusception (due to lymphoma as lead point)
**Radiation therapy
#Foreign body (bezoars)
**[[Mesenteric ischemia]]
#Trauma (duodenal hematoma)
*[[Intussusception]] (due to [[lymphoma]] as lead point)
#Gallstone ileus
*[[ingested foreign body|Foreign body]] ([[bezoar]]s)
*[[abdominal trauma|Trauma]] ([[duodenal hematoma]])
*Gallstone [[ileus]]
*Small bowel [[volvulus]] (3-6% of causes of SBO)<ref>Roline CE and Reardon RF.  Disorders of the Small Intestine.  Rosen's.  Edition 8.  Chapter 92.  2014.  1216-1224.</ref>


==Clinical Manifestations==
==Clinical Features==
#Abdominal pain
*[[Abdominal pain]]
##Colicky
**Colicky
##Periumbilical or diffuse
**Periumbilical or diffuse
##Paroxysms of pain occur q5min  
**Paroxysms of pain occur q5min  
#Vomiting
*[[Vomiting]]
##More common in proximal than distal obstruction
**More common in proximal than distal obstruction
##Bilious (proximal) or feculent (distal ileal)
**Bilious (proximal) or feculent (distal ileal)
### Abdominal pain relieved with vomiting positively predictive +LR (4.50-2.82) -LR (0.78-0.35)
***Abdominal pain relieved with vomiting positively predictive +LR (4.50-2.82) -LR (0.78-0.35)
#Abdominal distention
*Abdominal distention
##Seen more in distal than proximal obstruction
**Seen more in distal than proximal obstruction
## +LR (16.8-5.64) -LR (0.43-0.34)
**+LR (16.8-5.64) -LR (0.43-0.34)
#Inability to pass flatus
*Inability to pass flatus
##Pts may pass flatus/stool initially
**May pass flatus/stool initially
###Takes 12-24hrs for colon to empty
***Takes 12-24hrs for colon to empty
###History of constipation +LR 8.8 and -LR 0.59
***History of constipation +LR 8.8 and -LR 0.59
#Dehydration
*[[Dehydration]]
#Anorexia
*Anorexia
#Ischemia (increased intraluminal pressure initially leads to venous congestion, progresses to frank arterial ischemia)
*[[ischemic bowel|Ischemia]] (increased intraluminal pressure initially leads to venous obstruction, progresses to frank arterial ischemia)
##Fever
**[[Fever]]
##Leukocytosis
**[[Leukocytosis]]
# Abnormal Bowel sounds (+LR 6.33 -LR 0.27)
*Abnormal bowel sounds
**Studies suggest that auscultating bowel sounds is not clinically useful to differentiate between normal and pathologic<ref>Felder S, Margel D, Murrell Z, et al. Usefulness of Bowel Sound Auscultation: A Prospective Evaluation. J Surg. 2014; 71(5):768–773.</ref>


==Diagnosis==
==Differential Diagnosis==
#Labs
{{Abdominal Pain DDX Diffuse}}
##CBC
{{Constipation DDX}}
###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: [[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)
###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: 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


