Small Intestine: Small Bowel Obstruction (SBO)

Definitions & Presentation

Definitions

  • Small Bowel Obstruction: Interruption of the Normal Flow of Intraluminal Contents
    • Functional SBO: Dysfunctional Peristalsis
      • Also Known as Ileus
    • Mechanical SBO: Intraluminal or Extraluminal Compression
      • “Small Bowel Obstruction” Typically Refers to a “Mechanical Small Bowel Obstruction”
  • Partial SBO
    • Some Gas or Liquid Stool is Able to Pass the Obstruction
  • Complete SBO
    • Nothing is Able to Pass the Site of Obstruction
  • Closed Loop Obstruction
    • Both Proximal and Distal Ends Obstructed
      • No Outlets for Decompression
    • Rapid Progression with High Risk for Strangulation & Perforation

Causes Mn

  • Postoperative Adhesions – Most Common Cause in US
  • Hernia – Most Common Cause in “Virgin Abdomens” (No Past Surgery) & Most Common Cause Worldwide
  • Cancer – Most Common Cause of Large Intestine Obstruction (Regardless of Surgical History)
  • Inflammatory Bowel Disease
  • Stricture
  • Intussusception
  • Foreign Body
  • Midgut Volvulus
    • Most Common in Peds
    • Rare in Adults
      • Primary
        • Risk Factors: Long Mesentery, Deficient Mesenteric Fat & Narrow Mesenteric Base
      • Secondary (Most Common) – Due to Other Pathology (Adhesions/Malrotation)
  • Gallstone Ileus

Symptoms

  • Nausea & Vomiting
    • Proximal Obstructions Have More Severe N/V Than Distal Obstructions
  • Intermittent Pain (Periumbilical Cramping)
    • As Bowel Dilates & Pressure Overcomes Capillary Pressure Wall Ischemia Causes Peritonitis with Constant Sharp Pain
  • Abdominal Distention
  • Obstipation (Unable to Pass of Flatus or Stool)
  • *Colon Obstruction Has Constant Pain with Feculent Emesis & Significant Distention

Diagnosis

Diagnosis

  • Diagnosis: Radiology
  • CT (95% Sensitive) Better Than Plain Radiography (67% Sensitive)
  • Small-Bowel Follow Through (SBFT)
    • Given Oral Water-Soluble Contrast (Gastrografin) & X-Ray is Taken After a Period of Time
      • May Be Done at Periodic Intervals or a Single Image After a Few Hours
      • Generally No Benefit Extending Past 8 Hours
      • Pass if Patient Has a Bowel Movement or if Contrast is Seen in the Colon
    • Bowel Must First Be Decompressed & Not Actively Vomiting
    • Helps Identify Patients Unlikely to Resolve by Conservative Measures
    • May Also Be Therapeutic as a Cathartic Agent – Hyperosmolar Agent to Reduce Bowel Edema & Acts as a Laxative

General Radiographic Findings

  • Proximal Dilated Loops > 3 cm & Distal Decompressed Loops
  • Air-Fluid Levels (Air from Swallowed Nitrogen)
    • “Gasless Abdomen” without Air-Fluid Levels Can Be Seen When Obstruction Causes Fluid Sequestration
  • Paucity of Gas in the Colon
  • Transition Point
  • “Swirling” of Mesentery Suggests a Closed-Loop Obstruction

Radiographic Findings that Predict the Need for Operative Exploration

  • Absence of Fecalization of the Small Bowel – Fecalization is an Abnormal Sign But is a Reassuring Finding in the Setting of SBO (Indicates that the Obstruction has Been Present Long Enough for the Stasis to Allow Fecalization to Occur)
  • Mesenteric Edema
  • Bowel Wall Thickening
  • Free Intraperitoneal Fluid

Grade

  • Definitions are Varied & With Improved CT Imaging it is More Commonly Noted
  • Low-Grade SBO – Generally Describes Partial SBO without a Discrete Transition Point
  • High-Grade SBO – Generally Describes Complete SBO with a Discrete Transition Point

