GI Defences Flashcards by Elizabeth Stevens

What are the innate physical defences of the GI?

Sight, smell and memory
Saliva which contains lactoperoxidase, IgA, complement, polymorphs and washes toxins into the stomach
Gastric acid
Small intestine secretions including bile, proteolytic enzymes, lack of nutrients
Anaerobic environment
Shedding of epithelial cells
Rapid transit - peristalsis 
Mucus to protect colonic epithelium

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What toxins can the GI tract be exposed to?

Chemicals
Bacetrial
Viruses
Protozoa
Nematodes (round worms)
Cestodes (tapeworm)
Trematodes (flukes)

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What innate cellular defences are there in the GI tract?

Neutrophils
Macrophages 
Kupffer cells
Natural killer cells
Tissue mast cells
Eosinophils

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What are Kupffer cells and why do we need them?

Specialised macrophages in the liver

All venous blood from the GI tract passes through the liver

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What are the adaptive defences of the GI tract?

B lymphocytes - produce antibodies including IgA and IgE. Effective against extracellular microbes
T lymphocytes - directed against intracellular organisms
Gut-associated lymphoid tissue (GALT) - diffusely distributed. Found in tonsils, appendix and Peyer’s patches

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What is infection if the salivary glands called?

Parotitis

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What infectious consequences are there of xerostomia?

Parotitis caused by Staph aureus

Hairy tongue

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What can cause achlorydia? (Lack of gastric acid)

Pernicious anaemia
H2 antagonists
Proton pump inhibitors

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What infections are patients at a higher risk of if they have achlorydia?

Shigellosis
Cholera
Salmonella
Hospital patients on PPIs - C. difficile

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Which bacteria are resistant to gastric acid?

H pylori

Mycobacterium tuberculosis

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Which viruses are resistant to stomach acid?

Enteroviruses

hep A
polio
coxsackie

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What causes recruitment of mast cells in the gut and what do they cause?

Gut infections which activate complement
Recruit mast cells
Release histamine
Causes vasodilation and increased capillary permeability
Massive fluid loss

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What is the mortality of cholera if left untreated?

60%

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What infection of the gut can cause right iliac fossa pain?

Mesenteric adenitis caused by adenovirus or coxsackie virus. Affects ileocaecal GALT
Appendicitis

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What can cause appendicitis?

Lymphoid hyperplasia of the appendix base leading to obstructed outflow. Stasis and infection

Faecolith (calcified faecal matter)

Worm

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What complication in the gut can typhoid fever lead to?

Inflamed Peyer’s path in the terminal ileum which can perforate and kill the patient.

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What infectious complication occurs if blood supply to the GI tract is compromised?

Cannot carry out defence mechanisms

Overwhelming sepsis and rapid death within hours

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What can compromise blood flow to the gut?

Arterial disease
Systemic hypotension
Intestinal venous thrombosis

Causes of liver failure?

Viral hepatitis
Alcohol
Drugs eg paracetemol, halothane
Industrial solvents
Mushroom poisoning

What can you be more susceptible to with liver failure?

Infections
Toxins
Drugs
Hormones

What is hepatic encephalopathy?

High blood concentration of ammonia

How is ammonia produced?

Colonic bacteria

Deamination of amino acids

How do oesophageal varices occur?

Vein? drains into hepatic portal vein
If there is cirrhosis, can cause portal hypertension
Blood backs up in the oesophageal veins and causes them to dilate

What is caput medusae caused by?

Portal hypertension

Ligamentum teres opens up and blood radiates out from the umbilicus

How do haemorrhoids develop?

Portal hypertension At anorectal junction, vein? joins with hepatic portal vein. If pressure is increased in portal vein, can cause the junction to open up and causes haemorrhoids

How does the liver handle bile pigments?

Conjugates bilirubin and secretes it into the faeces which can then be excreted.

What is the most abundant plasma protein and what is it essential for?

Albumin | Maintaining osmotic pressure needed for proper distribution of body fluids.

What coagulation factors does the liver produce?

Fibrinogen (I) Prothrombin (II) V, VII, IX, X, XI Protein C, protein S, antithrombin

What is thrombopoietin and what does it do?

A glycoprotein hormone | Regulates production of platelets by bone marrow

What does a high level of alkaline phosphatase indicate and why?

When liver's biliary ducts are obstructed | It is an enzyme in the cells of these ducts

What does low albumin indicate?

Chronic liver disease

What does an increased prothrombin time show?

The clotting tendency of the blood | Would show if there is liver damage?

Signs of hyperbilirubinaemia?

Yellow pigmentation of skin | Yellow conjunctival membranes over the sclerae

What should bilirubin levels in the blood be below normally and when is it an issue?

Normally <22mmol/L | Clinically detectable above 44mmol/L

What is pre-hepatic jaundice caused by?

Excessive haemolysis - red cell membrane defects - haemoglobin abnormalities - metabolic defects - hyperbilirubinaemia - Gilbert's syndrome Acquired include - immune - mechanical (eg RBCs running across the metal heart valve) - membrane defects - infections - burns

What is hepatocellular jaundice caused by?

Deranged hepatocyte function | Can be an element of cholestasis

Lab findings in pre-hepatic jaundice?

``` Unconjugated hyperbilirubinaemia Reticulocytosis Anaemia High LDH (contained in RBCs) Low haptoglobin (normally bound to bilirubin) ```

Lab findings in hepatocellular jaundice?

Mixed conjugated and unconjugated hyperbilirubinaemia High ALT and AST Normal/high ALP (alkaline phosphatase??) Abnormal clotting

Causes of hepatocellular jaundice?

Congenital - Gilbert's syndrome - Crigler-Najjar syndrome Hepatic inflammation - EBV - Hep A-E - autoimmune hepatitis - alcohol - haemochromatosis - Wilson's disease Drugs Cirrhosis caused by - alcohol - hepatitis - metabolic disorders Hepatic tumours: hepatocellular carcinomas, metastases

What is post-hepatic/cholestatic jaundice?

Obstruction of biliary system affecting drainage of bile Causes a back up of bile acids into the liver Can be inta or extra hepatic Passage of conjugated bilirubin is blocked

Lab findings in post-hepatic jaundice?

Conjugated hyperbilirubinaemia Bilirubin in urine (dark) Increased canalicular enzymes (ALP) Normal or raised ALT/AST due to mild hepatocyte damage from pressure

Causes of post-hepatic jaundice?

Intrahepatic - hepatitis - drugs - cirrhosis - primary biliary cirrhosis Extra-hepatic (obstruction distal to bile canaliculi) - gallstones - biliary stricture - carcinoma - pancreatitis - sclerosis cholangitis

Where can carcinomas be which cause extra-hepatic jaundice?

``` Head of pancreas Ampulla Cholangiocarcinoma Porta hepatis Lymph nodes Liver metastases ```

Overall causes of pre-hepatic, hepatic and post-hepatic jaundices

Pre-hepatic - excessive bilirubin produced Hepatic - reduced capacity to conjugate or excrete bilirubin Post-hepatic - obstruction to biliary system