Gadolinium-enhanced MR Imaging of Renal Marga B. Rominger, MW PhilipJ. Kenney, MD Desiree E. Morgan, MD Wanda K Bernreuter, MD Jayj Listinsky, MD, PhD

Preliminary reports indicate that gadolinium-enhanced magnetic resonance (MR) imaging is highly accurate for diagnosis of renal masses. The authors demonstrate the clinical utility of MR imaging for evaluating renal masses in 26 patients for whom contrast material-enhanced computed tomography (CT) was contraindicated or inadequate for diagnosis or staging. Nine patients had complex cysts, one had a pennephnic hematoma, and 16 had a solid mass (three ofwhich were benign). All patients underwent MR imaging before and after administration ofgadopentetate dimeglumine. Multiple imaging techniques and sequences were used. All tumors and no cysts enhanced with gadolinium. Even though the three benign tumors enhanced, two were differentiated from renal carcinoma on the basis of other imaging features. Unenhanced MR imaging was accurate in staging of renal carcinomas, and use of gadolinium did not improve staging accuracy. Gadoliniumenhanced MR imaging is indicated when results of CT and sonography are indeterminate for malignancy and when contrast-enhanced CT is contraindicated because of renal failure or adverse reaction to iodinated contrast material. In this latter instance, MR imaging is useful for both diagnosis and staging. U INTRODUCTION The usefulness of magnetic resonance (MR) imaging for evaluating renal masses has been limited, despite high-resolution methods, multiplanar capability, and the ability to evaluate vascular patency without using contrast material, because the signal intensity

of renal

Abbreviations: Index

Kidney.

#{149} Magnetic

RadloGraphics From

the

Department

1991

July

6. Address

Current RSNA,

See

the

RSNA address:

is similar

fat suppression, cysts.

1

(MR),

reprint

=

#{149} Kidney,

contrast

of renal

gradient-recalled

MR. 81.1214

parenchyma

acquisition #{149} Kidney

on

in the

neopla.sms.

steady

81.324

both

Ti-

state, #{149} Kidney

SE

=

spin

neoplasms.

and

T2-

echo MR.

enhancement

12:1097-1116 ofRadiology.

scientific

to that

GRASS

81.31

resonance 1992;

the

2

=

FS

terms:

81.1214

tumors

assembly. requests

University

University Received

ofAlabama March

9. 1992;

at Birmingham. revision

requested

619

S 19th March

St. Birmingham. 20 and

received

AL 35233. July

From

6; accepted

to P.J.K. of (,iessen.

Germany.

1992 commentary

by I.autin

following

this

article.

1097

a.

b.

Figure 1. Limitation of unenhanced performed to stage a 3-cm right renal sonography. (a) Ti-weighted spin-echo shows an isointense bulge in the right

(b) T2-weighted

SE image demonstrates the bulge remains isointense compared with reDefinitive diagnosis of renal carci-

(arrow), which nal parenchyma.

noma

could

not be made,

and

no metastases

seen. (c) Enhanced CT scan shows enhancement of the mass, diagnostic

noma,

which

was proved

weighted unenhanced Thus, even though tages over computed staging

renal

images MR imaging tomography

tumors

agent

(2-4),

greatly

and characterization with MR imaging to that attainable hanced CT (6-8).

were

heterogeneous of renal

carci-

surgically.

useful for the detection renal neoplasms (2,4), the standard examination (5). Use ofgadopentetate contrast

MR imaging, mass found at (SE) image kidney (arrow).

(Fig 1) (1,2). has advan(CT) for

it has

not

been

or diagnosis of small and CT has remained for these purposes dimeglumine as a improves

the

detection

of small renal masses to a level perhaps superior with contrast material-enNevertheless, given the high

accuracy of CT and the greater cost of MR imaging, the proper role of MR imaging remains unclear. In this article, we report on the usefulness of MR imaging for diagnosis or staging in a series

of 26

cases.

These

cases

consist

of a se-

lected patient population for whom enhanced CT was contraindicated or had been madequate for diagnosis or staging. Eight patients had chronic renal insufficiency (serum creatinine levels varying from 2.2 to 1 i.0 mg/dL [194.5 to 972.4 p.mol/L]), and two had had a

1098

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U

Rominger

et a!

previous dia.

reaction

In these

as an

alternative

16 patients,

staging

to iodinated

patients,

contrast

MR imaging

me-

was

to contrast-enhanced

MR imaging

or because

was

the results

chosen CT.

performed

In

for

of CT had

been

indeterminate. Herein, we review our MR imaging techniques; describe the contribution of different pulse sequences; report the MR imaging findings for simple and complicated renal cysts, renal carcinoma, angiomyolipoma, and oncocytoma; and discuss the safety and usefulness of gadolinium-enhanced MR imaging in our series. U

IMAGING

TECHNIQUES

All MR imaging (either kee, Iselin, were aging routine with

was performed on i.5-T units Signa, GE Medical Systems, Milwauor Magnetom, Siemens Medical Systems, NJ). A variety of imaging parameters used, in part because of changes in imsoftware. In most cases, the following was used: 7-mm-thick axial sections a 2-mm gap, a matrix of 256 X 128, two

