Gastroenterology Flashcards
Is coeliac an autoimmune disease?
No, because driving antigen is exogenous
What HLA type is associated with coeliac disease?
HLA-DQ2/8
What is the pathophysiological basis of coeliac disease?
- tranglutaminase modifies gluten to increase binding affinity
- B-cells can acts as APCs
- pro inflammatory gluten-specific CD4+ T-cells
- transglutaminase antibodies
- small intestine enteropathy
- systemic effects
What is the treatment for coeliac disease?
Strict gluten free diet
What genetic syndromes are associated with coeliac disease?
Turners syndrome
Downs syndrome
What autoimmune diseases are strongly linked with coeliac disease?
Autoimmune thyroid disease
Type 1 diabetes
How is coeliac disease diagnosed?
Clinical history + serology + histology
Clinical History: improvement on gluten free diet
Serology:
tTG-IgA + total IgA OR tTG-IgA + DGP-IgG
(90% sensitivity and specificity)
Histology: villous atrophy, crypt hyperplasia, raised IELs in multiple biopsies in 1st and 2nd part of duodenum
What are other non-coeliac causes for villous atrophy?
- infection: tropical Sprue, H. pylori, giardia lamblia, SIBO
- immune: CVID, Crohn’s, cows milk protein intolerance, autoimmune enteropathy
- drugs: olmesartan, NSAIDs, mycophenylate
What is refractory coeliac disease and how is it managed?
Malabsorption + villous atrophy despite 12 months of gluten free diet
First rule out other causes/misdiagnosis
Type 1 = normal IELs, managed with immunosuppression
Type 2 = monoclonal IELs (precursor T-cell lymphoma), managed with chemotherapy +/- ASCT
What is the difference between NAFLD, NAFL and NASH?
NAFLD = term that describes fatty liver disease without significant alcohol use from hepatitis to cirrhosis
NAFL = hepatosteatosis without evidence of hepatocellular injury. Minimal risk of progression.
NASH = Hepatosteatosis with inflammation, hepatocyte ballooning +/- fibrosis. Can progress to cirrhosis, liver failure and cancer
What is the pathological basis of NAFLD?
Lipid and carbohydrate deposition within the liver, develops pro-fibrotic inflammatory response (key driver is often insulin resistance) resulting inflammation
How is NAFL diagnosed?
Either liver biopsy
OR increased hepatic echogenecity on USS compared to right renal cortex
OR MRI
How is NASH diagnosed?
Only on liver biopsy
How is NAFLD managed?
- weight loss (10%) and exercise
- metformin for NASH
- Bariatric surgery
- Liver transplant
What is the pathological basis of herediatry haemachromatosis?
AR inheritance
Biallelic mutations in HFE gene (most common = C282Y and H63D)
Increased intestinal absorption of iron due to hepcidin deficiency leads to organ damage from ROS
How is hereditary haemachromatosis diagnosed?
- screening with Tsat (>45%) and elevated serum ferritin
- HFE genotyping
How is hereditary haemachromatosis managed?
If C282Y homozygote:
- phlebotomy
- liver biopsy if Serum ferritin > 1000 or abnormal liver enzymes
Others:
- phlebotomy if ferritin >1000, evidence of tissue injury or iron deposition on MRI/biopsy
What muscle wasting signifies malnutrition?
1st dorsal interosseus
Masseter
Temporalis
What happens to serum potassium and phosphate in refeeding syndrome?
Both drop (due to increase in insulin)
What happens to sodium and water in refeeding syndrome?
Increased fluid and salt retention
Increased ADH
When is home TPN indicated for short bowel syndrome?
- <60-90 cm with colon
- < 150 cm small bowel alone
What is the daily TPN requirement?
Energy 25-30 kcal/kg/day
protein 1-1.25 g/kg IBW
What are indications for exclusive enteral nutrition in IBD?
