Oral Exam - GI Flashcards
Findings on hepatobiliary scintigraphy for acute chole
○ Normal: Gallbladder (GB) filling and biliary-to-bowel
transit within 1 hr
○ Acute cholecystitis (calculus or acalculous): NoGB filling on post-morphine or 3-4hr images (180-240 min)
– Angiographic phase
□ Hyperemic blush in GB fossa represents GB
inflammation
□ Abscess or gangrene in 36% of patients with
hyperemia
○ Low-grade common bile duct (CBD) obstruction: Delayed biliary-to-bowel transit > 1 hr and < 24 hrs
○ High-grade CBD obstruction: No biliary-to-bowel transit
on hepatobiliary scintigraphy > 24 hrs
Normal HIDA study
– Normal □ Radiotracer taken up by liver □ Radiotracer progresses through intrahepatic/extrahepatic biliary ducts □ Gallbladder (GB) filling and biliary-to-bowel transit within 1 hr
Rim sign
□ Hepatic retention of tracer due to adjacent inflammation around GB fossa with no GB filling
□ Seenwithin1sthrofimaging
□ Although radiotracer clears from liver, rim sign
persists on delayed images
□ Almost 50% of cases with rim sign have
complicated cholecystitis
Acute chole protocol
– Fasting>2hrs but <24hrs
– Premedication with cholecystokinin (CCK) if > 24 hr
fasting or parenteral nutrition
□ 0.02 mcg/kg of CCK over 30-60 min
□ 15-30 min before radiotracer administration
– Recent opioid administration can yield false-positive: Delay study for 4 t1/2 of opioid
– Hyperbilirubinemia: Hepatic uptake of mebrofenin higher than with disofenin; use if bilirubin > 30 mg/dL
– Iminodiacetic acid (IDA) derivate
□ Tc-99m mebrofenin/disofenin 3-5 mCi (111-185 MBq)
○ Imagingacquisition
– Patientsupine
– Imageoverabdomen
– Large field-of-view camera equipped with low-energy
all-purpose or high-resolution collimator
– Matrix:128x128
– Angiographic phase x 1min (4sec/frame)
– Dynamic acquisition (1frame/min) for 60min
□ May also take static images at 15-30 min intervals up to 60min
– Delayed images as necessary
□ If small bowel is present but no GB within 60min
□ Morphine 0.04mg/kg IV over 2-3 min and additional imaging up to 60 min to evaluate for GB uptake
□ If morphine contraindicated, 4hr delayed images to evaluate for GB uptake
If discordant or equivocal results -
○ Tc-99m HMPAO white blood cell (WBC) scan
– Wait 24 hrs after hepatobiliary scan to inject
– Inject Tc-99m HMPAO WBCs 1-2 hrs before imaging
○ In-111 WBC scan
– Can inject In-111 WBCs immediately after Tc-99m IDA
– Image at 24 hrs
Acute chole DDx
• Severe illness ○ Shock/sepsis • GB torsion • Chroniccholecystitis ○ Severe chronic GB dysfunction&/or dyskinesia ± cholelithiasis • Postcholecystectomy • Improper patient preparation
Functional hepatobiliary disease
• Chronic calculous cholecystitis
○ Decreased GBEF in presence of cholelithiasis
• Chronic acalculous cholecystitis/GBdyskinesia
○ Decreased GBEF in absence of cholelithiasis
• Sphincter of Oddi dysfunction
○ Delayedbiliary-to-bowel radiotracer transit
GBEF protocol
– If GB filling and bowel activity is seen by 45-60 min,
GBEF can be calculated
– Best-validated reference database, which resulted in
least variability of reference values, recommends □ Infusion of IV CCK at 0.02 μg/kg for 60 min with
normal GBEF > 38%
– FattymealoftenusedasalternativetoCCK;however,
it is not reproducible and normal gastric emptying is
needed
Functional hepatobiliary ddx
Acute chole Medications Liver dysfunction Cystic duct syndrome (rare) Partial CBD obstruction
Chronic chole findings
○ Chronic cholecystitis
– Delayed GB filling > 60min
– Delayed biliary-to-boweltransit > 60min
– Calculated GBEF < 38%
Sphincter of oddi dysfunction
– Delayed biliary-to-bowel transit > 30min
– Time of biliary visualization > 15 min
– Prominent biliarytree
Hepatic hemangioma findings
○ Focal area of activity > liver parenchyma that increases
over time on Tc-99m red blood cell (RBC) scintigraphy
○ Photopenic on angiographic phase images
Tc99m RBC scintigraphy
– Patient preparation
□ Inquire about heparin allergy (usedinlabeling
process)
□ Rule out hemolysis (can decrease percentage of
labeled RBCs)
□ 20-25mCi(740-925MBq) Tc-99mpertechnetate to label RBCs
– Dosimetry
□ Heart receiveslargestradiationdose
– Imaging acquisition
□ Patientsupine
□ Image abdomen
□ LEAPcollimator
□ 128x128matrix
□ Anteriorflowstudy(1-5sec/framex1min)
□ Static planar anterior and posterior images at 30,
60, and 120 min
□ SPECT/CTifneededforbetterlocalization,multiple
lesions, lesion near main vessels, &/or size 1-2 cm
FNH
○ Tc-99m IDA scintigraphy
– Typical fndings (~90%ofFNHlesions): Focal activity > liver parenchyma, better seen with lesions > 2 cm
