GASTROINTESTINAL 1 Flashcards
what are the imaging modalities used to image GI tract?
ultrasound, endoscopy, plain radiographs (intestinal obstruction), CT, MRI
what is MRI T1 weighting used to identify?
normal anatomy- shows fat as white, water as black
what is MRI T2 weigthing used to identify?
pathology- fluid appears white (pathology adds water to tissue)- CSF appears white
how does MRI identify perfusions?
gadolinium
what do you normally find in an ab radiograph?
gas, solid organ outlines, air fluid levels, extra luminal air, calcifications, organ size
where does gas in bowel come from?
from swallowed air- always gas in stomach, som air in small intestine, no air in rectum & sigmoid colon
what are loops of bowel called when they’re filled with gas and beyond their normal size?
distended & dilated
what is the normal diameter of intestinal loops?
SI (3cm), LI (6cm), caecum (9cm)
what are the characteristics for small intestine?
centrally located in abdomen, more tightly curved loops than large intestine, has valvulae conniventes which are close together & cross the width of the bowel
what are the characteristics for large intestine?
peripherally located, has haustra which do not cross entire width of bowel & further apart than valvulae, contains solid faeces
what areas have air-fluid levels?
always air-fluid level in stomach on upright abdominal image, small amount of fluid is normal in small intestine, no air fluid levels in colon
where is extra-luminal air in GI tract?
always abnormal (indicating rupted organs- viscus), upright image allows intra-abdominal gas to form a crescent beneath diaphragm, gas may accumulate in intestinal wall or gallbladder
are radiographs good at indicating organ size?
limited value in evaluating size of soft tissue, edges may be directly visualised, enlarged organ may displace gas-filled intestinal loops
does the stomach normally contain gas and air-fluid levels?
yes
does small intestine normally contain gas & air-fluid levels?
yes (2-3 loops) & yes
does the large intestine normally contain gas & air-fluid levels?
yes (especially sigmoid colon & rectum) & no
what can pneumonia at lung base mimic?
symptoms of an acute condition in abdomen
what can pleural effusion be secondary to?
intraabdominal process
what can pancreastitis be associated with?
left pleural effusion
what can some ovarian tumours be associated with?
associated with right-sided or bilateral pleural effusions
what is the function of the oesophagus?
transport of fluid/solids from pharynx to stomach by paristalis
what are common pathologies of the oesophagus?
swallowing disorders & excessive gastroesophageal reflux
what is the most common test for evlauting the GI tract?
endoscopy - also barium radiography
what can contrast radiography demonstrate about the oesophagus?
reflux of contrast media, histal hernia, mucosal erosions, ulcerations & strictures
what is the cervical (upper 1/3) & thoracic (lower 2/3)oesophagus composed of?
mainly composed of striated muscle the smooth muscle
what regulates the bolus transport in thoracic oesophagus?
true peristalsis regulated by autonomic nervous system
what are the 2 parts of peristaltic wave?
initial relaxation that accomodates the bolus & contraction that propels it- gravity also assist peristalsis in upright position
what is the function of lower oesophageal sphincter?
it is tensioned at rest to prevent regurgitation from the stomach
what is dysphagia?
abnormal swallowing - leads to dehydration, malnutrition, pneumonia
what causes dysphagia?
neurological disorder & stroke, structural lesions, psychiatric disorder, CT disease, surgical resection, radiation fibrosis, medication
what does GORD result in?
troublesome symptoms and/or oesophageal & oesophageal & oextraesophageal manifestattion including adenocarcinoma
what is oesophagitis?
most common- refluxed gastric acid & pepsin acid & pepsin cause necrosis of the oesophageal mucosa & possible oesophageal stricture- due to histal hernia
what are symptoms of GORD mistaken for?
myocardial infarction (vice versa)
what is oesophageal stricture caused by?
intrinsic disease that narrows lumen through inflammation, fibrosis or neoplasia- extrinsic disease that invade directly or cause lymph node enlargement and diseases that disrupt peristalsis and/or lower sphincter function- 80% caused by GORD
what can CT be used to investigate in oesophagus?
neoplasia
what is a histal hernia?
part of stomach prolapses through diaphragmatic oesophageal hiatus- mostly asymptomatic & discovered incidentally
what is the function of the stomach?
storage of food, initial digestion by acid & pepsin also mixing
what are the common pathologies of the stomach?
peptic ulcer disease & gastric carcinoma (diagnosed by endoscopy & CT to visualise spread)
what can CT and barium sow in the stomach?
