Gastroenterology Flashcards
What are the sites of absorption in the intestine for iron,
IRON = proximal duodenum
-> needs acidic environment
FOLIC acid = first 1/3 small intestine (duodenum/jejunum)
VITAMIN B12 = ileum
-> needs intrinsic factor
Which part of the small intestine has maximal absorption of zinc?
Proximal jejunum
All three segments (duodenum, jejunum and ileum) have the ability to absorb zinc
What is the MoA of cholera in producing diarrhoea?
(1) Cholera enterotoxin -> activation of ADENYLATE CYCLASE -> increase cAMP in intestinal epithelial cells
(2) cAMP on intestinal epithelial transport -> stimulation of active Cl secretion (crypts) and inhibition of Na-Cl absorption (villi)
Why is ORS important in treating cholera?
Cholera enterotoxin (cAMP) does NOT inhibit glucose-stimulated Na (and thus fluid) absorption
What is the MoA of ORS?
Glucose to stimulate Na and fluid absorption in the small intestine via cyclic AMP-independent process
Glucose absorption requires luminal Na -> absorption markedly enhanced by the presence of luminal glucose
Which part of the small intestine (microscopic) does electrolyte absorption vs secretion take place?
Electrolyte ABSORPTION = villi (peaks)
SECRETION = crypts
What is the major site of the intestine for absorption?
Jejunum
Majority of nutrient absorption takes place in jejunum, EXCEPT:
Iron = duodenum Folate = duodenum and jejunum Calcium = duodenum and upper jejunum (transcellular active transport process); throughout length of intestine (paracellular, passive process) Vitamin B12 = terminal ileum Bile salts = terminal ileum
Name the disaccharides and their components (monosaccharides)
Maltose = glucose + glucose
Lactose = glucose + galactose
Sucrose = glucose + fructose
*Remember, glucose in all; two of the three monosaccharides start with ‘G’
What syndromes are associated with Hirschsprung disease?
Mowat Wilson syndrome Down syndrome (T21) Bardet-Biedl syndrome Smith-Lemli-Opitz syndrome Waardenburg syndrome
What are the symptoms caused by deficiency in the fat-soluble vitamins?
A = night blindness (late), scaly skin, infection susceptibility of epithelia (lung, GI, GU)
-> vitamin A involved in maintenance of epithelial functions
D = rickets, craniotabes (softening skull), rachitic rosary, growth plate widening
E = haemolysis (usually 2nd month life), neurologic manifestations (cerebellar disease, posterior column dysfunction, retinal disease)
-> vitamin E functions as in antioxidant
K = bleeding (GI, mucosal, cutaneous)
-> required for clotting factors
What is the initial finding (usually) in vitamin E deficiency?
Loss of deep tendon reflexes
-> limb ataxia, truncal ataxia, dysarthria, opthalmoplegia (limited UPward gaze), decreased proprioception
What is an example of diarrhoea getting worse with ORS instead of IVT?
Glucose-galactose malabsorption
Autosomal RECESSIVE disorder = inheritance of two defective copies of the SGLT1 gene (chromosome 22)
MoA = lack of transportation (the protein product of SGLT1) of the broken down lactose (into glucose and galactose by lactase) from the lumen into intestinal cells -> osmotic diarrhoea
What syndromes is coeliac disease associated with?
Down (T21)
Turner
William
What are the types of autoantibodies seen in autoimmune hepatitis type 1 vs. 2?
Type I
- Antinuclear (ANA) antibodies
- Anti-smooth muscle (anti-SMA) antibodies
Type II
- Antiliver-kidney microsomal-1 antibodies (anti-LKM-1)
- Antiliver cytosol-1 antibodies (anti-LC-1)
Both typically have hyPERGAMMAglobulinaemia (IgG levels >16g/L)
Type II > I in severity Type II (almost exclusively) female
What are the 3 Rome criteria functional disorders for abdominal pain?
FUNCTIONAL ABDOMINAL PAIN (school age) 1. Periumbilical pain 2. Normal growth 3. Appetite not usually affected 4. Symptoms better on weekend/vacation 5. Social stressors exacerbate
FUNCTIONAL DYSPEPSIA (school age/adolescent) 1. Midepigastric 2. Correlation to meals 3. Normal growth
IRRITABLE BOWEL
(adolescent)
1. Lower abdomen
2. Female
3. Pain improves with defacation
4. Frequent changes in stool caliber/frequency
5. Normal growth and appetite
What disease is abdominal pain that wakes from sleep typically seen in?
