Clinical characteristics

• An autosomal dominant condition with 80% penetrance that is characterised by a myriad of (∼1000) colonic adenomatous polyps.

• The polyps develop at the age of puberty.

• Symptoms include vague abdominal pain, bloody diarrhoea and protein-losing enteropathy.

• The main complication is malignant transformation. By 20 years following diagnosis, almost 100% will have developed colonic carcinoma. There is also a lesser increase in the incidence of gastric and small-bowel malignancy.

• The treatment is total colectomy in the late teens or early twenties.

Radiological features

• Generally now diagnosed in family members by colonoscopy, but sporadic cases may present at barium enema with a myriad of small polyps forming a ‘carpet’ throughout the colon. There may be evidence of carcinoma, often with more than one synchronous tumour.

• CT colonography can reliably detect polyps of 5mm and smaller but represents a significant radiation dose in patients who are usually in their teens at the time of investigation.

Familial polyposis coli. The colon is ‘carpeted’ in multiple small polyps.

Familial polyposis coli (same patient; enlarged view of the sigmoid colon). Multiple polyps are clearly evident (arrowheads).