Renal scintigraphy-Nuclear Medicine

Dr.J.M.C.Udugama

RENAL SCINTIGRAPHY

INDICATIONS

Renal perfusion and function

Obstruction (Lasix renal scan)

Renovascular HTN (Captopril renal scan)

Infection (renal morphology scan)

Pre-surgical quantitation (nephrectomy)

Renal transplant

Congenital anomalies, masses

(renal morphology scan)

Evaluation of:

Blood flow - 20% cardiac output to kidneys (1200 ml/min

blood, 600 ml/min plasma)

Filtration - 20% renal plasma flow filtered by glomeruli (120

ml/min, 170 L/d)

Tubular secretion

Tubular reabsorption (1% ultrafiltrate - urine)

Endocrine functions

RENAL FUNCTION

RENAL RADIOTRACERSEXCRETION MECHANISMS

GF TS TF

Tc-99m DTPA >95%

Tc-99m MAG3 <5% 95%

I-131 OIH 20% 80%

Tc-99m GHA 40%-60% 20%

Tc-99m DMSA some 60%

Semin NM Apr.92

RENAL RADIOPHARMACEUTICALS

Extract. fraction Clearance

Tc-99m DTPA 20% 100-120 ml/min

Tc-99m MAG3 40-50% ~ 300 ml/min

I-131 OIH ~100% 500-600 ml/min

DTPA MAG3 GHA DMSA I -131OIH rad/10 mCi rad/5mCi rad/300µCi

Kidney 0.2 0.15 1.6 3.5 0.01

Bladder 2.8 5.1 2.7 0.3 0.3

EDE (rem) 0.3 0.4 0.4 0.3 0.03

RENAL RADIOPHARMACEUTICALS

DOSIMETRY

CHOOSING RENAL RADIOTRACERS

Perfusion MAG3, DTPA, GHA

Morphology DMSA, GHA

Obstruction MAG3, DTPA, OIH

Relative function All

GFR quantitation I-125 iothalamate,

Cr-51 EDTA, DTPA

ERPF quantitation MAG3, OIH

Clin. Question Agent

BASIC RENAL SCAN

PROCEDURE

Patient must be well hydrated

Give 5-10 ml/kg water (2-4 cups)

30-60 min. pre-injection

Can measure U - specific gravity (<1.015)

Void before injection

Void @ end of study

BASIC RENAL SCINTIGRAPHY

PATIENT PREPARATION

Supine position preferred

Do not inject by straight stick

Flow (angiogram) : 2-3 sec / fr x 1 min

Dynamic: 15-30 sec / frame x 20-30 min

(display @ 1-3 min/frame)

BASIC RENAL SCINTIGRAPHY

ACQUISITION

DTPA NORMAL

DTPA NORMAL

RELATIVE (SPLIT) FUNCTION

ROI’S

Contribution of each kidney to the total fct

net cts in Lt ROI% Lt kid = --------------------------------------- x 100%

net cts Lt + net cts Rt ROI

Normal 50/50 - 56/44

Borderline 57/43 - 59/41

Abnormal > 60/40

RELATIVE UPTAKE

Taylor, SeminNM Apr 99

Time to peak

Best from cortical ROI

Normal 3 - 5 min

Residual Cortical Activity (RCA 20 or 30)

Ratio of cts @ 20 or 30 min / peak cts

Use cortical ROI

Normal RCA20 for MAG3 < 0.3

Residual Urine Volume

(post-void cts x void. vol) (pre-void cts - post void

cts)

BASIC RENAL SCINTIGRAPHY

PROCESSING

DTPA flow + scan

GFR = 29 ml/’

Creat = 2.0

L= 33%

R= 67%

RENAL ARTERY OCCLUSION

RT RENAL INFARCT

I . Vascular phase (flow study): Ao-to-Kid ~ 3”

I I . Parenchymal phase (kidney-to-bkg): Tpeak < 5’

III . Washout (excretory) phase

RENOGRAM PHASES

RENOGRAM CURVES

Diuretic (Lasix) Renal Scan

EVALUATION OF HYDRONEPHROSIS

OBSTRUCTION

Obstruction to urine outflow leads to obstructive uropathy

(hydronephrosis, hydroureter)

and

may lead to obstructive nephropathy

(loss of renal function)

OBSTRUCTION

Hydronephrosis - tracer pooling in dilated renal pelvis

Lasix induces increased urine flow

If obstructed >>> will not wash out

If dilated, non-obstructed >>> will wash out

Can quantitate rate of washout (T 1/2)

DIURETIC RENAL SCAN

PRINCIPLE

Evaluate functional significance of hydronephrosis

Determine need for surgery

obstructive hydronephrosis - surgical Rx

non-obstructive hydronephrosis - medical Rx

Monitor effect of therapy

DIURETIC RENAL SCAN

INDICATIONS

Rapidly cleared tracer

Well hydrated patient

Good renal function

DIURETIC RENAL SCAN

REQUIREMENTS

Pt. preparation:

prehydration

adults - oral or 360ml/m2 iv over 30’

peds - 10-15 ml/kg D5 0.3-0.45%NS

void before injection

bladder catheterization ?

