GI and Liver Disorders Flashcards
What nutrients are absorbed in the stomach?
H+
Alcohol
H2O
What nutrients are absorbed in the Jejunum?
CHO sugars Proteins Lipids Vitamins Fe2+ Trace elements
What nutrients are absorbed in the terminal ileum?
Vitamin B12
Bile Salts
What are the 11 gut hormones?
- Gastrin
- Secretin
- Cholecystokinin
- Somatostatin
- Ghrelin
- Neuropeptide Y
- Peptide YY3-36
- Glucagon, GLP, GIP
- Pancreatic Polypeptide
- Substance P
- Serotinin
What is the structure of the gut hormones?
All peptides
What is the function of gastrin?
Secreted by Gastric antral G cells
Stimulates gastric acid secretion
What is the function of Secretin?
Secreted by duodenal cells
Stimulates pancreas to secrete bicarbonate
What is the function of Cholecystokinin?
Secreted by duodenal cells
Stimulates Gallbladder contraction, Pancreatic digestive enzyme release
How are carbs broken down?
Carbohydrates are broken down by amylase to oligosaccharides: sucrose, isomaltose, lactose
How are lipids broken down?
Lipid (TG) are broken down by lipase to monoacylglycerol, FFA and phospholipids, which are broken down by bile salts into Micelles
How are proteins broken down?
Proteins are broken down by exo/endo peptidase into amino acids
What are the causes of malnutrition?
Gastric bypass Thyrotoxicosis Infective diarrhoea Pancreatic insufficiency - chronic pancreatitis, CF genetic, pancreatic cancer Bile salt insufficiency - cholestasis, bacterial overgrowth Radiation enteritis Lymphoma Short gut syndrome Mucosal disorders - coeliac disease - infective (inc. tropical sprue) - Crohn’s disease - immunodeficiency Intestinal lymphangiectasia
What are the mechanisms of malnutrition?
Intestinal hurry
Impaired secretion of bicarbonate and enzymes
Decreased availability of bile salts
Infiltration and destruction of cells
Decreased absorptive area, lactase deficiency
Lymphatic obstruction
What are the investigations for malabsorption?
Basic Investigations Biochemistry profile CRP, ESR FBC Haematinics - B12, folate, ferritin Antibodies – Anti-endomysial – Anti-tissue transglutaminase – Gastric parietal cell/intrinsic factor Abs
What are the consequences of malabsorption?
Skin and mucosal lesions (due to vitamin and trace element deficiency)
Muscle weakness (due to reduced muscle mass and Ca2+ and Mg2+ deficiency)
Tetany (due to Ca2+ and Mg2+ deficiency)
Weight loss
Bone pain
Anaemia (due iron, folate and B12 deficiency)
Peripheral neuropathy (due to vitamin deficiency)
Oedema (due to hypoalbuminaemia)
Failure to thrive in neonates
Growth retardation
Diarrhoea
What is Coeliac Disease?
Coeliac disease, also spelled celiac disease, is an autoimmune disorder affecting primarily the small intestine that occurs in people who are genetically predisposed against Toxic Factor α-gliadin in gluten
What are the symptoms of Coeliac disease?
Diarrhoea, which may smell particularly unpleasant abdominal pain Bloating and flatulence (passing wind) Indigestion Constipation Fatigue as a result of malnutrition (not getting enough nutrients from food) Unexpected weight loss An itchy rash (dermatitis herpetiformis) Problems getting pregnant Nerve damage (peripheral neuropathy) Disorders that affect co-ordination, balance and speech (ataxia) Growth problems Delayed puberty
How is Coeliac disease diagnosed?
Tests for Tissue Transglutaminase & Anti-endomysial
antibodies
Small Bowel Biopsy: Partial villous atrophy
How is Coeliac Disease treated?
Gluten Free diet
What are the causes of Chronic Pancreatitis?
Idiopathic
Genetic
Cystic Fibrosis
What are the symptoms of Chronic Pancreatitis?
- Abdominal Pain
- Malabsorption -Steatorrhoea (excess fat in faeces)
- Diabetes Mellitus
- Pancreatic Calcification
How is chronic pancreatitis diagnosed?