Volume

12

Number

6

MR Imaging

Pulse

Sequences

for Detection

of Renal

Masses Repetition

Pulse Before

Sequence

gadolinium

Time

Spoiled

After

SE SE with

GRASS,

gadolinium

300-500 2,000-2,500 1,800-2,500 30-50

FS

35#{176} flip angle,

with

FS

Ti-weighted

signals weighted

SE with GRASS, GRASS,

Note.-FS

FS

20#{176}-35#{176} flip angle 35#{176} flip angle, with

acquisition

in the

(GRASS)

(35#{176} flip angle),

quences

except

spoiled

during

presaturation

steady

state

GRASS,

a single was

used

which

was

breath-hold. for

Spa-

Ti-weighted,

proton-density, and T2-wemghted SE sequences; flow compensation was employed for proton-density SE, T2-weighted SE, and spoiled GRASS sequences. Fat suppression (FS), when this technique became available, was accomplished with use of a radio-frequency presaturation pulse centered on the fat resonance. The FS technique offers numerous advantages. It increases contrast-to-noise ratio between renal parenchyma and surrounding fat on T2-weighted images and gadolinium-enhanced images. It reduces chemical shift artifact, which allows use of a variable band width to increase signal-tonoise ratio on second echos. The FS technique also reduces respiratory artifact, because much of it is produced by motion of the high-signal-intensity fat in the abdominal wall, and suppression of the fat signal decreases the ghost artifact amplitude. FS or water suppression methods can also be useful in interrogating

12-20

FS

and four signals averaged for Ti-weighted SE sequences. All of the sequences are listed in the Table and illustrated in Figure 2. Respiratory compensation was used during imaging with all pulse Se-

tial

12-20

300-500 50 50

averaged for proton-density or T2SE sequences and for spoiled gradi-

performed

300-500

5 5

fat suppression.

=

ent-recalled

12-20 30-60; 70-i20 12-60; 60-120 5

enhancement

Ti-weightedSE Spoiled Spoiled

Time

(msec)

enhancement

Ti-weightedSE

T2-weighted T2-weighted

Echo

(msec)

a lesion

for

presence

of fat:

A

Gadopentetate dimeglummne (Magnevist; Berlex Imaging, Wayne, NJ) was administered intravenously (0.1 mL/0.45 kg of body weight) over 1-2 minutes. MR imaging was started 2 minutes after the injection was completed. This timing was selected so that images would be acquired when the renal pa-

renchyma

was relatively

homogeneously

enhanced rather than during the hyperintense cortical phase (9, iO). Contrast material enhancement can be recognized as a visible increase in brightness of tissue after gadopentetate dimeglumine has been administered. Signal intensities can be measured before and after the contrast agent is injected to document enhancement; however, the same pulse sequence must be used both times, since

alteration

or flip change U

MR

RENAL

of repetition

time,

echo

angle or use of FS techniques signal intensities. IMAGING

time,

will

APPEARANCE

OF

MASSES

. Cysts The most common renal mass in the adult is a cyst. In general, cysts are benign and require no treatment. Simple cysts are usually readily diagnosed with ultrasound (US), and no further evaluation is needed. The greater challenge for radiologists is distinguishing a complicated cyst from cystic or necrotic renal carcinoma. This usually cannot be accom-

decrease in signal intensity with FS or persistance of high signal intensity despite water suppression indicates the presence of fat.

November

1992

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e.

Figure

f. 2.

MR images

obtained

with

various

tech-

niques ofnormal kidneys. (a) Ti-weighted SE image. (b) T2-weighted SE image shows chemical shift artifact and low tissue contrast between renal parenchyma and peninephric fat. (c) T2-weighted SE im-

age with

FS shows

that

renal

outlines

are more

dis-

tinct with reduced fat signals. (d) Spoiled GRASS image (35#{176} flip angle) with FS obtained during 11second breath-hold shows high-signal-intensity blood. (e) Enhanced Ti-weighted SE image shows poor contrast between the kidneys and fat. (1) On the enhanced Ti-weighted SE image with FS, contrast enhancement is more striking than in e, without FS. (g) Enhanced spoiled GRASS image (35#{176} flip angle) with FS also shows strong renal enhancement.

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Volume

12

Number

6

.

-p

a.

b

image

3. Simple renal cyst. shows a homogeneous

signal

intensity

Figure

lower

than

(a)

Ti-weighted

mass

that

SE

(arrows)

of renal

with

parenchyma

(arrowheads) and with a thin imperceptible rim. There is slight respiratory artifact within the mass. (b) T2-weighted SE image shows the mass (arrows) with homogeneous signal intensity higher than that of renal parenchyma (arrowheads). There is chemical shift artifact, which makes assessment of wall thickness difficult. (c) On the enhanced Tiweighted SE image with FS, no enhancement of the mass

is seen

and

both

artifacts

have

been

reduced.

C-

pushed with US or unenhanced CT. Enhancement of tissue within the mass after contrast material administration on either CT or MR images is the key finding in determining whether a cystic renal mass is malignant or benign (6,7, 1 1, 12). Use of gadopentetate dimeglummne in MR imaging is peculiarly effective for making this determination. Both renal parenchyma and vascular tumors en-

hance

after administration

dimeglumine

because

of gadopentetate it equilibrates

weighted images show the cyst contents to be homogeneous and very low in signal intensity, with no internal architecture or debris. On T2-weighted images, the cyst contents are homogeneously hyperintense. With both pulse sequences, the cyst wall is thin and almost imperceptible. There is no enhancement of any portion of the cyst after administration of gadopentetate dimeglumine (Fig 3). Demonstration of the homogeneity of the cyst

in the

contents

is improved

by elimination

enhanced

respiratory artifact. The cyst seen if chemical shift artifact

cysts,

using

extracellular

fluid

space.

