GI Endoscopy Flashcards
how does transmission work in endoscopy?
light source transmits light into body cavity
resulting image is transmitted to eyepiece/monitor
what are the overall roles of endscopy?
diagnostic and therapeutic
how can endoscopy aid diagnostics?
observation and sampling
what types of sampling can be done via endoscopy?
fluid (BAL)
brush cytology (cells from lining)
FNA
biopsies
how can endoscopy be therapeutic?
foreign body removal
stricture dilation
feeding (gastrotomy) tube placement
what are the benefits of endoscopy?
minimally invasive
low morbidity/mortality (mainly GA related)
no convalescence required
why is it advantageous that there is no significant convalescence required after endoscopy?
commonly used for diagnosis of chronic inflammatory enteropathies (immune-mediated) - no need to delay to start steroids like there would be with surgical biopsy
what are the limitations of endoscopy?
cannot visualise whole GI tract
assesses appearance, not function
mucosal evaluation only (visual and histopathological)
cannot evaluate extra-GI disease
why can’t the whole GI tract be visualised?
GI tract 12ft long, can only access proximal and distal 3 feet
how can the entire GI tract be visualised?
capsule endoscopy - cannot visualise
what are the contraindications to endoscopy?
known GI surgical disease (perforation, mass lesion)
inadequate investigation of other causes
unsuitable for anaesthesia (CP/hepatic/renal function impaired)
coagulopathy
inadequate preparation - gut not cleansed properly
how does gastric distension affect the endoscopist?
challenging pyloric intubation due to increased angle of lesser curvature
increased antro-pyloric motility
how does gastric overdistension affect the anaesthesia?
caudal vena compression –> reduced venous return –> reduced CO –> reduced BP
diaphragmatic splinting –> decreased tidal volume
what are the possible complications during endoscopy?
acute bradycardia +/- AV block due to vagal reflex
aspiration (inc during recovery)
bacteraemia (transient during colonoscopy)
GI perforation
haemorrhage - mucosal or laceration of major vessels
how can acute bradycardia +/- AV block be reduced during endoscopy?
abolish with atropine or glycopyrrolate
how can risk of bacteraemia be reduced?
prophylactic abs if at risk e.g. patients with pacemaker
why might GI perforation occur during endoscopy?
usually if pre-existing ulcer/severe pathology
does haemorrhage commonly occur from mucosal biopsy?
rare unless underlying coagulopathy
when might laceration of a major vessel happen during endoscopy?
FB removal (fish hook)
stricture dilation
what are the different parts of the endoscopy system>
light source
air/water insufflator
suction pump
endoscope + insertion tube
forceps/other biopsy equipment
why isn’t tungsten halogen light used for endoscopy any more?
cheap but not bright, red hue
what light is commonly used in endoscopes today?
xenon arc - brighter, white light, long-lasting
what is housed by the light source?
air pump for insufflation
separate suction pump for deflation
water reservoir for washing lens
what type of illumination is fibre-optic?
non-coherent
what are the fibre optics made of?
individual glass fibre, coated in lower optical density glass ‘cladding’
how is light transmitted in fibre optics?
by total internal reflection
how are the fibres arranged in fibre optic light transmission?
coherent bundles
how is the image transmitted in video endoscopy?
via wire, from video chip (CCD) behind lens
what are the advantages of fibre optic endoscopes?
portable
wide range of sizes
moderate cost
what are the disadvantages of fibre optic endoscopes?
faceted image (appears as ‘honeycomb’)
fragile
size of endoscope dictates image quality
eye piece vs video
is video endoscopy any different to fibre optic mechanically?
identical
what type of illumination does video endoscopy utilise?
non-coherent
how is the image transmitted in video endoscopy?
CCD detects image and transmits it to screen
what is the advantage of not having an eyepiece on an endoscope?
more hygienic
what are the advantages of video endoscopy?
excellent image obtained
image control buttons available
what are the drawback of video endoscopy?
expensive
not portable
smallest diameter not possible
what diameter insertion tubes are used for gastroscopy?