H. pylori infection
What are the major differences between omphalocele vs. gastroschisis?
OMPHALOCELE
- Central defect (umbilical ring)
- Covering membrane (peritoneal membrane internal, amniotic membrane external)
- Congenital anomalies (thoracoabdominal syndorme, BWS, lower midline syndrome, trisomies)
- Staged surgery
- +/- midgut volvulus
- Lower survival rate (affected by congenital)
GASTROSCHISIS
- Lateral (right) - accident involving right umbilical vein or omphalomesenteric artery
- No membrane
- Midgut volvulus
- Immediate surgery
Where are the two vomiting centers of the brain located?
Vomiting center (neural) = in the nucleus solitarius in MEDULLA
Chemoreceptor trigger zone (chemical) = floor of 4th ventricle
What is the best test for chronic vomiting?
Endoscopy
Main causes = oesophagitis, gastritis
Less common = duodenitis, giardiasis
What other disease is cyclic vomiting associated with?
Migraines
What is the treatment for cyclic vomiting?
Cyproheptadine (1st choice < 5 years)
Propanolol
Amitriptyline
Which grains contain gluten?
BRWS
B - barley
R - rye
W - wheat
S - spelt (a species of wheat)
Oats previously thought to be harmful - but appears to be from contamination with wheat flour
-> still included in gluten-free diet
Which patients are at high-risk for coeliacs?
- First and second-degree relatives with coeliacs
- Down syndrome (T21)
- T1DM
- Selective IgA deficiency
- Autoimmune thyroiditis
- Turner syndrome
- William syndrome
- Juvenile chronic arthritis
What is the best serologic test for diagnosis of coeliac disease?
IgA antibodies against tissue transglutaminase (tTG-IgA)
= highly specific, sensitive and cost-effective
OTHER
= IgA antibodies to endomysium (EMA)
-> as accurate as tTG-IgA, but more expensive and operator interpretation-dependent
What does gluten react with in coeliac disease?
Intestinal damage due to immunological cross-reaction
= reaction to human transglutaminase (hence serology test)
What lesion is pathognomonic for coeliac disease?
Dermatitis herpetiformis
= itchy, vesicular rash
-> erupts symmetrically on extensor surface of arms, legs and buttocks
What are the 2 mandatory requirements for diagnosis of coeliac disease?
- Characteristic histology on small-intestine biopsy
a) increased epithelial lymphocytes
b) crypt hyperplasia
c) villous atrophy - Complete clinical remission with a gluten-free diet
What is the enzyme that conjugated bilirubin in the liver (from unconjugated to conjugated)?
Glucuronyltransferase
Does Dubin-Johnson syndrome cause conjugated or unconjugated bilirubinaemia?
Conjugated
= ABCC2 gene affected
-> provides instructions for making a protein that transports bilirubin out of hepatocytes into bile -> accumulation in body
What is the most common genetic cause of liver disease in children?
Alpha1-antitrypsin deficiency
What is giant cell hepatitis seen in?
Alpha1-antitrypsin deficiency
What is periodic acid-Schiff positive staining of the liver seen in?
Alpha-1 antitrypsin deficiency
Are ceruloplasmin levels low or high in Wilson disease?
Low
Failure of copper to be incorporated into ceruloplasmin leads to a plasma protein with shorter half life, and therefore reduced steady-state concentration of ceruloplasmin in the circulation
Wilson = absence/malfunction of ATP7B -> decreased biliary copper excretion -> accumulation of copper in cytosol of hepatocytes
What is the difference between progressive familial intrahepatic cholestasis (PFIC) 1 and 2 vs. 3?
PFIC3 has elevated GGT, 1 and 2 do not
PFIC = inherited disorders where bile is not properly formed
What is used for hepatitis A prophylaxis?
Hepatitis A vaccine OR immunoglobulin
Given within 2 weeks of exposure
HepA vaccine = preferred >/= 12 months
IG = preferred < 12 months
HepA vaccine given universally at 1 year of age -> protection for 20 years
Which hepatitis virus is DNA?
Hepatitis B
How do you interpret hepatitis B serology?
HepB SURFACE antigen
= either carrier or early hepatitis B
-> IgG antibodies to surface antigen means (1) past exposure; (2) immunity
HepB CORE antigen
= free core antigen does not circulate in serum
-> antibodies (first IgM, then IgG) appears early in disease; persist for life
= most reliable marker for previous exposure
HepB e antigen
= marker of actively replicating virus -> infectivity/inflammation
-> found in serum
What is the first hepatitis B marker detectable in serum when infected?
