29 -. Diarrhoeal Disease Flashcards
Why does the definition of diarrhoea have little clinical value?
People don’t measure their stool and there is no normal bowel habit (greater than 200g and 3 times a day)
What is important in diarrhoea
Knowing what is normal for the individual patient and so when a change in bowel habit is occurring
What 2 things do you need to diagnose diarrhoea
loose consistency and increased frequency
Boundary between acute and chronic diarrhoea
14 days
What is most acute diarrhoea caused by
bacterial infection (99%)
Causes of acute diarrhoea
- viral, parasitic, bacterial infection
- salmonella
- E Coli
- campylobacter
- cholera
- staph
- norovirus
- CMV
- rotavirus
Chronic diarrhoea causes
Many causes so grouped according mechanism but several mechanisms can contribute at once
- Inflammatory
- Secretory
- Osmotic
- FATTY
Inflammatory
Damaged epithelium leads to exudate/excessive secretion. May be BLOOD (only kind of diarrhoea where there is blood)
Secretory
Is an active process where there is stimulation causing excessive fluid secretion (similar to inflam but no inflam)
Osmotic
Increase in osmotic load in colon drags in water
Fatty
(also see steatorrhoea)
due to fat malabsortion
bulky, pale, oily and hard to flush
If there is blood in the diarrhoea what must the mechanism be?
Inflammatory chronic diarrhoea
Are all mechanisms of acute diarrhoea the same
no even though they are all grouped under infective different bacteria use different mechanisms i.e.
- Campylobacter causes mucosal inflammation
- Giardia causes villous atrophy > malabs > osmotic
- E coli causes secretory
What can cause inflammatory diarrhoea
- IBD
- Diverticulitis
- SI Bacterial Overgrowth (SIBO)
- radiation and ischaemic colitis
- colon cancer
Diverticulitis
Inflammation of diverticula that usually occur due to constipation due to it being blocked with stool
SIBO and inflam diarrhoea
- the bacteria cause direct damage and inflammation of enterocytes
- often occurs in people who have had surgery or motility problems that allow the bacteria to proliferate
What can cause osmotic diarrhoea
> usually due to malabsorption
- carbohydrate malabsorption; lactose intolerance and celiac
- IBS
- SIBO
- laxative abuse
SIBO and osmotic diarrhoea
By products of bacteria are osmotically active
What can cause secretory diarrhoea
> when colon is irritated so secretes to flush
- terminal ileum resection
- causes bile acid malabs > irritates bowel
- cholecystectomy; GB removal so bile straight into SI
- microscopic colitis
- inflammatory and collagenous
- IBD
- Diverticulitis
- Neuroendocrine tumours
- SIBO
- Disordered motility such as IBS
- Colon Cancer
- Laxative abuse
- Addison’s disease
What can cause fatty diarrhoea
(fat malabs due to insufficient enzymes usually)
- Pancreatic exocrine insufficiency
- bile acid malabsorption
- SIBO
- celiacs
- short bowel syndrome (not enough mucosal surface to absorb fats and bile salts)
SIBO and fatty diarrhoea
- bacteria cause deconjugation of bile acids and so they can’t form micelles and be absorbed
What type of diarrhoea does SIBO cause
all 4 mechanisms
What is SI bacterial overgrowth
When there is excessive LI bacteria in the SI due to migration
What does SIBO cause
flatulence, bloating, distension, diarrhoea and steatorrhoea) and malabsorption
Why does SIBO occur?
Largely due to stasis
- impaired motility of the bowel causes stasis causes a build up of bacteria i.e. diabetes
- anatomic disorders causing SI stasis such as adhesions (scar tissue), strictures due to inflammation, diverticula, blind loops caused by bilroth operations
- metabolic disorders
- immune deficiency
How does bacterial overgrowth lead to diarrhoea?
