Gastroenterology Flashcards
What substances are transported by SGLT1?
Galactose Glucose H2O Na
What transporter uptakes fructose in the small intestine?
GLUT 5 (Way to remember 5 starts with an F)
Describe the chloride secretory process in the small intestine
Chloride can be secreted actively throughout the small + large intestine Enters the intestinal lumen from the blood by the Na/K/2Cl co transporter Intracellular mediators of secretion (cAMP, cGMP, Ca) open apical Cl- channels (CFTR) Ca activated Cl- channels + basolateral K+ channels
Where are bile salts absorbed?
Terminal ileum
Where is calcium absorded?
Maximally absorbed in the duodenum + proximal jejunum
Where is B12 absorbed?
Terminal ileum
What is predominantly absorbed in the terminal ileum?
The 2 B’s Bile salts/ acids B12
What location are medium chain triglycerides directly absorbed into?
Portal circulation
Where is zinc primarily absorbed?
Jejunum
Where is iron absorbed?
Duodenum / proximal jejunum
Where is folic acid primarily absorbed?
Duodenum
What is the difference between fatty acid globules + fatty acid crystals?
Fatty acid globules indicate presence of triglycerides = liver disease OR lipase deficiency (CF, cholestasis, pancreatic disease). - Suggests fats are unable to be broken down - Further investigations = sweat test for CF, assess degree of malabsorption (e.g. 3 day faecel study, breath test), LFT’s Fatty acid crystals indicate presence of FFA (free fatty acids) = mucosal damage = malabsorption (e.g. coeliac disease, short gut) - Suggests fat broken down but not absorbed
Would you expect stool alpha 1 anti-trypsin to be reduced or elevated in lymphangiestasia?
Elevated
True or false T21 is associated with an increased risk of coeliac disease
True! 5-16 fold increase compared with the general population
Definition of coeliac disease
T cell auto-immune mediated malabsorptive disorder characterised by a permanent gluten sensitive enteropathy resulting in malabsorption, FTT + GIT symptoms Gliadin is the toxic component of gluten in coeliac disease
Incidence, prevalence + age of onset of coeliac disease
Incidence= 20 / 100 000 Prevalence = 1/1000 Age of onset = usually develops before 2yrs
Risk factors for coeliac disease
Family history - 1st degree relative 5-7.5% affected - 2nd degree relative 2-3% affected Food: BROW (barley, rye, oats, wheat) Female Infection with adenovirus type 12 Immunologic - Strongest association with HLA DQ2 + DQ8 - 90-95% express HLADQ2, 5-10% carries HLA DQ8 - 40% of the white population +’ve f Autoimmune conditions - T1DM - Autoimmune thyroid / hepatitis/ cholangitis - Addison - Sjogren - Rheumatoid arthritis - Primary biliary cholangitis Conditions -T21 - Williams - IgA deficiency - Turner’s
What are common extra-intestinal manifestations of coeliac disease?
Chronic fatigue Iron deficiency (usually unresponsive to iron supplements) Osteoporosis Short stature Delayed puberty Arthritis / arthralgia Epilepsy Peripheral neuropathies Dental enamel hypoplasia Apthous stomatitis Dermatitis herpetiformis
When is coeliac testing recommended?
•Persistent unexplained abdominal or gastrointestinal symptoms • Faltering growth • Prolonged fatigue • Unexpected weight loss • Severe or persistent mouth ulcers • Unexplained iron, vitamin B12, or folate deficiency • Type 1 diabetes • Autoimmune thyroid disease • Irritable bowel syndrome • First degree relatives of people with coeliac disease • Dermatitis herpetiformis
What are the tests for the diagnosis of coeliac disease?
Initial approach - Anti TG2 IgA antibodies (declines if the patient is on a gluten free diet) - Total IgA serum (to exclude IgA deficiency) - If selective IgA deficiency present test IgG antibodies to TG2 HLA status (strongest association with HLA DQ2 + DQ8) Duodenal histology
Where should a biopsy be taken from to diagnose coeliac disease?
Descending part of the duodenum / duodenal bulb
Histological features of coeliac disease on biopsy?
- Increased intraepitheral lymphocytes - Flat mucosa with total mucosal atrophy - Crypt hyperplasia - Epithelial apoptosis - Mucous membrane inflammation
What are the different test for coeliac disease?
