26th April 2024

A 70-year-old man presents with a 6-month history of progressively worsening constipation, despite no significant changes in diet or lifestyle.

A 70-year-old man presents with a 6-month history of progressively worsening constipation, despite no significant changes in diet or lifestyle. He reports straining with bowel movements, feeling of incomplete evacuation, and having bowel movements fewer than three times per week. He has not noticed any blood in his stool. His appetite is good, and there is no significant weight loss. His past medical history includes hypertension and type 2 diabetes.

On examination, his abdomen is soft with no palpable masses. Rectal examination reveals hard stool in the rectum.

Investigations:

Complete blood count: Normal

Serum electrolytes: Normal

Thyroid function tests: Normal

Colonoscopy: Normal

Which is the most likely cause of his presentation?