Renal Classic NM Flashcards
Excreted by glomerular filtration
Tc-DTPA
DTPA advantage over CR-EDTA
Wide availability
Low cost
Low radiation dose
Gamma ray suitable for gamma camera
Excreted by tubular secretion
I123-Hippuran
Tc-MAG 3
MAG 3 excreted
By tubular secretion and very small hepatobiliary excretion - - gallbladder activity
Fast blood clearance vs DTPA
Mag3 clearance approximates
Effective renal plasma flow
MAG3 indications
Children
Transplanted kidney
Impaired kidney function
Cortical binding
Tc-DMSA binds to proximal tubular cells
Dehydration cause
Delay in intraparenchymal transit and excretion
Drink 7 ml/kg over hour before
Dynamic scan frames
Phase 1: 1 frame/sec for 1 min = angiogram, renal perfusion - - normal if renal cortex seen within 1-3 sec after aorta
Phase 2: 1 frame/10 sec for 4 min = parenchymal uptake
Phase 3: 1 frame/20 sec for 15 min = renal excretion
No obstruction
Rapid washout
Shape - upward concavity
T1/2 fusid <10-15 min
Obstructive uropathy
Normal or delayed angiogram
Delayed time to peak, progressive rise in activity even after fusid
Absent, incomplete or slow washout
No bladder activity
T1/2 fusid >20 min
Uncertain equivocal response
Normal angiogram, bladder activity delayed if bilateral
Washout delayed until fusid or postvoid
T1/2 fusid 15-20 min, partial obstruction
Poorly functioning kidney
Hydronephrosis - - reservoir effect
Repeat test with F-15 or calculation of mean transit time
Tracer accumulation in parenchyma is proportional to GFR, ERPF
Parenchymal phase
Hilson perfusion index for Transplanted kidney
Ratio area over iliac artery / kidney curve
>1.5 - - kidney hypoperfusion - - acute rejection
ROI background
Perirenal below lower pole or from upper to lower pole laterally
Caudal and lateral
Transit time
Time for passing through single nephron
Tonnensen formula
From 50:50 to 43:57
Not accurate for patients with kyphoscoliosis, ptosis, ectopic or malformed kidney
Indication for mean transit time
Suspected RAS
Obstruction
Kidney transplant rejection
In these cases mean transit time is prolonged
About GFR
Usually becomes abnormal before serum creatinine levels become abnormal (when GFR is reduced by 50%)
Renal function reduced - - creatinine clearance not accurate
Inulin clearance = gold standard, but complex and high cost
Obtained through Tc-DTPA clearance
Two compartment
Central compartment - plasma
Second compartment - extravascular space (tracer diffuses and redistributes back into plasma due to concentration gradient)
6 blood samples after tracer injection up to 180 min
Time consuming, require plasma samples
Single compartment
Draw blood when redistribution from extravascular to intravascular space depends on renal clearance
Ignore first exponential - - GFR overestimated
Impaired renal function - - error smaller
1-3 blood samples
Methods rely on urine collection
Severe renal failure
Ascites
Edema