adhesive small bowel obstruction
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Small bowel obstruction (SBO)
Mechanical obstruction of the small bowel preventing free passage of intraluminal material
May be due to: Bowel wall inflammation, edema or tumor Intraluminal obstruction (bezoar, gallstone,
foreign body) Extrinsic compression (adhesion, hernia,
tumor, volvulus)
Background
Obstruction is the most common small bowel pathology requiring surgical consultation
Accounts for 20% of acute surgical admissions
Costs $800 million annually
Background
Most common causes of SBO
Adhesive 60-75% Malignancies 9-11% Hernias 8-18% IBD 5%
SBO in the virgin abdomen
Historically Primary causes: hernia and volvulus
Currently Primary causes: malignancy, IBD
All cases of SBO in a virgin abdomen should be taken for operative exploration due to high failure rate of NOM and concern for malignancy
Pathophysiology Adhesions are fibrous bands of connective
tissue that form in response to trauma, surgical manipulation, or inflammation
Capillaries & Migration of Fibroblasts
Capillaries & Migration of Fibroblasts
Peritoneal Damage
Bleeding Inflammation
Stable Fibrin matrixFibrinogen
AdhesionBarmparas et al, J Gastrointest Surg 2010
Pathophysiology
Postmortem study Minor procedure: 51% had adhesions Major procedure: 72% had adhesions Multiple operations: 93% had adhesions
93% of 210 patients with abdominal procedures, had intra-abdominal adhesions at re-laparotomy.
Weibel MA. Am J Surg 1973Menzies D. Ann R Coll Surg Engl 1990
Risk factors for SBO
Age Comorbid conditions Prior surgery
Stepwise increase with number of prior procedures
Surgical technique Open technique associated with
significantly higher rates of SBO Risk increased 2-8x’s
Surgery Technique Total # of patients
Adhesion-related readmission
AppendectomyOpenLap.
266,6954,445
1.4%1.3%
CholecystectomyOpenLap.
1417,103
7.1%0.2%
ColectomyOpenLap.
121,058930
9.5%4.3%
Ileal pouch-anal anastomosis Open 5,268 19.3%
Laparotomy for Trauma Open 1,913 2.5%
Gynecological procedures
OpenLap.
24,998773
17.1%0%
Procedure related risk
Barmparas et al, J Gastrointest Surg 2010
Trends over time? ↓risk of SBO with laparoscopy compared
to open Laparoscopy rate ↑over time Has this resulted in ↓rate of SBO?
No
Scott, et al Am J Surg 2012 and Angenete, et al Arch Surg 2012
Etiology
Overall incidence of SBO 4.6%
Top operations leading to SBO
Appendectomy 14-30% Colorectal 21-34% Gynecological surgery 12-28%
Diagnosis: Clinical presentation
Anorexia, nausea, vomiting, obstipation (90%), constipation (80%), abdominal pain
Abdominal distension, high pitched bowel sounds, tympany, TTP, feculant NGT output/vomitus
Hypocholoremic, hypokalemic metabolic alkalosis
Diagnosis: Radiology findings
Plain films
Benefits: rapid, repeatable, no contrast required, patient does not have to be supine for prolonged time period, can be done at bedside
Diagnosis: Radiology findings
Findings:
Distended loops of bowel Air-fluid levels Step laddering of bowel Lack of air in colon, rectum
Diagnosis: Radiology findings
CT scans
Benefits: high sensitivity and specificity (90%), gives information on intra and extraluminal pathology, highly sensitive for free air/fluid, can identify transition zones, hernias, and bowel ischemia
Diagnosis: Radiology findings
Findings:
Dilated bowel Transition zone from dilated to
collapsed Passage of contrast material (partial)
or not (complete) Bezoars, masses
Treatment
Initial management of all patients should include:
NGT decompression Judicious fluid resuscitation Correction of electrolyte imbalances Foley catheter and close monitoring or
UOP +/- central venous and/or arterial catheters
Treatment
Majority of cases (60-82%) can be treated conservatively with non-operative management (NOM)
Three indications for Early Operative Management (EOM):
1: Perforation
Any patient with peritonitis or free air-indicating perforation should go straight to OR
2: Ischemia
Any patients with concerning signs/symptoms for gangrenous or ischemic bowel should also go to the OR ASAP
Signs of bowel ischemia
Clinical: sensitivity 40-50%
Hypotension Tachycardia Fever or leukocytosis, Lactic acidosis SIRS response Deterioration in exam
1983
Physical signs Strangulated(N=21) Sensitivity Specificity PPV
Temp (°F) 99 ± 0.9 24 70 36
Pulse 104 ± 23 52 43 39
No bowel sounds 5/20 25 83 50
Peritonitis 6/21 29 97 86
Clinical symptoms, base deficit, leukocytosis, blood glucose, and SIRS were assessed
→SIRS and base deficit were independently associated with gangrenous bowel
Sensitivity: 92%, Specificity: 96%
PPV: 92%, NPV: 96%
2004
Signs of bowel ischemia
Plain films Bowel wall edema, portal venous gas
CT: sensitivity 85-90% Thickened bowel wall, target sign,
mesenteric stranding, congestion, ascites, pneumatosis, portal venous gas, decreased bowel wall enhancement
TreatmentPeritonitis
Free air?
