Chronic constipation is a polysymptomatic heterogeneous disorder. Patients define constipation on the basis of:

• excessive straining
• a sense of incomplete evacuation
• failed or lengthy attempts to defecate
• hard stools
• (less frequently) by the number of stools per week

Aetiology

• Dietary e.g. inadequate fibre intake, inadequate fluid intake
• Behavioural e.g. inactivity, avoidance of defecation
• Electrolyte disturbance e.g. hypercalcaemia, hypokalaemia
• Drugs, particularly opiates, calcium channel blockers and some antipsychotics
• Neurological disorders e.g. spinal cord lesions, Parkinson's disease, diabetic neuropathy
• Endocrine disorders e.g. hypothyroidism
• Colon disease e.g. stricture, malignancy, IBD
• Anal disease e.g. anal fissure, proctitis

We can also divide the causes of constipation into peristalsis related causes, hard faeces related causes, bowel obstruction, patient not pushing.

Classification

• Normal transit constipation (59%): stool traverses at a normal rate but patients believe they are constipated due to hard stools or difficulty of evacuation - can be diagnosed using colonic transit radioopaque markers (abdo x-rays)