Chronic constipation

Probability diagnosis

Simple constipation: low-fibre diet, poor fluid intake, lifestyle and bad habit

Slow transit (idiopathic) constipation

Normal transit (irritable bowel syndrome)

Serious disorders not to be missed

Intrinsic neoplasia: colon, rectum or anus, especially colon cancer

Extrinsic malignancy (e.g. lymphoma, ovary)

Hirschsprung (children)

Pitfalls (often missed)

Impacted faeces

Local anal lesions (e.g. anal fissure)

Drug/purgative abuse

Hypokalaemia

Depressive illness

Acquired megacolon

Diverticular disease

Rarities:

• lead poisoning

• hypercalcaemia

• hyperparathyroidism

• dolichocolon (large colon)/megarectum

• Chagas disease

• systemic sclerosis

Masquerades checklist

Depression

Diabetes (rarely)

Drugs (opiates, iron, others)—see list

Thyroid disorder (hypothyroidism)

Spinal dysfunction (severe only)

Is the patient trying to tell me something?

May be functional (e.g. depression, anorexia nervosa).

Key history

Define what exactly the patient means by constipation. The history should include stool consistency, frequency, ease of evacuation, pain on defecation and the presence of blood or mucus. A dietary and drug history is important.

Key examination

• The important aspects are abdominal palpation and rectal examination

• Test perianal sensation and the anal reflex

• Perform sigmoidoscopy

Key investigations

• Basic tests are FBE/ESR, occult blood in stool

• Consider serum calcium, potassium, CEA and TFTs

• If appropriate refer for sigmoidoscopy or colonoscopy and radiological studies (e.g. CT colonography, bowel transit studies)

Diagnostic tips

• Alarm symptoms are rectal bleeding, recent constipation in those >40 years and family history of cancer.

• Bleeding suggests cancer, haemorrhoids, diverticular disorder and inflammatory bowel disease.

• Beware of hypokalaemia causing constipation in the elderly patient on diuretic treatment. Drugs selected associated with constipation: analgesics, opioids esp. codeine, TCAs, antacids esp. aluminium hydroxide, Ca channel blockers, SSRIs, cough mixtures, anti-cholinergics, benzodiazepines.