- Faecal Elastase - low values indicative of pancreatic exocrine insufficiency
- Amylase - acute pancreatitis- 3-4x ULN, chronic pancreatitis may not elevate plasma amylase
- Lipase - greater specificity
- Others - Para-aminobenzoic acid (PABA) Test, Pancreolauryl Test
How is Chronic Pancreatitis treated?
Lifestyle changes:
- Avoiding alcohol
- Stopping smoking
- Dietary changes (A low-fat, high-protein, high-calorie diet with fat-soluble vitamin supplements is usually recommended)
Enzyme supplements
Steroid medication
Pain relief
Surgery (endoscopic to remove stones, pancreatic resection, total pancreatectomy)
What are the causes of peptic ulcer disease?
- Helicobacter Pylori
- Hyperacidity
- Non-Steroidal Anti-inflammatory Drugs (NSAIDs)
How is peptic ulcer disease diagnosed?
Testing for H. pylori infection - urea breath test - stool antigen test - blood test Gastroscopy (may include biopsy)
What is the mechanism for Urea Breath test?
H Pylori contains urease
14C-Urea -Urease–> NH3 + 14CO2
Infection indicated by increase breath 14CO2
If a biopsy is performed in a Gastroscopy, how is H. Pylori infection detected?
• CLO Test:
Biopsy tissue is placed in a medium containing urea & phenol red. If H Pylori is present the NH3 liberated increases pH and solution goes from yellow to red.
How is Peptic Ulcer disease treated?
Treatment depends on the cause of the ulcer:
- If ulcer is due to H. Pylori infection, a course of antibiotics and PPI is prescribed
- If caused by NSAIDs, PPI’s are prescribed, and NSAID use is reviewed
What is IBS?
IBS is a functional bowel abnormality: altered motility and increased sensitivity ‘hyper vigilance’
How is IBS diagnosed?
Using Rome III criteria:
At least 3 months recurrent abdominal pain associated with 2 or more of the following:
- improvement with defecation
- onset associated with a change in frequency of stool
- onset associated with a change in form (appearance) of stool
What are the different types of Inflammatory Bowel Disease?
Ulcerative Colitis
Crohn’s disease
What is Ulcerative Colitis?
Diffuse mucosal ulceration presenting with bloody diarrhoea and abdominal pain, with increased risk of colorectal cancer
What is Crohn’s disease?
Transmural patchy inflammation any part of GI tract, usually the terminal ileum.
Symptoms include diarrhoea, pain, weight loss
Complications are strictures, fistulae, malabsorption
How is IBD diagnosed?
Physical examination – nutrition, anaemia, fluid status, abdomen (?mass), rectal, perineum
Laboratory:
- FBC, CRP, U+E, LFTs
- pANCA (Perinuclear Anti-Neutrophil Cytoplasmic Antibodies) - 40-80% UC, 5-20% Crohn’s
- anti-Saccharomyces cerevisiae Abs(ASCA) – 60-70% Crohn’s, 10-15% UC
- Microbiology: stool MC&S test, parasites, C. difficile toxin
How is IBD treated?
There is currently no cure for ulcerative colitis or Crohn’s disease. Treatment aims to relieve symptoms and prevent them from returning.
Aminosalicylates, or in more severe cases, corticosteroids – to reduce inflammation
Immunosuppressants – to reduce the activity of the immune system
In very severe cases, where inflammation does not respond to medication, the inflamed section of the digestive system may be surgically removed
What is faecal calprotectin?
Faecal Calprotectin is a protein that accounts for 60% of neutrophil cytoplasmic protein
It is a calcium binding protein
When is faecal calprotectin released?
It is released into faeces when neutrophils gather at the site of GI tract inflammation
How is faecal calprotectin measured?
It is measured in faeces as it is stable in faeces with next to no degradation
- Good correlation with Indium labelled WBC
What are the functions of the liver?
Metabolism
Excretion and Detoxification
Storage
How is the liver involved in the metabolism of carbohydrates?
