Prof Mahmoud Mosli — IBS vs IBD: how to tell them apart in three minutes
A short, high-yield clinical primer on the most common diagnostic confusion in gastroenterology — irritable bowel syndrome versus inflammatory bowel disease — covering symptom overlap, red flags, the diagnostic workup, and the treatment direction for each.
Topics covered
"The test that costs the least and changes the most decisions in IBS-vs-IBD is the one most clinicians forget to order — faecal calprotectin."
Show notes
Prof Mosli opens by naming the real problem: IBS and IBD share a great deal at the surface — chronic abdominal pain, altered bowel habit, bloating, fatigue — and the patient in front of you usually cannot tell you which one they have. The clinician's job is to separate the two efficiently, because the consequences of getting it wrong run in both directions: an IBD patient labelled as IBS will keep losing bowel; an IBS patient labelled as IBD may end up on biologics they never needed.
The next minute is given to red flags. Prof Mosli walks through the short list every clinician should commit to memory: rectal bleeding, nocturnal symptoms that wake the patient, unintentional weight loss, persistent fever, family history of IBD or colorectal cancer, anaemia, and onset after age 50. Any one of these moves the case out of the IBS bucket and into a structured IBD workup — full blood count, CRP, ferritin, faecal calprotectin, and colonoscopy.
The closing segment focuses on the practical pivot point — faecal calprotectin. A normal calprotectin (< 50 µg/g) in a patient without red flags strongly supports IBS and can spare a colonoscopy. A raised value (> 150 µg/g) demands endoscopic and histological evaluation. Prof Mosli closes with the practice-changing line: the test that costs the least and changes the most decisions in this clinical question is the one most clinicians forget to order.