- alternative to corticosteroids for remission induction in crohn’s disease
- ileal disease
- able to tolerate EEN
- complicated crohn’s disease
- downstage crohn’s severity pre-op
- ERAS
What are advantages of EEN over corticosteroids for crohn’s?
- avoid steroid side effects
- improve nutrition
- improve quality of life
- improves bone mineral density
- treats complications to avoid surgery
- results in mucosal healing
What is the role of metallothionien in the enterocyte?
Competitive absorption of
- zinc
- copper
- phytates
- calcium
Where is GLP-2 produced and what does it do?
Enter-endocrine L-cells of distal small bowel and colon
Also released in CNS
Increase proximal bowel mucosal absoprtion
What changes happen with liver cirrhosis to cause portal hypertension?
- increase vascular resistance due to change in architecture (fixed component)
- altered metabolism leads to imbalance in vasoconstrictors and vasodilators ->localised hepatic sinusoidal vasoconstriction (alterable component)
- systemic vasodilation
What mechanism leads to ascites and renal failure in cirrhotic liver disease?
- RAAS overactivation (salt + water retention, afferent renal vasoconstriction)
What is the gold standard for diagnosing portal hypertension?
Measure hepatic venous gradient (HVPG)
HVPG = WHVP - FHVP
HVPG > 5 = portal hypertension
HVPG > 10 = clinically significant (pressure at which ascites and varices occur)
Note HVPG could be normal in non-cirrhotic portal hypertension
What are surrogate markers for diagnosing portal hypertension?
- dilated portal vein
- reversal of flow in portal vein
- recanalised ligamentum teres
- splenomegaly
- thrombocytopenia
- presence of varices and porto-systemic shunts
What is cALCD and the rule of 5s?
cACLD = compensated advanced chronic liver disease
Rule of 5s:
- liver stiffness < 5 kpa = normal
- liver stiffness < 10 kpa rules out cACLD
- liver stiffness > 15 kpa rules in cACLD
- liver stiffness < 20 kpa and PLT > 150 rules out clinically significant portal hypertension
- liver stiffness > 25 kpa = clinically significant portal hypertension
What is compensated liver disease?
Hepatic synthetic function is preserved without current or prior complication of cirrhosis
Child-Pugh A, normal bilirubin and INR
No symptomatic ascites or hepatic encephalopathy or prior variceal bleeding
What is decompensated liver disease?
- ascites
- variceal bleeding
- hepatic encephalopathy
- jaundice
What is the median survival of compensated and decompensated liver disease?
Compensated: 12 years
Decompensated: 2 years
What is the most decompensating event in advanced liver disease?
ascites
How is portal hypertension as a cause of ascites determined?
Serum-ascites albumin gradient > 11
What total protein level is considered high risk for SBP?
< 15 g/L
How is cirrhotic ascites managed?
- sodium restriction to 4.6-6.9 g salt
- diuresis: spirinolactone (max 400 mg), frusemide
- paracentesis
How should albumin be replaced in large volume paracentesis to prevent circulatory dysfunction and AKI?
Replace 1 bottle 20% for every 2L drained
How is SBP diagnosed?
Neuts > 250 mm3 on diagnostic tap
How is SBP treated?
- 3rd generation cephalosporin (ceftriaxone, ceftazidime) or tazocin for 5-7 days (note 60% culture resistant)
- drained dry
- 1-1.5g/kg/day albumin for 3 days
- secondary prophylaxis with co-trim until resolution of ascites
Who should get primary prophylaxis for SBP?
Low protein < 10 g/L
What is the most common site of varices in chronic liver disease?
oesophageal
What is the major determinant of ongoing variceal bleeding?
Portal pressure
What are risks of variceal bleeding?
- large varix size
- High Child class
- red wale mark on varix
- excessive alcohol consumption
- HVPG > 12
- previous bleed
What prophylaxis is used for high risk varices?
- primary: 1st line = non-selective beta blockade (carvedilol > propanolol), 2nd line = endoscopic banding and ligation
- secondary = non-selective beta blockade + endoscopic banding and ligation
How should acute variceal bleeding be managed?
