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
Findings on Infection/inflammation imaging:
a) Acute Splenic/Hepatic Infarct &/or Hematoma
b) Gastrointestinal Bleeding due to Bowel Ischemia or Infarct/Swallowed WBC due to Pneumonia or Epistaxis
c) Lymphoma/Acute Heterotopic Bone/Myositis
d) Ostomy Sites/Catheter and Intravenous Lines
e) Renal transplant
f) Acute/Chronic Renal Failure and Nephritis
a) Focal area of activity on WBC scan up to 7 days
b) Mimics bowel inflammation on WBCs can
c) Can be positive on WBC imaging
d) Subtle to moderate uptake on WBC or Ga-67 scan
e) Non infected transplant can show faint, diffuse uptake on WBC and Ga-67 scan
f) Diffuse up take on Ga-67scan
Spleen vs Liver on Heat damaged RBC study
○ Activity in splenic tissue increases over time due to
accumulation of heat-damaged RBCs
– Activity in liver is stable or decreases over time
Sphincter of Oddi dysfunction findings
Abnormal GBEF
Dilated CBD
Delayed biliary to bowel transit
Cystic duct syndrome
Partial CD obstruction due to fibrosis, adhesions, etc
Delayed gastric emptying
> 90% retention at at 1 hr
60% retention at 2 hrs
10% retention at 4 hours (>35% = severe, >20 = moderate)
Rapid gastric empyting
<30% retention at 1 hr
Things to clarify before calling a study postiive for acute chole
After 30 minutes of morphine or 3-4 hours of delayed imaging
No prolonged fasting
No serious concurrent illness
No chronic cholecystitis
No hepatic insufficiency
Delayed biliary to bowel transit with gallbladder visualized
Partial CBD obstruction (not high grade if still have excretion into intrahepatic ducts and CBD)
Recent narcotics - hold for 6 hrs
CCK administered?
Chronic cholecystitis
If no bowel activity by 60 minutes, do 2-3 hour delays or give CCK
Prompt hepatic uptake but no excretion into biliary system
High grade obstruction
Cholangitis
Hepatic dysfunction
Cholestatic jaundice
Post-cholecystectomy syndrome
Dilated CBD but still get normal biliary to bowel transit
Ddx: Retained stones
Inflammatory stricture
Partial obstruction
Low GB EF
Chronic acalculous cholecystitis
Meckel’s ddx
Ectopic gastric mucosa in an intestinal duplication cyst
Ectopic renal pelvis/ureteric activity
GI bleed
Regional enteritis
Additional things to comment on during gastric emptying
Contour
Lag phase
Emptying phase
FNH findings
Iso or hot on SC, can be hot on HIDA
Cold on RBC can
Hot lesion on RBC scan
Cavernous hemangioma
Angiosarcoma
FNH
Hepatic lesions that take up SC
Contain Kupffer cells
FNH
Regnerating nodule
Malignant ascites on bone scan ddx
Bowel necrosis
Peritoneal mesothelioma
Rim sign
Suggests gangrenous cholecystitis
Reflux of bile into stomach
Can cause gastritis and explain patient’s symptoms
Cold defect on HIDA
Non-specific, anatomic imaging comparison suggested
Cyst
Hemangioma
Metastasis
Primary/secondary liver lesion
