Flashcards in CM-GI Radiology and Imaging Deck (64):
What is the difference between KUB, flat/upright abdominal series, and acute abdominal series?
KUB- patient is supine
flat/upright- supine and standing (bowel gas pattern and air fluid levels are better seen standing)
acute flat/upright/CXR (free air in the peritoneum which is seen easily under the right hemidiaphragm)
Describe how a normal colon would look on KUB.
1. bubbly apearance of fecal matter
2. peripheral location
3. widely spaced haustral markings
Describe the normal small bowel on KUB.
1. centrally located
2. smaller than 3cm in diameter
3. valvulae conniventes (folds) - usually seen with distention (go the whole way across, unlike colonic haustra)
What are the four common indications for KUB of the abdomen?
1. abdominal pain
2. suspected small bowel obstruction
3. suspected renal stones
4. suspected swallowed foreign body
(5. enteric tube positioning)
What are 4 classic KUB diagnoses?
1. pneumoperitoneum (acute)
2. mechanical small bowel obstruction (flat/upright)
3. paralytic ileus
4. abdominal calcifications
What is pneumoperitoneum a sign of? What imaging technique is best to see one? Describe what it would look like.
It is air in the peritoneal cavity and is a sign of bowel perforation.
The study of choice is acute abdominal series. (the CXR view is best for detection)
It is a dark area below the right hemidiaphragm
What do you do if a patient cannot tolerate an upright film when you suspect a perforated bowel?
Left lateral decubitus (patient lies on the left, right side is up)
The air in the peritoneum should rise to be above the liver
How does peritoneum show up on supine film?
air on both sides of the bowel wall = double wall sign
What imaging modality is used for suspected small bowel obstruction? Describe the appearance.
You would do flat/upright abdominal series.
You would see:
1. small bowel dilation (greater than 3cm)
2. paucity of colonic gas
3. air-fluid levels on upright film (can also be seen in paralytic ileus, gastroenteritis, normally)
What is the distinction between small bowel obstruction and paralytic ileus?
bowel sounds are reduced/absent in paralytic ileus
PI - small bowel and colon are slightly dilated and gas will be seem EVERYWHERE (small bowel, colon, rectum)
SBO - paucity of gas in the colon and more dilated small bowel
What imaging test is used to see abdominal calcifications?
In general, how can you tell the difference between a gallstone, kidney stone and pancreas?
KUB- but precise location of the stones is hard to ascertain
Gallstones tend to be in a clump and are faceted. They are always in the RUQ
Kidney stones can be on the left or right and are rarely faceted. Staghorn
Chronic calcified pancreatitis- small BB like calcifications outline the whole course of the pancreas (CT would be test of choice for pancreas though)
Describe the process of barium swallow. When is using barium sulfate contraindicated?
What can be used in its place?
A patient swallows barium and while the contrast is being given the radiologist takes focused X-rays of the GI tract, specifically from cervical esophagus to the GE junction
Barium is contraindicated if bowel perforation is suspected because it can lead to barium pertonitis.
Gastrografin - don't use if they could aspirate (lung edema)
What are the 5 types of GI contrast studies?
1. Barium Swallow
2. Upper GI Series (UGI)
3. Small Bowel Follow Through (SBFT)
4. Barium Enema
What are the 3 most common indications for a barium swallow?
1. Dysphagia (trouble swallowing)
2. chest pain (non-cardiac)
What are 4 common diagnoses made by barium swallow?
1. Esophageal carcinoma
3. Hiatal hernia
What test is done for esophageal carcinoma? What would it look like?
Endoscopy has largely replaced it, but barium swallow.
You would see strictures, sharp overhanging edges, irregular mass with ulcerations.
Benign tumors tend to be smoother
What test is done for esophagitis?
Barium swallow- multiple irregular mucosal ulcerations
What is a hiatal hernia and what test is used to diagnose hiatal hernias?
It is when part of the stomach herniates through the esophageal hiatus into the thorax.
It can be seen on barium swallows AND UGI. The stomach rugal folds are seen above the diaphragm
What is achalasia and what test is used to diagnose?
