Gastro Flashcards
What are the defence mechanisms of the GI microbiome?
Intestinal microflora:
- prevent infection by interfering and competing with pathogens
- produce its own antibacterial substances
Gastric acid kills most organisms that are swallowed
Bile has antibacterial properties
What is diarrhoea?
The passage of loose or watery stools, typically at least three times in 24hrs.
What are the types of diarrhoea?
Acute - 14 days or fewer in duration
Persistant diarrhoea - 14-30 days duration
Chronic diarrhoea - >30 days duration
What are the causes of diarrhoea?
Infective: intraluminal infection, systemic infections (sepsis, TSS, tropical infections, COVID)
Non-infective: cancer, chemical (poisoning, sweeteners, medications), IBD, IBS/malabsorption, endocrine (thyrotoxicosis), radiation
What are the characteristics and causes of watery diarrhoea?
Non-inflammatory
Infection in proximal small bowel
Bacteria implicated: vibrio cholerae, E. coli, Clostridium perfringens, Bacillus cereus (reheated rice), S. aureus, C. difficile
Viral causes: Rotavirus, norovirus
Parasitic: Giardia, Cryptosporidium
What condition is associated with rice water diarrhoea?
V. cholerae infection
What is dysentery?
bloody diarrhoea
What is H. pylori?
Gram -ve rod, commensal bacteria, usually asymptomatic acquisition
What conditions are caused by H. pylori?
Peptic ulcer disease (PUD), chronic gastritis, gastric adenocarcinoma, gastric mucosal lymphoma
What is the pathophysiology of H. pylori infection?
- H. pylori synthesises urease, an enzyme which produces ammonia
- Ammonia damages the gastric mucosa as well as neutralising the protective stomach acid which allows the organs, to survive in the stomach
What are the diagnostic tests for H. pylori infection?
Biopsy
Stool antigen
C-urea breath test
What is the treatment for H. pylori infection?
Triple therapy: clarithromycin, amoxicillin, PPI (lansoprazole, omeprazole)
What is E. coli?
Gram -ve rod, often commensal bacteria
Most strains are harmless but some serotypes are pathogenic:
- ETEC (EnteroToxigenic), EAEC (EnteroHaemorrhagic), EPEC (EnteroPathogenic) → watery diarrhoea
EHEC (EnteroHaemorrhagic) → bloody diarrhoea
Serotype 0157:H7 → Haemolytic Uremic Syndrome
( → haemorrhagic diarrhoea + nephritic syndrome)
What is the treatment for E. coli?
Amoxicillin, trimethoprim, nitrofurantoin
What is C. difficile?
Gram +ve spore-forming, toxin-producing bacteria
Mainly induced w/ antibiotics (ciprofloxacin, co-amoxiclav, cephalosporins, clindamycin)
What is the pathophysiology of C. difficile infection?
Causes pseudomembranous colitis
- Normal GIT flora killed by antibiotics and C. difficile replaces them
- Results in dangerous severe diarrhoea (very watery; ↑↑dehydration)
Highly infectious
What is the treatment for C. difficile?
Stop using C-antibiotics (ciprofloxacin, co-amoxiclav, cephalosporins, clindamycin)
Give vancomycin
Which bacteria cause dysentry?
C - Campylobacter
E - E. coli
S - Shigella
S - Salmonella
What factors are essential to refer to in the history for GI infections?
Onset/duration
Characteristics of stool
Food/drink
Travel
Immune status
Unwell contacts
Hobbies + fresh water
Animal contact
Medications
What are the indications for testing in GI infections
Severe illness: signs of hypovolemia, severe abdo pain, hospitalization
Bloody diarrhoea+ mucus
High-risk host: Age ≥70 years, immunocompromising condition , IBD , pregnancy
Symptoms persisting for more than one week
Public health concerns (eg, diarrhoeal illness in food handlers, HCW, individuals in day care centers)
What can be tested in a stool sample?
Microscopy
Culture
Multi-pathogen molecular panels (GE PCR panel)
Ova, cysts and parasites x3
Toxin detection (C difficile)
What is Acute Cholecystitis?
Gallbladder inflammation caused by cystic duct obstruction by gall stones
What are the symptoms of acute cholecystitis?
Right upper quadrant or epigastric pain, fever and leukocytosis
What is the diagnostic test for acute cholecystitis?
