Diarrhoea

Diarrhoea is both a symptom and a sign. As a symptom, it is whatever the patient says it is. As a sign, diarrhoea is an increase in stool weight of more than 200g per 24 hours in a person on a western diet.

Pathophysiology:

The pathophysiological mechanisms resulting in diarrhoea can be divided into 4 major groups.

1) Osmotic diarrhoea occurs when non-absorbable solutes accumulate within the small intestine - Carbohydrates, Fat, bile salt and other substances such as lactulose & magnesium.

It is helpful to know the effect of fasting on stool output: when the diarrhoea ceases with fasting, a dietary component is likely to be the cause.

The most common carbohydrate malabsorption is lactose intolerance secondary to primary lactase deficiency or lactase nonpersistance.

2) Secretary diarrhoea results when the secretagogues increase the chloride secretion through the activation of cystic fibrosis transmembrane regulator ( CFTR ) or inhibit the sodium and chloride absorption.

Bacterial toxins are the common cause of secretary diarrhoea. However, Non-osmotic laxatives, bile salts and short chain fatty acids are other agents that can damage electrolyte transport and result in secretary diarrhoea. Hormonal secretion from tumor can also cause secretary diarrhoea ( such as gastrin and vasoactive intestinal peptide ).

3) Inflammatory diarrhoea - includes invasive infective agents, irradiation, cancer, inflammatory bowel disease, gluten sensitive enteropathy, ischaemia and drugs.

4) Dysmotility such as thyrotoxicosis, diabetes mellitus, irritable bowel syndrome and laxative abuse.

WHO definition of bone mass

Normal bone mass: T score > -1
Low bone mass: T score -1 to -2.5
Osteoporosis: T score < - 2.5
Established ( severe ) osteoporosis: T score < - 2.5 and one or more osteoporotic fractures