A 55-year-old man develops constipation that has been present for 6 weeks, a change from his lifelong normal habit. What is the single most important consideration in his assessment?

Answer: B. Exclude a mechanical cause such as a colorectal neoplasm

Acute (new) constipation - think mechanical cause

Constipation of under 3 months' duration (acute), especially a change in habit in someone over 40, should always prompt a search for a mechanical cause - a stricture, a neoplasm, or faecal impaction.

Why this matters

• A recent change in bowel habit in an older adult is a red flag for colorectal cancer.
• In acute constipation, barium enema or sigmoidoscopy/colonoscopy is mandatory to exclude a mechanical obstruction.

Acute versus chronic

Clinical relevance

Jumping to reassurance or a functional diagnosis risks missing a curable cancer; a thorough clinical examination including a digital rectal examination is a must.