Functional GI and Motility Disorders
Core concepts
Functional disorders are defined by symptom patterns, not by absence of disease. Know Rome criteria for irritable bowel syndrome (recurrent abdominal pain with altered stool form or frequency), functional dyspepsia, and functional constipation. Understand the brain-gut axis and the role of visceral hypersensitivity and motility.
For motility, distinguish gastroparesis (delayed emptying with nausea, vomiting, early satiety) from functional dyspepsia (normal emptying). Recognize achalasia (dysphagia to solids and liquids, bird-beak on imaging) versus mechanical obstruction (solids first). Understand that rumination and cyclic vomiting are distinct from gastroparesis.
Traps
Questions test whether alarm features are present; if they are, functional labels are premature. Do not order gastric emptying studies before excluding obstruction. Also avoid attributing all bloating to bacterial overgrowth without evidence; breath testing is imperfect.
Rule of thumb
Diagnose functional disorders only after excluding structural disease when alarm features exist, and treat with a biopsychosocial approach including diet, neuromodulators, and behavioral therapy.
Worked example
A patient with chronic nausea and early satiety but normal endoscopy and no obstruction may have gastroparesis or functional dyspepsia; an emptying study distinguishes them, but only after obstruction is excluded.