GIT week 1

Pathology

100

What type of epithelium normally lines the oesophagus?

How does the epithelium change in GORD? Outline the stages and the end result if GORD is uncontrolled.

Non-keratinising stratified squamous epithelium (NKSSE)

Reflux of gastric acid into the lower oesophagus causes NKSSE to undergo metaplasia into columnar glandular epithelium ('intestinal metaplasia' rich in goblet cells)

--> dysplasia --> adenocarcinoma

200

What is achalasia?

Lack of coordinated muscle contractions

Impaired relaxation of the lower oesophagus

Retention of food bolus and impaired swallowing

Megaoesophagus complication

'Bird beak' sign

300

What are the 2 types of oesophageal cancer? Compare their location & risk factors.

Squamous cell carcinoma - middle/lower oesophagus (heavy alcohol and smoking)

Adenocarcinoma - lower oesophagus, metaplasia (Barrett's oesophagus, GORD)

400

Define 'hiatus hernia' and explain the different types.

Upper part of stomach moves through the diaphragm/oesophageal hiatus into the thorax

Sliding - stomach herniates through the hiatus, impaired lower oesophageal sphincter

Paraoesophageal/rolling - stomach protrudes ALONGSIDE the oesophagus, lower oesophageal sphincter is intact thus there is rarely reflux

500

What are the major causes of chronic gastritis? Briefly explain the pathophysiology

Helicobacter pylori - bacteria colonises the epithelium, causes damage and inflammation, usually antrum location, ulceration

Autoimmune (pernicious anaemia) - antibodies to parietal cells or IF, impaired secretion of HCl and impaired absorption of B12 with megaloblastic anaemia

Reactive - alcohol, toxins directly damage mucous layer

Clinical

100

What are the classic symptoms of GORD?

Reflux, waterbrash

Cough, belching

Bloating

Retrosternal burning pain radiating to the jaw

200

List 3 differentials for upper GI bleed

Oesophageal varices

Peptic ulcer

Oesophageal tear (Mallory-Weiss)

Gastric cancer, polyp

300

Draw an abdomen with 4 quadrants, and list 2-3 differential diagnoses for abdominal pain in each quadrant.

RUQ - cholecystitis, biliary colic, hepatitis

RUQ/LUQ - pancreatitis, gastritis, GORD, MI, lower lobe pneumonia

LUQ - splenic infarction/rupture, renal colic

LIF - diverticulitis, renal colic, torsion (ovarian/testicular)

RIF - appendicitis, Crohn's, renal colic, torsion (ovarian/testicular)

400

Thinking about the 4 ways to block a tube, what are some differential diagnoses for dysphagia?

Luminal - foreign bodies

Wall - neoplasm (oesophageal adenocarcinoma), stricture

Extrinsic - mediastinal tumours/mass, thyroid/goitre

Function - achalasia, motor neuron disease

500

What symptoms might someone with a peptic ulcer complain of?

What investigations would you order?

Reflux, retrosternal chest pain/epigastric pain, haematemesis, malena

Burning may increase with food (gastric) or empty stomach (duodenum)

H. pylori urease breath test

Gastroscopy 

Pharmacology

100

Where is the Chemoreceptor Trigger Zone and what is its function?

In medulla, outside BBB (can detect toxins/chemicals in blood and CSF).

Input from labyrinth (inner ear and vestibular system) and GIT.

Contains receptors - serotonin, dopamine, opioid...

200

List the dopamine receptor antagonists used in nausea/vomiting. Which one/s cross the BBB and why is this significant?

Domperidone

Cross BBB - Prochlorperazine, Metoclopramide (can bind to basal ganglia and substantia nigra causing Parkinsonism)

300

What system is involved in motion sickness?

What receptors are involved and what medications can be used to combat motion sickness?

Labyrinth/vestibular system (inner ear) with acetylcholine and histamine receptors.

Acetylcholine M1 receptor blockers - hyoscine (scopalamine) 

Histamine H1 receptor blockers - dimenhydrinate, pheniramine, promethazine

400

What is the MoA of Ondasetron? Explain why it may be useful in surgery and chemotherapy-related nausea.

5HT3 (serotonin) receptor antagonist

Surgery/chemo can cause GIT ECL cells to release 5HT which then binds to 5HT3 receptors in GIT --> impulses sent to CTZ

Ondansetron blocks 5HT3 receptors in both GIT and CTZ

500

List 4 types of laxatives based on their MoA and give an example of each.

Stool softeners (allow water to enter stool) e.g. Docusate

Bulk-forming (trap water and increase bulk) e.g. Psyllium husk, bran

Osmotic (draw water in via osmotic pressure) e.g. Macrogol, Lactulose, Mg

Stimulants (increase peristalsis) e.g. Bisacodyl, Senna

Anatomy

100

Draw a stomach and label the different parts.

200

Outline gastric acid secretion (the cell types involved).

Parietal cells are stimulated by G cells (gastrin) and ECL cells (histamine) to secrete HCl

300

There are 3 zones of constriction in the oesophagus - can you name them?

Cervical (cricopharyngeal sphincter)

Thoracic (aortic arch, primary bronchus)

Diaphragm (hiatus)

400

Outline the venous drainage of the foregut, midgut, hindgut

Foregut --> portal vein --> IVC

Midgut --> superior mesenteric vein --> portal vein --> IVC

Hindgut --> inferior mesenteric vein --> splenic --> portal --> IVC

500

What is the major arterial supply to the stomach? What branches help to perfuse the stomach?

Coeliac trunk - L gastric, common hepatic, splenic

Splenic - L gastro-omental, short gastric

Common hepatic - R gastric, gastroduodenal, hepatic artery proper