Summarize vascular ileus.

Vascular Ileus: Clinical Summary

Definition and Pathophysiology

Vascular ileus refers to intestinal dysmotility resulting from compromised mesenteric blood flow, representing a critical subset of acute mesenteric ischemia (AMI) that can progress to bowel necrosis and death if untreated. This condition encompasses both occlusive causes (arterial embolism, arterial thrombosis, venous thrombosis) and non-occlusive mesenteric ischemia (NOMI), with mortality rates remaining around 50% despite modern interventions 1.

The pathophysiology involves:

• Arterial insufficiency leading to hypotonic or paralytic ileus due to impaired bowel perfusion
• Venous obstruction causing hemorrhagic infarction and bowel wall edema
• NOMI resulting from mesenteric vasospasm in low-flow states (cardiac failure, shock)

Clinical Presentation and Diagnosis

Key Clinical Features

Patients typically present with:

• Acute abdominal pain disproportionate to physical findings (early stage)
• Peritoneal signs indicating bowel infarction (late stage)
• Associated risk factors: atrial fibrillation (embolic), atherosclerosis (thrombotic), recent cardiac surgery or hypotension (NOMI)

Diagnostic Imaging

CT angiography (CTA) is the diagnostic modality of choice, revealing 2:

• Arterial occlusion: Filling defects in SMA/celiac axis, bowel wall thinning (late finding)
• Venous occlusion: Mesenteric vein thrombosis, bowel wall thickening (early finding), faster progression than arterial
• NOMI: Patent vessels with poor bowel wall enhancement, involvement of multiple vascular territories
• Critical findings mandating immediate surgery: Lack of bowel wall enhancement, pneumatosis intestinalis, portal venous gas, free intraperitoneal air 3

Management Algorithm

Without Peritoneal Signs (Early Stage)

For NOMI, intra-arterial papaverine infusion is the primary treatment, reducing 30-day mortality from 96.8% to 65.7%. 3 Time from diagnosis to vasodilator infusion directly impacts survival—every hour counts 3.

Management steps:

1. Immediate angiography with catheter-directed vasodilator therapy (papaverine)
2. Systemic anticoagulation if low cardiac output state present 3
3. No role for angioplasty in NOMI 3
4. Serial clinical assessment for development of peritonitis

For embolic/thrombotic arterial occlusion without peritonitis:

1. Immediate systemic anticoagulation to prevent clot propagation 3
2. Consider endovascular thrombectomy/thrombolysis if no peritoneal signs
3. Close monitoring for progression to infarction

With Peritoneal Signs (Bowel Infarction)

Prompt surgical exploration with revascularization is mandatory when peritoneal signs or CT evidence of bowel necrosis exists. 3 Endovascular therapy alone has limited role once infarction occurs 3.

Surgical approach:

1. Emergency laparotomy for bowel assessment
2. Revascularization (open retrograde SMA stenting or bypass) with 30-day mortality 25%, 1-year survival 65% 3
3. Bowel resection of necrotic segments
4. Adjunctive intra-operative angiography in hybrid suite if needed 3
5. Systemic anticoagulation initiated perioperatively 3

Type-Specific Considerations

Arterial Ischemia

• Slower damage progression than venous
• Bowel wall thinning difficult to detect early
• Requires aggressive revascularization

Venous Ischemia

• Faster progression despite less acute symptoms 2
• Bowel wall thickening is early, easily detected finding
• Higher index of suspicion needed

NOMI

• Associated with cardiac disease, vasopressor use
• May involve large bowel and solid organs 2
• Vasodilator therapy cornerstone of treatment

Critical Pitfalls

• Delayed diagnosis: The "pain out of proportion to exam" window is narrow—once peritonitis develops, mortality escalates
• Misclassifying NOMI: No role for anticoagulation as primary therapy in NOMI; vasodilators are essential 3
• Endovascular-only approach with infarction: Surgery cannot be delayed when imaging shows necrosis 3
• Time dependency: Both diagnosis-to-vasodilator and diagnosis-to-surgery intervals directly correlate with mortality 3

Prognosis

Even with optimal management, vascular ileus carries significant mortality. The incidence is 0.09-0.2% of acute surgical admissions but increases dramatically with age 1. Early recognition and aggressive intervention within hours of symptom onset offers the only chance to reduce the baseline 50% mortality rate.