Diarrhoea and its mechanisms

Diarrhea is defined as increase in frequency of passage of liquid stool weighing more than 200 gm/day, usually more than 3 bowel movement/day.

Pseudodiarrhoea - frequent passage of small volumes of formed stool usually associated with anorectal disorders

What is the mechanism  of diarrhea

1.Secretory diarrhoea is due to secretion of chloride and water with or without inhibition of normal active sodium and water absorption.

• Increased secretion of electrolytes
• Enterotoxins - V. cholera, E.coli
• Vipoma - Pancreatic cholera
• Villous adenoma

2.Osmotic diarrhoea is due to increased amounts of poorly absorbable osmotically active solutes in the gut lumen.

• Poorly absorbed solutes - MgS04, laxatives
• Maldigestion
• Disaccharidase deficiency
• Lactose intolerance

3.Exudative diarrhea is due to the exudation of mucus, blood and protein from sites of active inflammation into bowel lumen - IBD – ulcerative colitis

4.Infections - Shigella, Entamoeba histolytica

5.Malabsorption diarrhea - Small bowel diarrhea ,Tropical Sprue

6.Motility disorder is due to abnormal intestinal motility when an increased or decreased contact between luminal contents and mucosal surface-IBS, thyrotoxicosis

Classification of diarrhea

Аcute diarrhoea - 7 to 14 days

Persistent diarrhoea - 2 to 4 weeks

Chronic diarrhoea — > 4 weeks

Difference between Small Bowel and Large bowel  diarrhoea

Features                     Small bowel             Large bowel

Volume of stool         Large                        Small

Type of stool             Watery                      Mucoid

Blood in stool            Rare                         Common

Nature of stool          Soupy / greasy          Mucinous/ jelly like

Tenesmus                  Absent                      Present

Abdominal pain        Central                     Left iliac fossa