Diarrhoea and Malabsorption Flashcards
How much fluid enters the gastrointestinal tract?
9 L
Where and how much fluid is absorbed in the gastrointestinal tract?
Small bowel - 7 L
Colon - 1.8 L
On what does absorption of water depend?
Absorption of solutes, especially Na
How are carbohydrates digested?
Salivary and pancreatic amylases
Brush border enzymes
Ho are proteins digested?
HCl
Gastric pepsin
Pancreatic peptidases
How is fat digested?
Bile
Pancreatic lipase
What is diarrhoea?
Abnormal frequency and liquidity of stool
Can cause excess fluid and electrolyte loss
Stool >200 g/day and >3 movements/day
When is diarrhoea defined as chronic?
Persists for >4 weeks
What investigations on faeces could help establish the mechanism or diagnosis for diarrhoea?
Microscopy and culture Faecal electrolytes and osmolarity Faecal fat Faecal elastase Clostridium difficile toxin Faecal calprotectin Faecal laxative screen Faecal alpha1-antitrypsin
Of what is faecal elastase a marker?
Exocrine pancreatic sufficiency
Of what is faecal calprotectin a marker?
GI inflammation
Used if
- May have IBD, and can’t have diagnostic colonoscopy
- Not sure if have IBD
What can be included in a faecal laxative screen?
Anthroquinones
Bisacodyl
Phenolphthalein
Of what is alpha1-antitrypsin a marker?
Protein losing enteropathy
What causes osmotic diarrhoea?
Presence of excess unabsorbed substrates in gut lumen
What is a common cause of osmotic diarrhoea?
Fermentable carbohydrate (FODMAPs) malabsorption
What is the stool volume in osmotic diarrhoea?
Typically <1 L
What is the effect of fasting on osmotic diarrhoea?
Stops with fasting
Are there stool leukocytes in osmotic diarrhoea?
No
What causes secretory diarrhoea?
Active anion secretion from enterocytes
What are the common causes of secretory diarrhoea?
Bacterial toxins - Cholera - ETEC Hormone secreting tumours - Carcinoid - Gastrinomas Laxative abuse Hyperthyroidism
What is the stool volume in secretory diarrhoea?
Usually >1 L
What is the effect of fasting on secretory diarrhoea?
Persists during fasting
Are there stool leukocytes in secretory diarrhoea?
No
What causes inflammatory diarrhoea?
Altered membrane permeability > exudation of
- Protein
- Blood
- Mucus
What are the common causes of inflammatory diarrhoea?
Invasive bacteria - Shigella - Salmonella - Campylobacter - Clostridium difficile Entamoeba hystolytica CMV colitis IBD
What is the stool volume in inflammatory diarrhoea?
Usually small
Are there leukocytes and erythrocytes present in the stool in inflammatory diarrhoea?
Yes, increased RBCs and leukocytes
What other symptoms can inflammatory diarrhoea be associated with?
Urgency
Tenesmus
Constitutional symptoms; eg: fever
What is the mechanism of deranged intestinal motility causing rapid transit?
Inadequate time for absorption of fluid and nutrients
What are the causes of deranged intestinal motility causing rapid transit?
IBS
Thyrotoxicosis
Diabetic neuropathy
What is the mechanism of deranged intestinal motility causing slow transit and associated malabsorption?
Bacterial overgrowth > nutrient consumption > bile salt inactivation
What are the causes of deranged intestinal motility causing slow transit?
Anatomical defects > intestinal stasis
- Strictures
- Blind loops
- Surgical procedures
What intraluminal disorders can lead to malabsorption?
Mechanical - mixing disorders
- Post-gastrectomy
Reduced nutrient availability
- Co-factor deficiency; eg: pernicious anaemia
- Bacterial overgrowth > nutrient consumption
Defective nutrient breakdown
- Pancreatic insufficiency; eg: chronic pancreatitis
Reduced bile salt concentration > reduced fat solubilisation
- Cholestasis
- Bacterial overgrowth
What intramural and transport disorders can lead to malabsorption?
