23.1
Troubles intestinaux chroniques : introduction
Les maladies chroniques de l'intestin sont un groupe de maladies chroniques affectant le tube digestif, caractérisées par une inflammation et des lési…
Les troubles intestinaux chroniques sont des affections médicales à long terme affectant le tube digestif, y compris des troubles tels que le syndrome du côlon irritable ou SCI et les maladies inflammatoires de l’intestin ou MICI.
Le SCI entraîne des douleurs abdominales chroniques et des habitudes intestinales altérées.
Il se manifeste soit par un SCI-C à prédominance de constipation avec une fréquence réduite des selles, soit par un SCI-D à prédominance diarrhéique caractérisé par une gêne abdominale récurrente et des selles molles fréquentes.
La MICI implique une inflammation intestinale chronique récurrente due à des attaques immunitaires d’un système immunitaire hyperréactif sur des bactéries résidentes de l’intestin.
Cela déclenche la diarrhée, des douleurs abdominales et des saignements intestinaux. Les principaux sous-types de MII sont la colite ulcéreuse et la maladie de Crohn.
La colite ulcéreuse affecte principalement le rectum et le côlon avec une inflammation continue de la couche muqueuse rectale.
En revanche, la maladie de Crohn affecte l'ensemble du tube digestif, l'iléon terminal étant le plus souvent touché. Il provoque une inflammation transmurale discontinue dans tout le tractus gastro-intestinal, entraînant une fibrose, des rétrécissements ou une fistule.
View the full transcript and gain access to JoVE Core videos
Q1: What is the difference between IBS-C and IBS-D?
IBS-C, or constipation-predominant IBS, is characterized by reduced bowel movement frequency. IBS-D, or diarrhea-predominant IBS, involves recurrent abdominal discomfort and frequent loose stools. Both manifest chronic abdominal pain but differ in bowel habit patterns and require distinct treatment approaches for symptom management.
Q2: How does ulcerative colitis differ from Crohn's disease in terms of inflammation?
Ulcerative colitis causes continuous mucosal inflammation limited to the rectum and colon. Crohn's disease features discontinuous transmural inflammation affecting the entire digestive tract, with the terminal ileum most commonly involved. Transmural inflammation in Crohn's damages all intestinal layers, potentially causing fibrosis, strictures, or fistulas.
Q3: What role does the immune system play in inflammatory bowel disease?
IBD involves an abnormal immune response to gut microbiota in genetically predisposed individuals. Ulcerative colitis exhibits TH2 and TH17-mediated inflammation with lymphocytic and neutrophilic infiltrates. Crohn's disease shows TH1-mediated inflammation with elevated IL-12, IL-23, IFN-γ, and TNF-α levels, causing macrophage and lymphocyte infiltration.
Q4: Why do psychological factors influence IBS symptoms?
IBS pathophysiology involves visceral motor and sensory dysfunction linked to the gut-brain axis, connecting gastrointestinal function with mood and stress. Heightened visceral sensitivity in IBS responds to both normal physiological stimuli and harmful stimuli, with psychological stress amplifying symptom severity. This complex interplay requires dietary, stress management, and drug therapy.
Q5: What complications can develop from chronic inflammatory bowel disease?
IBD can lead to extraintestinal manifestations involving joints, skin, or eyes, and increases colorectal cancer risk. Crohn's disease may develop fibrosis, strictures, or fistulas from transmural inflammation. Ulcerative colitis can rarely progress to primary sclerosing cholangitis, causing inflammation and fibrostenosis of the biliary tree.
Q6: What are the primary treatment goals for inflammatory bowel disease?
Medical treatment for IBD aims to suppress the inflammatory response, achieve mucosal healing, and maintain remission. Specific complications such as fistulas require targeted intervention. Treatment strategies vary based on disease subtype and severity, with drugs for treatment of Crohn's disease in IBD using biologic agents anti TNF and other approaches available.
Q7: How does IBS pathophysiology differ from IBD pathophysiology?
IBS involves visceral motor and sensory dysfunction with heightened sensitivity to normal and harmful stimuli, often linked to mood disorders and the gut-brain axis. IBD involves chronic intestinal inflammation from immune attacks on gut bacteria, causing structural damage. IBS lacks the immune-mediated inflammation and tissue damage characteristic of IBD.