Flashcards in Surgical Radiology Deck (46):
What defines a technically adequate CXR?
Rotation (clavicular heads are equidistant from the thoracic spinous processes)
Inspiration (diaphragm is at or below ribs 8-10 posteriorly and ribs 5-6 anteriorly)
Penetration (disk spaces are visible but there is no bony detail of the spine, bronchovascular structures are seen through the heart)
Exposure (make sure all of the lung fields are visible)
How should a CXR be read?
Tubes and lines (check placement); Patient data (name, date, history number); Orientation (up/down, left/right); Technique (AP or PA, supine or erect, decubitus); Trachea (midline or deviated, caliber); Lungs (CHF, mass); Pulmonary vessels (artery or vein enlargement); Mediastinum (aortic knob, nodes); Hila (masses, LAD); Heart (transverse diameter should be less than half the transthoracic diameter); Pleura (effusion, thickening, PTX); Bones (fractures, lesions); Soft tissues (periphery and below the diaphragm)
What CXR is better: PA or AP?
PA, less magnification of the heart (heart is closer to the XR plate)
Classically, how much pleural fluid can the diaphragm hide on upright CXR?
Up to 500 cc
How can CXR confirm that the last hole on a chest tube is in the pleural cavity?
Last hole is through the radiopaque line on the chest tube.
Thus, look for the break in the radiopaque line to be in the rib cage.
How can a loculated pleural effusion be distinguished from a free-flowing pleural effusion?
Ipsilateral decubitus CXR.
If fluid is not loculated (or contained), it will layer out.
How do you recognize a PTX on CXR?
Air without lung markings is seen outside the white pleural line (best seen in the apices on an upright CXR)
What XR should be obtained before feeding via a NG or nasoduodenal tube?
Low CXR to ensure the tube is in the GI tract and not in the lung
What C-spine views are used to rule out bony injury?
What is used to look for ligamentous C-spine injury?
Lateral flex and extension C-spine films, MRI
What CXR findings may provide evidence of traumatic aortic injury?
Widened mediastinum (> 8 cm); apical pleural capping; loss of aortic knob; inferior displacement of left main bronchus; NG tube displaced to the right; tracheal deviation; hemothorax
How should a CT scan be read?
Cross section with the patient in supine position looking up from the feet
How should an AXR be read?
Patient data (name, date, history number); Orientation (up/down, left/right); Technique (AP or PA, supine or erect, decubitus); Air (free air under the diaphragm, air-fluid levels); Gas dilatation (3, 6, 9 rule); Borders (psoas shadow, per peritoneal fat stripe); Mass (organomegaly, kidney shadow); Stones (urinary, biliary, fecalith); Stool; Tubes; Bones; Foreign bodies
How can you tell the difference between a SBO and an ileus?
In SBO there is a transition point between the distended proximal bowel and the distal bowel of normal caliber (may be gasless), whereas the bowel in ileus is diffusely distended
What is the significance of an air-fluid level?
Seen in obstruction or ileus on an upright XR.
Intraluminal bowel diameter increases, allowing for separation of fluid and gas
What are the normal calibers of the small bowel, transverse colon, and cecum?
Small bowel: < 3 cm
Transverse colon: < 6 cm
Cecum: < 9 cm
What is the "rule of 3s" for the small bowel?
Bowel wall should be < 3 mm thick
Bowel folds should be < 3 mm thick
Bowel diameter should be < 3 cm wide
How can the small and large bowel be distinguished on AXR?
By the intraluminal folds.
The small bowel plicae circulares are complete, whereas the plicae semilunares of the large bowel are only partially around the inner circumference of the lumen.
Where does peritoneal fluid accumulate in the supine position?
Morison's pouch (hepatorenal recess), the space between the anterior surface of the right kidney and the posterior surface of the right lobe of the liver
What percentage of kidney stones are radiopaque?
What percentage of gallstones are radiopaque?
What percentage of patients with acute appendicitis have a radiopaque fecalith?
What are the radiographic signs of appendicitis?
Fecalith; sentinel loops; scoliosis away from the right because of pain; mass effect (abscess); loss of psoas shadow; loss of preperitoneal fat stripe; free air (rare)
What does KUB stand for?
Kidneys, Ureters, Bladder.
Commonly used term for a plain film AXR (abdominal flat plate)
What is the parrot's beak or bird's beak sign?
Evidence of sigmoid volvulus on barium enema.
Evidence of achalasia on barium swallow.
What is a cut-off sign?
Seen in obstruction, bowel distention, and distended bowel that is cut-off from normal bowel
What are sentinel loops?
Distention or air-fluid levels near a site of abdominal inflammation
What is loss of the psoas shadow?
Loss of the clearly defined borders of the psoas muscle on AXR.
Loss signifies inflammation or ascites.
What is loss of the peritoneal fat stripe?
Loss of the lateral peritoneal/preperitoneal fat interface.
What is thumb-printing?
Nonspecific colonic mucosal edema resembling thumb indentations on AXR
What is pneumatosis intestinalis?
Gas within the intestinal wall (usually means dead gut) that can be seen in patients with congenital variant or chronic steroids
What is free air?
Air free within the peritoneal cavity (air or gas should only be seen within the stomach or bowel).
Results from bowel or stomach perforation.
What is the best position for the detection of free air?
Upright CXR (air below right diaphragm)
If you cannot get an upright CXR, what is the second best plain XR for free air?
Left lateral decubitus, because it prevents confusion with gastric air bubble.
With free air both sides of the bowel wall can be seen.
Can detect as little as 1 cc of air.
How long after a laparotomy can there be free air on AXR?
Usually 7 days or less
What is Chilaiditi's sign?
Transverse colon over the liver simulating free air on XR
When should a postoperative abdominal or pelvic CT for a peritoneal abscess be performed?
POD #7 or later, to give time for the abscess to form
What is the best test to evaluate the biliary system and gallbladder?
What is the normal diameter of the common bile duct with gallbladder present?
< 4 mm until age 40, then add 1 mm per decade
What is the normal common bile duct diameter after removal of the gallbladder?
What U/S findings are associated with acute cholecystitis?
Gallstones, thickened gallbladder wall (> 3 mm), distended gallbladder (> 4 cm), impacted stone in gallbladder neck, pericholecystic fluid
What type of kidney stone is not seen on AXR?
What medication should be given prophylactically to a patient with a true history of contrast allergy?
Methylprednisolone or dexamethasone.
The patient should also receive nonionic contrast (associated with 20% as many reactions as ionic contrast, the less expensive standard)
What is a C-C mammogram?
Cranio-Caudal mammogram, in which the breast is compressed top to bottom
What is a MLO mammogram?
MedioLateral Oblique mammogram, in which the breast is compressed in a 45 degree angle from the axilla to the lower sternum