Gastrointestinal Flashcards
What layer of the trilaminar disc forms the inner linings of the digestive tract & respiratory system?
Endoderm
What weeks of development does the embryo form the primitive gut?
4-8
In weeks 4-8, what structure is the gut tube suspended from?
Dorsal mesentery
What layer of the trilaminar disc forms the epithelium of the mouth & rectum?
Ectoderm
What layer of the trilaminar disc forms the muscular & fibrous elements of the gut?
Mesoderm
What layer of the trilaminar disc forms the inner epithelium and glands of the gut?
Endoderm
Describe the 4 steps of the dilatation of the stomach & its rotation
- Fusiform dilatation of the caudal end of the gut tube. 2. Dilatation - greater dorsally than ventrally, forming the greater curvature. 3. Rotates 90 degrees clockwise around the longitudinal axis. 4. The greater curvature is now on the left, and the lesser curvature is on the right.
Is the duodenum intraperitoneal or retroperitoneal?
Parts 2, 3, & 4 are retroperitoneal
What process pulls the duodenum into a C-shaped loop in the embryo?
Rotation of the stomach
The liver bud splits into cranial & caudal parts - what structures do each consist of?
Cranial - liver and bile duct. Caudal - gallbladder and cystic duct
Which structures do the two pancreatic buds develop from - dorsal bud & ventral bud?
Dorsal bud - dorsal mesentery, ventral bud - bile duct
What structure is formed when the ventral pancreatic bud moves to lie posteriorly & inferiorly to the dorsal bud?
Uncinate process of the pancreas
What is annular pancreas?
When the ventral bud of the pancreas fails to rotate, and partially or fully encircles the duodenum.
What structures does the foregut consist of?
The oesophagus to the first two parts of the duodenum
What structures does the midgut consist of?
The last two parts of the duodenum to 2/3rds along the transverse colon
What structures does the hindgut consist of?
The last 1/3rd of the transverse colon to the proximal 2/3rds of the rectum
Stomach retro or intraperitoneal?
Intraperitoneal
Jejunum and ileum retro or intraperitoneal?
Intraperitoneal
Caecum and appendix retro or intraperitoneal?
Intraperitoneal
Transverse colon retro or intraperitoneal?
Intraperitoneal
Liver and gallbladder retro or intraperitoneal?
Intraperitoneal
Sigmoid colon retro or intraperitoneal?
Intraperitoneal
Ascending and descending colon retro or intraperitoneal?
Retroperitoneal
Tail of pancreas retro or intraperitoneal?
Intraperitoneal
Spleen retro or intraperitoneal?
Intraperitoneal
Rectum retro or intraperitoneal?
Retroperitoneal
Head, neck & body or pancreas retro or intraperitoneal?
Retroperitoneal
Kidneys, suprarenal gland & ureters retro or intraperitoneal?
Retroperitoneal
Abdominal aorta retro or intraperitoneal?
Retroperitoneal
Inferior vena cava retro or intraperitoneal?
Retroperitoneal
What process results in the formation of the umbilical cord?
Liver growth reduces cavity space and causes intestinal loop herniation
What does the superior mesenteric artery act as a rotatory axis for?
90 degree anticlockwise rotation of the midgut
At what week does the coiling of the small intestine occur?
8 weeks
What is an omphalocoele/exomphalos?
Herniation of the bowels into the umbilical cord
What layer of the trilaminar disc forms the bladder & urethra?
Endoderm
What week does the cloaca separate into the rectum and urogenital sinus?
8 weeks
What investigations does new-onset unexplained dysphagia warrant? (3)
Endoscopy, barium swallow, MRI
What investigation does epigastric pain/vomiting warrant?
CT abdo
What investigations would you perform in suspected bowel obstruction? (2)
XR abdo, CT abdo
What investigations would you perform in suspected bowel perforation? (2)
XR chest, CT abdo
What investigation would you perform in a suspected swallowed foreign body?
XR
What investigations are used for staging of oesophageal cancer? (2)
CT, PET-CT
What muscle provides voluntary control of the oesophagus?
Cricopharyngeus/Upper oesophageal sphincter
What muscle types does the oeseophagus have? (2)
Striated muscle proximally, smooth muscle distally
What muscle provides involuntary control of the oesophagus?
