Diarrhoea Flashcards
Why is there little clinical value in ‘standard measures’ of normal and abnormal stools?
It is hard to determine what is normal, many people are different, so instead look at what is normal for the PATIENT.
medical aid designed to classify poop consistency?
Bristol Stool Chart.
This is helpful for the patient.
How can you determine acute vs chronic diarrhoea? How do their causes differ?
Acute= upto 14 days
95% infectious cause
Chronic = over 14 days
many different causes
Therefore it’s important to ask patient for TIME FRAME
Causes of Acute Diarrhoea?
INFECTION
1) Bacteria- salmonella, E.Coli, campylobacter
2) Viruses- norovirus(rest homes), rotovirus
3) Protozoa
Infective causes can have different mechanisms, give examples of this.
Campylobacter > INFLAMMATORY diarrhoea
Glardia > OSMOTIC diarrhoea
mild villous atrophy> carb malabsorption> osmotically active sugars> water drawn in
E.Coli > SECRETORY
toxin stimulates fluid secretion
Causes of Chronic diarrhoea
There are many causes that can be grouped into…
Inflammatory: damaged epithelium lead to exudate, eg) IBD
Osmotic: osmtically active compound draws water in
Secretory: stimulation of excessive fluid secretion
Fatty: Fat malabsorption
These are classifications of BOTH acute and chronic, and there is often overlap
Inflammatory diarrhoea is often due to
- IBD
- Diverticulitis (diverticula > stool filled > infection > inflamm)
- SIBO (direct inflammation of enterocytes)
- Radiation colitis
- Ischaemic colitis (lack of BF to colon)
- colon cancer
Osmotic Diarrhoea is often due to
Carb malabsorption: lactase intolerance, IBS
Coeliac disease
SIBO:: malabsoption of proteins, carbs fats and other osmotically active by-products of bacteria metabolism
Laxative Abuse: (can be OSMOTIC or stimulative)
Types of Lactose intolerance
Primary LI: due to lactase deficiency
Secondary LI: due to enterocytes that produce lactase being damaged
Secretory Diarrhoea can be caused by
- Terminal Ileal Resection
- Cholecystectomy: GB removed, bile flows straight into SI
- Microscopic Colitis
- IBD
- Diverticulitis
- Neuroendocrine Tumors
- SIBO
- Disordered motility (IBS, post-vagotomy)
- Colon cancer
- Laxative abuse- stimulatory type
Neuroendocrine tumors
Rare increase in hormones that can drive water secretion (gastrinoma- excess gastrin, carinoid- excess serotonin)
-secretory diarrhoea
How does TI resections cause Secretory diarrhoea
Where BAs are normally absorbed, post-surgery they enter colon (malabsorb), irritate it = fluid response
Fatty diarrhoea can be caused by
- Pancreatic Exocrine insufficiency (esp. LIPASE)
- Bile acid malabsorption (not enough bile)
- SIBO
- Coeliacs disease
- Short bowel syndrome (too much SI removed, not enough surface)
What is SIBO? Symptoms?
Small Intestine Bacterial Overgrowth
-Excessive amounts of LI bacteria in the SI
Symptoms (siimilar to IBS): bloating/abdo discomfort, diarrhoea, flatulence, steatorrhea, malabsorption
Predisposers of SIBO
Impaired motility- usually a motor complex prevents SIBO by clearing debris eg) scleroderma, diabetes
Anatomical Disorders- lead to SI stasis. eg) strictures, adhesions, SI diverticula, blind loops
- metabolic/systemic diseases
- immune deficiency
How does SIBO affect MALDIGESTION
- bacteria deconjugate BAs leading to impaired micellar formation and fat digestion (FATTY DIR.)
- Bacterial degradation of carbs in the intestinal lumen > osmo active byproducts (OSOTIC DIR.)
- bacterial degradation of protein precursors
How does SIBO affect MALABSORPTION
bacteria can directly damage enterocytes by direct adherence > enterotoxins (INFLAMMATORY DIR) leads to malabsorption of -BAs -fats -carbs -proteins -B12 (bacteria competes with B12 for nutrition) (SECRETORY DIR)
what type of diarrhoea can SIBO cause
all four types
Maelena
Black stools. indicates bleeding from upper GI track (SI). Digested blood is altered by acid
Delayed vomiting after meals suggests?
Pyloric obstruction
Ulcers around the pylorus
eg) pre-pyloric or duodenal
cause a distrotion of the normal pylorus, this can lead to a change in gastric emptying, pain and eventually fibrosis.
Over months a pyloric stenosis can formed, blocking food.
if an ulcer gets deep enough, active bleeding > maelena
Pyloric Stenosis (obstruction) is treated with?
1) Endoscopic balloon dilation (temp fix)
2) gastro-jejunostomy and truncal vagotomy (cut bits out)
eg) billroth 1 & 2 -distal stomach and prox duodenum removed
3) now lots of successful drugs (surgery uncommon)
What can happen post gastro-jejunostomy and truncal vagotomy?
Upper Abdo discomfort after eating.
- rapid gastric emptying as no pylorus
- High osmotic load pulls fluid into jejunum
Diarrhoea
- Osmotic diarrhoea
- vagotomy leads to increased SI motility
Why is the symptoms bleeding with diarrhoea helpful?
Because it only occurs with inflammatory diarrhoea.
Therefore excludes many other potential causes
Colectomy
Surgical procedure to remove all or part of the colon. Can sometimes be avoided with instead using some drugs.
However, if people fail to respond to medication, a colectomy and/or ileostomy may be done
Ileostomy is?
Usually done in parr with a colonoscopy, where all or part of the LI is removed. SI taken to the skin at the mid-portion of the abdomen, usually on the right, contents emptied into a bag. Patients empty this bag several times a day.
When your ileostomy is temporary it most often means all of your large intestine was removed but you still have at least part of your rectum.
Some are permanent
Usual Ileostomy output
0.6-1L/day
thick fluid
dark green/brown
-no odour (no bacteria)
Contains electrolyes, increased sodium loss. Kidneys usually adapt to this and increase sodium reabsorption.
Increase sodium intake
How can you decrease small bowel motility?
With medication
loperamide (anti-diarrhoea agent)
so absorption is increased
Crohns Disease
Chronic inflammatory condition that can occur at any part of the GI tract (usually colon or TI). Over time fibrous/scarring occurs, and this can lead to strictures.
The narrowing of the SI is a common complication, there are drugs to fix BUT once it becomes a fibrotic stricture the meds wont work (they only target inflamm). Then an operation would be needed
Two common consequences of Crohns disease.
1) B12 malabsorbtion- loss of TI’s specialised receptors for B12/IF
2) Bile salt malabsorption- reduced reuptake of bile salts via enterohepatic circ, instead lost thrugh colon/faeces, where they irritate the colon > water and electrolyte sectretion (secretory dir.)
Also the lack of BAs leads to fat malabsorbtion (Fatty dir.)
Usually one of the two dirrhoeas will predominate/drive
A drug that binds BAs (used for Crohns)
Cholestryamine
Short Bowel Syndrome
Too much SI removed, complication of SI surgery, leads to malsborption of everything.
- vitamins, minerals
- water, electrolytes
- proteins, fats, carbs
- bile acids
People with colon and illeocaecal valve do better.
colon reabsorbs water
valve acts as brake
Adaption to Short bowel syndrome. If this doesn’t work, how is it managed?
Ileal adaption: villi hypertrophy
Colon increases water absorption
Dietary (iso-osmotic) Anti-motility drugs (slow down) Acid suppressant meds Cholestyramine TPN (IVF)
