Causes
Causes of chronic diarrhoea also include reactions to drugs, parasitic and fungal infections; malabsorption; bowel tumours; as a consequence of endocrine disorders such as thyrotoxicosis; secondary to diabetes; and as a problem with overflow in a patient who is actually constipated.

Diarrhoea can occur as a result of stress in the irritable bowel syndrome and following antibiotic treatment where a condition called pseudomembranous colitis can occur.

Complications of Diarrhoea
Complications of diarrhoea include dehydration; weight loss if malabsorption is a feature; anaemia if the diarrhoea is bloody; and an imbalance of the chemicals in the blood stream, particularly sodium and potassium. 

Tests
Blood tests to look at the sodium and potassium levels in the bloodstream in acute diarrhoea is usual if the diarrhoea is severe. Specimens of the stool are sent to the laboratory to look for parasites and to check for bacteria which cause diarrhoea. In chronic diarrhoea, then an endoscopic test where a flexible fibre optic endoscope is passed into the rectum or back passage and advanced into the lower colon (flexible sigmoidoscopy) is often performed. Some times a full colonoscopy (where the entire large bowel is inspected) is required to make a diagnosis. Where the bowel lining is abnormal then specimens (biopsies) may be taken for study in the laboratory. In many patients no tests are required and a wait and see policy is adopted.

Treatment
In acute diarrhoea the most important treatment is the replacement of fluid and salts plus glucose which have been lost in the watery diarrhoea. Oral rehydration therapy is of particular importance and special solutions of Sodium Chloride and Glucose powder are available (e.g. Dioralyte). Antibiotics are sometimes used in travellers diarrhoea but are usually not necessary. Codeine Phosphate or Loperamide may be useful for short term relief of diarrhoea particularly where travel is essential but should not be used long term without prior investigation of the cause of the diarrhoea. In some cases food avoidance, e.g. gluten-free diet in coeliac disease or dairy product avoidance in a lactose intolerance may be advised. In inflammatory bowel disease (Crohn’s disease, ulcerative colitis), steroids may be necessary to reduce inflammation together with more specific treatment. Other tests used in chronic diarrhoea include barium enema, which is an Xray test of the large bowel.