– Early visualization with persistent tracer/delayed washout
○ Tc-99m sulfurcolloid (SC )scintigraphy
– Focal activity ≥ liverparenchyma in ~2/3 of cases; 1/3
show low uptake
– Presence of functioning Kupffer cells allows Tc-99m SC accumulation
– Lesions iso-or hyperintense when compared to liver parenchyma do not require biopsy
Hepatic adenoma
○ Always photopenic on Tc-99m HIDA, Tc-99mSC, or Tc-
99m RBC scintigraphy
Sulphur colloid protocol
– Radiopharmaceutical
□ 4-6mCi (198-222MBq) Tc-99mSC
□ Particlesize: 0.1-1μm
□ Optimal accumulation in 5-10 min; could be
delayed with liver failure or portal hypertension
(20-30 min)
– Dosimetry
□ Liver receives largest radiation dose
– Imaging acquisition □ Patient supine □ LargeFOVcameraLEAPcollimator □ 128x128matrix □ Angiographic phase x 1min (4sec/min) □ Static anterior and posterior images at 10-20min □ SPECT/CT
Ddx benign hepatic lesion
HCC
- Tc-99m IDA: Initially cold to ≥ 1 hr; delayed fill-in can be seen (bile lakes)
- Tc-99m RBC scan: Could have increased flow without increasing activity over time
Regenerative nodule
- Can show increased uptake on Tc-99mSC scan
SVC obstruction
- Redistribution of Tc-99mSC to leftlobe secondary to collateralization
○ Focal hepatic hotspot sign: Focally increased Tc-99mSC
uptake in segment IV
Budd Chiari
- Tc-99mSC accumulates normally in caudate lobe secondary to drainage by inferior vena cava; remaining liver parenchyma is decreased
GI Bleed scintigraphy findings
Focal activity, increases in intensity, conforms to bowel
If suspected free tech - image thyroid
RBC bleeding study protocol
○ Tc-99m RBC scintigraphy
– Useful in intermittent bleeding
– One injection can monitor bleeding over several hrs
(up to 24)
– 8-12mCi Tc-99m pertechnetate labeled RBCs
– Patient supine
– Image abdomen and pelvis
– LEAP – 128x128matrix
– Anterior angiographic phase (1-5sec/framex1min)
– Dynamic anterior images; 10-60sec/frame
– Lateral or post-void view for rectal bleeding/confirmation of genitourinary activity
○ Tc-99mSCscintigraphy
– Useful in patients with heparin allergy
Gastric emptying curve analysis
– Phase1(lagphase): Retainedingastricfundus, transported to antrum where diluted, ground (~ 60 min post ingestion)
– Phase2: Antropyloricwave-likecontractionsdilute, empty into duodenum (linear)
WBC imaging distribution
Normal biodistribution of In-111WBC
– Spleen>liver>bonemarrow
Normal biodistribution ofT c-99m HMPAO WBC
– 1-4hours:Bloodpool,spleen>liver,GItract,kidneys, and bladder
– After 4hours: Bowelactivity normal
○ Bloodpool
– Normal:Tc-99mHMPAO WBC shows marked blood pool; In-111 WBC shows faint activity
– If focal > 24hrs: Consider vasculitis, recentl ine placement, or infected graft
○ Lung
– Diffuse uptake: Normal up to 18hours
– Diffuse uptake > 18hours: Nonspecific, butcanbe
seen in ARDS
– Focaluptake > 18hours: Pneumonia/abscess
○ Bowel
– Faint activity in 1/3 of normal patients
– Focal activity: Consider infection or inflammatory
bowel disease (IBD)
□ IBD: Bowel activity on Tc-99m HMPAO WBC (early
uptake, increasing activity at 2 and 4 hours)
– Moderate/high activity that moves intraluminally over
time
□ Epistaxis, pneumonia with cough (tagged WBCs
swallowed and move through GI tract)
□ Gastrointestinal bleeding should also be considered
○ Kidneys and bladder
– Abnormal if evident on In-111 WBC scan
□ Can have normal, low-level uptake in renal transplants
– Mild/moderate activity on Tc-99m HMPAO WBC can be normal due to free Tc-99m
Ga-67 distribution
○ Normal biodistribution: Skeleton, liver>spleen, large
intestine, lacrimal glands, nose
○ Kidney
– Normal:Faint/diffuse uptake first 48hours if no renal failure
– Diffuse uptake > 48hours: Possible nephritis or renal failure
– Focal or patchy uptake>48hours:Abscess&/or pyelonephritis
Best uses for In111-WBCs
– FUO
– Cardiovascular infection
– Abdominal abscess
– Peritoneal cavity and retroperitoneal infection/abscess
– Sensitivity decreased with chronic abscess&/or
administration of antibiotics > 3 weeks
Best uses for Tc99m-HMPAO
– Pediatric patients, decreased radiation exposure
– Acute cholecystitis
– Inflammatory bowel disease
– Extremity imaging (osteomyelitis)
– Sensitivity decreased with chronic abscess &/or
administration of antibiotics > 3 weeks
Best uses for Ga-67
– Immunosuppressed &/or neutropenic patient with
fever; no minimum WBC count required
– Spondylitis&/ordiscitis
– Sarcoidosis/granulomatousdisease,
opportunistic/fungal infections
– Nonsuppurative or lymphocyte-mediated infections
– Chronic (> 2 weeks) osteomyelitis/otitis
– FUO
– Splenic abscess
– Avoids handling/reinjection of blood products