==Treatment==
==Evaluation==
#IV fluid resuscitation with [[electrolyte repletion]]
[[File:Upright X-ray demonstrating small bowel obstruction.jpg|thumb|Upright abdominal X-ray demonstrating a small bowel obstruction. Note multiple air fluid levels.]]
#Assessment of need for operative vs nonoperative management
[[File:SBO plain.png|thumb|Small bowel obstruction]]
##Nonoperative Management
[[File:SBO_Cai_Maurelus.gif|thumbnail|Ultrasound shows dilated, non-compressible loops of bowel with characteristic to-and-fro motion of bowel contents<ref>http://www.thepocusatlas.com/bowel/</ref>]]
###Sometimes successful in patients with partial SBO (must rule-out strangulation first)
[[File:SBO.gif|thumbnail|Ultrasound shows dilated loops of bowel steep precipice and tumbling feces<ref>http://www.thepocusatlas.com/bowel/</ref>]]
###NG tube
[[File:PSBOCT.png|thumb|A small bowel obstruction as seen on CT.]]
####14 French
===Labs===
####Intermittent low wall suction
*CBC
####Nasogastric fluid losses can be replaced w/ NS + KCL (30-40 meq)
**WBC >20K suggests bowel gangrene, abscess, or peritonitis
###Contrast
**WBC >40K suggests mesenteric vascular occlusion
####Both diagnostic and therapeutic (draws water into the bowel stimulating peristalsis)
*Chemistry - degree of dehydration, evidence of ischemia ([[acidosis]])
####Associated with decreased hospital stay, more rapid resolution of symptoms
*[[Lactate]] - sensitive (90-100%), though not specific marker of strangulation
###If increasing pain, distention, or peristent high NGT output, consider sx
###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
###Indicated for pts with:
####Complete SBO
####Closed-loop obstruction
#####E.g. incarcerated hernia
####[[Fever]], leukocytosis, peritonitis
#[[Antibiotics]]
##Indicated if e/o ischemia or infection
###[[Piperacillin-tazobactam]] 3.375gm IV q6hr OR
###[[Ampicillin-sulbactam]] 3gm IV q6hr


==Source==
===Imaging===
*Use the 3/6/9 rule for bowel imaging
**Upper limit of 3cm for small bowel, 6cm for colon, and 9cm for cecum
*'''Xray'''
**[[Acute Abdominal Series]]
**Upright chest film: rule out free air
**Upright abdominal film: air-fluid levels:
**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<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>
**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: 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
 
==Management==
===[[Volume resuscitation]]===
*IV fluid resuscitation with [[electrolyte repletion]]
*Assessment of need for operative vs nonoperative management
 
===[[Nasogastric tube]]===
*14 French
**Intermittent low wall suction
*Nasogastric fluid losses can be replaced with NS + KCL (30-40 meq)
*There is some evidence to suggest nasogastric tube decompression was not associated with decreased bowel ischemia or need for surgery<ref>Berman, DJ et al. Nasogastric decompression not associated with a reduction in surgery or bowel ischemia for acute small bowel obstruction. Am J Emerg Med. 2017 Dec;35(12):1919-1921.PMID: 28912083</ref>
 
===Oral 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<ref>Assalia A, Schein M, Kopelman D, et al. Therapeutic effect of oral Gastrografin in adhesive, partial small-bowel obstruction: A prospective randomized trial. Surgery 1994; 115: 433-437.</ref>
**Diagnostic and therapeutic<ref>Chen SC, Lin FY, Lee PH, et al. Water-soluble contrast study predicts the need for early surgery in adhesive small bowel obstruction. Br J Surg 1998; 85: 1692-1694.</ref>
**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%<ref>Choi HK et al. Therapeutic Value of Gastrografin in Adhesive Small Bowel Obstruction After Unsuccessful Conservative Treatment: A Prospective Randomized Trial. Annals of Surgery. 2002;236(1).</ref>
*Avoid barium as it becomes inspissated in bowel, causing complete obstruction<ref>Choi HK et al. Therapeutic Value of Gastrografin in Adhesive Small Bowel Obstruction After Unsuccessful Conservative Treatment: A Prospective Randomized Trial. Annals of Surgery. 2002;236(1).</ref>
**Gastrografin is water-soluble and relatively safer if perforation occurs
 
===Non-operative Management vs. Operative===
*75% of patients are amenable to non-operative management
 
====Operative Management====
*25% of patients admitted for SBO require surgery
*Surgery is indicated for patients with:
**Increasing pain, distention, or peristent high NGT output
**Necrotic bowel
**Closed-loop obstruction (incarcerated hernia, small bowel volvulus, cecal volvulus)
**[[Fever]], leukocytosis, peritonitis
 
===[[Antibiotics]]===
*Not typically indicated, unless evidence of concurrent ischemia or infection
*See [[Peritonitis#Management|peritonitis antibiotics]]
 