5.5 - 9.5mm diameter / 1 - 1.5m length
what diameter insertion tubes are used for colonoscopy?
10-13mm
what variations can be seen between insertion tubes?
diameter and length
viewing direction/angle
steering - uni-planar vs multi-planar
accessory channel
why is tip retroflexion important?
allows visualisation of the cardia and entering duodenum
useful in foreign body retrieval
how does size of channel affect biopsy quality?
smaller channel = poorer quality biopsies
what size channel are typically used for gastroscopes?
2.2-2.8mm
what endoscopy accessories might be used?
cytology brush
biopsy forceps
sheathed needles for FNA
lavage tubes
what are the different types of biopsy forceps available?
reusable / disposable
ellipsoid / round
fenestrated / whole
no spike / spike
alligator / smooth
swing jaw / fixed angle
rotatable / non-rotatable
what are the key factors determining biopsy quality
cup size and pressure
how can we confirm endoscopy is indicated for a patient?
exclude extra-GI causes of signs
exclude surgical disease
consider contraindications
how long should patients be fasted for gastroscopy?
12 hours for visualisation/manoeuvrability - food clogs channels
why should we wait 24 hours after barium to perform a gastroscopy?
barium damages the scope
why might 12 hours fasting not be sufficient for some patients?
many GI diseases cause reduced GI motility
stress impairs motility
what is involved in patient pre for colonoscopy?
fast 24-36 hours
oral lavage
multiple ‘high’ enemas
what is a ‘high’ enema?
enema performed as far up the colon as safe and sensible to perform
what is used for oral lavage?
poly ethylene glycol (PEG) electrolyte solutions (klean-prep)
when is klean-prep given?
day prior to endoscopy
how much klean-prep is given?
25-30ml/kg x 3 doses (dogs)
20ml/kg x 2 doses (cats)
2-4 hours apart
how is klean-prep administered?
can be orally vs NO tube (usually cats)
what are the risks of oral lavage?
tracheal intubation - likely obvious
aspiration - contraindicated if significant pre-existing aspiration risks e.g. brachy, laryngeal paralysis
trauma (rare)
what is used for ‘high’ enemas?
warm water
why shouldn’t phosphate enemas be given?
can result in marked hyperphosphataemia
how are multiple ‘high’ enemas administered?
higginson pump or enema bucket
how much water should be used for enema?
1L/30kg dogs /until clear
20ml/kg cats
when should enema be performed?
1-2hrs before colonoscopy - sometimes not tolerated and must be done under GA
what are the general GA considerations for endoscopy?
avoid atropine impact on GI motility and tone
smooth induction (avoid aerophagia)
familiar routine
cuffed ET tube in dogs
avoid nitrous
care with gastric dilation and reflux/aspiration on recovery
why should nitrous oxide be avoided during GI scopes?
accumulates in gas-filled organs
is it ok to give opioids for endoscopy?
fine to give - allegedly affect sphincter tone but this is actually more dependent on endoscopist skill
which position should a patient be in for GI endoscopy?
left lateral
why is left lateral the best position for endoscopy?
pylorus and ascending colon air-filled - will sit dorsally and be easier to intubate
why might we have a patient in right lateral recumbency for GI endoscopy?
g-tube placement
FB removal - sometimes useful to try multiple orientations
why should spring-loaded mouth gags not be used in cats?
contraindicated as potential for reduced blood supply to brain and central blindness afterwards
why should the ET tube be secured to the mandible/maxilla?
scope will move tube if tied to back of head
why should endoscopic examination reports be filled out?
for record keeping, consistency and completeness
how should endoscopes be cleaned/disinfected/sterilised after use?
ensure channels clear - blow air and water through immediately post-scope
ethylene oxide gas sterilisation
approved disinfectant
why shouldn’t endoscopes be autoclaved?
will melt scope
