Oral Exam - GU

Question 1

Acute pylonephritis findings

Answer 1

DMSA
Striated uptake appearance on Tc-99m DMSA
□ Pattern usually extends toward hilum (scar tends to
be more superficial)

WBC study
○ In-111 WBC scan: No normal uptake in kidneys; ↑ uptake
sensitive and specific for pyelonephritis

○ Tc-99m HMPAO WBC scan: Normal uptake in kidneys
and bladder; ↓ sensitivity, specificity for pyelonephritis

Ga-67
○ Normal symmetrical Ga-67 renal uptake up to 48hr post
injection

○ Bilateral renal Ga-67 uptake > 48hr post injection:

• Interstitial nephritis
• Renal failure
• Acute pylonephritis (unusual to be bilateral)
• Lymphoma

○ Focal increased Ga-67 uptake:

• Acute pyelonephritis
• Malignancy - lymphoma, leukemia, metastases

Question 2

DMSA protocol

Answer 2

– Tc-99m DMSA: 40-65% injected dose bound to cortical
proximal convoluted tubules 2 hr post injection

Alternative:
○ Tc-99m glucoheptonate scan

○ Posterior and anterior supine planar images with low- energy, all-purpose parallel hole collimator at 2 hr post injection
– Differential renal function calculated using geometric
mean method
□ Geometric mean: Square root of product of
anterior and posterior counts

○ SPECT for best 3D cortical evaluation
– If SPECT not available, anterior, posterior, and bilateral posterior oblique images
– High-or ultra-high-resolution collimator; 300-500 K/image
– If known or suspected horseshoe kidney, image from anterior to discern connecting bridge of renal tissue between lower pole moieties ventral to spine

Question 3

Ddx cortical defect DMSA

Answer 3

Pylenephritis
Cortical scar

Renal mass
Renal cyst
Fetal lobulation - normal indentation between lobules
Interstitial nephritis - mimics diffuse bilateral pyelo on Ga-67
Splenic impression

Question 4

Renogram - normal angiographic phase

Answer 4

○ Flow to kidneys is seen quickly after aorta
○ Cortex should accumulate radiotracer over 1-3 min
– Should be homogeneous
– Cortical defects may indicate scar
○ If decreased renal function, uptake will be delayed

Question 5

Renogram - clearance phase

Answer 5

○ Calyceal activity within 5 min

○ Bladder activity within 10-15 min

Question 6

Renogram - protocol

Answer 6

□ Adults: Up to 10 mCi Tc-99m MAG3 IV

– Patient supine ,gamma camera posterior

– Angiographic sequence
□ 1-2 sec images for 1-2 min

– Dynamic sequence
□ 15-60 sec images for 20-30 min

– Diuresis sequence
□ Patient given furosemide and additional 15-60 sec images for 20-30 min

Lasix
□ Adults: 0.5mg/kg (max:40mg)
□ Pediatrics: 1mg/kg (max:20mg)

Question 7

High grade obstruction findings

Answer 7

Relative function: Cannot predict functional potential in face of high- grade obstruction

Angiographic - Normal to delayed

Clearance phase - Calyceal activity usually normal, unless renal function is impaired secondary to obstruction; no bladder activity if obstruction is upper tract and bilateral

Renogram: Progressive rise in activity, even after furosemide; delayed time to cortical peak; washout t1/2 > 20 min

Question 8

Partial obstruction

Answer 8

Angiographic phase - Normal

Clearance phase - Normal calyceal activity time, bladder activity may be delayed if bilateral

Renogram: Washout delayed until furosemide or postvoid procedure, then will decrease but still delayed; low-grade (questionable clinical significance): t1/2 10-15 min; partial obstruction, clinically significant: t1/2 15-20 min +

Question 9

Functional obstruction

Answer 9

Angiographic phase: Normal

Clearance phase - Calyceal activity < 5 min; may have delayed bladder activity

Renogram: Washout delayed until furosemide or postvoid procedure; then washes out normally (t1/2 < 10 min)

Question 10

Renal artery stenosis

Answer 10

Angiographic phase - delayed

Clearance phase: Delayed calyceal activity time

Renogram: Normal time-activity curve appearance, but peak is delayed

Question 11

VUR findings:

Answer 11

Nuclear cystogram
○ Reflux of Tc-99m pertechnetate from bladder into
ureter &/or renal collecting system on filling or voiding
○ Dynamic images during filling and voiding increases
detection of VUR, including transient reflux
○ Difficult to grade VUR on nuclear cystogram due to lack
of anatomic resolution
– Qualitatively reported as mild, moderate, or severe

Question 12

Nuclear cystogram protocol

Answer 12

– Tc-99m pertechnetate or SC
□ 0.25-0.5mCi for infants and toddlers

– Bladder volume goal: [Ageinyears+2]x30cc
– Normal saline, water
– Gravity instill fluid 70-100 cm above patient via
catheter
– Record volume at which VUR occurs
– Record volume of voided urine

– 64x64 matrix
– Posterior images of pelvis and abdomen, unless
calculation of residual bladder volume is planned
– Fillingandvoidingdynamicimagesat5-10sec/frame,
posterior
– Oncebladdergoalvolumeisreached,instructpatient
to void
– Prevoid and postvoid static images, 3-5 minutes each

Question 13

Ddx VUR

Answer 13

Urine contamination

Bladder diverticulum

Question 14

VUR Grading Nucs

Answer 14

○ Mild: Reflux in ureter
○ Moderate: Reflux to nondilated ureter and renal pelvis
○ Severe: Reflux to dilated collecting system

