What is the clinical significance of an incidental small duplication cyst of the sigmoid colon found on pelvic ultrasound in a female?

Clinical Significance of Incidental Small Sigmoid Colon Duplication Cyst on Pelvic Ultrasound

An incidental small duplication cyst of the sigmoid colon found on pelvic ultrasound in a female is a rare benign congenital anomaly that warrants surgical consultation and consideration for excision, even when asymptomatic, due to potential for future complications including malignant transformation, obstruction, and perforation. 1, 2

Understanding the Lesion

Duplication cysts are congenital anomalies resulting from embryonic foregut development errors that contain gastrointestinal epithelium and share a wall with the adjacent bowel. 1 Key characteristics include:

• Colorectal duplications represent only 6.8% of all gastrointestinal duplications and are exceedingly rare in adults 2
• The cysts are typically cystic (rather than tubular) and usually do not communicate with the intestinal lumen 1, 2, 3
• On ultrasound, duplication cysts appear as anechoic, smooth, spherical or tubular structures with well-defined walls 1
• The cyst wall demonstrates the characteristic "gut signature" showing multiple layers of bowel wall structure 4

Clinical Implications and Risks

Despite being congenital and often asymptomatic when discovered incidentally, these lesions carry significant risk for complications:

Malignant Potential

• Malignant changes, though uncommon, occur most frequently in colonic duplications compared to other gastrointestinal sites 2
• Dysplasia (both high-grade and low-grade) has been documented in adult sigmoid duplication cysts 2
• Heterotopic gastric mucosa may be present, which can lead to additional complications 2

Mechanical Complications

• Duplications can cause intestinal obstruction through volvulus or mass effect as they enlarge 2, 5, 4
• Perforation, bleeding, and infection are documented complications 4
• The cysts can enlarge over time since they typically do not communicate with the bowel lumen 1

Recommended Management Approach

The treatment of choice is surgical excision, typically requiring en bloc resection of the cyst with the adjacent sigmoid colon due to intimate wall attachments. 2, 5, 3

Surgical Planning

• Preoperative imaging with CT or MRI may be helpful for surgical planning, though accurate diagnosis is often made at laparotomy 5
• En bloc resection with the adjacent colon segment is necessary because the duplication shares a common wall with the sigmoid colon 2, 3
• Primary anastomosis (end-to-end colo-colostomy) is typically performed after resection 5, 3

Pathologic Evaluation

• Thorough sampling of the resected specimen is mandatory to detect any malignant changes or dysplasia 2
• The specimen should be examined for heterotopic gastric mucosa and any areas of dysplasia 2

Critical Pitfalls to Avoid

Do not adopt a "watch and wait" approach for sigmoid duplication cysts, even when small and asymptomatic:

• Unlike simple ovarian cysts which can be safely observed, duplication cysts do not spontaneously resolve and carry risk of complications 1, 2
• The preoperative diagnosis may be difficult and can be confused with other cystic lesions (giant diverticulum, mesenteric cyst) 5
• Do not attempt biopsy via colonoscopy if the cyst communicates with the lumen, as this is not diagnostic and risks complications 2

Differential Considerations

This finding should not be confused with:

• Ovarian or adnexal cysts, which follow different management algorithms 1
• Parapelvic renal cysts, which are typically benign and require no treatment 6
• Pneumatosis cystoides intestinalis, which appears as multiple gas-filled cysts and is managed conservatively 7

Referral to a colorectal surgeon for evaluation and surgical planning should be made promptly upon identification of a sigmoid duplication cyst, regardless of size or symptoms. 2, 5