It is an esophageal motility disorder where the LES is dysfunctional
You do a barium swallow. You will see a massive dilation of the esophagus with smooth narrow sphincter
What are four common indications for a UGI series?
1. abdominal pain
2. suspected gastric or duodenal ulcer
3. suspected hiatal hernia
4. suspected gastric mass
What are the two types of UGI series? When would you use each?
1. Double-contrast where the patient swallows barium and then an effervescent tablet to distend the GI tract with air. This allows better eval of fine mucousa detail (small masses, ulcerations)
2. Single-contrast- used when the patient cannot tolerate effervescent granules, positioning for the UGI or you are only checking for a bowel perforation
What test is used for duodenal ulcers? what does it look like?
UGI series and it has:
1. persistent contrast collection
2. smooth mound surrounding edema
3. thickened folds radiating to ulcer crate
What test is done for gastric ulcers? What do you see for benign? Malignant?
Benign- smooth mounds of edema surrounding the ulcer, persistent contrast collection, smooth craters
Malignant- irregular ulcer crater, irregular mass around crater, irregular folds
Describe the process of SBFT.
Patient drinks barium solution and overhead KUBs are done to evaluate contrast passing through the small bowel. Also fluoroscopy can be done to "watch it live'
What are 5 indications for small bowel follow through?
1. obstruction (intermittent or partial)
3. chronic GI bleed w/o source
4. malabsorption syndromes and diarrhea
5. IBD (Crohn's)
What test is used to diagnose Crohn's disease? What does it look like?
Crohn's is diagnosed with SBFT because it most often affects the terminal ileum. You see:
1. thickened, nodular folds
3. "cobblestone" mucousa
4. fistulae to other organs
5. Skip areas
What are the six common indications for barium enema?
1. chronic Gi bleed -hemoccult + stool
2. large bowel obstruction
3. left lower quadrant pain
What are the 2 types of barium enema and when is each used?
1. Double contrast- barium and air contrast
2. single contrast- just barium. only used when rapid gross information is needed (large bowel obstruction, colonic leak/perforation, diverticulosis)
What test is done to look for colonic carcinoma? How would it look?
It is a polyploid mass with irregular strictures. It looks like an apple core (irregular lumen narrowing with sharp overhanging edges
What test is done to look for colonic polyps?
Barium enema -
Filling defect in the contrast column.
Retained stool can look like polyps so make sure adequate laxatives are done prior to barium enema
What is diverticulosis and how is it diagnosed?
It is outpouchings of mucous from the bowel wall. They are found on barium enemas as smooth round contrast collections protruding from the colon (most commonly sigmoid)
What is diverticulitis and how is it diagnosed?
It is inflammation of the diverticulum and is diagnosed with barium enema. It will look like intramural and pericolonic abscesses, and bowel wall thickening
What is ulcerative colitis and how is it diagnosed?
It is IBD and it is diagnosed with barium enema. You will see:
1. loss of normal haustra
2. shallow ulcerations
3. "collar button" ulcers
What are the common indications for an abdominal ultrasound?
1. RUQ pain (suspected gallstones)
2. Jaundice (biliary obstruction)
3. increased LFTs (biliary obstruction/liver mass)
4. Liver masses
5. Hepatomegaly and splenomegaly
What does a typical abdonimal ultrasound image? What about in a RUQ ultrasound?
Typical- liver, gallbladder, biliary tree, spleen, kidneys, and pancreas.
RUQ- gallbladder, biliary tree, liver
What are the two most common abdominal ultrasound diagnoses?
1. cholelithiasis and acute cholecystitis
2. biliary obstruction
What test is best for diagnosing cholelithiasis? How does it look?
US - echogenic (white) foci in the gallbladder with a dark shadow (triangle with apex at the stone)
Polyps, clots etc can also be white on the US, but only stones will cast the shadow
What test is performed for acute cholecystitis?
Cholecystitis can be calculous or acalculous.
Calculous can be see as a stone on US with a positive sonographic Murphy's sign. There may also be wall thickening and pericholecystic fluid.