Renal

neoplasms

are

on gadolinium MR images, and which are avascular, are not; thus, the focus of contrast-enhanced MR imaging is the attempt to document absence of enhancement, since this excludes the possibility of

renal

carcinoma.

Simple cated simple other

Renal Cyst.-MR imaging is not mdifor evaluation of a mass shown to be a renal cyst by means of sonography or methods. Ifobtained, however, Ti-

November

1992

FS techniques.

of

wall is better is eliminated

Section

thickness

by should

be appropriate for the size of the lesion. For large masses, 10-mm-thick sections are acceptable, but, ifthe lesion is 2.5 cm or less, 5-mm-thick sections should be used to minimize volume averaging.

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Figure atinine

4. Complicated cyst in a 64-year-old man with urosepsis and chronic renal insufficiency (serum crelevel, 2.3 mg/dL [203.3 jimol/L]; creatinine clearance, 53 mL/min [0.88 mL/sec]). A 3-cm echogenic mass, discovered incidentally at US, was isoattenuating relative to renal parenchyma at unenhanced CT. (a) Ti-weighted SE image shows a mass (arrow) isointense relative to renal parenchyma. (b) T2-weighted SE image with FS shows the homogeneously hypenintense mass. (c) Enhanced Ti-weighted SE image with FS demonstrates no enhancement of the mass (arrowhead). FS techniques allow better evaluation of a cyst wall. In this case, it is nearly invisible, since cyst contents, cyst wall, and peninephric fat (suppressed) are all dark. Follow-up s ‘ erformed 9 months later showed no chan e in the mass.

:

:1 .

a.

b

Complicated Cyst-Pnesence hemorrhage within a cyst alters tensity characteristics (1 1,13,14). usually

variable

Ti-weighted (Figs rhagic

4-7). cysts

increased

images due On T2-weighted often

appear

of protein or the signal inThere is

signal

intensity

on

to Ti shortening images, hemormore

hyperintense

than solid renal carcinomas (Figs 4, 5). Thick walls, internal septations, and heterogeneity of contents (Fig 6) may be seen in complicated cysts. Calcification cannot be readily detected with MR imaging. The appearance of complicated cysts can overlap that of cystic on necrotic renal carcinoma, and documentation of absence of contrast material enhancement is crucial in distinguishing

these

two

entities.

C-

ent factors, ofhemoglobin

Because

complicated cysts can be hypenmntense on Tiweighted images, signal intensities before and after contrast material administration should be compared and FS techniques used to exclude the possibility ing

lesions

(Fig

should be of fat-contain-

7).

tive

oxyhemoglobmn

in

or

low

Signs

changes

in signal of months.

may

contain

paramagnetic distinguish rhagic cyst

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properties (14). Naand

has

intensity. Several breakevolve in an aging hemoror superparamagnetic intensity on Ti-weighted

signal

images. nod

magnetic products

is diamagnetic

little effect on signal down products that rhage are paramagnetic and have high signal images

On CT scans, hemorrhage causes change attenuation. On MR images, the appearance of hemorrhage relates to a number of differ-

including the breakdown

intensity

on

of hemorrhage

intensity Because

T2-weighted

and

resulting

evolve renal

hemorrhagic

cystic

contrast agent renal carcinoma on MR images.

Volume

over

a pe-

carcinomas areas,

use

is necessary from a hemor-

12

Number

of a

to

6

Figure

5.

Complicated

cyst in the left kidney

of a 66-year-old

man

was incidentally

detected

during

evalua-

tion of an aortic aneurysm. US had shown internal echoes. Unenhanced CT, performed because the patient had had an anaphylactoid reaction during intravenous urography, revealed an indeterminate mass. (a) Tiweighted SE image shows a barely detectable, nearly isointense mass. (b) T2-weighted SE image demonstrates the markedly hyperintense, homogeneous mass (arrow). (c) On the enhanced Ti-weighted SE image, the mass did not enhance, and it was diagnosed as a cyst. (d) T2-weighted SE image with FS, obtained at fol-

low-up image

6 months

later,

shows

no change

in the mass

(arrow)

(cfb).

(e) On the enhanced

with

FS, there is no enhancement of the mass (arrow) (cfc). (f) Enhanced spoiled flip angle) with FS obtained at i 4 months follow-up shows no change in the cyst (arrow). .---. --I flow artifacts, with hir nal-intensir’ blood in the renal vein (arrowheads).

a.

SE

b.

d.

C.

f.

C.

November

Ti-weighted

GRASS image (35#{176} Note lack of respi-

1992

Rominger

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U

1103

I.

#{149}IH

a

b.

Figure 6. 55-year-old

Hemorrhagic

man

with

dominant

polycystic i 1.4 mg/dL F1007.8

echogenic shows

mass. a mass

cyst

renal disease p.mol/L).

