An irregular ulcer in the rectum

A man in his 50s was referred to hospital by his general practitioner with a suspected rectal lesion after rectal examination. He had also experienced intermittent constipation without rectal pain for five years, which he had managed with self-administered simple enemas once a week for the past three years, but these were not effective at relieving the constipation. He had a medical history of intolerance to penicillin. Full details of his sexual history could not be elicited. Digital rectal examination showed a non-tender rectal lesion of about 3 cm in diameter on the left side of the rectum; it had a smooth base, was slightly raised, and had indurated borders. Relevant laboratory test results are shown in table 1. View this table: Table 1 Relevant laboratory test results Magnetic resonance imaging showed irregular low rectal wall thickening (about 4 cm …