A 58-year-old woman with a history of left-sided colonic carcinoma (treated with left hemicolectomy 2 years ago) presents with a 5-day history of progressive abdominal distension, constipation, and mild colicky pain in the left lower abdomen. She denies vomiting. On examination, her abdomen is distended but soft, with normal bowel sounds. Blood pressure is 110/70 mmHg, heart rate 88/min. Abdominal X-ray shows dilated colon proximal to the splenic flexure with a transition point, and the rectum is collapsed. CT abdomen with contrast shows a stricture at the anastomotic site with proximal colonic dilation. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Anastomotic Stricture Causing Mechanical Obstruction ### Key Clinical Features **Key Point:** Anastomotic strictures are a late complication of colorectal surgery, typically presenting 6 months to several years after the initial operation. This patient is 2 years post-hemicolectomy, fitting the typical timeline. ### Distinguishing Features of Anastomotic Stricture | Feature | Anastomotic Stricture | Recurrent Carcinoma | Adhesion | |---------|----------------------|--------------------|-----------| | **Timeline** | Months to years post-op | Variable; often progressive over weeks | Usually within first year | | **Symptom onset** | Gradual, progressive | Progressive; may have constitutional symptoms | Acute or subacute | | **Pain character** | Mild colicky or dull | Constant, severe if advanced | Colicky, intermittent | | **Imaging** | Smooth narrowing at anastomosis | Shouldering, irregular margins, shouldering | Transition point away from anastomosis | | **CT findings** | Smooth stricture, preserved wall layers | Wall thickening, shouldering, mass | Kinking or angulation of bowel | | **Vomiting** | Late or absent | May be present early | Early and prominent | ### Radiological Findings in This Case **High-Yield:** The CT shows a **stricture at the anastomotic site** — this is pathognomonic for anastomotic stricture. The key findings are: 1. **Location:** Stricture at the anastomosis (splenic flexure region, site of left hemicolectomy) 2. **Morphology:** Smooth narrowing (not irregular or shouldered) 3. **Proximal changes:** Dilated colon proximal to stricture 4. **Distal changes:** Collapsed rectum distal to stricture 5. **Absence of mass:** No bulky tumor or shouldering **Clinical Pearl:** The **5-day history** and **mild symptoms** suggest a chronic partial obstruction rather than acute mechanical obstruction or malignancy. Anastomotic strictures often present insidiously with progressive constipation and distension. ### Pathophysiology of Anastomotic Stricture ```mermaid flowchart TD A[Colorectal anastomosis]:::outcome --> B[Healing phase]:::outcome B --> C[Inflammation and fibrosis]:::outcome C --> D{Excessive collagen deposition}:::decision D -->|Normal healing| E[Patent anastomosis]:::outcome D -->|Excessive scarring| F[Stricture formation]:::action F --> G[Progressive luminal narrowing]:::outcome G --> H[Mechanical obstruction]:::urgent ``` ### Risk Factors for Anastomotic Stricture - **Ischemia** at anastomotic site - **Tension** on the anastomosis - **Infection** or anastomotic leak (most important) - **Radiation therapy** (adjuvant or neoadjuvant) - **Inflammatory bowel disease** (if present) - **Poor surgical technique** **Key Point:** Prior anastomotic leak or infection significantly increases stricture risk, even if the leak was managed conservatively. ### Management of Anastomotic Stricture 1. **Conservative management** (first-line for partial obstruction): - High-fiber diet or liquid diet - Stool softeners and laxatives - Serial follow-up 2. **Endoscopic management**: - **Balloon dilation** — effective for short, simple strictures; response rates 60–80% - **Endoscopic incision** — for refractory strictures - **Stent placement** — temporary bridge in select cases 3. **Surgical management** (for refractory cases): - **Stricturoplasty** — if stricture is short and amenable - **Resection and re-anastomosis** — for long or complex strictures **High-Yield:** Most anastomotic strictures respond well to **endoscopic balloon dilation**, making it the preferred initial intervention for symptomatic patients. ### Why This Is NOT Recurrent Carcinoma **Warning:** Recurrent carcinoma at the anastomosis would show: - Irregular, shouldered margins on imaging - Asymmetric wall thickening - Often constitutional symptoms (weight loss, anemia) - More aggressive clinical course - Imaging would show a **mass**, not just a smooth stricture The **smooth, concentric stricture** seen on CT is the hallmark of benign anastomotic stricture, not malignancy. [cite:Schwartz's Principles of Surgery 11e Ch 33; Sabiston Textbook of Surgery 21e Ch 45]