A case of diarrhoea Flashcards
What is the definition of diarrhoea?
- Three or more loose or liquid stools per 24 hours and or
- Stools that are more frequent than usual for the individual lasting more than 14 days and or
- Stool weight greater than 200g/day
How is diarrhoea classified?
- Acute (<14 days)
- Persistent (>14 days)
- Chronic (>4 weeks)
Why does diarrhoea occur?
When there’s decreased absorption or increased secretion of fluid and electrolytes, or an increase in bowel motility meaning a greater than usual amount of fluid is excreted in the faeces
What are the two categories of diarrhoea?
Inflammatory and non-inflammatory
What is inflammatory diarrhoea?
Diarrhoea caused by the presence of an inflammatory process eg. bacterial, viral or parasitic infection or due to bowel ischaemia, radiation injury or IBD
What are the characteristics of inflammatory diarrhoea?
- Mucoid and bloody stool
- Tenesmus
- Fever
- Severe crampy abdominal pain
- Small in volume with frequent bowel movements
What is the most common cause of infectious diarrhoea in the US?
Bacterial infection: campylobacter, salmonella, shigella, E.coli, C. difficile
What are common causes of acute diarrhoea in developing countries?
Protozoa and parasites
What would a stool examination of inflammatory diarrhoea show?
Leukocytes, positive faecal occult blood test
What would the histology of the GI tract in inflammatory diarrhoea look like?
Abnormal
What are the characteristics of non-inflammatory diarrhoea?
- Watery
- Large-volume
- Frequent stool >10-20 per day
What is not present in non-inflammatory diarrhoea?
- Tenesmus
- Blood in the stool
- Fever
- Faecal leukocytes
What is the GI histology like in non-inflammatory diarrhoea?
Preserved
What can non-inflammatory diarrhoea be further sub-divided into?
Secretory and osmotic diarrhoea
What is secretory diarrhoea?
When there’s an altered transport of ions across the mucosa which results in increased secretion and decreased absorption of fluids and electrolytes from the GI tract
Does fasting decrease secretory diarrhoea?
No
What are some of the causes of secretory diarrhoea?
- Enterotoxins: infections such as vibrio cholerase, staphylococcus aureus, E.coli, HIV and rotavirus
- Hormonal agents: vaso-active intestinal peptide, small-cell cancer of the lung, neuroblastoma
- Laxative use, intestinal resection, bile salts and fatty acids
What is osmotic diarrhoea?
Unabsorbed or poorly absorbed solute in the intestinal tract that causes an increased secretion of liquids into the gut lumen
What is the stool volume like in osmotic diarrhoea?
Stool volume is relatively small (compared with secretory diarrhoea) and diarrhoea improves with fasting
What can osmotic diarrhoea be further divided into?
Maldigestion and malabsorption
What is maldigestion?
Impaired digestion of nutrients within the intestinal lumen or at the brush boarder membrane of mucosal epithelial cells
Seen in pancreatic exocrine insufficiency and lactase deficiency
What is malabsorption?
Impaired absorption of nutrients
Seen in small bowel overgrowth, mesenteric ischaemia, post bowel resection (short bowel syndrome) and in mucosal disease (coeliac disease)
How much fluid should normally be excreted in faeces?
0.1L
What are the enterocytes?
Cells lining the large and small intestines
Give an overview of the different forms of diarrhoea and whether they’re enterocyte or luminal issues
- Inflammatory diarrhoea: problem with the enterocytes meaning they’re unable to absorb compounds from the lumen, lots of fluid left in the lumen
- Secretory diarrhoea: channels in the enterocytes are activated meaning solutes in the enterocytes will cross into the lumen therefore water will be retained in the lumen eg. cholera- cystic fibrosis transmembrane conductance regulator is activated meaning Cl- and Na+ pass into the lumen
- Osmotic maldigestion: compounds aren’t digested (broken down) meaning they can’t be absorbed eg. lactose intolerance
- Osmotic malabsorption: compounds aren’t absorbed properly eg. laxative effect of prunes, sorbitol present which isn’t absorbed by enterocytes meaning water is retained in the lumen
How does oral rehydration solution work?
Insert a solution of 2:1 Na+:glucose into the colon which causes SGLT1 transporters to take the compounds across into enterocytes, leading to movement of water from the lumen into the enterocytes
What does SGLT1 stand for?
Sodium glucose linked transporter 1
Why does diarrhoea lead to death?
Due to massive dehydration
What is a functional cause of diarrhoea?
There are no known structural changes causing the patient’s symptoms aka. IBS
Non-progressive and non-fatal
What is an organic cause of diarrhoea?
There is a structural change causing diarrhoea eg. IBD, colon cancer, coeliac disease
What are the symptoms of IBD?
- Weight loss
- Fever
- Blood in the stool
What are the symptoms of IBS?
- Alternating constipation and diarrhoea
- Mucus in stool
- Bloating
What are the symptoms of IBS and IBD?
- Abdominal pain
- Faecal urgency- feels the need to open their bowels
- Fatigue
What is the function of a FBC?
To look for anaemia and signs of inflammation/ infection
What is the function of a urea and electrolytes test?
To check renal function and electrolyte status
What is the function of examining CRP?
To look for infection/ inflammation
What would red, fresh blood in the stool indicate?
A lower GI bleed
What would darker blood in the stool indicate?
An upper GI bleed, as the blood has been digested
How would the bleeding from stomach ulcers manifest?
Either in vomit or as darker blood in the stool
What is the function of a fecal occult blood test?
A test that looks for traces of blood that aren’t visible to the human eye
What is the function of a LFT?
A liver function test, albumin levels are also obtained: low albumin can indicate an acute inflammatory process, can also be used as a surrogate marker for malnutrition- low albumin suggests malnourishment
How can thyroid function affect diarrhoea?
Hyperthyroidism can lead to diarrhoea
Which antibody is screened for in coeliac disease?
Tissue transglutaminase antibody
What do stool tests screen for?
Microbiology, ova and cysts associated with parasite disease, faecal calproctectin
Why should stool samples be repeated even if an initial sample has come back negative?
Because ova a cysts are shed intermittently, need to take three samples two days apart
What is faecal calproctectin?
A surrogate marker for inflammation in the bowel, it indicates migration of neutrophils into the intestinal mucosa
When would faecal calproctectin be raised?
Coeliac, colon cancer and IBD as it doesn’t detail the site or extent of inflammation- non-specific test
What is the difference in location between crohn’s disease and ulcerative colitis?
look up pic
Crohn’s can occur anywhere along the GI tract
What are granulomas?
Collections of neutrophils
Which tissue layers does Crohn’s disease affect?
- Mucosa
- Submucosa
- Muscularis
- Serosa
Which tissue layers does ulcerative colitis affect?
Just the mucosa
What can treatments for conditions be split into?
- Conservative
- Medical
- Surgical
Why does smoking worsen Crohn’s disease?
It causes small areas of infarction in the gut
Why is smoking protective in ulcerative colitis?
It dampens the immune system
What is the conservative management for Crohn’s disease?
- Smoking cessation
- Dietary advice
- Psychological support
- Patient support groups
What is the medical management for Crohn’s disease?
Acute/ flare up:
- Corticosteroids
Long-term:
- Biologics: monoclonal antibodies
What is the surgical management of Crohn’s disease?
Patients at risk of fistulas and strictures as all layers of the bowel are affected, often not used as a first line treatment as the chance of the patient needing surgery again later on is high
Bowel re-section