Inadequate absorptive surface - Intestinal resection/bypass due to disease Diffuse mucosal disease - Coeliac disease - Crohn's disease - Giardia infection - Brush border enzyme deficiency Mucosal absorptive defects - Lymphoma - Lymphatic obstruction - Radiation damage - Vascular problems
What are the differential diagnoses for bloody, mucousy diarrhoea with tenesmus?
Infection - dysentery - Salmonella - Shigella - Yersinia - Entamoeba histolytica - CMV colitis IBD Ischaemic colitis Radiation colitis
How is the diagnosis of IBD confirmed?
Colonoscopy
Colonic biopsy
What are the histological features of ulcerative colitis?
Superficial ulceration with distortion of crypts
Acute and chronic diffuse inflammatory infiltrate
Goblet cell depletion
Crypt abscesses
Lymphoid aggregates
No granulomas
Which inflammatory bowel disease has a higher risk of colorectal cancer?
Ulcerative colitis
What are the symptoms of ulcerative colitis?
Frequent episodes of rectal bleeding Urgency and tenesmus Abdominal cramps Weight loss Fever
What is the treatment for ulcerative colitis?
Sulphasalazine (5-ASA compound) and steroids
Start with topical therapy
Immunosuppressants used in severe/recurrent disease
For severe/refractory cases
- Biologics
- Surgery
What part of the bowel does ulcerative colitis affect?
Starts at rectum
Proceeds proximally
No skip lesions
What are the pathological features of Crohn’s disease?
Focal transmural inflammation Fissures Ulcers Granulomas Healthy intestine between lesions = skip lesions
What part of the bowel does Crohn’s disease affect?
Gum to bum
What are some extra-intestinal features of Crohn’s disease?
Arthritis, especially sacro-ileitis
Uveitis
Rashes
What are the symptoms of Crohn’s disease?
Abdominal pain Diarrhoea Weight loss Fever Failure to thrive
What is the treatment for Crohn’s disease?
Steroids Sulphasalazine Immunosuppressants - Azathioprine - Methotrexate Biologics Surgery
How is irritable bowel syndrome diagnosed?
Rome IV criteria
- Recurrent abdominal pain on average at least 1 day/week in last 3 months, associated with 2+ of
- Related to defaecation
- Change in frequency of stool
- Change in form of stool
Symptoms must have started at least 6 months ago
Exclude other diagnoses
What secondary deficiencies can coeliac’s disease present with?
Fe
Ca
Folate
Vitamin B12
Of what are people with coeliac’s disease at an increased risk?
GI cancers, especially unusual ones including
- MALT
- Lymphomas
What is a screening test for coeliac’s disease?
Blood test measuring Abs against
- Transglutanimase (tTG-IgA)
- Deamidated gliadin peptides (DGP-IgG)
What is the gold standard for diagnosis of coeliac’s disease?
Small bowel biopsy showing - Villous atrophy - Crypt hyperplasia - Raised intra-epithelial lymphocytes Person has to be consuming gluten
What can cause false negative serology results in coeliac’s disease?
Gluten free diet, especially if >4 weeks
IgA defiency - always concurrently order total IgA
Immunosuppression
Which test can be used to exclude coeliac’s disease?
HLA-DQ2/8 gene test
What is the epidemiology of irritable bowel syndrome?
15-20% of general population in Western countries
More common in females
What sort of symptoms can irritable bowel syndrome cause?
Constipation-predominant
Diarrhoea-predominant
Pain-predominant
Mixed pattern
What is the pathogenesis of irritable bowel syndrome?
Serotonin key mediator Disordered intestinal motility Altered perception of nociceptive stimuli Psychogenic factors Post-infectious component in some people
What are some triggers of irritable bowel syndrome?
Stress
Small bowel bacterial overgrowth
FODMAP malabsorption
What is the first-line treatment for irritable bowel syndrome?
Low FODMAP diet
What is the outline of treatment in irritable bowel syndrome?
Dietary modification - Avoiding common food triggers - Avoiding - Caffeine - Alcohol - Smoking Pharmacological therapies - Probiotics - Antispasmodics - Antidiarrhoeals - Laxatives - Abx to treat bacterial overgrowth Psychological therapies - Relaxation - CBT - Hypnotherapy
