Etymology: L, in, not, activus, active; Gk, kolon, colon
hypotonicity of the bowel that results in decreased contractions and propulsive movements and a delay in the normal 12-hour transit time of luminal contents from the cecum to the anus. Colonic inactivity may be caused by acquired or congenital megacolon, anticholinergic drugs, depression, faulty habits of elimination, inadequate fluid intake, lack of exercise, a low-residue or starvation diet, neuroendocrine response to surgical stress, prolonged bed rest, or a neurological disease such as diabetic visceral neuropathy, multiple sclerosis, parkinsonism, or spinal cord lesions. Normal motility of the colon is frequently compromised by the continued use of laxatives. Acquired megacolon, characterized by an abnormally large, inactive bowel and chronic constipation, is common in mentally retarded children and adults with chronic mental illness. In congenital megacolon (Hirschsprung's disease), congenital absence of myenteric innervation in a distal segment of the colon causes loss of motility and massive dilation of the proximal segment of the large bowel and extreme constipation. The disorder is more common in males than females and in severe cases retards growth. Treatment of colonic inactivity includes a stimulus-response training program to establish regular bowel habits, the use of stool softeners and hydrophilic colloids to increase fecal bulk, and a diet containing adequate roughage.