Lower oesophageal sphincter
What layers does the oesophageal wall consist of, inner to outer? (5)
Mucosa -> submucosa -> circular layer muscularis -> longitudinal layer muscularis -> adventitia
What foods decrease LOS pressure (relaxes)? (6)
Chocolate, fatty foods, caffeine, citrus, garlic, tomato
What drugs decrease LOS pressure (relaxes)? (11)
Alcohol, anticholinergics, beta-agonists, calcium channel blockers, dopamine, nicotine, nitrates, progesterone, oestrogen, tricyclic antidepressants
What foods increase LOS pressure? (3)
Protein, carbohydrates, refluxed acid
What drugs increase LOS pressure? (5)
Alpha-agonists, beta-blockers, cholinergics, metoclopramide, domperidone
What do parietal cells secrete, and where are they?
HCl, gastric body
What do G cells secrete, and where are they?
Gastrin, gastric antrum
What do ECL (Enterochromaffin-like Cells) cells secrete, and where are they?
Histamine, gastric body
What do D-cells secrete, and where are they?
Somatostatin, whole stomach
Function of gastrin?
Stimulates HCl secretion via histamine release & direct parietal cell stimulation, stomach distension,
Function of histamine in the stomach?
Stimulates H2 receptors on parietal cells; stimulates HCl release
Function of somatostatin?
Inhibit secretion of gastrin, ghrelin, secretin, cholecystokinin (CCK), etc.
What is Zollinger-Ellison syndrome?
Excessive gastrin secretion (10x normal upper limit), resulting in a reduced gastric pH (more acidic!)
What is pyloric stenosis?
Congenital hypertrophic pyloric stenosis - obstruction that presents from 3-6wks old, with visible peristalsis & a palpable mass after feeding. Can be acquired - ulcer scar, antral tumour, tumours of the pancreatic head
What can cause acute gastritis? (5)
Irritants (smoking, alcohol), drugs (aspirin, NSAIDs, oral steroids), severe stress (burns, trauma, surgery, shock, sepsis), radiation, chemotherapy
Characteristics of acute ‘stress’ ulcers? (5)
Does not penetrate the muscularis propia, no scarring under ulcer, no endarteritis obliterans, heals by regeneration, can be anywhere and multiple
Characteristics of chronic ‘peptic’ ulcer?- (5)
Penetrates muscularis propia, scarring under ulcer, endarteritis obliterans (arterial occlusion), heals by repair with fibrous scar, single & usually antral
Complications of peptic ulcers? (4)
Perforation, haemorrhage, pyloric stenosis, malignant change
Characteristics of gastric vs duodenal ulcers? (4)
Gastric - slightly more common in males, no genetic factors, pain on eating, slightly older average age of onset. Duodenal - much more common in males, genetic factors very important, pain relieved by eating, slightly younger age of onset.
Primary malignant gastric neoplasia types? (3)
Adenocarcinoma, malignant gastrointestinal stromal, lymphoma
Risk factors for gastric neoplasia? (8)
Genetic, blood group type A, carcinogenic diet, pernicious anaemia, operated stomach, atrophic gastritis, adenomas, more common in males >50y/o.
Gastric lymphoma type & treatment?
Mucosa Associated Lymphoid Tissue (MALT), B-cell lymphoma, treated with abx.
What do chief cells secrete? (2)
Pepsinogen, leptin
What are the stages of gastric secretion?
Cephalic - thought or oral ingestion of food, vagus nerve. Gastric - food in stomach, distension, vagal stimulation. Intestinal - food in small intestine, gastrin, followed by enteric inhibitors.
What type of feedback loop is gastrin secretion?
Negative
Function of PGE2 in digestion?
Directly inhibits parietal cells.
