imaging of acute abdomen Flashcards
what imaging is used for bowel obstruction?
supine AXR
what imagine is used for assessing a hollow viscus perforation?
erect CXR
pros of xray
-widely available
-quick
-well tolerated
-inexpensive
cons of xray
-overall sensitivity low
-rarely changes management
-ionising radiation
USS pros
-easy
-safe (no ionisation)
-clear visualization of solid organs, free fluid, aorta, female pelvic organs
-correlate imaging with tenderness
USS cons
-operator and patient dependant
-challenging in obese and/or immobile patients
pros of a CT
-quick
-relatively widely available and tolerated
-accurate (sensitivity CT vs USS= 89% vs 70%)
-allows imaging of multiple structures at the same time
-allows better planing for surgical approach or any other intervention
cons of CT
-radiation exposure (risk of complications increases as dose increases)
-contrast induced nephropathy (more likely in peeople with pre existing renal impairement)
-contrast allergy
pros mri
no radiation and good soft tissue delineation
cons MRI
long examination times
not 14/7 in most regions
contraindications/ claustrophobia
what is MRI used second line for?
hepato biliary
small bowel
pelvis
RIF- possible diagnosis?
-appendicitis
-renal colic
-tubo ovarian pathology
imaging used for appendicitis?
1st= USS
CT if USS is inconclusive
USS findings- acute appendicits
-Aperistaltic, non compressible, dilated appendix (>6mm outer diameter)
-appears round when compression is applied
-periappendiceal fluid collection
-target appearance (axial section)
-periappendicreal reactive nodal prominence/ enlargement
-wall thickening (3mm or above)
CT findings- acute appendicitis
-appendiceal dilatation (>6 mm diameter)
-wall thickening (>3 mm) and enhancement
-thickening of the caecal apex
-periappendiceal inflammation
(fat stranding, thickening of the fascia or mesoappendix, extraluminal fluid, phlegmon , abscess)
-focal wall nonenhancement representing necrosis
-perforation
presentation of right ureteric calculus?
loing to groin pain
test or right ureteric calculus (loin to groin pain)
non contrast CT KUB= gold standard
LIF pain- differentials
Diverticulitis
Colitis
Colorectal cancer
Tubo-ovarian pathology
Renal colic
who is most at risk of acute diverticulitis?
-elderly patients
presentation of acute diverticulitis?
-left iliac fossa pain
-unremitting pain with associated tenderness
-possibly, an ill-defined mass
-as the disease progresses, symptoms become more generalised
investigations for acute diverticulitis?
CT with IV contrast
epigastric and RUQ pain- differentials
Biliary colic
Cholecystitis
Pancreatitis
Perforation
what is acute cholecystitis secondary to?
always secondary to gallstones
what is acute cholecystitis diagnosis based on?
-sign of inflammation (RUQ pain etc)
-sign of inflammation (fever ,WCC, CRP)
-Confirmatory imaging
first line investigation for acute cholecystitis?
USS first line to assess gall bladder and biliary tree
CT can be for false calculi
MRI if biliary tree dilatation
US findings- acute cholecystitis?
gallbladder wall thickening (>3mm)
pericholecystic fluid
also assess biliary tree
CT findings- acute cholecystitis
cholelithiasis: gallstones isodense to bile will be missed on CT
gallbladder distension
gallbladder wall thickening
mural or mucosal hyperenhancement
pericholecystic fluid and inflammatory fat stranding
enhancement of the adjacent liver parenchyma due to reactive hyperaemia
pancreatitis presentation
acute onset of severe central epigastric pain (over 30-60 min)
poorly localised tenderness and pain
exacerbated by supine positioning
radiates through to the back in 50% of patients
Elevation of serumamylase 90-95% specific for the diagnosis
role of imaging in pancreatitis?
to clarify the diagnosis when the clinical picture is confusing
to assess severity and determine prognosis
to detect complications
to determine possible causes
pancreatitis on CT presentation
focal or diffuse parenchymal enlargement
indistinct pancreatic margins owing to inflammation
surrounding retroperitoneal fat stranding
liquefactive necrosis of pancreatic parenchyma
infected necrosis/abscess formation
Vascular complications
causes of perforation?
Common:
Perf. Ulcer (decrease incidence)
Diverticular (1-2% generalized, most localised)
Less common
Secondary to cancer
Secondary to ischaemia
first line imaging- perforation?
CT
if there is a lot of gas- is it more likely to be upper or lower bowel problem
high volume of gas- more likely to be lower bowel as theres more gas in large bowel wall
abdominal pain + distention differentials
Bowel obstruction (small or large)
Masses
Ascites
symptoms/ signs of small bowel obstruction
Symptoms: vomiting, pain and distension
Signs: Increased bowel sounds, tenderness, palpable loops
common causes of small bowel obstuction?
adhesions, cancer, herniae and gallstone ileus
1st line imaging for small bowel obstruction
XRAY
what can be seen on Xray of small bowel obstruction?
valvulae conniventesare visible
Loops are central
Dilatation > 2.5 - 3 cm
Paucity of gas distally
what can be seen on CT of small bowel obstruction?
dilated small bowel loops >2.5 cm up from outer wall to outer wall
normal calibre or collapsed loops distally
small bowel faeces sign
may identify a mass
causes of large bowel obstruction?
Colorectal cancer 60%
Volvulus 15%
Diverticulitis 10%
large bowel obstruction presentation on xray?
peripheral
>5cm
haustra
-colonic distension
-collapsed distal colon
-small bowel dilatation, which depends on
duration of obstruction and incompetence of theileocaecal valve
-rectum has little or no air
-Caecum can reach upto 10cm
what imaging is used for large bowel obstruction
Xray and CT
sudden abdominal pain and shock- differentials
Bowel ischaemia
Perforation
Pancreatitis
Leaking AAA
Ruptured ectopic pregnancy
causes of bowel ischaemia?
Arterial occlusion – 60-70%
Venous occlusion – 5-10%
Non-occlusive hypoperfusion – 20-30%
presentation of bowel ischaemia on CT?
Lack of enhancement of the lumen of the affected vessel
mucosal/serosal enhancement reduced or increased
Altered wall thickness
ileus / dilated loops of bowel >3 cm in diameter
Pneumatosis intestinalis
other changes:
mesenteric oedema
free fluid
intrahepatic portal venous gas: due to pneumatosis intestinalis
free intra-abdominal gas
imaging of bowel ischaemia?
CT
imaging for AAA
CT
what is seen on CT of AAA?
Retroperitoneal haemorrhageadjacent to the aneurysm is the most common finding
large aorta