Involved in glycogen synthesis and metabolism
How is the liver involved in the metabolism of fats?
Cholesterol, bile acid, and lipoprotein synthesis
How is the liver involved in the metabolism of proteins?
Protein and urea synthesis
How is the liver involved in the metabolism of hormones?
Vitamin D, regardless of origin, is an inactive prohormone and must first be metabolized to its hormonal form before it can function.
Once vitamin D enters the circulation from the skin or from the lymph, it is cleared by the liver or storage tissues within a few hours.
What are the current liver function tests?
Serum aminotransferases e.g. AST, ALT – For parenchymal injury Serum bilirubin – For cholestasis Serum alkaline phosphatase,γ glutamyltranspeptidase – For biliary epithelial damage and biliary obstruction (alcohol), cholestasis Serum albumin – For synthetic function Prothrombin time (INR) – For clotting (dynamic indicator)
What is AST?
Aspartate aminotransferase
What is ALT?
Alanine aminotransferase
Where is AST found?
Liver Heart Skeletal Muscle Erythrocytes Kidney
What causes high AST in the liver?
Mitochondrial and cytoplasmic injury
Where is ALT found?
Mainly Liver
Lesser extent Heart, Skeletal Muscle, Kidney
What is causes high ALT in the liver?
Cytoplasmic injury
What causes ALT>AST?
Cytoplasmic disease
- Necrotic liver disease (eg viral hepatitis)
- NAFLD
Obstructive liver disease
What causes AST>ALT?
Cytoplasmic & mitochondrial disease
- chronic liver damage (cirrhosis),
- infiltrative disease (eg alcohol, neoplasms
- Metabolic
What causes a minor (<100iu/l) increase in ALT and AST?
Chronic Hepatitis B
Chronic Hepatitis C
Haemochromotosis
Fatty Liver
What causes a moderate (100-300 iu/l) increase in ALT and AST?
Chronic Hepatitis B Chronic Hepatitis C Haemochromotosis Fatty Liver Alcoholic hepatitis Non-alcoholic steatohepatitis Autoimmune hepatitis Wilson's Disease
What causes a major (>1000 iu/l) increase in ALT and AST?
Drug toxicity, particularly paracetamol
Acute viral hepatitis
Autoimmune hepatitis
Ischaemic liver
Where is ALP found?
Mainly liver and bone, but also intestinal, placental (pregnancy) and biliary isoenzymes.
What causes increased hepatic ALP?
Hepatobiliary obstruction causes increased sinusoidal hepatocyte synthesis of ALP
Where is γGT found?
Mainly Liver but also kidney, pancreas and prostate
What is γGT?
Most sensitive but non-specific marker of liver disease
Sited in endoplasmic reticulum and increased in;
- ER damage: hepatocellular damage and obstruction
- ER proliferation: Enzyme induction eg alcohol & drugs
What is albumin a marker of?
Reduced hepatic functioning mass
But also occurs in:
- Negative acute phase protein
- Malnutrition including malabsorption
- Protein loss: e.g. nephrotic syndrome
What is jaundice?
- Elevation of bilirubin in the serum (normal <20umol/L)
* May be unconjugated and/or conjugated bilirubin.
What is normal bilirubin level?
20μmol/L
What causes jaundice to be visible in the sclera?
Serum bilirubin >50μmol/L may be visible in sclera as
jaundice
What causes jaundice to be visible in the skin?
Serum bilirubin >100μmol/L the patient's skin may appear yellow (“jaundiced”)
Describe bilirubin metabolism
Haem is catabolized to unconjugated bilirubin in the reticuloendothelial system.
Unconjugated bilirubin is bound to albumin in the plasma and transported bound to albumin to the liver and is conjugated with glucuronic acid in the hepatocytes; the conjugation is catalyzed by glucuronyl transferase.
Conjugated bilirubin is secreted into the bile and enters the duodenum. In the small bowel, some of the bilirubin is hydrolyzed to yield unconjugated bilirubin and glucuronic acid.
Most unconjugated bilirubin is excreted in the stool, but some is reabsorbed and returned to the liver for reconjugation (enterohepatic circulation).