Yes
OR
NoIschemia?
Fever, Tachycardia, Acidosis
Portal air, pneumatosis, ascites mesenteric stranding
Yes
OR
3: High grade, or closed loop SBO
Patients with high grade SBO, or those with closed loop obstruction should be strongly considered for early operative management
Signs of high grade SBO
> 25mm
Air-fluid levels of differential heightin the same loop
Air fluid width of25 mm or more
Accuracy of plain X-ray to diagnose a high grade SBO
Sensitivity 66-75%
Results of this technique are: Equivocal in about 20%–30% Normal, nonspecific, or misleading in
10%–20%
Maglinte AJ, AJR Am J Roentgenol 1997
Signs of high grade SBO
Sensitivity 80-93%
Contrast does not pass transition zone
Colon with little gas or fluid
Fecalization of small bowel
Diagnosis: Radiology findings
EAST Guidelines 2012
Level 1 recommendation for CT scans in SBO as they can provide incremental increase in information compared to plain films in differentiating grade, severity and etiology that may lead to changes in management
Treatment Peritonitis
Free air?
Yes
OR
No
Ischemia?
Fever, Tachycardia, Acidosis
Portal air, pneumatosis, ascites mesenteric stranding
Yes
OR
No
Closed loop or high grade
SBO?
Yes-OR
Summary: treatment
Three indications for early operative management:
Perforation Ischemia Closed loop or high grade obstruction
All others can be considered for NOM
Treatment Peritonitis
Free air?
Yes
OR
No
Ischemia?
Fever, Tachycardia, Acidosis
Portal air, pneumatosis, ascites mesenteric stranding
Yes
OR
No
Closed loop or high grade
SBO?
Yes-OR No-obs
Principles of NOM
Bowel rest, NGT decompression, fluid resuscitation
Serial abdominal exams and blood tests, consider serial abdominal films
Explore if deterioration in clinical exam, or new e/o ischemia or perforation
Keep in mind…
NOM
Delay to OR is associated with:
Longer LOS Increased incidence of bowel
necrosis and need for bowel resection Increased mortality Increased morbidity
NOM
Given risks of delay to surgery:
How long should NOM trial last?Studies suggest 48hrs although can
be longer in pSBO
NIS data suggest delay of ≥4d associated with 64% increase in mortality and increased LOS
Schraufnagel et al, J Trauma 2013
NOM
EAST Guidelines 2012
Level 2 recommendation
Consider water soluble contrast administration for prognosis and/or treatment in patients who fail to improve within 48hrs
Water soluble contrast
Hyperosmolar radiopaque agent
Potential aid in prognosis Passage of contrast into LB may predict
successful NOM Failure of progression predicts need for OR
Theoretically decreases bowel wall edema and may promote resolution of SBO
Br J Surg. 2010 Apr;97(4):470-8.
Water-Soluble Contrast (WSCA) – Diagnostic and Therapeutic role
• 50–100ml Gastrografin or 40ml Urografin administered orally
• Abdominal plain radiographs after 4 h, 8 h or 24 h to follow contrast through the GI-tract
Br J Surg. 2010 Apr;97(4):470-8.
Water-Soluble Contrast (WSCA) – Diagnostic and Therapeutic role
Meta-analysis of 14 prospective randomized controled studies
If the contrast reaches the colon within 4–24 h, obstruction will resolve without operation in 99% of patients.
Br J Surg. 2010 Apr;97(4):470-8.
Water-Soluble Contrast (WSCA) – Diagnostic and Therapeutic role
Timing n Sensitivity Specificity PPV NPV
4-8h 312 95 99 100 85
24h 196 99 97 99 97
Conclusion
Water-soluble contrast was effective in predicting the need for surgery in adhesive SBO (sensitivity 96%, specificity 98%)
In addition, it reduced the need for operation and shortened hospital stay.
Br J Surg. 2010 Apr;97(4):470-8.
Water-Soluble Contrast (WSCA) – Diagnostic and Therapeutic role
Outcomes
Mortality 3-8%
Rates of recurrence 15-20% over 5 years
Rate of recurrence, # of recurrences, and time to recurrence significantly better in Operatively Managed compared to NOM group
Outcomes California OSHPD database 32,583 patients admitted in 1997 with
SBO 76% NOM 24% OM
OM group associated with Decreased mortality, decreased rate of
readmissions, fewer readmissions, and longer time to readmission
Foster, et al JACS 2006
Summary
1. Adhesions account for the majority of SBO in the US
2. Clinical exam and xrays reliably diagnose SBO
3. Early OM should be undertaken in patients with perforation, ischemia, and high grade or closed loop SBO
Summary: When to operate?
4. NOM successful in majority of patients, but shouldn‘t exceed 4d
5. Consider use of Water-soluble contrast agents for both diagnostic and therapeutic purposes
6. Operative management can decrease the rate and number of recurrences, and prolong the time to recurrence
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