AAST Grade

  • I: Partial SBO
  • II: Complete SBO; Bowel Viable & Not Compromised
  • III: Complete SBO; Bowel Viable but Compromised
  • IV: Complete SBO; Bowel Nonviable or Perforation with Local Spillage
  • V: Perforation with Diffuse Peritoneal Contamination

SBO on Plain Film 1

SBO on CT

Management

Initial Management

  • Preferred: Conservative Management
  • Immediate Surgery Indications:
    • Closed-Loop
    • Signs of Strangulation or Ischemia
    • Perforation
    • Multiple Recurrence
  • *Previously Believed that All “Virgin Abdomens” (No Surgical History) with SBO Should Undergo Surgery Due to Risk of Malignancy Has Since Fallen Out of Favor – Improved CT Scans Allow for Better Recognition of Malignancy & Many Have Other Reasons for Scar Tissue that May Have Been Unrecognized

Conservative Management

  • Managements:
    • NPO
    • IV Fluids
    • Nasogastric Tube for Decompression
  • Failure Duration Prior to Proceeding with Surgery: 3-5 Days (Debated)
  • Success for Adhesive SBO Resolution: 65-80%
  • Recurrence Rate for Adhesive SBO: 16-53%

Surgical Management

  • Open Laparotomy Generally Preferred Over Laparoscopy
  • Laparoscopic Indications:
    • Mild Abdominal Distention (Bowel Diameter ≤ 4 cm & Early Presentation)
    • Partial Obstruction
    • Proximal Obstruction
    • Few Operative Procedures

Adhesiolysis

  • General Procedures:
    • Run Bowel from Ligament of Treitz to the Ileocecal Valve
    • Lysis of Adhesion (Enterolysis)
      • Address Principal Site of Obstruction & Major Adhesions
      • Total Lysis of All Adhesions Unnecessary & Risks Damage to Healthy Bowel
    • Reduce & Repair Hernias
    • Perforations:
      • Serosal Injuries: Oversew to Imbricate Mucosa
      • Circumference < 50%: Primary Repair
      • Circumference > 50%: Resect
    • Resect Nonviable Bowel
      • Consider Open Abdomen with Reexploration in 24-48 Horus if Viability Uncertain
    • Preform an Oncologic Resection for any Mass (5-10 cm Margin with Associated Lymph Nodes)
    • Consider Manual Bowel Decompression (“Milking”) – Debated Effects
      • Decompresses the Abdominal Compartment with Less Tension for Closure
      • May Reduce Risk for Aspiration Pneumonia
      • May Induce Paralytic Ileus Although Transit Time Generally Not Affected
  • Surgical Management of Strictures:
    • Single Stricture: Stricturoplasty
    • Multiple Strictures: Resection
    • Large Intestine: Resection
      • High Malignancy Risk

Other Considerations

  • Patients Admitted to a Surgical Service (Opposed to Medical Service) Have Better Outcomes
    • Shorter Length of Stay
    • Shorter Time to Surgery
    • Lower Hospital Costs
    • Lower Rate of Readmission
    • Lower Mortality
  • Malignant Obstruction:
    • Palliative Treatment for Nausea/Vomiting: Octreotide
    • Consider Palliative Bypass if Large & Unresectable
    • Consider Decompressive Gastrostomy if Multiple Points of Obstruction

Mnemonics

General Causes of SBO

  • “SHAVING”
    • Stricture
    • Hernia
    • Adhesions
    • Volvulus
    • Intussusception/IBD
    • Neoplasia
    • Gallstone Ileus

References

  1. Polat C, Aktepe F, Turel S, Yazicioglu B, Ozkececi T, Arikan Y. A giant mesenteric fibromatosis case presenting with mechanical intestinal obstruction and successfully resected with partial duodeno-jejunectomy and right hemicolectomy. Clinics (Sao Paulo). 2010;65(1):110-3. (License: CC BY-4.0)