What is hyperbilirubinaemia?
Hyperbilirubinaemia is a condition in which there is too much bilirubin in the blood.
What are the types of bilirubinaemia?
Pre-hepatic (eg Haemolysis)
- Unconjugated hyperbiliribinaemia
Hepatic
- Unconjugated hyperbilirubinaemia e.g. Gilberts
- Usually unconjugated & conjugated hyperbilrubinaemia
Post-hepatic (Extrinsic Obstruction of biliary drainage)
- Conjugated Hyperbilirubinaemia
What causes prehepatic jaundice?
Haemolysis
- Unconjugated hyperbilirubinaemia - Fat soluble, crosses blood brain barrier if protein carrying capacity is exceeded.
- Increased urine urobilinogen
- Anaemia
- Reticulocytosis: Increased red cell production
What are the features of hepatocellular jaundice?
- Unconjugated & conjugated hyperbilirubinaemia
- Increased liver transaminases (AST/ALT)
- Increased ALP and γGT)
- Reduced synthetic activity.
What is Gilbert’s Syndrome?
Gilbert’s syndrome is a common autosomal dominant
benign condition producing a mild unconjugated
hyperbilirubinaemia with an estimated prevalence of
3-8% in the general population
What defect causes Gilbert’s Syndrome?
Defect is a TA insertion in the TATA repeat box of the
gene promoter region. Homozygosity reduces the
capacity for gene expression
How is bilirubin conjugation mediated?
Bilirubin conjugation is mediated by UDPglucoronosyl
transferase 1A
When does plasma bilirubin increase in patients with Gilbert’s syndrome?
In situations of increased demand e.g. illness, infections, fasting a marked rise in plasma bilirubin (40-80 umol/L) can occur
What are the various types of hepatitis?
Viral hepatitis A, B and C
Alcoholic hepatitis
Autoimmune hepatitis
What are the diagnostic features of alcoholic hepatitis?
Transaminases not usually so raised
Often high GGT, urate, triglycerides and macrocytosis
What are the diagnostic features of autoimmune hepatitis?
F:M ratio - 4:1
Hepatic pattern-↑ALT, ↑Bilirubin, ALP normal, ↑gammaglobulins, autoantibodies - antinuclear and antismooth muscle antibodies
What is NAFLD?
Non-alcoholic fatty liver disease
What is NASH?
Non-alcoholic steatohepatitis
What are the features of NAFLD and NASH?
Fatty infiltration not due to excessive alcohol
Associated with insulin resistance and metabolic syndrome
NAFLD is benign and reversible
NASH which is a severe form of NAFLD there is cellular damage, elevated liver enzymes, 28% of patients with NASH may progress to cirrhosis
How can NAFLD and NASH be detected?
Definitive test : liver biopsy
- Liver enzymes : differences in AST and AST/ALT ratio in patients with fatty liver alone and those with NASH (AST, AST/ALT ratio higher in NASH)
- Markers of liver fibrosis : type IV collagen, hyaluronic acid (higher in patients with NASH)
How many patients with NASH progress to cirrhosis?
28%
What is cirrhosis?
End result of almost any liver disease, fibrous scar tissue distorts architecture leading to increased pressure in portal vein
What are the biochemical test results for cirrhosis?
LFTs often completely normal
Slight rise in transaminases
Low albumin – impaired synthesis
Rise in bilirubin is late feature
What is obstructive jaundice?
Obstructive jaundice is a particular type of jaundice and occurs when the essential flow of bile to the intestine is blocked and remains in the bloodstream.
What features are characteristic of obstructive jaundice?
Impaired biliary excretion of conjugated bilirubin & increased synthesis of alkaline phosphatase.
How does obstructive jaundice present?
Conjugated hyperbilirubinaemia
Increased hepatic Alkaline Phosphatase
Increased Urine Bilirubin (Dark Urine)
{Pale stools –reduced faecal stercobilin}
May be intrahepatic or extrahepatic
- Intrahepatic: e.g. Primary Biliary Cirrhosis
- Extrahepatic: e.g. Cancer head of pancreas, gall stones