(a) Coronal

(arrows)

with

in the

failure

left kidney

due

of a

to autosomal

(serum creatinine level, US had shown an Ti-weighted SE image a hyperintense periph-

ery and a less intense center, as well as many other cysts. The pattern of signal intensities in the mass suggests subacute hemorrhage in a cyst. (b) Axial T2-weighted SE image with FS shows that the periphery of the mass remains hyperintense (arrows). The presence of fat is excluded. (c) On the enhanced Ti-weighted SE image with FS, the periphery remains hypenintense (arrows), but lack of enhancement within the lesion is indicative of its cystic nature.

. Solid Masses Early detection of renal tumors is important, since only surgical resection is curative. Use of new MR imaging pulse sequences on 1 . 5-T imagers allows detection of lesions smaller than 2 cm (8). MR imaging provides information about local stage and lymph node involvement that is similar to that available from

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CT (2,4, ing

1 5, 16).

The

over

CT

affords

ter detection sensitivity

and

advantages for

cancer

of tumor

thrombus

better

characterization

that staging

due

MR imagare

bet-

to flow of local

invasion of adjacent organs due to higher tissue contrast (17,18). At present, MR imaging offers no significant advantage over other modalities for characterization of the type of tumor. In our experience, MR imaging is most useful in patients who cannot tolerate iodinated contrast material. MR imaging can be

Volume

12

Number

6

b.

a.

d.

C.

Figure

7. Complicated cyst in a 67-year-old man with chronic renal insufficiency. US had shown a complex renal mass. (a) Unenhanced CT scan shows a mass (arrow) that measures 23 HU. (b) Ti-weighted SE image shows the hypenintense mass (arrow), nearly isointense with fat. (C, d) On Ti- (c) and T2(d) weighted SE images with FS, the mass remains hypenintense (signal intensity, 291), indicating it is not a fat-containing lesion. Note another less hypenintense lesion (arrow in c). (e) On the enhanced Ti-weighted SE image with FS, the mass is not enhanced (signal intensity, 290), indicating it is a complex

cyst. A fluid-fluid

level is visible. The smaller lesion (arrow) appears dark. On review, it correlated with a simple cyst seen at US.

e.

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d.

C-

Figure

8.

Renal

carcinoma in a 5 i-year-old woman with a solitary kidney and renal insufficiency not yet requiring dialysis (serum creatinine level, 4.0 mg/dL 1353.6 pmol/L]). (a) Longitudinal sonogram shows a mass (arrows) in the echogenic right kidney (arrowheads). (b) Ti-weighted SE image demonstrates the mass (straight arrows), which is slightly more intense than the normal kidney; the inferior vena cava is free of thrombus (curved arrow). (c) On the T2-weighted SE image with FS, the mass is heterogeneous and hypenintense (arrow) but less hypenintense than complex cysts shown in previous cases (cf Fig 4b) . (d) On the enhanced Ti-weighted SE image with FS, the mass clearly enhances (and has increased heterogeneity) (arrows), indicating a diagnosis of tumor. A stage 1 renal carcinoma was removed.

performed gadopentetate diagnosis

before

and after dimeglumine

in patients

with

administration for noninvasive contraindications

contrast-enhanced CT or arteniography 8). Invasive procedures such as biopsy also

U

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to

(Fig can

be avoided.

Renal Carcinoma.-The pearance of renal carcinoma pending on the histologic the tumor and the presence

1106

of

U

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MR imaging is variable, differentiation of necrosis

et a!

apdeof or

cystic

change.

Small,

mostly

solid

to have signal intensity parenchyma on both

similar Ti- and

unenhanced

They

images.

may

tumors

tend

to that of renal T2-weighted be

difficult

to

identify unless they alter the shape of the kidney (Fig 1). Detection ofsmall tumors is much improved with use of gadopentetate dimeglumine (Fig 9). Although renal carcinoma increases in signal intensity after administration of contrast material, the enhancement is different than that of renal parenchyma, and the tumor is clearly recognizable (Figs 10, 1 1). Larger tumors tend to be more heterogeneous and sometimes contain areas of hyper-

Volume

12

Number

6

cL

Figure 9. 10.0 mg/dL mass. mine

Renal

carcinoma

in a 52-year-old

[884

p.mol/L).

(a) Unenhanced

A retroperitoneal mass whether it represented

geneous mass signal intensity enhances

(signal

carcinoma

and

intensity

on

regular

Ti-

and

mass

with

(Fig

The

indicating

T2-weighted

of the

visually

a diagnosis

images.

ofan

Ir-

of the may

be

enhancing,

in our

series.

If

not, signal intensity readings within a region of interest can be compared to quantify the increase in signal intensity after administration ofgadopentetate dimeglumine (Figs 9, 10). However, the imaging parameters used before and after contrast material enhance-

November

1992

after

on another scan, (b) T2-weighted

wall is indicative of carcinoma the possibility of a complex cyst. of renal carcinomas was usuapparent

diagnosed

obtained

and

renal

ureteral

failure

stent

(serum

creatinine

placement

shows

MR imaging was performed SE image reveals a hypenintense,

level,

no renal to deterhetero-

oftumor.