USS
What is the treatment for acute cholecystitis?
IV fluids, analgesia and antibiotics
Surgery: cholecystectomy
What is ascending cholangitis?
Obstruction of the common bile duct resulting in inflammation
What are the symptoms of ascending cholangitis?
Charcot’s triad: Fever, abdominal pain and jaundice
What is the management of ascending cholangitis?
Prompt admission + IV antibiotics
ERCP (Endoscopic retrograde cholangiopancreatography) - also used for diagnosis
Cholecystectomy
What is the most common cause of upper GI bleeding?
Peptic ulcer (50%)
what is the Glasgow-Blatchford score?
A scoring method to decide whether a patient presenting with upper GI bleeding should be admitted or sent home.
What factors are considered in the Glasgow-blatchford score?
- Systolic blood pressure
- Blood urea
- Haemoglobin
- Pulse ≥ 100
- Melaena (black, tarry stools due to blood)
- Syncope
- Hepatic disease
- Cardaic failure
What are the two types of upper GI bleeding?
Variceal and Non-variceal bleeding
When is variceal bleeding suspected?
In patients with a history of liver disease or alcohol excess
What is the first line treatment for variceal bleeding?
Antibiotics and terlipressin (inhibits portal circulation) reduce mortality
What is the endoscopic treatment for variceal bleeding?
Band ligation (within 12 hours)
When is non-variceal bleeding suspected?
In patient with a history of peptic ulcers, using certain medications; NSAIDs, anticoagulation or antiplatelets
What is the first line treatment for non-variceal bleeding?
Consider proton pump inhibitors
What are the causes of intraluminal obstruction of the GI tract?
tumour - carcinoma, lymphoma block lumen
diaphragm disease - diaphragm-like membranes of mucosa and submucosa form in bowel lumen creating pinhole lumen and subsequent obstruction
meconium ileus - meconium = first stool produced by neonate, in meconium ileus it gets stuck and blocks the ileum
gallstone ileus - impacted gallstone blocks lumen of small instestine
What are the causes of intramural GI obstruction?
inflammatory - Crohn’s, diverticulitis
tumours
neural - Hirschsprung’s disease - occurs in babies when the nerve cells do not migrate all the way down to the distal colon/rectum –> immobile distal colon/rectum so can’t pass stool
What are the causes of extramural bowel obstruction?
adhesions
volvulus
tumour (peritoneal deposits)
Where does volvulus occur most often?
Sigmoid colon
What are the 2 types of oesophageal cancer?
- adenocarcinoma - lower 1/3 oesophagus, associated with Barrett’s oesophagus
- squamous cell carcinoma - upper 2/3 oesophagus, smoking + alcohol
What are the risk factors for oesophageal cancer?
male
older age
smoking
alcohol use (SCC)
Barrett’s oesophagus (AC)
GORD (AC)
hiatus hernia (AC)
FHx
where are the typical sites of oesophageal cancer metastasis?
perioesophageal lymph nodes, liver, lungs
What are the key presentations of oesophageal cancer?
usually presents at advanced stage
anaemia
weight loss
anorexia
melaena
haematemesis
odynophagia (progressive difficulty swallowing)
What are the risk factors/causes of gastric carcinoma?
H. pylori infection
smkoing
CDH-1 mutation –> 80% risk
FHx
pernicious anaemia (autoimmune chronic gastritis)
What are the key presentations of gastric carcinomas?
severe epigastric pain
anaemia
weight loss
fatigue
progressive dysphagia
what are the signs of gastric carcinoma metastases?
jaundice (liver mets), Krukenberg tumour (ovarian mets)
what are the investigations for gastric carcinoma?
gastroscopy + biopsy
CT/MRI for staging, PET to ID mets
What is the chemotherapy for gastric carcinoma?
ECF - epirubicin, cisplatin, fluorouracil
Which 2 inherited conditions massively increase the risk of colorectal polyps?
Familial adenomatous polyposis (FAP)
- autosomal dominant APC gene (tumour suppressor) mutation
- 95% risk of corectal polyps by 50
Hereditary non-polyposis colon cancer/Lynch syndrome
- autosomal dominant MSH-1 mutation = DNA mismatch for repair gene
- rapidly increases progression, adenoma –> adenocarcinoma
What are the risk factors for colorectal polyps/cancer?
familial inherited genetic disposition
adenomas/polyps
alcohol
smoking
ulcerative colitis
what are the key presentations of colorectal polyps/cancer?
mostly in distal colon –> LLq pain, bloody mucousy stools, tenesmus
What are the investigations for colorectal polyps/cancer?