==Disposition==
*Admit
 
==Prognosis==
*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==
<references/>
<references/>
*UpToDate
*Tintinalli
*ACR Appropriateness Criteria for suspected SBO (guidelines.gov/content.aspx?id=32636)
*Academic Emergency Medicine June 2013, Vol. 20, No. 6 Evidence-Based Diagnostics Series "Adult Small Bowel Obstructions" Taylor and Lalani


[[Category:GI]] [[Category:Surg]]
[[Category:GI]]  
[[Category:Surgery]]

Latest revision as of 11:43, 23 April 2022

Background

Small bowel anatomy with surrounding structures.
  • 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

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)
  • Abnormal bowel sounds
    • Studies suggest that auscultating bowel sounds is not clinically useful to differentiate between normal and pathologic[2]

Differential Diagnosis

Diffuse Abdominal pain

Constipation

Evaluation

Upright abdominal X-ray demonstrating a small bowel obstruction. Note multiple air fluid levels.
Small bowel obstruction
Ultrasound shows dilated, non-compressible loops of bowel with characteristic to-and-fro motion of bowel contents[3]
Ultrasound shows dilated loops of bowel steep precipice and tumbling feces[4]
A small bowel obstruction as seen on CT.

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

  • Use the 3/6/9 rule for bowel imaging
    • Upper limit of 3cm for small bowel, 6cm for colon, and 9cm for cecum
  • Xray
    • Acute Abdominal Series
    • Upright chest film: rule out free air
    • Upright abdominal film: air-fluid levels:
    • 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[5]
    • 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

Nasogastric tube

  • 14 French
    • Intermittent low wall suction
  • Nasogastric fluid losses can be replaced with NS + KCL (30-40 meq)
  • There is some evidence to suggest nasogastric tube decompression was not associated with decreased bowel ischemia or need for surgery[6]

Oral 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[7]
    • Diagnostic and therapeutic[8]
    • 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%[9]
  • Avoid barium as it becomes inspissated in bowel, causing complete obstruction[10]
    • Gastrografin is water-soluble and relatively safer if perforation occurs

Non-operative Management vs. Operative

  • 75% of patients are amenable to non-operative management

Operative Management

  • 25% of patients admitted for SBO require surgery
  • Surgery is indicated for patients with:
    • Increasing pain, distention, or peristent high NGT output
    • Necrotic bowel
    • Closed-loop obstruction (incarcerated hernia, small bowel volvulus, cecal volvulus)
    • Fever, leukocytosis, peritonitis

Antibiotics

Disposition

  • Admit

Prognosis

  • 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

References

  1. ↑ Roline CE and Reardon RF. Disorders of the Small Intestine. Rosen's. Edition 8. Chapter 92. 2014. 1216-1224.
  2. ↑ Felder S, Margel D, Murrell Z, et al. Usefulness of Bowel Sound Auscultation: A Prospective Evaluation. J Surg. 2014; 71(5):768–773.
  3. ↑ http://www.thepocusatlas.com/bowel/
  4. ↑ http://www.thepocusatlas.com/bowel/
  5. ↑ 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
  6. ↑ Berman, DJ et al. Nasogastric decompression not associated with a reduction in surgery or bowel ischemia for acute small bowel obstruction. Am J Emerg Med. 2017 Dec;35(12):1919-1921.PMID: 28912083
  7. ↑ Assalia A, Schein M, Kopelman D, et al. Therapeutic effect of oral Gastrografin in adhesive, partial small-bowel obstruction: A prospective randomized trial. Surgery 1994; 115: 433-437.
  8. ↑ Chen SC, Lin FY, Lee PH, et al. Water-soluble contrast study predicts the need for early surgery in adhesive small bowel obstruction. Br J Surg 1998; 85: 1692-1694.
  9. ↑ Choi HK et al. Therapeutic Value of Gastrografin in Adhesive Small Bowel Obstruction After Unsuccessful Conservative Treatment: A Prospective Randomized Trial. Annals of Surgery. 2002;236(1).
  10. ↑ Choi HK et al. Therapeutic Value of Gastrografin in Adhesive Small Bowel Obstruction After Unsuccessful Conservative Treatment: A Prospective Randomized Trial. Annals of Surgery. 2002;236(1).
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