Left nephrectomy

revealed

a stage

1 renal

fibrosis.

periphery center

presence

newly

GRASS image (35#{176} flip angle) with FS shows the lesion (arrow), which has enhanced spoiled GRASS image (35#{176} flip angle) with FS, the mass (arrow)

retroperitoneal

a nonenhancing

12).

thick, irregular and excludes Enhancement readily

171),

with

CT scan

had been detected fibrosis or metastasis.

(c) Spoiled (d) On the

intensity,

idiopathic

enhancement

seen

ally

(arrow). of 87.8.

man

ment must be identical. In particular, images obtained without FS cannot be compared with those obtained with FS, since the scaling of signal intensities is different when FS is used. Unfortunately, the effectiveness of FS techniques varies in practice, and artifactual inconsistencies

may

occur.

inhomogeneities, shimming factors (eg, signal intensities brated and, in fact, do not any

specific

tissue

Because

parameter),

Rominger

of field

errors, and other are not calidirectly relate to differences

et a!

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d.

Figure

10.

isointense weighted a baseline

e. in a 61-year-old woman with hematuria. (a) Ti-weighted SE image shows an mass bulging the contour of the left kidney, well outlined by hyperintense fat. (b) On the TiSE image with FS, neither the kidney nor the mass can be easily seen; the image is valuable only as for documentation ofgadolinium enhancement. The mass (arrow) had signal intensity of i64, and

Renal

carcinoma

the renal parenchyma signal intensity was i60. (c) Enhanced Ti-weighted SE image with renal parenchyma and the mass enhance, but the mass (arrowheads) is clearly recognizable. ties of the mass and kidney angle) with FS clearly show

vaded.

signal care. as well

The inferior

intensity The signal as of the

were that

enhancing

readings intensities tissue

524 and the renal mass (M)is

395, vein well

respectively. (d, e) Enhanced (arrow in d) and inferior vena seen. A stage i renal carcinoma

should be used with of control tissues, of interest,

should

be

measured. Signal intensity measurements of the renal parenchyma, liver, and psoas muscle are useful because both the liver and kidneys should increase in signal intensity with gadolinium

enhancement,

but

muscle

change.

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shows

little

Visualization

FS shows Signal

that both intensi-

spoiled GRASS images cava (arrow in e) are was resected.

(35#{176} flip not in-

of tumor

margins

on contrast-

enhanced MR images can be improved with FS techniques. The contrast-to-noise ratio between brightly enhanced tumor and fat on Ti-weighted images and between high-signalintensity

tumor

and

fat on

T2-weighted

im-

ages is low; FS techniques improve the contrast-to-noise ratio (Fig 1 ib). Determination of the signal intensity characteristics of a mass is best done with standard SE Ti- and T2-weighted pulse se-

Volume

12

Number

6

b.

L

Figure 11 Renal carcinoma incidentally discovered on an angiogram obtained because of peripheral vascular disease. MR imaging was performed .

for staging.

slightly

(a)

Ti-weighted

hyperintense,

in the

lower

could

be due

SE image

renal

pole.

Such

to blood

with

SE image

FS clearly

slight

shows

in the penirenal

such lipid with

persistent hyperintensity lesion. (c) Enhanced FS shows the enhanced

was done,

mass

or glycogen.

mass

phrectomy carcinoma.

shows

heterogeneous

space

the

(arrow),

a

(arrow)

hypenintensity

(b) T2-weighted margin

of the

despite

FS;

is indicative of a nonTi-weighted SE image mass (arrow). Nerevealing a stage 2 renal

C.

quences. Detection of enhancement after administration of gadopentetate dimeglumine requires Ti-weighted imaging. Although, theoretically, gradient-recalled techniques provide poorer spatial resolution and signal-tonoise

ratio

than

SE techniques,

spoiled

GRASS

or similar pulse sequences performed during suspended respiration are very effective. Motion artifact is eliminated, which improves signal-to-noise ratio because, although signal intensity

may

be

low,

noise

from

motion

arti-

fact is very low. Relative Ti weighting can be achieved with the proper parameters, and FS techniques can be used (Fig 2). In one study, however, more lesions were found with enhanced Ti-weighted SE sequences than with

November

1992

enhanced fast low-angle shot (FLASH) Sequences (however, the FS technique could not be used with the FLASH sequence in this study)

(8).

Although gadolinium enhancement is useful for differentiating renal carcinoma from a complex cyst, it does not offer obvious advantages in staging and may make staging more difficult. Local and retroperitoneal adenopathy,

renal

vein

local extension, metastases are

or

inferior

vena

cava

bone metastases, important findings

Rominger

et a!

invasion,

and liver in staging.

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d. man with hematunia. a large renal or adrenal

C.

12.

Figure

quadrant vena

Renal carcinoma mass. (a) Enhanced

cava

involvement (M). The nodes (straight arrow). veals the heterogeneous also enhances, becoming

intense

mass

plane

ofseparation

spoiled

GRASS

image

rows).

