Imaging of Acute Abdominal Pain Flashcards
What are the primary imaging tools used for abdominal pain?
X-ray, CT, US
What are the secondary imaging tools used for abdominal pain?
MRI, fluoroscopy
What are the benefits of using x-rays?
Used to exclude bowel obstruction and perforation
Overall sensitivity = 30%
Changes management in 4% of cases
What are some features of US?
Shows solid organs, free fluid, aorta and pelvis
Can correlate imaging with tenderness
Gives useful info in 56% of patients
Confirms diagnosis in 66%
What are some features of CT?
89% sensitivity
Changes management in 46-60%
Allows better planning of surgery or intervention
Contrast may cause renal impairment
How common is acute appendicitis?
14% of admissions for abdominal pain
What are the symptoms of acute appendicitis?
Periumbilical pain that localises to RIF
Nausea and vomiting
What imaging is done for acute appendicitis?
Use US first and then do CT if this isn’t conclusive
CT will show fat stranding and wall thickness >3mm
How does age affect diverticulosis?
Incidence increases with age = 10% of population aged <40 compared to 60% of population aged >80
How common is misdiagnosis of acute diverticulitis?
Over 1/3 of cases initially misdiagnosed
What are some complications of acute diverticulitis?
Abscess, obstruction, perforation, fistulae
What investigations should be done for acute diverticulitis?
Do x-ray to exclude obstruction/perforation then do CT
What is acute cholecystitis almost always secondary to?
Gallstones
What imaging is done for acute cholecystitis?
US = shows gallstones, gallbladder wall thickening and local fluid
MRI if there is biliary tree dilation
MRCP will show stones
What is emphysematous cholecystitis?
Air in the gallbladder wall = occurs in diabetics, may need surgery or interventional radiology
What are some common causes of small bowel obstruction?
Adhesions, cancer, herniae, gallstone ileus
What are the symptoms and signs of small bowel obstruction?
Vomiting, pain, distension, increased bowel sounds, tenderness, palpable loops
What investigations are done for small bowel obstruction?
X-ray is first line = 70% sensitivity, may miss fluid filled loops
CT = sensitivity >95%, transition point is key, adhesions not seen
What are the causes of large bowel obstruction?
Colorectal cancer (60%), volvulus (15%), diverticulitis (10%)
Why are x-rays not used to diagnose large bowel obstruction?
May not show the underlying cause
Why are CT scans used for large bowel obstruction?
Show underlying mass, state of caecum and distant disease
What are some causes of perforation?
Common = perforated ulcers, diverticular disease Uncommon = secondary to cancer to ischaemia
What are the disadvantages of using x-ray to image perforation?
May miss small gas pockets and doesn’t show site of origin
Why are CT scans used to image perforation?
Shows free fluid
Can see site of origin in 86% = gas distribution, defect in wall, localised inflammatory change
When does bowel ischaemia develop?
When normal GI blood flow is <10%
What are the causes of bowel ischaemia?
Arterial occlusion (60-70%), venous occlusion (5-10%), non-occlusive hypoperfusion (20-30%)
What are the symptoms and signs of bowel obstruction?
Sever abdominal pain, may have vomiting or diarrhoea, raised WCC, borderline amylase, acidotic
What are the differentials of bowel ischaemia?
Perforation, pancreatitis, obstruction, diverticulitis
What is the first line investigation for bowel ischaemia?
Biphasic CT = shows site of occlusion and length of bowel affected
What kind of pain is US usually used for?
RIF and RUQ pain
What is the first line investigation for ureteric obstruction?
Non-contrast CT (CT-KUB)
What is epiplotic appendagitis?
Benign mimic of acute diverticulitis = has target sign appearance
How long do you have to wait before doing a CT for acute pancreatitis?
8-10 days after symptom onset = allows for complications to be seen
What is the imaging modality of choice for a leaking AAA?
CT