Due to Maldigestion
How does SIBO affect fat absorption
The bacteria deconjugates bile acids so that micelles can’t be formed and fats can’t be absorbed
How does SIBO affect carbohydrates
Bacteria ferments and degrades carbohydrates producing osmotically active particles
How does SIBO affect protein
Bacteria degrades protein precursors
How does the bacteria affect the enterocytes?
The bacteria damage the enterocytes by direct adherence and producing enterotoxins and enzymes which impairs SI absorption
What absorption does SIBO affect
fat, carb, protein, B12 (bacteria compete for the B12), iron, bile acids
How is each kind of diarrhoea formed in SIBO
Fatty
- deconjugation of bile acids leads to impaired micelle formation and fat malabsorption leading to steatorrhoea
Osmotic
- malabs and influx of osmotically active particles
Secretory
- unabsorbed/digested food particles and bile irritate the mucosa (serotonin stimulates gut motility)
Inflammatory
- bacteria causes direct inflammation of enterocytes
What does delayed vomitting suggest
Pyloric obstruction
Not vomitting until the stomach reaches capacity
Chronic inflammation > scarring and fibrosis > stenosis > buildup in stomach
How to treat duodenal ulcer and pyloric obstruction
Vagotomy or gastro-jejunostomy (billroth 1 or 2)
What is a consequence of a gastro-jejunotomy?
Likely to get upper abdominal discomfort due to having no pylorus to regulate chyme passage resulting in rapid gastric emptying, high osmotic load into smaller capacity SI causes distension, pain and osmotic diarrhoea
Patient then gets inflammation from rectum through to transverse colon continuously. Diarrhoea gets a lot worse with pain, mucus, blood and urgency. What is this likely to be?
Ulcerative Colitis
Inflammation and damage so causes inflammatory diarrhoea
As a result of the ulcerative colitis what surgery is she likely to have
Colectomy and ileostomy
where the colon and damaged distal ileum are removed and then diverted into an opening in the abdominal wall rather than rectum
Ileostomy
SI brought to surface of abdomen so contents drained into stoma bag
- contents larger volume
- thick liquid that is green/brown
- no bacteria so no smell
- electrolytes similar to blood plasma
- increase sodium loss
Significant loss in ileostomy is…
sodium initially is lost
may need to have increased sodium in their diet initially
later adapts to increase sodium reabsorption in the kidney
Why may this patients ileostomy output be more increased than usual?
Due to her previous gastric surgery which causes an osmotic diarrhoea
How to manage this increased diarrhoea in ileostomy
Need to decrease the motility of the SI in order to increase time for absorption
Anti-diarrhoea drugs
Why does a person with crohns and subsequently having terminal ileum resection have diarrhoea
- crohns affects the SI and LI and so can cause stricturing in the terminal ileum hence the surgery
- loss of receptors for both B12/IF complex and bile acids and lose both of these
- can get 2 types of diarrhoea
1. Secretory due to bile acid irritation of LI
2. Steatorrhoea due to the lack of bile acids remaining (as only 5% made) and fat malabsorption
How to prevent diarrhoea from bile acids?
Cholestyramine
Cholestyramine binds bile acids so stops irritation
The patient later has more SI removed resulting in severe diarrhoea and dehydration why?
Short Bowel Syndrome
Complication of SI surgery
Get major malabsorption of almost everything
What do patients with small bowel syndrome do better with
ileocaecal valve as acts as a brake to slow some fluid movement and allow abs in the SI especially of fluid
What are 2 adaptations with small bowel syndrome
- Villous hypertrophy
- Colon gets an increased absorptive capacity
Despite these patients still can’t eat normally
How to manage short bowel syndrome
- diet. Less salt as this causes fluid retention and low osmotic diet
- anti-motility
- acid suppressant (usually a lot of acid is secreted a day - 1.5L)
- cholestyramine
Cholestyramine
Binds bile acids
Stops irritation, itching and diarrhoea
Helps eliminate cholesterol