If after ultrasound the cause of cholecystitis remains unclear, do HIDA (hepatobiliary nuclear studies) to see if there is acalculous cholecystitis
What is the drawback of using US for biliary obstructions?
US is great at detecting the presence of an obstruction, but it does not give information for determining the cause of the obstruction.
How is biliary obstruction diagnosed on US?
Common bile duct should be less than 6mm on the ultrasound. If there is a biliary obstruction, this common bile duct will be greater than 6mm
What are the 3 types of nuclear medicine studies?
1. liver spleen scan (sulfur colloid)
2. Tagged RBC
Describe how a liver spleen scan works. What does it detect?
You radioactively tag sulfur colloid which is taken up by Kupffer cells in the liver and RES cells in the spleen.
Liver masses are photopenic and do not take up contrast (except for focal nodular hyperplasia) so you can see if there is a mass.
CT has basically replaced this except for FNH
What are the two indications for using tagged RBCs?
1. Acute GI bleeding
Describe what is shown in a positive GI bleeding study.
Tagged RBCs will track to a sight of active GI bleeding and pool there.
The blood must be atleast 0.2ml/min to be detected by this technique but that is much more than angiography.
Once you have located the specific bowel loop of the bleeding, you can perform angiography OR direct the surgeon to the area for therapeutic intervention
What test is used to diagnose hemangiomas?
How large must it be to be detected?
Tagged RBCs because in a liver hemangioma the sinusoids are dilated, blood flow is slow, and there is pooling.
SPECT can be used with the tagged RBCs.
It must be at least 1 cm to be detected by this technique
What are two common indications for a HIDA/DISIDA scan?
1. acute cholecystitis
2. biliary leak/ biloma
What is the single best test for determining cholelithiasis?
When is it not sufficient?
It is not sufficient in confusing cases or with acalculous cholecystitis in which case HIDA is used to see if the cystic duct is blocked.
What is a limitation of HIDA for diagnosing cholecystitis?
It can only diagnose ACUTE because the cystic duct will be completely blocked.
Chronic there is incomplete blockage and the radioactive agent can get into the gallbladder.
When is a hepatobiliary scan considered positive for acute cholecystitis?
When there is lack of visualization of the gallbladder out to 4 hours due to complete cystic duct obstruction
What are common indications for abdominal CT?
1. ab pain
2. ab masses
3. staging primary malignancies
4. staging mets
5. LFT abnormalities
When does a CT of the abdomen usually require IV or oral contrast?
When visualizing the liver or pancreas
How do liver masses appear on CT?
They enhance differently from the rest of the liver. They can be darker or lighter.
What needs to be done after you see a liver mass on CT?
a liver biopsy because you cannot tell if it is malignant or benign
How do liver metastases look different from primary liver tumors?
Mets- hypodense (darker) and are multiple and varying in size
Primary- hyper or hypodense and are single
What four diagnoses are typically made by CT?
1. primary liver masses/tumors
3. other abdominal malignancies (pancreas, adrenal gland, kidneys)
4. abdominal infections
How does abdominal infection appear on CT?
Abscess that is loculated and fluid filled with a thick enhancing wall
What is the difference between T1 and T2 MRI?
T1- fat is white, fluid is dark
T2- fat is dark, fluid is white
Why is MRI rarely the test of first choice?
It is very expensive.
1. After you do other tests if the question is unanswered, then do MRI
2. allergy to contrast--> MRI
3. Pediatrics--> MRI
What are the 2 most common indications for MRI?
1. liver mass characterization (hemangiomas)
2. adrenal mass characterization
What is the most specific modality for detection of liver hemangiomas? What is another technique that is often used to clarify CT and US findings?
1. tagged RBC
MRI can also be used
How does hemangioma look on T1? T2?
T1- dark spot
T2- bright white "light bulb"
What are the four common indications of abdominal angiography?
1. abdominal aortic anuerysm
2. mesenteric ischemia
3. acute or chronic GI bleeds
4. vascular trauma (splenic artery laceration)
What must be the flow of the active GI bleed to be picked up by angiography?
0.5-1.0 ml/min AND they must be bleeding at the exact time of the injection (so it must be a continuous bleed)