Week 10 - GI Imaging Flashcards
When do you request an AXR
Acute abdominal pain Small/large bowel obstruction Acute exacerbation of IBD Renal colic (1st line is CT)
ABC approach of an AXR
Air - bowel gas pattern
Bowel - and other soft tissue
Calcification - bones and stones
Describe the bowel gas pattern
Colon - slow transit as faeces and gas
Small bowel - fast transit as fluid
Stomach - medium transit as fluid and lots of gas
Dilation in obstruction of different parts of the GI tract
Small bowel obstruction if small bowel dilated >3cm
Large bowel obstruction if large bowel dilated >6cm or if caecum >9cm (competent ileoceacal valve)
AXR appearance of small bowel
Central
Valvulae conniventes across whole lumen
Often not visible
AXR appearance of large bowel
Peripheral
Haustra across part of lumen
‘Clouds’ of faeces and gas visible
Transverse colon hangs down to pelvis (longer in women)
Symptoms of small bowel obstruction
Early - vomiting, mild abdominal distension
Late - absolute constipation
Colicky pain every 2-3 mins
Causes of small bowel obstruction
Post op adhesions
Inguinal, femoral and incisional hernias
Tumours
Inflammation
Symptoms of large bowel obstruction
Early - absolute constipation, significant abdominal distension
Late - faeculant vomiting
Colicky pain every 10-15 mins
Causes of large bowel obstruction
Colorectal carcinoma (assume until disproven)
Hernias
Volvulus
Strictures
Types of volvulus
Sigmoid (common)
Caecal - if anatomical defect reducing caecum’s attachment to abdominal wall
Abnormalities that can be visualised with AXR
Obstruction Inflammation Toxic megocolon Lead pipe colon Thumb printing Calcification Foreign bodies e.g nasojejunal tube, colonic stent, ingested objects Gall/Kidney stones
Appearance of inflammation on AXR
Mucosal thickening
Lead pipe colon
Bowel wall oedema
What is toxic mega colon and give some causes
Colonic distension with no obstruction Causes: Oedema Pseudopolyps Acute deterioration of colitis
Describe thumb printing
Oedematous thickened haustra often seen in active inflammation
When might you see calcification on a AXR
Chronic pancreatitis (fat necrosis)
Atherosclerosis
Calcified lymph nodes
Gall/renal stones
Diagnosis of bowel perforation
Erect CXR (need to be sat upright for at least 10 mins)
Causes of bowel perforation
Peptic ulcer Diverticular disease Tumour Bowel obstruction Iatrogenic
What are contrast studies
Used to define hollow viscera
May use barium or iodine
Give examples of contrast studies and what they are used for
Barium swallow - achalasia, check aspiration
Barium enema - check anastomoses before reversing ileostomy
Barium meal
Water soluble (iodine)
Compare abdominal CT, MRI and USS
CT - high dose radiation, better spacial resolution, quick
MRI - no radiation, better contrast resolution , time consuming
USS - no radiation, cheaper, portable, highly user dependent
What does the transpyloric plane cross
L1 vertebra Liver (and round ligament) Gall bladder Kidneys Pylorus Superior duodenum Spleen Pancreas Transverse colon Jejunum
What is an MRCP
Magnetic resonance cholangiopancreatogram - MRI to visualise gall bladder and biliary tree
What can you view with an abdominal USS
Liver Portal vein Appendix Gallstones Dilated common bile duct
What is a GI angiography
IV radio opaque contrast injected to visualise GI blood supply in bleeding and ischaemia
Which blood vessels can be seen in a GI angiogram
Aorta
Coeliac trunk
SMA
Iliac vessels
