Definition/General
Introduction:
Small intestinal infarction represents tissue death due to complete vascular occlusion
It results from cessation of blood flow to intestinal segments
It shows coagulative necrosis of all bowel wall layers
It requires emergency surgical intervention.
Origin:
Results from complete arterial occlusion or severe venous compromise
Thrombotic occlusion: atherosclerosis, hypercoagulable states
Embolic occlusion: cardiac emboli, atherosclerotic plaques
Mechanical obstruction: volvulus, intussusception
Leads to transmural necrosis.
Classification:
Arterial infarction: superior mesenteric artery occlusion
Venous infarction: mesenteric vein thrombosis
Mechanical infarction: volvulus, strangulation
Watershed infarction: hypoperfusion
Segmental vs extensive involvement.
Epidemiology:
Surgical emergency with high mortality (50-80%)
Elderly population most affected
Male predominance (slight)
Associated with cardiovascular disease
Peak incidence: >60 years.
Clinical Features
Presentation:
Sudden severe abdominal pain
Pain out of proportion to physical findings
Nausea and vomiting
Bloody diarrhea
Abdominal distension
Signs of peritonitis.
Symptoms:
Excruciating abdominal pain
Hemodynamic instability
Peritoneal signs
Bloody bowel movements
Tachycardia and hypotension
Altered mental status (shock).
Risk Factors:
Atrial fibrillation
Recent myocardial infarction
Atherosclerosis
Hypercoagulable states
Previous abdominal surgery
Heart failure
Age >60 years.
Screening:
CT angiography (urgent)
Mesenteric angiography
Laboratory tests: lactate (elevated), WBC (leukocytosis)
Arterial blood gas (metabolic acidosis)
D-dimer (venous thrombosis).
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Gross Description
Appearance:
Hemorrhagic necrosis of bowel wall
Dark red to black discoloration
Complete loss of viability
Gangrenous bowel
Sharp demarcation from viable tissue
Absence of peristalsis.
Characteristics:
Transmural involvement
Hemorrhagic serosa
Thickened, rigid bowel wall
Loss of normal architecture
Putrid odor
Gas bubbles in bowel wall (pneumatosis).
Size Location:
Variable extent depending on vessel occluded
Superior mesenteric territory: jejunum, ileum, right colon
Segmental involvement common
Skip areas possible
Entire small bowel (massive infarction).
Multifocality:
Segmental distribution typical
Sharp boundaries between infarcted and viable bowel
Multiple segments possible
Concurrent colonic involvement
Sparing of duodenum (dual blood supply).
Microscopic Description
Histological Features:
Coagulative necrosis of all layers
Ghost cell architecture
Hemorrhage and thrombosis
Acute inflammatory infiltrate
Bacterial overgrowth
Perforation (complications).
Cellular Characteristics:
Loss of cellular detail
Nuclear pyknosis and karyolysis
Cytoplasmic eosinophilia
Red blood cell extravasation
Fibrin thrombi
Neutrophilic infiltration.
Architectural Patterns:
Complete loss of architecture
Mucosal sloughing
Muscle layer necrosis
Vascular thrombosis
Serosal necrosis
Bacterial invasion.
Grading Criteria:
Extent of necrosis: partial vs complete
Layer involvement: mucosal, transmural
Time since onset: acute, subacute
Complications: perforation, sepsis.
Immunohistochemistry
Positive Markers:
CD31 (endothelial cells, thrombosed vessels)
Fibrinogen (thrombi)
Neutrophil elastase (inflammatory infiltrate)
Bacterial antigens (secondary infection).
Negative Markers:
Smooth muscle markers (lost in necrotic areas)
Epithelial markers (mucosal necrosis)
Endothelial markers (vessel damage).
Diagnostic Utility:
Confirms vascular occlusion
Demonstrates thrombosis
Identifies extent of necrosis
Assesses inflammatory response
Excludes other causes of bowel necrosis.
Molecular Subtypes:
Arterial infarction: coagulative necrosis pattern
Venous infarction: hemorrhagic necrosis
Reperfusion injury: neutrophilic infiltration
Secondary infection: bacterial overgrowth.
Molecular/Genetic
Genetic Mutations:
Thrombophilia mutations: Factor V Leiden, prothrombin G20210A
MTHFR mutations
Protein C/S deficiency
Antithrombin deficiency
JAK2 mutations.
Molecular Markers:
Lactate dehydrogenase (tissue necrosis)
D-dimer elevation
Inflammatory markers: IL-6, TNF-α
Tissue hypoxia markers
Endothelial damage markers.
Prognostic Significance:
Extent of infarction: determines survival
Time to intervention: critical factor
Age and comorbidities: affect outcome
Sepsis development: poor prognosis
Short gut syndrome: long-term complication.
Therapeutic Targets:
Emergency surgery: resection of necrotic bowel
Vascular intervention: thrombectomy, bypass
Anticoagulation
Supportive care: fluid resuscitation, antibiotics
Management of complications.
Differential Diagnosis
Similar Entities:
Ischemia without infarction
Inflammatory bowel disease
Infectious enteritis
Toxic megacolon
Necrotizing enterocolitis
Radiation enteritis.
Distinguishing Features:
Infarction: transmural necrosis, vascular occlusion, acute onset
Ischemia: mucosal involvement only
IBD: chronic inflammation, skip lesions
Infection: organisms identified
NEC: neonatal, pneumatosis.
Diagnostic Challenges:
Distinguishing infarction from severe ischemia
Identifying underlying cause
Assessing extent of viable bowel
Timing of vascular occlusion
Recognizing watershed areas.
Rare Variants:
Non-occlusive mesenteric infarction
Cocaine-induced infarction
Hypotension-related infarction
Iatrogenic infarction
Neonatal necrotizing enterocolitis.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
Small bowel resection, [length] cm, showing transmural infarction
Diagnosis
Small intestinal infarction with transmural necrosis
Extent of Infarction
Transmural infarction involving [length] cm of small bowel
Necrosis Pattern
Complete coagulative necrosis of all bowel wall layers
Vascular Changes
Mesenteric vessels show [thrombosis/embolism/occlusion]
Complications
Complications: [perforation/sepsis/none identified]
Resection Margins
Resection margins: [viable/necrotic], adequate resection: [yes/no]
Recommendations
Clinical correlation, vascular surgery consultation, anticoagulation consideration
Final Diagnosis
Small intestinal infarction with transmural necrosis, [extent] cm involvement