SCAD in Gastrointestinal Disease with Sigmoid Thickening
SCAD in the context of GI disease with sigmoid thickening refers to Segmental Colitis Associated with Diverticulosis, NOT Spontaneous Coronary Artery Dissection. This is a chronic inflammatory process confined to the sigmoid colon in areas with diverticulosis, characterized by colonic wall thickening and inflammation 1, 2.
Definition and Key Diagnostic Features
SCAD is a distinct inflammatory entity localized exclusively to diverticular segments of the colon, almost always affecting the sigmoid region 1, 3. By definition, both the rectum and proximal colon must be endoscopically and histologically normal—this "rectal sparing" is a critical diagnostic criterion 1, 3.
Distinguishing SCAD from Inflammatory Bowel Disease
The key differentiating features include:
- Age and demographics: SCAD develops almost exclusively in older adults, predominantly males, whereas IBD typically presents in younger patients 3
- Location specificity: Inflammation remains localized to the sigmoid colon with diverticulosis, with mandatory rectal sparing 1, 2
- Histopathology: Non-specific inflammatory changes without granulomas (if granulomas are present, consider Crohn's disease instead) 1, 3
- Clinical course: SCAD typically has a more benign outcome with low complication rates compared to IBD 2
Endoscopic and Histologic Findings
The sigmoid colon shows chronic inflammatory changes with wall thickening, but the adjacent rectum and proximal colon remain completely normal 1. Histologically, you may observe:
- Architectural distortion and crypt hyperplasia 1
- Infiltration of lamina propria by mononuclear cells, eosinophils, and histiocytes 1
- Intraepithelial neutrophils, cryptitis, and crypt abscesses in active disease 1
- Occasionally Crohn's-like features including fissuring ulcers, transmural lymphoid aggregates, but these occur in the diverticular segment only 1
Clinical Presentation
Patients most commonly present with rectal bleeding, and endoscopy reveals well-localized inflammation confined to the sigmoid 3. The inflammatory process:
- Presents with rectal bleeding as the primary symptom 3
- Shows well-localized endoscopic changes 3
- Has negative bacteriologic and parasitic studies 3
- Demonstrates normal rectal mucosa on biopsy 3
Imaging Considerations
Sigmoid wall thickening on CT or ultrasound in the setting of diverticulosis should prompt consideration of SCAD 4. However, be aware that:
- Perforated sigmoid diverticulitis or carcinoma can cause secondary appendiceal thickening, creating a diagnostic pitfall 4
- Combined US and CT imaging improves assessment of disease origin and extension 4
Management Approach
SCAD often resolves spontaneously or with limited 5-aminosalicylate therapy, distinguishing it from typical IBD 3. The treatment algorithm:
- First-line: Observation alone, as many cases are self-limited 3
- Second-line: Short course of 5-aminosalicylate if symptoms persist 3
- Rarely needed: Corticosteroids for refractory cases 3
- Surgical resection: Reserved for exceptional cases with complications 3
Prognosis
Most patients experience an entirely self-limited clinical course with complete resolution 3. Recurrent episodes may occur but are uncommon, and the overall prognosis is favorable compared to inflammatory bowel disease 2, 3.
Critical Pitfall to Avoid
Do not confuse SCAD (gastrointestinal) with SCAD (cardiac—Spontaneous Coronary Artery Dissection) when reviewing medical records or discussing cases. The acronym is identical but refers to completely different disease processes in different organ systems. Always clarify the clinical context when encountering this abbreviation.