{"version":"v1","chain":{"id":"bile-acid-proximal-overgrowth","title":"Bile-acid pool failure → proximal small-bowel overgrowth","question":"Why does bile-acid dysfunction predispose to proximal SIBO?","summary":"Conjugated bile acids exert direct antimicrobial activity in the proximal small bowel; impaired conjugation, accelerated deconjugation, or reduced flow lifts that microbial brake.","steps":[{"nodeId":"concept:bile-acid-dysfunction","rationale":"Hepatic conjugation, ileal reabsorption, or flow is impaired.","evidence":"established"},{"nodeId":"pathway:fxr","rationale":"FXR signalling and bile-acid pool composition shift.","evidence":"established"},{"nodeId":"concept:sibo-host-capacity-model","rationale":"Loss of proximal antimicrobial pressure permits commensal expansion.","evidence":"established","claimIds":["conjugated-bile-acids-restrict-small-bowel-overgrowth"]}],"relatedConcepts":["bile-acid-dysfunction","sibo-host-capacity-model"],"relatedArticles":["the-hidden-driver-of-sibo-and-chronic-gut-dysfunction-bile-a"],"evidenceFloor":"established","lastReviewed":"2026-05-11"}}