HepB surface antigen
- HBsAg
(WINDOW PERIOD) - HBcAb
Best test during window period = anti-HBc IgM
What autoimmune disease in hepatitis B associated with?
Polyarteritis nodosa
Which of the 2 hepatitis viruses cause chronic infection that potentially leads to cirrhosis and carcinoma?
Hepatitis B and C
What hepatitis virus requires a concomitant or previously existing HBV infection to become pathogenic?
Hepatitis D
What are the tests for each of the hepatitis viruses in an ACUTE infection?
Hepatitis A = IgM HAV
Hepatitis B = HBsAg & IgM HBc (window period)
Hepatitis C = anti-HCV antibody
What are the two types of exocrine secretory cells in the stomach?
PARIETAL
= secrete HCl and intrinsic factor
CHIEF
= secrete pepsinogen and chymosin
Is celiac disease B cell or T cell mediated?
T-cell mediated chronic inflammatory disorder
What skin manifestation is pathognomonic for coeliac disease?
Dermatitis herpetiformis
What is the most common extraintestinal manifestation of coeliac disease?
Iron deficiency anaemia
What are examples of extraintestinal manifestations of coeliac disease?
THIAMINE/B12 DEFICIENCY Peripheral neuropathy Epilepsy Cerebral calcifications Cerebellar ataxia
AUTOIMMUNITY
Dermatitis herpetiformis
Alopecia
Erythema nodosum (rare)
CALCIUM/VIT D MALABSORPTION
Short stature
Secondary hyperparathyroidism
OTHER
Arthritis/arthralgia
Cardiomegaly
Aphthous stomatitis
What is the main cause of death in coeliac disease patients?
Non-Hodgkin lymphoma
What histologic changes are seen on biopsy of intestine in coeliac disease?
Small bowel mucosal inflammation = short, often flattened, villi + crypt hyperplasia
What are the radiological findings of intussusception?
USS
1. ‘Target’ sign
XR
- Crescent sign = soft tissue density projecting into gas of large bowel
- Obscured liver margin
- Meniscus-shaped mass outlined by air in the colon
What anatomic structure marks the formal division between the first and second parts of the small intestine (i.e. duodenum and jejunum)?
Ligament of Trietz
= normally to LEFT of spine (at level of gastric antrum)
a.k.a. suspensory muscle of duodenum
***In malrotation, ligament is on right of spine + inferior to duodenal bulb -> thus contrast fills the jejunal loops on RIGHT side of abdomen
What is the ‘rule of 2’s’ for Meckel diverticulum?
Present in 2% of population
Located within 2 feet of ileocoecal valve
Measures 2 inches in length
Measures 2 cm in diameter
2:1 = M:F
Usually symptomatic before 2 years of age
What is the main symptom of Meckel divertucula?
PAINLESS GI bleeding (bright red or maroon)
= from ectopic gastric mucosa
+/- colicky abdominal pain
How do you diagnose a Meckel diverticula?
Technetium-99m pertechnetate scan (a.k.a. Meckel scan)
= technetium-99m pertechnetate concentrates in parietal cells of gastric mucosa and bladder
-> +ve if uptake outside stomach and bladder
Is a Meckel diverticulum associated with other congenital abnormalities?
Yes
Oesophageal atresia (6x) Imperforate anus (5x) Neurologic anomalies (3x) Cardiovascular anomalies (2x)
Which of the following is associated with congenital anomalies - duodenal or jejunal atresia?
Duodenal
(D)uodenum -> (D)own syndrome
Also: cardiac, GU, anorectal, oesophageal
What disease has periodic acid -Schiff positive granules in the lamina propria (of intestine)?
Whipple disease = Tropheryma whipplei
Where is lactase found in the intestine?
On the brush border near the tips of the intestinal villa
What is the most common reliable diagnostic test for lactase deficiency?
Breath hydrogen test
When carbs malabsorbed, bacteria in colon produce hydrogen gas -> absorbed across colon into blood and expired in lungs
Abx give false -ve
Too early rise in H+ = bacterial gut overgrowth
What are the different types of jejunoileal atresia?
4 types. Not associated with T21
Type 1 = mycosal obstruction cased by intraluminal membrane
Type 2 (35%) = a solid, fibrous cord connects blind ends of the proximal and distal bowel
Type 3 = blind ends of distal and proximal bowel separated by small (type IIIa) and extensive (type IIIb) mesenteric defects
Type 4 = multiple segments of bowel atresia