DIURETIC RENAL SCAN

PROCEDURE

Tracers: Tc-99m MAG3 5-10 mCi

(preferred over DTPA)

Acquisition: supine until pelvis full

(can switch to sitting post- Lasix)

Flow (angiogram) : 2-3 sec / fr x 1 min

Dynamic: 15-30 sec / frame x 20-30 min

DIURETIC RENAL SCAN

PROCEDURE (CONT’D)

Void before Lasix

Lasix: 40mg adult, 1mg/kg child iv

@ ~10-20 min (when pelvis full)

or @ -15min (“F -15” method)

Acquisition for 30 min post Lasix

Assess adequacy of diuresis

Measure voided volume

Adults produce ~200-300 ml urine post-Lasix

DIURETIC RENAL SCAN

PROCEDURE (CONT’D)

Don’t give Lasix if

Collecting system still filling

Collecting system not full by 60 min

Collecting system drains spontaneously

Poor ipsilateral fct (< 20%)

DIURETIC RENAL SCAN

PROCEDURE (CONT’D)

DIURETIC RENAL SCAN

PROCEDURE (CONT’D)

PRE-LASIX

POST-LASIX

NO UPJ OBSTRUCTION

T1/2

R = 6’

L = 2’

POST-LASIX CURVE

PRE-LASIX

10 y/o M

POST-LASIX

RT UPJ OBSTRUCTION

T1/2

R = N/A

F/U - nephrostomy tube placed

31648973-wk old baby

Lt hydronephrosis

3164897

Lt UPJ obstruction

RT UPJ OBSTRUCTION

T1/2

R = N/A

F/U - nephrostomy tube placed

3164897

Lt UPJ obstruction

T1/2

time required for 50% tracer to leave

the dilated unit

i .e. time required for activity to fall

to 50% of peak

DIURETIC RENAL SCAN

WASHOUT

(DIURETIC RESPONSE)

T1/2 WASHOUT

cts

100%

50%

T1/2 min

Variables influencing T1/2 value:

Tracer

State of hydration

Volume of dilated pelvis

Bladder catheterization

Dose of Lasix

Renal function (response to Lasix)

ROI (kidney vs. pelvis)

T1/2 calculation (from inj. vs. response, curve fit)

T1/2 VALUE

Normal < 10 min

Obstructed > 20 min

Indeterminate 10 - 20 min

Best to obtain own normals for each institution, depending on

protocol used

T1/2

Interpret whole study, not T1/2 alone

Visual (dynamic images)

Washout curve shape (concave vs. convex)

T1/2

DIURETIC RENAL SCAN

INTERPRETATION

False positive for obstruction

Distended bladder

Gross hydronephrosis

T(transit time) = V (volume) F (flow)

Poorly functioning / immature kidney

Dehydration

False negative

Low grade obstruction

Poorly functioning / immature kidney

DIURETIC RENAL SCAN

PITFALLS

EFFECT OF CATHETERIZATION (1)

full bladder,

no catheter

with catheter

in bladder

EFFECT OF CATHETERIZATION (2)

EFFECT OF CATHETERIZATION (3)

with catheter without catheter

Captopril Renal Scan

(ACEI Renography)

EVALUATION OF RENOVASCULAR

HYPERTENSION

Renal artery stenosis (RAS)

Ischemic nephropathy

Renovascular hypertension (RVH)

RAS RVH

RENOVASCULAR DISEASE

Caused by renal hypoperfusion

Atherosclerosis

Fibromuscular dysplasia

Mediated by renin - AT - aldosterone system

Potentially curable by renal revascularization

RENOVASCULAR HYPERTENSION

Prevalence

<1% unselected population with HTN

Clinical features

Abrupt onset HTN in child, adult < 30 or > 50y

Severe HTN resistant to medical Rx

Unexplained or post-ACEI impairment in ren fct

HTN + abdominal bruits

If these present - moderate risk of RVH (20-30%)

RENOVASCULAR HYPERTENSION

RENIN-ANGIOTENSIN SYSTEM

RAS

Captopril

Angiotensinogen

Angiotensin I

Angiotensin II

Aldosterone Vasoconstriction

HTN

Renin

ACE

EFFECT OF RAS ON GFR

Gold std: angiography

Initial non-invasive tests:

ACEI renography

Duplex sonography

Other tests:

MRA - insensitive for distal / segmental RAS

Captopril test (PRA post-C.) - low sensitivity

Renal vein renin levels

DIAGNOSIS OF RAS

ACEI RENOGRAPHY

Off ACEI & ATII receptor blockers x 3-7 days

Off diuretics x 5-7d

No solid food x 4 hrs

Patient well hydrated

10 ml/kg water 30-60 min pre- and during test

ACEI

Captopril 25-50 mg po (crushed), 1 hr pre-scan

Enalaprilat 40 µg/kg iv (2.5 mg max), 15 min pre-scan

Monitor BP q 15 min

ACEI Renography

Patient Preparation

Tracer: Tc-99m MAG3 (or DTPA)

Protocol: 1 day vs . 2 day test

1 day test: baseline scan (1-2 mCi) followed by

post-Capto scan (8-10 mCi)

2 day test: post-Capto scan,

only if abnormal >> baseline

Acquisition: flow & dynamic x 20-30 min.