What can cause too little acid secretion in the stomach? (3)
Inflammation & gastric atrophy (autoimmune gastritis, H. Pylori gastritis), iatrogenic (drugs, fundoplication-related dysphagia, vagotomy), associated with infectious diarrhoea/gastric adenocarcinoma
Causes of acute epigastric pain? (9)
Acute pancreatitis, perforated peptic ulcer, peptic ulcer, acute cholecystitis, biliary colic, acute cholangitis, mesenteric vascular disease, perihepatitis, supradiaphragmatic pathology
Causes of dyspepsia? (5)
Functional (sensitisation), GORD, peptic ulcer, oesophageal cancer, gastric cancer
Risk factors for gastric cancer? (4)
Age, smoking, atrophic gastritis, H. Pylori
Risk factors for GORD? (2)
Smoking, BMI
Risk factors for peptic ulcers? (3)
H. Pylori, NSAIDs/aspirin, smoking
Risk factors for oesophageal cancer? (4)
Smoking, BMI, Barrett’s oesophagus, age
What are the NICE referral guidelines for suspected oesophageal cancer? (5)
Dysphagia, OR >55y/o AND weight loss, with any of the following: upper abdo pain, reflux, dyspepsia
Tests for H. Pylori? (7)
Urea breath test, faecal antigen, serology, biopsy - urease, histology, culture, PCR
1st line treatment for H. Pylori? (3)
One to two weeks - PPI BD + amoxicillin 1g BD + clarithromycin 500mg BD
2nd line treatment for H. Pylori? (5)
Esomeprazole 40mg BD + 2 or 3 of: amoxicillin 1g BD / levofloxacin 500mg OD / metronidazole 400mg TDS / tetracycline 500mg QDS
3rd line for H. Pylori? (2)
Endoscopy & biopsy (for antibiotic sensitivities)
Treatment for functional dyspepsia? (8)
H. Pylori eradication, PPI, prokinetics, amitriptyline/imipramine, buspirone, mirtazepine, sulpiride, behavioural interventions (diaphragmatic breathing, psychological)
What is linitis plastica?
‘Leather bottle stomach’ - diffuse gastric cancer
What investigation is used in staging gastric cancer alongside CT contrast?
Staging laparoscopy
Curative treatment for gastric cancer? (2)
Perioperative chemotherapy & gastrectomy, or straight to gastrectomy if >80y/o and/or significant comorbidities
Palliative treatment for gastric cancer? (4)
Best supportive care, stent (e.g. pyloric stent for obstruction), drain (e.g. ascites), palliative chemotherapy
What is the standard chemotherapy regime in curative treatment for gastric cancer? (2)
3 cycles before gastrectomy, then 3 cycles of adjuvant chemotherapy (75% dose) after surgery
What anastomosis is made in gastrectomy surgery?
Oesophago-jejunal. Maintain & anastomose section of duodenum with ampulla of Vater.
Which form of oesophageal cancer is most common in the West?
Adenocarcinoma
Which form of oesophageal cancer is most common worldwide?
Squamous cell carcinoma
Risk factors for oesophageal SCC? (5)
Alcohol, smoking, chewing betel nut, frequent consumption of very hot drinks, achalasia
Risk factors for oesophageal adenocarcinoma? (6)
GORD, obesity, older males, hiatus hernia, smoking, Barrett’s oesophagus
Where is oesophageal adenocarcinoma most commonly located?
Oesophagogastric junction
What is the cell type lining the oesophagus until the Z-line?
Pale pink stratified squamous epithelium
What cell type lines the stomach?
Salmon coloured columnar epithelium
Red flags for oesophageal cancer? (6)
Progressive dysphagia (cancer until proven otherwise), self-adapted liquid diet, weight loss, food regurgitation, persistent reflux not responding to tx with PPI, food bolus obstruction
What is the name of the current standard chemotherapy for oesophageal cancer, and what is its mode of delivery?
FLOT chemotherapy, PIC line
Why are barium swallows not helpful in oesophageal cancer?
Does not tell if benign or malignant, gastroscopy would be required for biopsy.
What investigations are used to stage oesophageal cancer? (4)
CT, CT-PET, endoscopic ultrasound, staging laparoscopy
Management for oesophageal adenocarcinoma?
3 cycles chemo, surgery, 3 cycles adjuvant chemo (75% dose)
Management for oesophageal SCC?
CROSS regime - chemoradiotherapy
What surgery is performed for oesophageal cancer?
Ivor-Lewis oesophagectomy
What structures remain in the Ivor Lewis oesophagectomy?
Top 3rd of the oesophagus, anastomosed to the bottom 2/3rds of the stomach.
What structure slings around the lower oesophageal sphincter, and when the stomach emerges past creates a hiatus hernia?
Crural diaphragm
What is classed as a small hiatus hernia?
<2cm
What is classed as a large hiatus hernia?