CT shows wall thickening due to diffuse tumour or infection/inflammation- barium show ulcer pits or scar
what are secondary stomach cancers?
breast or melanoma
what is the function of the small intestine?
important site of digestion by enzymes from pancreas or mucosal brush border- significant absorption of digestion of nutrient and fluid- sites of neutralisation of gastric acid- site of solubilisation of lipids by bile salts
what are common pathologies of the small intestine?
obstruction/dilation, inflammation, tumour
what does small intestine obstruction result in?
distended loops of intestine with air/fluid levels (viral enteritis may increase small intestinal gas), absence of colonic gas
what is small intestine obstruction fatality rate?
high due to ischaemia (aka strangulation)
where can obstruction be located?
bowel lumen (intraluminal), bowel wall (intramural), outside bowel wall (extraluminal), SBO (postsurgical obstructions)
what can cause obstruction in bowel lumen?
foreign bodies + gallstones
what can cause obstruction in bowel wall?
crohns disease, neoplasia, structures/anastomoses
what can cause obstruction outside bowel wall?
adhesions (post-surgical), hernia, neoplasia
what can small intestinal obstruction cause?
abdominal pain, nausa & vomiting, abdominal distention, diarrhea or constipation, bowel sounds are hyperactive in early stages or hypoactive in late stages
how does small intestinal destruction cause proximal dilation?
due to accumulation of GI secretions & air
how are small bowel loops suspended & how does strangulation occur?
suspended by mesentery in which blood vessels are located- strangulation occurs when mesentary twists including blood flow
how are small bowel obstructions seen?
plain radiographs but CT is imaging modality of choice
what is the normal small intestinal gas pattern?
no gas or small amounts of gas within up to 4 variably shaped, nondistended loops with normal large intestinal gas & faeces
what is small intestine obstruction indicated by?
multiple gas or fluid filled loops of dilated small intestine, moderate amount of colonic gas, increased distance between valvulae conniventes, gas trapped between valvulae conniventes
what is an absolute confirmation of small intestine obstruction?
absence of colonic gas
how big is a dilated proximal bowel loop & collapsed distal loop?
more than 2.5cm & less than 1cm
what indicates a partial obstruction?
passage of contrast agent into collapsed segment
what indicates mechanical obstruction?
accumulation of feces & gas proximal to obstruction (feces sign)
what does MRI of small bowel require?
distention using an oral contrast agent
what is a intussusception?
a segment of intestine telescopes into an adjoining section causing obstruction
what is the most reliable diagnoses of intussusception?
contrast enema- radiographs & CT are relatively unreliable
what is crohns disease?
inflammatory bowel disease- idiopathic- transmural process
what can crohns disease affect?
any part of GIT from mouth to anus- segmental & can skip areas in midst of diseased intestine
what is irritable bowel syndrome?
an inappropriate immune response to microbiota
how many people have small intestinal disease only?
30-40%
how many people have disease in small & large intestines?
40-55%- small % have coltis only - terminal ileum is involved in 90% of patients with small intestinal disease
how does crohns disease appear in plain radiograph?
non-specific but may show thickening of wall & intestinal dilation; abnormal faecal distribution
what is recommended to diagnose crohns disease?
contrast radiologic studies are recommended to determine disease extent, disease severity and complications & treatment strategy
how does barium enema show crohns disease?
allows identification of structural changes - not used in patients with known perforations
what is CT used for in crohns disease?
assessing extramural complications
what type of tumours develop in small intestine?
carcinoid tumour
what are carcinoid tumours?
arises from endocrine cells & small intestine - causes intestinal obstruction- CT is used as tumours are highly vascular making them easily visible with contrast