ACEI RENOGRAPHY

PROCEDURE

Relative renal uptake (bkg corrected)

Time to peak (Tp) - from cortical ROI

normal < 5 min

RCA20 (20 min/peak ratio) - from cortical ROI

normal < 0.3

ACEI RENOGRAPHY

PROCESSING

ACEI Renography

Grading renogram curves

High probability RVH (>90%)

Marked C-induced change

Low probability RVH (<10%)

Normal Captopril scan

Abnormal baseline, improved p-C.

Type I curve - pre- and post-C.

Intermediate probability RVH

Abnl baseline, no change p-C.

ACEI RENOGRAPHY

INTERPRETATION

CAPTOPRIL RENAL SCAN

MAG 3

Captopril Renal Scan MAG3

Captopril Renal Scan

MAG 3

Captopril Renal Scan

MAG 3

In normal renal function - sens/spec ~ 90%

In poor renal fct / ischemic nephropathy, ACEI renography often

indeterminate

>>> do MRA, Duplex US, angio

ACEI RENOGRAPHY

Renal Morphology Scan

(Renal Cortical Scintigraphy)

EVALUATION OF RENAL

INFECTION

UTI

VUR

risk factor for PN,

not all pts w PN have VUR

PN may lead to scarring >>> ESRD, HTN

early Dx and Rx necessary

Clinical & laboratory Dx of renal involvement in UTI unreliable

RENAL CORTICAL SCINTIGRAPHY

INDICATIONS

Determine involvement of upper tract

(kidney) in acute UTI (acute pyelonephritis)

Detect cortical scarring (chronic pyelonephr.)

Follow-up post Rx

RENAL CORTICAL SCINTIGRAPHY

PROCEDURE

Tracers

Tc-99m DMSA

Tc-99m GHA

RENAL CORTICAL SCINTIGRAPHY

INTERPRETATION

Acute PN

single or multiple “cold” defects

renal contour not distorted

diffuse decreased uptake

diffusely enlarged kidney or focal bulging

Chronic PN

volume loss, cortical thinning

defects with sharp edges

Differentiation of AcPN vs . ChPN unreliable

RENAL CORTICAL SCINTIGRAPHY

“COLD DEFECT “

Acute or chronic PN

Hydronephrosis

Cyst

Tumors

Trauma (contusion, laceration, rupture,

hematoma)

Infarct

DMSA

PARALLEL HOLE COLLIMATOR

Normal DMSA

pinhole

LPO RPO

DMSA

ACUTE PYELONEPHRITIS

DMSA

post L

LPO pinhole

post R

RPO

LEAP

RENAL CORTICAL SCINTIGRAPHY

CONGENITAL ANOMALIES

Agenesis

Ectopy

Fusion (horseshoe, crossed fused ectopia)

Polycystic kidney

Multicystic dysplastic kidney

Pseudomasses (fetal lobulation, hypertrophic

column of Bertin)

DMSA

HORSESHOE KIDNEY

parallel pinhole

DMSA

LT AGENESIS

parallel

GHA

Crossed ectopia

74%

26%

RADIONUCLIDE

CYSTOGRAM

Evaluation of children with recurrent UTI

30-50% have VUR

F/U after initial VCUG

Assess effect of therapy / surgery

Screening of siblings of reflux pts.

INDICATIONS

Tc-99m S.C. or TcO4

via Foley

can do at any age

VUR during filling

catheterization

Tc-99m DTPA or Tc-99m MAG3

i.v.

no catheter

info on kidneys

need pt cooperation

need good renal fct

METHODS

Advant.

Disadv.

Direct Indirect

1 mCi S.C. in saline via Foley

Fill bladder until reversal of flow

(bladder capacity = (age+2) x 30

Continuous imaging during fill ing & voiding

Post void image

Record volume instilled

volume voided

pre- and post- void cts

DIRECT CYSTOGRAPHY

Lower radiation

dose

(5 vs 300 mrad to

ovary)

Smaller amount of

reflux detectable

Quantitation of

post-void residual

volume

Cannot detect distal

ureteral reflux

No anatomic detail

Grading difficult

RN CYSTOGRAM VS. VCUG

Advantages Disadvantages

NORMAL CYSTOGRAM

filling voiding post-void

VUR - FILLING PHASE

A

VUR - VOIDING PHASE & POST-

VOID

B

POST VOID RESIDUAL VOLUME

voided vol x post-void cts

pre-void cts - post void ctsRV =

Reflux nephropathy

16% 84%