Sigmoid Colon Cancer

Sigmoid colon cancer is adenocarcinoma arising between the descending colon and rectosigmoid junction.

Its relatively narrow lumen and increasingly solid stool explain why sigmoid tumours frequently present with altered bowel habit, obstruction or progressive colicky pain.

The operative objective is removal of the sigmoid tumour together with its regional mesocolic lymphovascular drainage.

Typical findings are:

• Progressive constipation or altered bowel habit
• Rectal bleeding
• Lower abdominal discomfort
• Iron deficiency anaemia
• Weight loss

Circumferential lesions may produce progressive large bowel obstruction with distension, constipation and late vomiting.

Perforation can occur through the tumour or proximally, particularly at a severely distended caecum when the ileocaecal valve is competent.

Colonoscopy with biopsy: establishes diagnosis and detects synchronous lesions.

CT chest, abdomen and pelvis: stage regional and metastatic disease.

Obtain baseline carcinoembryonic antigen and tumour mismatch repair or microsatellite instability status.

Elective curative treatment is sigmoid colectomy with adequate proximal and distal margins and mesenteric lymphadenectomy.

Mesenteric resection should encompass the relevant sigmoid and inferior mesenteric vascular drainage while maintaining perfusion of the remaining colon and rectum. At least 12 lymph nodes should be assessed.

Restore continuity with a tension free, well perfused descending colorectal anastomosis when appropriate.

Locally invasive tumours require en bloc resection of involved adjacent structures.

Adjuvant treatment follows colon cancer stage. Stage III disease receives FOLFOX or CAPOX. High risk stage II disease is considered individually.

Obstructing sigmoid cancer

Resuscitate, correct fluid and electrolyte deficits and decompress where appropriate.

A self expanding metal colonic stent can provide a bridge to elective surgery in selected potentially curable left sided cancers when experienced endoscopic expertise is available. It allows physiological optimisation, complete staging and a higher likelihood of one stage resection.

Perforation, peritonitis or threatened bowel requires emergency surgery.

A stable patient with viable colon may undergo oncological sigmoid resection with primary anastomosis, with selective diverting ileostomy when leak risk is significant.

Severe sepsis, gross faecal contamination, poor perfusion or major physiological compromise favours an end colostomy with rectal stump or another staged strategy rather than a high risk anastomosis.