FIT test
Colonoscopy + biopsy
What is dyspepsia?
indigestion –> early satiation, epigastric pain + reflux, extreme fullness
What is achalasia?
oesophageal dysmotility (impaired peristalsis), LOS fails to relax
what are the key presentations of achalasia?
non-progressive dysphagia (difficulty swallowing anything)
substernal pain
food regurgitation
aspiration pneumonia (food or liquid breathed into the airways)
What are the investigations for achalasia?
1st line = upper GI endoscopy
GS = oesophageal manometry
other = barium swallow (bird’s beak sign)
What is the treatment for achalasia?
only curative option = surgery (balloon stenting)
nitrates + nifedipine can help pre-surgery to relax the LOS
What does achalasia increase the risk of?
oesophageal squamous cell lung cancer
What is ischaemic colitis?
ischaemia of colonic arterial supply (inferior mesenteric artery); colon inflamed due to hypoperfusion
What are the risk factors for ischaemic colitis?
> 60 yrs old
female
clotting problems
high cholesterol
heart failure
previous abdominal surgery
what are the most common sites affected by ischaemic colitis?
splenic flexure, sigmoid colon + cecum (watershed areas between the two major arteries supplying the colon - SMA/IMA)
what are the key presentations of ischaemic colitis?
LLQ pain + bright red bloody stool
signs of hypovolemic shock (pallor, agitation, confusion)
What is the gold standard test for ischaemic colitis?
colonoscopy + biopsy
What are the treatments for ischaemic colitis?
IV fluid + antibiotics (prophylactic)
Surgery only treatment if becomes gangrenous
What is pseudomembranous colitis?
infection of the colon caused by clostridium difficile
what are the risk factors for pseudomembranous colitis?
antibiotic exposure
advanced age
hospitalisation or residence in a nursing home
exposure to infected family member
IBD
CKD
HIV
What is the pathophysiology of pseudomembranous colitis?
C. difficile bacteria produce toxins which cause an inflammatory response in the large intestine, leading to increased vascular permeability and pseudomembrane (raised yellow and white plaques on inflamed mucosa made up of neutrophil, fibrin, mucin and cellular debris) formation.
What are the key presentations of pseudomembranous colitis?
diarrhoea
abdominal pain
fever
abdominal tenderness
nausea + vomiting
abdominal distension
shock symptoms
What are the investigations for pseudomembranous colitis?
FBC, stool sample (FIT, PCR, immunoassay)
Abdo XR
Sigmoidoscopy/colonoscopy
What is the management for pseudomembranous colitis?
antibiotics (fidaxomicin, vancomycin, metronidazole)
supportive care
what is mesenteric ischaemia?
ischaemia of the small intestine
AMI = acute attack
CMI = longer lasting (month +)
What are the risk factors for mesenteric ischaemia?
Older age
low/high bp
Heart disease
High cholesterol
Smoking
Clotting problem
Inflammatory problems e.g. pancreatitis, diverticulitis
What are the key presentations for mesenteric ischaemia?
triad:
1. acute severe pain in the central/right iliac fossa
2. No abdo signs on exam
3. rapid hypovolemic shock
What are the investigations for mesenteric ischaemia?
FBC + ABG = persistent metabolic acidosis
CT angiogram
What is the treatment for mesenteric ischaemia?
Fluid resuscitation, antibiotics, IV heparin
infarcted bowel –> surgery
What are haemorrhoids?
Swollen veins around anus disrupt anal cushions causing prolapse of parts of the anal cushions through the anal passage
what is the classification of haemorrhoids?
1st degree: no prolapse
2nd: prolapse when straining and return on relaxing
3rd: prolapse when straining, do not return on relaxing, but can be pushed back
4th: prolapsed permanently
What are the risk factors for haemorrhoids?
constipation
anal sex
age 45-65
pregnancy
pathological pelvic lesions
What are the 2 types of haemorrhoid presentation?
Internal - originate above internal rectal plexus (dentate line), less painful as has decreased sensory supply
external - originate below dentate line, so painful patient can’t sit down