> 5cm
Symptoms of reflux? (9)
Heartburn, chest pain, regurgitation, sensitivity to certain foods (especially cold), acid brash (metallic taste in back of mouth), worse leaning forwards & lying flat, worse at night, cough, dental issues
Initial management of reflux (no red flag symptoms)?
Trial PPIs full dose for 4-8 weeks.
Lifestyle changes for GORD? (7)
Weight loss, adjusting head of bed/sleep angle, dietary (e.g. fizzy drinks, alcohol, spicy food, etc.), smoking cessation, stress reduction, eat 3h before bed, reduce caffeine intake
2nd line treatment for GORD?
H2 receptor antagonists
What surgery is performed in refractory GORD?
Nissen fundoplication
What does a Nissen fundoplication involve?
Taking the fundus 360 degrees around the LOJ and suturing together to form an artificial sphincter.
What does the first tier of obesity management involve? (2)
Tier 1 = universal interventions - environmental & population wide services, identifying & reinforcing healthy eating and physical activity messages.
What does the second tier of obesity management involve? (3)
Tier 2 = lifestyle interventions, diets, pharmacotherapy - multicomponent weight management services, identification & primary assessment.
What does the third tier of obesity management involve? (1)
Tier 3 = specialist services - MDT, specialist assessment.
What does the fourth tier of obesity treatment involve? (1)
Tier 4 = surgery - preoperative assessment, bariatric medical & multidisciplinary team.
What three types of bariatric surgery are available?
Sleeve gastrectomy, Roux-en-Y gastric bypass, laparoscopic adjustable gastric band (LAGB)
What does a sleeve gastrectomy involve?
Removal of fundus & significant portion of body, with the pylorus remaining.
What does a Roux-en-Y gastric bypass involve?
Two anastomoses - gastrojejunostomy & a jejuno-jejunostomy. The stomach is bypassed, with food & bile mixing in the common channel in the jejunum.
What does a laparoscopic adjustable gastric band involve?
A port is made, leading to an inflatable band which separates the stomach into a smaller portion and a larger portion.
What is Ludwig’s angina?
Infection of hypoglossal tissue - oedema & exudate cause the tongue to be pushed up and back. May become an emergency. Stridor, bull-neck, pain, dysphagia, fever
Presentation of strep throat? (7)
Fever, rapid-onset sore throat, pain on swallowing, grey-yellow tonsillar exudate. No cough, runny nose, don’t lose voice
Presentation acute epiglottitis? (8)
Severe sore throat, difficulty swallowing, high fever, malaise, rapid development, tenderness of neck, stridor, most common in children
Management of acute epiglottitis? (5)
High dose abx (cefotaxime, chloramphenicol), corticosteroids (reduce oedema), sit patient upright, oxygen, emergency tracheostomy
Bilirubin blood test & normal value?
Breakdown product of RBCs, isolated rise can be benign (Gilbert’s), total <21umol.
ALP blood test & normal value?
Alkaline phosphatase, raised in bile duct blockage/pressure, bone disease, low vitamin D. 30-130.
ALT blood test & normal value?
Alanine transaminase, released by damaged cells (direct hepatocyte damage). 10-60 male, 10-40 female.
AST blood test & normal value?
Aspartate aminotransferase, long term hepatocyte damage (helpful in indicating fibrosis), <50 male, <35 female
GGT blood test & normal value?
Gamma glutamyl transferase, rises with alcohol, rises with ALP in bile duct blockage. <55 male, <38 female.
Features of Crohn’s disease on imaging? (7)
Skip lesions, ulcers, fistulas, fissures & oedema (cobblestoning), stenosis, wall thickening, inflammatory masses & abscesses
Indications for imaging the large intestine? (4)
Change in bowel habit, PR bleeding, iron deficiency anaemia, palpable mass
What are polyps of the large intestine classed as?
Premalignant adenomas, progressing to carcinoma
Causes of small bowel obstruction? (6)
Adhesions, hernias, Crohn’s, malignancy, intussusception, gallstone (ileus)
What are taeniae coli?
3 bands of smooth muscle, making up the longitudinal muscle layer at the muscularis of the large intestine (except at terminal end)
What are the folds of the small bowel called (seen on AXR)?
