deck_1666180 Flashcards
What are the main categories of imaging for the GI Tract?
Plain X-raysContrast studiesUltrasoundCross-sectional imagingAngiography
What are the types of X-rays used?
Abdominal and chest
Give four types of contrast studies
Barium swallowBarium enemaBarium meal/follow throughWater soluble contrast studies
Which methods of imaging give the patient a dose of radiation?
X-raysCT scan
What are the risks of radiation?
CarcinogenesisGenetic Developmental risk to foetus in pregnant women
What are contrast studies used to visualise?
Allow us to define hollow viscera
Describe what happens in a barium swallow
Contrast such as barium sulphate (appears opaque on x-rays) is swallowed and fluoroscopy images are taken from multiple angles in order to visualise the oesophagous as it is coated with a thin layer of barium. This process produces gas in the stomach and can be uncomfortable for the patient.
Describe what happens in a barium meal
Barium sulphate is ingested and it allows for the visualisation of the oesophagous, stomach and duodenum – lines the lumen of these structures.
Describe what happens in a barium enema.
Contrast medium is inserted rectally which allows for the visualisation of the colon. Double contrast can also be used to define certain structures (put air in as well).
How does ultrasound work?
Use sound waves to generate an image of subcutaneous body structures.
Why use ultrasound compared to other imaging techniques?Give a disadvantage
Cheap compared to CT adn MRIIs portable Is very user dependent
What are ultrasounds commonly used for medically?
Determines presence of gall stonesDilation of the common bile ductVisualisation of liver, portal vein and appendix.
What is GI angiography and how is it done?
Allows for visualisation of GI blood vesselsPerformed by injecting a radio-opaque contrast intravenously then capture images by CT, MRI and sometimes X-ray.
What does GI angiography allow you to visualise?
AortaSuperior mesenteric arteryCoeliac trunkInferior mesenteric artery and its branches are harder to see
What are the main things that can be seen on an abdominal x-ray?
StomachSmall bowel– has circular folds running around itLarge bowel– has haustra/folds that do not fully circle the circumferenceSoft tissues– liver, spleen, kidneys, psoas muscle, lung basesBones
Why can you see certain soft tissue structures on an abdominal x-ray?
Hollow tubes are visible on x-rays when filler with air– low density gas acts as a contrast– lumens containing fluids will not be seen
What are some common reasons for requesting an abdominal x-ray?
Acute abdominal painSmall or large bowel obstructionAcute exacerbation fo irritable bowel syndromeRenal colic
What are the characteristics of the small bowel on x-ray?
Usually has a central positionCan see circular folds/valvulae conniventes– lines which cross the whole lumen of the bowel
What are the characteristics of the large bowel on x-ray?
Found more peripherallyCan see haustra – incomplete lines running across the bowel lumenCan sometime see faeces – clouds in the lumen
What rule can you use to distinguish abnormal gas patterns on x-ray?
Rule of 3/6/9- small bowel is filated when it is greater than 3cm- large bowel is dilated when greater tan 6cm- caecum is dilated when it is greater than 9cm (when ileocecal valve is working)ONLY APPLIES TO XRAYS SHOWN TO SCALE
What is the presentation of someone with a small bowel obstruction?
Vomiting and mild distension early on. Absolute constipation is a late featureColicky pain that lasts every 2-3 minutes
Why do you vomit with a small bowel obstruction?
Obstruction is nearer the mouth than a large bowel obstruction. This is why constipation is a late feature of small bowel obstruction.
Give some causes of small bowel obstruction
Adhesions such as in chrons diseaseHernias (femoral, inguinal and incisional)TumoursInflammation
Give some features of large bowel obstruction
Abdominal painDistensionConstipation is an early featureColicky pain every 10-15 minutesVomiting is a late feature, it can be faeculant
Give some causes of large bowel obstruction
Colorectal carcinomaDiverticular strictureHerniaVolvulusPseudo-obstruction
What is a volvulus?
Where the mesentery for an organ twists around on itself. It either cuts off its own blood supply, causing an ischaemic bowel as well as causing the loop of bowel to dilate which puts it at a risk of perforating.
Where is a common site for a volvulus to occur?
Sigmoid colonCaecum
When can toxic megacolon occur and what does it lead to?
Is an acute deterioration of ulcerative colitisLeads to oedema, colonic dilation or pseudopolyps
What are the characteristics of lead pipe colon?When does it occur?
Featureless colonLoss of haustraOccurs in chronic ulcerative colitis
Give some other abnormalities that can be observed on and x-ray
Chronic pancreatitisAAANodesBonesArtefactsForeign bodyKidney stones
What can cause a perforated bowel?
Peptic ulcerDiverticular diseaseTumourObstructionTraumaIatrogenic
What type of imaging can be used to diagnose a perforated bowel?
Erect chest x-ray
Why does the chest x-ray need to be erect to look for a perforated bowel?
Looking for:Diaphragm to be elevated from other visceraPresence of air or gas in the peritoneal cavity(air/gas will rise to the top of the cavity so need to sit patient up for 10mins to see this)
Why does gas present in the peritoneal cavity give an indication of a perforated bowel?
Normally, peritoneal cavity contains a small amount of fluid. Gas presence is abnormal and is usually due to a perforated bowel
What are the characteristics of a CT scan?
Gives a high dose of radiationGives a good spatial resolutionCan use IV or oral/rectal contrastCan see major vessels coming off the AACan produce virtual colonoscopies from multiple imagesCan view in multiple planes
Why are virtual colonoscopies beneficial?
Prevent discomfort and worry from patient.
Give some characteristics of MRI
No radiationGet good spatial and contrast recognitionIs quite time consumingCannot be used for patient with metal screws, plates, pacemakers or metal tattoos
What is an MRCP?
Magnetic resonance cholangio-pancreatogramMRI scan that allows you to visualise the gall bladder and the biliary tree
