Assessment of chronic diarrhoea

Anatomical classification of causes of diarrhoea

Colonic causes include:

• Inflammatory bowel disease (ulcerative colitis, Crohn's colitis)

• Microscopic colitis (lymphocytic/collagenous/eosinophilic colitis)

• Infective gastroenteritis (bacterial/viral/parasitic)

• Ischaemic colitis

• Colonic cancer/infiltrating malignancy

• Graft-versus-host disease.

Small bowel causes include:

• Coeliac disease

• Crohn's disease

• Bile salt malabsorption

• Brush border enzyme deficiency

• Small bowel bacterial overgrowth

• Radiation enteritis

• Eosinophilic enteritis

• Lymphoma

• Tropical sprue

• Lymphangiectasia/impaired lymphatic drainage

• Protein-losing enteropathy

• non-steroidal anti-inflammatory drug enteropathy.

Pancreatic insufficiency causes include:

• Chronic pancreatitis

• Pancreatic carcinoma

• Cystic fibrosis.

Functional:

• Irritable bowel syndrome.

Endocrine causes include:

• Hyperthyroidism

• Diabetes

• Hypoparathyroidism

• Addison's disease

• Hormone-secreting tumours (VIPoma, gastrinoma, carcinoid).

Systemic causes include:

• Drug effects

• Alcohol

• Abetalipoproteinaemia

• Advanced liver disease

• Common variable immune deficiency

• Amyloidosis.

Finally, miscellaneous causes include:

• Surgical resections (short gut syndrome) or bypass

• Faecal impaction (overflow diarrhoea).