Because

both

was

confirmed

These

can

images

hancement less

with

be well 12,

may

recognizable,

the liver

(arrowheads)

(35#{176} flip angle)

the tumor

seen 13).

make

with

is lost at the point FS shows

and the liver enhance,

the

ofinvasion

enhancing

mass

the tumor

margin

on unenhanced Contrast

nodes

material

and on

MR en-

metastases SE images

FS. On Ti-weighted images, nodes are conspicuous surrounded by high-signal-

intensity

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U

(e) Sagittal

from

the

right

is less well seen.

fat;

metastatic

U

(arrow).

arising

enhanced

kidney

Renal

(ar-

carcinoma

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when

the

nodes

increase

in sig-

nal intensity after contrast material administration, there is less contrast-to-noise ratio (Fig 1 2). Liver metastases become less obvious within several minutes after contrast material administration because there is equilibration of enhancement of liver tissue and obvious

1 1 10

right upper and inferior

of biopsy.

particularly

obtained without low-signal-intensity because they are

e.

Urography revealed a large tumor (M). Liver invasion

(arrow) were suspected. (b) T2-weighted SE image shows the heterogeneous, hyperinferior vena cava is free ofthrombus (curved arrow) but is displaced forward by Liver involvement is eyident (arrowheads). (c) Enhanced Ti-weighted SE image reenhancement of the mass typical of malignant tumor. The metastatic node (arrow) less obvious. (d) On the sagittal spoiled GRASS (35#{176} flip angle) image with FS, the

by means

(Figs

in a 52-year-old CT scan shows

deposits. on

Bone

enhanced

obtained

with

between

the

metastases

Ti-weighted

FS because

the

usual

low-signal-intensity

Volume

are

less

images contrast

metastasis

12

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C.

Figure mg/dL

13. [945.9 mass (M) but (arrows) The (M) and liver tastasis (arrow). the vertebral .

d. e. Renal carcinoma in a 72-year-old man with end-stage renal failure (serum creatinine level, 10.7 mol/LI). US had shown a right renal mass. (a) Unenhanced CT scan demonstrates a renal no metastases. (b) Ti-weighted SE image shows an isointense mass (M) and liver metastases inferior vena cava is clear of tumor. (c) On the T2-weighted SE image with FS, the renal mass metastases (arrows) are hyperintense. (d) Coronal Ti-weighted SE view shows a vertebral me(e) On the enhanced Ti-weighted SE image with FS, the renal tumor enhances (arrows), but lesion is not as well seen. Contrast between tumor and marrow is reduced by both FS and con-

trast agent enhancement. because of the metastases

The diagnosis was confirmed found on MR images.

and high-signal-intensity marrow fat is lost; enhancement may also make the lesion more inconspicuous. For lesions that have invaded adjacent organs, enhanced MR images may fail

to demonstrate

both

tumor

(Fig

12).

and

the

invaded

tumor

organ

margin

because

enhance

with

biopsy,

and

pensation

unnecessary

are

the

surgery

preferred

was

MR

avoided

imaging

tech-

nique for clear depiction of the extent of tumon thrombus (Fig 14) (19). SE sequences are more likely to demonstrate intraluminal signal from slow flow, a finding that simulates thrombus. Although Ti-weighted images obtamed

with

gadolinium

show

enhancement

of

Venous invasion by renal carcinoma can be seen with SE pulse sequences; however, gradient-recalled sequences with flow com-

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Figure tumor Upper

14. Renal carcinoma in a 68-year-old man with hematunia. (a) Enhanced containing calcification (arrow) and invasion of the renal vein and inferior extent of the caval tumor was uncertain, and MR imaging was performed (b) T2-weighted SE image shows the heterogeneous mass, but its margins

ning. were not available). Calcification cyst are visible (arrow) Invasion

within

the mass

is not seen,

CT scan reveals a left renal vena cava (arrowheads). for staging and surgical planare indistinct (FS techniques

but the hypenintense

contents

of the renal vein and inferior vena cava is detectable heads). (c) Spoiled GRASS image (20#{176} flip angle) clearly shows the tumor thrombus ual flow in the inferior vena cava (arrow). (d) Spoiled GRASS image (20#{176} flip angle) shows that the thrombus (arrow) extends 4 cm superiorly. It did not extend to the phrectomy was successful, and the patient is free of disease 2 years later. Gadolinium aid in the diagnosis of this case.

tumor thrombus, such a demonstration does not add any useful information for a patient with renal carcinoma, since all thrombus must be considered tumor thrombus. Thus, gadolinium-enhanced sequences are not necessary for evaluation for tumor thrombus. Angiomyolipoma.-Angiomyolipoma benign tumor composed of fat, smooth muscle,

ofvariable and blood

is a amounts vessels. Be-

cause high

they

contain

signal

fat, angiomyolipomas

intensity

on

cysts,

which

may

sity on Tito diagnosis

U

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Ti-

and

lesion

contains

ing either on images of signal

also

have

high

have T2-

signal

and T2-weighted images, is precise demonstration fat.

persistence obtained

This

can

be

inten-

the key that the

done

by show-

of high signal intensity with water suppression

intensity

on

with FS (Fig 1 5). Because the lesion, enhancement

RadioGraphics

both

weighted images. The amount of fat can be quite variable, however. Because these tumors must be differentiated from complex

loss

U

calcified

d.

C.

