Colonic inertia is a severe motility disorder in which the colon loses effective muscle function, causing extreme, treatment-resistant constipation. Stool moves through the bowel hardly at all, leading to bloating, pain, and infrequent, difficult passage despite laxatives and dietary measures. Diagnosis involves transit studies showing markedly delayed movement. Management starts with fibre, fluids, and laxatives, but many patients need stronger prokinetic drugs or biofeedback, and in the most severe cases surgical removal of the colon is considered. The condition devastates quality of life, and care combines gastroenterology, dietetics, and psychological support.