Valvulae conniventes
What are the folds of the large intestine called (seen on AXR)?
Haustra
What are epiploic appendages?
Fat-filled sacs of visceral peritoneum found on the taeniae coli
How many rectal valves are there?
3
What is the purpose of the rectal valves?
To separate gas and faeces, preventing simultaneous flatus and faeces passage
How long is the rectum?
20cm
How long is the anal canal?
3.8-5cm
What type of muscle makes up the internal anal sphincter?
Smooth involuntary
What type of muscle makes up external anal sphincter?
Skeletal voluntary
What cell type makes up the anal canal surface?
Stratified squamous epithelial mucosa
What purpose do anal canals serve?
Mucus secretion to facilitate defecation
What is is the band marking the junction between hindgut & external skin called?
Dentate/pectinate line
What innervates above the dentate line?
Visceral sensory fibres - fairly insensitive.
What innervates below the dentate line?
Somatic sensory fibres - very sensitive.
What cells secrete mucus in the digestive tract?
Goblet
How frequently do the haustra contract & for how long?
Every 30 minutes, lasting approximately 1 minute
Which reflex increases gastric motility, and in response to what?
Gastrocolic reflex, stomach distension & breakdown products in the small intestine
What process produces gas in the colon?
Saccharolytic fermentation
What is faeces composed of? (6)
Undigested food residue, unabsorbed digested substances, bacteria, old epithelial cells, inorganic salts, water
Defecation reflex is caused by what?
Faeces in the anal canal gives choice of relaxing or keeping it temporarily closed. Parasympathetic reflex mediated by the spinal cord.
What is the definition of dysentery?
Severe diarrhoea with blood or mucus
What is gastroenteritis?
Inflammation of the stomach & intestinal mucosa
What is the leading cause of gastroenteritis?
Food poisoning
What type of viruses are responsible for 90% of cases of acute viral gastroenteritis? (2)
Norovirus, rotovirus
What is protozoan diarrhoea usually related to? (2)
Travel, part of an outbreak
What microbes are commonly associated with raw seafood (3)
Norwalk-like virus, Vibrio sp, hepatitis A
What microbes are commonly associated with raw eggs? (1)
Salmonella sp
What microbes are commonly associated with undercooked meat or poultry? (4)
Salmonella sp, Campylobacter sp, STEC, Clostridium perfringens
What microbes are commonly associated with unpasteurised milk or juice? (4)
Salmonella sp, Campylobacter sp, STEC, Yersinia enterocolitica
What microbes are commonly associated with unpasteurised soft cheese? (5)
Salmonella sp, Campylobacter sp, STEC, Y. enterocolitica, S. aureus
What microbes are commonly associated with homemade canned goods?
Clostridium botulinum
What microbes are commonly associated with fruits & vegetables? (5)
Cyclospora, C. perfingens, B. cereus, EHEC, STEC
What microbes are commonly associated with water? (3)
Cholera, Vibrio sp, giardia
What bacteria causes Guillain-Barre & bloody diarrhoea?
Campylobacter jejuni
EHEC (Enterohaemorrhagic E. Coli) causes what problems? (3)
Bloody diarrhoea, haemolytic-uraemic syndrome, neurological complications. Toxin damages vascular endothelial cells.
Salmonella typhi causes what disease?
Enteric fever/typhoid
Salmonella enterica causes what disease?
Loads of types of food poisoning differentiated by O & H antigens
Properties of viral stools? (4)
Watery diarrhoea, no pus, no blood, self-limiting
Properties of bacterial stools - toxigenic? (2)
Large volume, watery or greasy
Properties of bacterial stools - invasive (3)
Extreme urgency of defecation, small volume of stool, contains pus & blood.
Symptoms of botulism? (2)
Visual disturbances, potentially life-threatening descending paralysis
How do enterotoxins cause diarrhoea? (4)
Increase chloride ion permeability of the apical membrane of intestinal mucosal cells, pores activated, chloride leakage into lumen, sodium & water movement results. Causes secretory diarrhoea within a few hours.
How is C. Diff diagnosed?
Detection of GDH/glutamate dehydrogenase
Characteristics of C. Diff on colonoscopy?
Inflamed colon mucosa with raised, yellowish plaques/nodules.
What is C. Diff also commonly referred to as?
Pseudomembranous colitis