1 1 12

ofthe

but subtle (arrow(arrowheads), with residobtained at a higher level right atrium. Radical neenhancement did not

.

images

or

obtained

of the vascularity of after contrast mate-

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Figure 15. Angiomyolipoma in a 41-year-old woman who sought evaluation because ofanxiety over a family history ofbreast cancer. US revealed an echogenic mass in the right kidney. (a) Enhanced CT scan shows a very heterogeneous mass (arrows) Despite some low-attenuation pixels, the presence of fat could not be documented. (b) Ti-weighted SE image shows the heterogeneous mass with some hypenintensity (arrow). (c) On the Ti-weighted SE image with water suppression, the hypenintensity persists, indicating the presence offat. Note the decrease in intensity ofthe liver and renal cortex (cfb). (d) On the Ti-weighted SE im.

age

with

FS, the

mass

(arrow)

spectively.

(e) On the enhanced

indicatin

enhancement,

but

is darker

(cfb).

Ti-weighted the

kidney

Signal

intensities

SE image enhances

more

with

of the

mass

FS, the mass

(signal

intensity,

and

kidney

has a signal

were

intensity

103

and

72,

re-

of 209,

324).

C.

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Figure 16. Oncocytoma in a 61-year-old man with prostate hypertrophy. An incidental renal mass was discovered at sonography. (a) Enhanced CT scan shows an enhancing mass (M) with a central scar. (b, c) Ti-weighted which is slightly chyma (arrowheads

SE images show the mass (M), intense than renal parenin b), and the central scar (arwhich is slightly darker than the rest more

rowheads in C), ofthe mass. (d) On the T2-weighted FS, the

mass

is slightly

less

intense

SE image than

normal

with renal

parenchyma of the right lower pole (arrow), but the central scar is more intense (arrowheads) (e) Enhanced Ti-weighted SE image with FS shows enhancement of the mass, but the central scar remains dark. The patient refused surgery or biopsy because he was asymptomatic. He has been followed up for 3 years, and the mass has not changed in size. .

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rial administration, as expected, does occur. In most cases, MR imaging is not needed to diagnose angiomyolipoma, since presence of fat can be demonstrated by thin-section CT, even without use of contrast agents. Other Tumors.-Although renal carcinoma is the most common solid renal neoplasm, a wide variety of other tumors occur in the kidney, including oncocytoma, transitional cell carcinoma, sarcoma, metastases, and lymphoma. To our knowledge, there has been little reported experience with MR imaging of such lesions, and imaging criteria that might allow accurate distinction of renal carcinoma from other renal neoplasms have not been described. Use ofgadopentetate dimeglumine may not be helpful in the differential diagnosis. This agent diffuses through the extracellular fluid space; thus, any perfused mass can be expected to show some enhancement and the mere presence of increased signal intensity does not necessarily indicate malignancy. Other imaging features must be used to make a correct diagnosis. Although probably not specific, there may be patterns of findings that allow certain diagnoses to be made. For example, an oncocytoma may have signal intensity similar to that ofthe kidney on Ti- and T2-weighted images. The tumor typically contains a central scar#{149} that has low signal intensity on Ti-weighted images and high signal intensity on T2weighted images. After contrast material administration, rather homogeneous enhancement of the tumor occurs, but the central scar remains dark (Fig 16). ‘

U SAFETY AND EFFECTWENESS GADOPENTETATE DIMEGLUMINE Although concern about the safety pentetate dimeglumine in patients disease is natural since it is excreted sively

by

the

kidney,

in fact,

the

agent

OF of gadowith renal excluis well

tolerated by such patients. None of the 26 patients we examined with gadopentetate dimeglumine had any adverse effect to the agent. Of the eight patients with preexisting renal insufficiency, none had alteration of renal function after undergoing gadoliniumenhanced MR imaging (serum creatinine values remaining unchanged) . Neither of the two patients with a prior reaction to iodinated contrast material experienced any adverse effect from gadopentetate dimeglumine.

November

1992

Of the 26 patients with suspected renal masses, nine had findings indicative of a complex cyst, and none of the nine has subsequently been shown to have a tumor during a follow-up of 2-20 months. One patient had a perinephric hematoma, with no mass. Sixteen patients had an enhancing mass, indicative of neoplasm. Of these 16, 1 1 had renal carcinoma proved by means of biopsy or nephrectomy, and one each had a myofibroma of the kidney (pathologically proved), an angiomyolipoma, and an oncocytoma (being followed up). One patient died of myocardial infarction the day before scheduled nephrectomy and one refused surgery; both were thought to have renal carcinoma. In summary, no lesion in our

series

that

enhanced

with

the

gadolin-

ium agent has been shown to be a cyst, but three benign neoplasms enhanced. The angiomyolipoma and oncocytoma were recognized by other imaging features (ie, presence of fat and central stellate scar, respectively). U CONCLUSIONS The use of gadolinium-enhanced sequences greatly improves the detection and characterization of renal masses with MR imaging. In our series, MR imaging enabled 100% accuracy in distinguishing complicated cysts from malignant tumors, although in some cases there was no pathologic verification and in some of those the follow-up period was relalively short. Not

all

patients

benefit

from

MR

imaging;

those with obvious advanced disease demonstrated by CT do not need to undergo MR imaging. Because CT is less expensive and widely available, it should remain the standard method for renal mass evaluation for patients with no contraindication to iodinated contrast material for enhanced CT. Patients with chronic renal failure (who seem prone to develop complicated renal cysts) or with a history of adverse reactions to iodinated contrast material benefit most from gadolinium-enhanced MR imaging, since it allows confirmation or exclusion of a diagnosis of renal carcinoma without significant risk. Adverse affects from gadopentetate dimeglumine in patients with renal failure have not been reported in the literature to our knowledge (12,20). However, the exact fate of the

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gadopentetate

dimeglumine

patients

remains

complex

unclear

imaging enhanced

in such

(21).

