Distal GI Tract Pathology - Diarrhoea + Constipation Flashcards
Define diarrhoea
Loose or watery stools 3+ times a day
How does diarrhoea occur?
- Unwanted substances in gut stimulates secretion + motility to get rid of it
- Colon is overwhelmed and cannot absorb volume of water from the ileum
Two types of diarrhoea
Osmotic
Secretory
What is osmotic diarrhoea?
Caused by osmotically active substances in the gut that draw water in (often due to malabsorption)
e.g. lactose deficiency
What is secretory diarrhoea?
Active water secretion in gut due to infectious toxins
What does osmotic diarrhoea lead to?
Moderately increased stool
What does secretory diarrhoea lead to?
Very large stool volume due to active secretion of water into gut
How can osmotic diahrreoa be alleviated?
Removing the substance causing it
Causes of diarrhoea
- osmotic
- secretory
- reduced SA for absorption
- mucosal disease e.g. coeliac or crohn’s
- reduced contact time e.g. IBS or diabetes
What is constipation?
- straining during >25% defecations
- lumpy or hard stools in >25% defecations
- feeling of incomplete evacuation in >25% defecations
- feeling of obstruction or blockage in >25% defecations
- having fewer than 3 unassisted bowel movements in a week
Risk factors for constipation
- F:M 3:1
- medications e.g. opioids, anti-diarrhoea drugs
- low level physical activity
- increasing age (also common in children <4)
Causes of slow colonic transport
- large colon
- fewer + shorter peristaltic movements
- fewer intestinal pacemaker cells (interstitial cells of Cajal)
- systemic disorders e.g. hypothyroidism, diabetes
- nervous system diseases e.g. Parkinson’s, MS
Why can a large colon cause slow colonic transport?
Larger diameter affects the pressure exerted on stool for movement
How can constipation be classified?
Transit types
- normal transit
- slow colonic transit
- defaecation problems
What is normal transit constipation often related to?
Psychological stressor