Sensitivity (percent) Specificity (percent) Tissue transglutaminase; tTG (IgA, human)[1-3] 90 to 100 95 to 100 1st line Anti-endomysial antibody (IgA)[1] EMA 93 to 100 98 to 100 As accurate as tTG IGA but more expensice + operator dependent Deamidated gliadin peptide; DGP (IgA)*[4] 80 to 91 91 to 95 Particularly sensitive in kids <2yrs Deamidated gliadin peptide; DGP (IgG)*[4] 88 to 95 86 to 98 Particularly sensitive in kids <2yrs NO LONGER RECOMMENDED ROUTINELY Anti-gliadin antibody IgA[1] 52 to 100 72 to 100 Anti-gliadin antibody IgG[1] 83 to 100 47 to 94
What types of cancers is coeliac disease associated with?
20 x risk of small bowel lymphoma 30 x risk of small bowel adenocarcinoma 2-4 x risk of oesophageal cancer
What does sucrose break up into?
Glucose + fructose Enzyme: sucrase isomaltase
What does maltose break up into?
Glucose + glucose Enzyme: sucrase isomaltase
What does lactose break down into?
Glucose + galactose Enzyme: lactase
Cow’s milk protein allergy vs. cow’s milk protein intolerance
Cow’s milk protein allergy - IgE mediated immunological reaction to cow’s milk protein Cow’s milk protein intolerance - Non immunologic reaction - Most common = lactase deficiency
I am a six month old female, fully breast feed and present with 2 months of diarrhoea + rash as shown with sparse scalp hair but I am NOT failing to thrive.
What do I have?
Acrodermatitis enteropathica
- Autosomal recessive
- Inability to absorb zinc = zinc deficiency
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Features
- Cutaneous eruption = vesiculobullous, eczematous, dry, scaly, or psoriasiform skin lesions symmetrically distributed in the perioral, acral, and perineal areas
- Hair = reddish tint + alopecia
- Occular = photophobia, conjunctivits, blepharitis + corneal dystrophy
- Chronic diarrhoea, stomatitis, glossitis, paronychia, irritability, delayed wound healing, infections (including superinfection with Candida albicans)
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Treatment
- Zinc supplementation
- Dilated lymphatics shown
- Stool alpha 1 anti-trypsin will be increased
- Lymphangiectasia
- Diffuse or localised ectasia of enteric lymphatics
- Associations: Turner’s, Noonan’s, Klippel-Trenaunay
- Clinical manifestastions: intermittent diarrhoea, N+V, steatorrhoea, chylothorax + chylous ascited, pleural effusions + ascites
- Treatment:
A six-year-old boy with Down syndrome presents to your practice with persistent diarrhoea for the past four weeks. Stool microscopy reveals the following findings: Fat globules: +; Fatty acid crystals: +++; Red blood cells: 0; White blood cells: 0; Faecal pH: 5.5 [> 6.5]; Reducing sugars: 1% [< 0.25%]. What is the most likely diagnosis?
a) coeliac disease.
b) cow’s milk enteropathy.
c) crohn disease.
d) infectious colitis.
e) lactose intolerance.
Predominant feature is fatty acid crystals.
Fat globules = intraluminal problem eg. failure of enzyme process or bile to suspend fats = maldigestion
Fatty acid crystals = mucosal/brush border problem (fatty acid not absorbed) = malabsorption
The presence of reducing substances suggests carbohydrate malabsorption.
Acidic stool (low pH) suggests osmotic diarrhoea, of which one of the major causes is malabsorption.
There is no evidence of inflammation (no white or red blood cells).
A: Coeliac disease is the most likely diagnosis. It should be noted that the incidence of Coeliac disease is increased in patients with Down syndrome.
B: Infants with food protein-induced enteropathy have malabsorption, failure to thrive, anaemia, diarrhoea, vomiting, and hypoproteinemia, which usually is induced by cow’s milk protein. It is most likely to occur in infants fed intact cow’s milk prior to nine months of age. The disorder generally resolves spontaneously after two years of age.
C: Crohn’s disease – no evidence of inflammation in the stool.
D: Infectious colitis – again, no evidence of inflammation in the stool.
E: Lactose intolerance – while you would get reducing substances and low pH, there should be no features of fat malabsorption.
The correct answer is A.