Question 15

Renal transplant tracers

Answer 15

○ Tc-99m MAG3
– Renal tubular agent, preferred for renal transplant evaluation

○ Tc-99m DTPA
– Slower clearance than MAG3, limited utility in cases of
poor renal function with extraction fraction &laquo_space;MAG3
(cleared by glomerular filtration)

Question 16

Renal transplant protocol

Answer 16

Baseline renogram at 24-48hr to assess function and
allow better differentiation of ATN and AR

○ Patient position: Supine with camera anterior, centered
over side of pelvis containing transplant
○ Camera: Low-energy, all-purpose collimator
○ Computer: Acquire study in 2 phases, angiogram and
functional

– Angiogram: Dynamic 1-2 sec/frame for 60 sec
– Functional: 15-60 -sec frames for 20-30 min followed
by prevoid and postvoid images

○ Radiotracer
– Tc-99m MAG3: Up to 10 mCi

Question 17

Renal transplant - normal findings

Answer 17

○ Perfusion to allograft: Normally within 4 sec of
radiotracer bolus passing through iliac artery
○ Normal peak cortical activity 3-5 min post injection
○ Normal renal transit: Tracer in collecting system, bladder
by 6 min
○ By end of exam, cortex should clear or be significantly
less than early in exam if no cortical retention

Question 18

ATN findings

Answer 18

• Classically presents with relatively preserved perfusion and delayed uptake/excretion (tubular agents)
• Abnormal baseline renal scan at 24hr (AR typically occurs later)
• Bladder activity classically absent; background activity increases over time (e.g., gallbladder with MAG3)

Question 19

Acute rejection

Answer 19

• Perfusion in AR generally worse than function: Often technically difficult to visualize
• ↑cortical retention compared with baseline from 1 week to < 1 year: Sensitive, fairly specific for AR

Question 20

Drug toxicity

Answer 20

• Imaging appearance is similar to and difficult to distinguish from ATN (preserved perfusion and poor tubular function)
○ Typically presents later than ATN (time course very
important)

Question 21

Renovascular HTN: high probability scan

Answer 21

○ High probability (> 90%)
– MAG-3: ↑ peak time (by 2-3 min or at least 40%)
– DTPA: ↓ peak and ↓ relative uptake or GFR > 10%
– MAG-3: Increase in 20-or30-min/peak ratio of ≥ 0.15
from baseline study
– Decrease in MAG-3uptake > 10%
– Marked unilateral parenchymal retention of DTPA
after ACEI compared with baseline study

Question 22

Renovascular HTN protocol:

Answer 22

Prep:
– Stop ACEI 3-7 days prior to exam
– Hydrate p.o.; 7 mL/kg 30-60 min before study
– Position patient supine with camera posterior for
native kidneys and anterior for renal transplant
– NPO 4-6 hrs for best absorption of ACE-i

– 1-day protocol (high probability of disease): 1mCi low-dose baseline followed by 5-10 mCi high-dose ACEI scan

Captopril 25-50mg PO crushed; BP Q5-10 min x 1hr

○ Acquisition
– Camera: Low-energy, parallel hole collimator; 15-20% photopeak centered at 140 keV; large field of view

Question 23

RVH - intermediate probability study

Answer 23

Abnormal baseline findings that are unchanged after ACEI
– Small, poorly functioning kidney (< 30%) may not
respond appropriately
– Symmetric bilateral abnormalities most often due to
factors such as dehydration
– Cortical retention, ratio counts at 20 to 3 minutes
(20/3 ratio) ~ 0.1-0.5
– Reduced uptake of DTPA of 5-9%

Question 24

Homsy’s sign

Answer 24

High grade obstruction induced by high flow states

Initially see normal clearance, then retention

Question 25

Renal infarction

Answer 25

Photopenia over kidney

Possible case - aneurysm on blood pool imaging, then photopenic kidneys due to dissection

Question 26

Duplicated collecting system

Answer 26

Look for bladder ureterocele + retained activity in obstructed upper pole

Question 27

RAS

Answer 27

Can have delayed uptake and excretion relative to normal side

Question 28

Nuclear cystogram

Answer 28

Assess prevoid phase, voiding phase, and post-void

Question 29

Non-visualized kidney

Answer 29

Nephrectomy
Ectopically located
RA stenosis/occlusion
High grade obstruction
MCDK/Poor function

Question 30

Renal transplant

Answer 30

Think about urinoma

Question 31

Photopenic transplant kidney.

Answer 31

Arterial or venous thrombosis
Hyperacute rejection
Acute cortical necrosis

Question 32

Dilated ureter on renogram

Answer 32

UVJ obstruction
VUR
Primary megaureter

Question 33

Acute pyleo ddx on DMSA

Answer 33

Renal scarring
Renal tumour
Cyst

Question 34

Photopenia in portion of the kidney on flow and delayed - no flow or function

Answer 34

Infarct

Cyst

Question 35

Normal flow and extraction but delayed or absent excretion

Answer 35

Obstruction
Medical disease
ATN

If transplant, also include
Rejection
Drug toxicity (cyclosporin)

Question 36

Renal transplant findings

Answer 36

Vascular occlusion/RA thrombosis/RV thrombosis - photopenia over whole kidney

Infarct - focal photopenia, sometimes with hyperemic rim

Hyperacute rejection - photopenia over whole kidney

Acute rejection - Decreased flow, otherwise similar to ATN. Worsens on short term follow-up

ATN - normal flow and extraction with impaired excretion. Should improve on F/U

Question 37

Hypertrophic column of Bertin

Answer 37

Renal cortex extends into Medulla, can appear mass-like

Question 38

Quantitative indices of renal function

Answer 38

Peak time - reflects cortical extraction/uptake ( normal 3-5 min)