- aim Hb > 70 (want to avoid exacerbating raised portal pressure)
- ocrteotide or terlipressin for 5 days
- antibiotics (ceftriaxone) for 5 days
- PPI until ulcer excluded
- endoscopy: danis stent or Sengstaken-Blakemore tube to tamponade
- TIPS if bleeding continues despite banding or if high risk for re-bleed (Child-Pugh 8-13)
How do non-selective beta blockers prevent complications of chronic advanced liver disease? What complications do they prevent?
- reduce portal pressure by reducing splanchnic in flow through splanchnic vasoconstriction AND reduce cardiac output through negative chronotropy
- carvedilol preferred as alpha blockade leads to vasodilatation of liver sinusoids
- variceal bleeds, decompendation with ascites, mortality
How is AKI managed in cirrhosis?
- remove precipitants
- volume expand with albumin (20-40g/day)
- look for infection, low threshold for empiric antibiotics
- with-hold non-selective B-blockers
- terlipressin for hepatorenal syndrome
What is the diagnostic criteria of hepato-renal syndrome?
AKI in cirrhosis with ascites and no alternate explanation
What is the most effective treatment for hepatorenal syndrome?
Liver transplantation
What is the mechanism of action of terlipressin?
Long-acting vasopressin analogue
Acts of vasopressin1 receptor to mediate vasoconstriction, preferentially expressed on vascular spooch muscle beds within splanchnic bed
reverses splanchnic vasodilation to improve renal perfusion
What are the key parts to pathogenesis of hepatic encephalopathy?
Portosystemic shunting to brain
Hepatic insufficiency (unable to detoxify)
Sarcopenia leading to reduced muscle ammonia clearance
How is hepato-encephalopathy managed?
- treat for precipitant
- lactulose
Secondary prophylaxis: lactulose, can add in rifaximin
What is the mechanism of action of lactulose for hepatic encephalopathy?
Acidifies colon, leading to conversion of NH3 (absorbale ) to NH4+ (non absorbable) and increases intestinal transit to increase faecal ammonia excretion
What is the mechanism of action of rifaximin?
non-absorbable antimicrobial antibiotic that alters the microbiome to reduce ammonia-producing colonic bacteria to reduce ammonia production
How is acute on chronic liver failure defined?
Acute decompensation with extra-hepatic organ failure
ACLF-1 = renal or cerebral failure only, or renal dysfunction with other organ failure
ACLF-2 = double organ failure
ACLF-3 = three or more orgnas failing
When is liver transplantation considered in acute on chronic liver failure?
ACLF-3
What is hepatopulmonary syndrome?
Intrapulmonary vascular dilatation resulting from systemic imbalance in vasoconstrictors and vasodilators from liver disease result in shunting and V/Q mismatch
Presents with SOB, hypoxia, clubbing, normal CXR
Diagnosed with ABG demonstrating elevated A-a gradient, TTE with agitated saline
Treated with supplemental O2, liver transplant
What is portopulmonary hypertension?
Circulating mediators lead to remodelling of pulmonary vasculature
Presents with dyspnoea, hypoxia and right heart failure
Screened with TTE, diagnosed on right heart catheter
Managed with pulmonary vasodilators (PDE5i, endothelin receptor antagonists), liver transplant
What is the King’s College Hospital criteria for liver transplantation in acute liver failure?
- Paracetamol induced AND pH < 7.3 on ABG AND all of:
- INR > 6.5
- Cr > 300
- grade III or IV encephalopathy - Non-paracetamol induced AND INR > 6.5 OR 3 of:
- age < 11 or > 40
- Bili > 300
- jaundice to coma time > 7 days
- INR > 3.5
- drug toxicity
What size cholangiocracinomas can be considered for liver transplant?
< 2cm intrahepatic
< 3 cm hilar
What nerves supplies the oesophagus?
Vagus