Gadolinium enhancement does not significantly improve the accuracy of staging renal tumors with MR imaging in our experience. Given this, and the limited amount of time that an ill patient will be able to remain in the imager, it may be more helpful to obtain 5everal unenhanced images to completely stage tumors in patients with advanced disease. Gadolinium

enhancement

patients

with

small

is most

masses

useful

in

the

key

in whom

9.

10.

plasms.

12.

any

vascular

lesion

will

en-

hance with gadolinium; thus, both benign and malignant lesions will show enhancement. Further study is needed to determine if there are differences in enhancement patterns that can allow renal carcinoma to be distinguished from benign renal neoplasms. U

13.

REFERENCES 1.

Quint

LE, Glazer

GM,

Chenevert

vivo and in vitro MR imaging histopathologic correlation

2.

3.

4.

5.

Detection

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masses:

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tomography,

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and pulse

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se-

quence optimization. Radiology 1988; 169: 359-362. Fein AB, Lee JKT, Balfe DM, et al. Diagnosis and staging of renal cell carcinoma: a comparison ofMR imaging and CT. AJR 1987; 148: 749-753. Amendola MA, King LR, Pollack HM, Gefter W, Kressel HY, Wein AJ. Staging of renal carcinoma using magnetic resonance imaging at i.5 tesla. Cancer 1990; 66:40-44. Hricak H, Thoeni RF, Carroll PR, Demas BE, Marotti M, Tanagho EA. Detection and staging of renal neoplasms: a reassessment of MR imaging. Radiology 1988; 166:643-649. Warshauer DM, McCarthy SM, Street L, et al. specificities

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TL, et al. of renal tumors:

is.

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17.

18. i988;

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comparison

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1.5-T

dimeglumine:

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Vorreuther R. Krestin GP, Franzen W, Engelking R, Friedmann G. Clinical value of new rapid nuclear magnetic resonance tomogra-

ofCT and MR. Urologe i990; 29:39-42. Cornud F, Bnis C, Distefano D, et al. Magnetic resonance imaging and preoperative

thrombi:

21.

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kidney: the results 1991; 25:11-

Ann Urol

Liedl B, Schmidt H, Mayr B, Beer G, Jocham D. NMR tomography clinical

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HausteinJ,

NiendorfP,

cava

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tial diagnosis and therapy. 1990; 57:447-450. Roubidoux MA, Dunnick NR, Sostman Leder RA. Renal carcinoma: detection venous extension with gradient-recalled imaging. Radiology 1992; 182:269-272. erance

MR

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spleen, stomach, and pancreas. AJR 1992; 158:303-307. Bosniak MA. The current radiological approach to renal cysts. Radiology 1986; 158:1io. Rofsky NM, WeinrebJC, Bosniak MA, Libes RB, Birnbaum BA. Renal lesion charactenization with gadolinium-enhanced MR imaging: efficacy and safety in patients with renal insufficiency. Radiology 1991; 180:85-89. Marotti M, Hnicak H, Fritzsche P, Crooks LE, Hedgcock MW, Tanagho EA. Complex and simple renal cysts: comparative evaluation with MR imaging. Radiology 1987; 162:679684. Hilpert PL, Friedman AC, Radecki PD, et al. MRi of hemorrhagic renal cysts in polycystic kidneydisease.AJR 1986; i46:ii67-ii72. Auberton E, Bellin MF, Richard F, Chatelain C, Delcourt A, Grellet J. Comparative study ofMRI and CT x-ray in evaluating the exten-

evaluation apropos 17.

um-enhanced and fat-saturation MR imaging ofrenal masses. Radiology 1991; 178:803-

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phy in preoperative assessment of hypernephroma: a prospective comparative study

and

MA, Macillalesions: con-

gadolinium-

70: 327-336.

i9.

Kroeker Renal

with

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sion of kidney

169:363-365. Eilenberg 55, LeeJKT, BrownJJ, Mirowitz SA, Tartar VM. Renal masses: evaluation with gradient-echo Gd-DTPA--enhanced dynamic MR imaging. Radiology i990; i76:333-338. Semelka RC, Hnicak H, Stevens 5K, Finegold R, Tomei E, Carroll PR. Combined gadolini-

809. Semelka RC, ShoenutJP, han RG, Greenberg HM.

and

spin-echo

breath-hold FLASH techniques. Radiology 1992; 182:425-430. Mirowitz SA, Gutierrez E, LeeJKT, BrownJJ, Heiken JD. Normal abdominal enhancement patterns with dynamic gadolinium-enhanced MR imaging. Radiology 1991; 180: 637-640. Hamed MM, Hamm B, Ibrahim ME, Taupitz M, Mahfouz AE. Dynamic MR imaging of the normal

11.

nonenhanced

fat-suppressed

abdomen

question is whether the mass is a tumor or a benign cyst. In our series, all masses that enhanced after contrast material administration were neoHowever,

with

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MR

G.

Renal

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patients with chronic renal failure. diol 1992; 27:i53-i56. Schuhmann-Giampieri G, Krestin

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