Contrast Jill V. Hunter,
MB,
BS, MRCP,
FRCR
Patricia
R. N. Kind,
#{149}
Media
PhD
Nonlonic lodinated Contrast Media: Potential Renal Damage Assessed with Enzymuria’ The potential of digital subtraction angiography (DSA) to enable study of the physiology of renal transplantation after a single intravenous injection of nonionic iodinated contrast material stimulated this investigation into the possible nephrotoxicity of the contrast material used. Levels of urinary enzyme activity, used as markers of renal damage, were measured before, immediately after, and up to 72 hours after intravenous injection of nonionic iodinated contrast material in two groups of patients undergoing DSA. Twenty-six patients had undergone renal transplantation and 10 control patients had normal renal function. Both groups showed a transient rise in the level of urinary enzyme activity that peaked within 24 hours and returned to levels obtained before DSA within 72 hours. In the transplantation group, the baseline levels of enzymes were higher, and the response after administration of contrast material was greater. Nevertheless, the duration of the response was the same as in the control group, and the enzyme levels of all patients returned to their pre-DSA baseline levels.
D
(DSA)
Contrast toxicity
giography,
81.12433
giography,
81.1243 1992;
Radiology
I
From
the
media, effects #{149} Con#{149} Digital subtraction an#{149} Enzymes #{149} Renal an-
183:101-104
Pathology
Address
reprint
Massachusetts
requests Division
General
Boston, MA 02114. C RSNA, 1992
contrast
material
dure
itself can
be
is able
to
simultaneously
about both structure and has been of use of the renal transplant and
ad-
and function in the assessment (1). The proce-
is relatively
noninvasive
performed (2).
on
tient basis The potential dinated contrast
an outpa-
nephrotoxicity media has
long
of iobeen
a cause for concern, especially in a transplanted kidney. The purpose of the study reported herein was to assess the degree and reversibility of any membrane damage to a trans-
planted an
kidney
that
intravenous
iodinated
contrast
compare
might
injection
this
of a similar
occur
material
finding
with
injection
after
of nonionic
and the
to effects
of contrast
rial in a group of patients kidneys. Nephrotoxicity
mate-
with normal was assessed
on the basis of changes in levels of urinary enzyme concentration, particularly (NAG), (AAP),
N-acetyl-3-D-glucosaminidase alanine aminopeptidase and y glutamyl transpeptidase
(GGT).
Measurement
zymes
has
index
been
of renal
of these shown
en-
of Radiology
(P.R.N.K.),
(J.V.H.)
St Thomas
to J.V.H., Department of Neurology,
Hospital,
Gray
II,
55 Fruit St,
with men,
cyclosporine aged 29-57
This
group
was
(six women years; mean, studied
and six 40 years).
17 days
to 9
months (mean, 3 months) after they had undergone transplantation. Five of the patients receiving azathioprine and 10 of the patients receiving cyclosporine had a serum creatinine concentration above the accepted upper limit of the reference range (ie, serum creatinine concentration > 120 p.mol/L). Ten consecutive patients referred to the radiology department for intravenous DSA were also invited to participate in the study. The patients in the control group were all normotensive, with normal renal function, as evidenced by a normal serum creatinine level and, when information was available, a normal glomerular filtration rate. They had no history of renal dysfunction. The control patients underwent DSA for reasons unrelated to renal disease. The nine men and one woman were aged 43-75 years (mean, 55 years). All patients were required to give written informed consent prior to entering the study, which had been approved by the local Ethics and Human Studies Committee. The characteristics of the patients who had undergone renal transplantation reflected those of a cross section of the transplantation population being monitored and managed at our institution.
to be a sensi-
tubular
damage
Clinical
Methods
(3-5). All patients were asked to fast for 4 hours prior to DSA, but no fluid restriction
AND
METHODS
Patients
Hospital, London. From the 1990 RSNA scientific assembly. Received November 29, 1990; revision requested January 3, 1991; revision received November 19; accepted December 2. of Radiology,
angiography
intravenously
information
PATIENTS
Departments
and Chemical
with
ministered
yield
tive Index terms: trast media,
subtraction
IGITAL
A total of 36 patients were studied. Twenty-six consecutive renal transplantation patients who were attending the outpatient clinic for a routine follow-up examination were invited to participate in the study. Fourteen of the transplantation patients were being treated with azathioprime (Wellcome Diagnostics, Research Triangle Park, NC) and prednisolone (Miles, Elkhart, Ind) (six women and eight men, aged 26-55 years; mean, 40 years). This group of patients was studied 6 weeks to 10.75 years (mean, 5.5 years) after they had undergone transplantation. Twelve of the patients were being treated
was
imposed;
mL H20
indeed,
was
examination. by
given
a water
orally
DSA studies
inserting
a 5-F
catheter
load
I hour
were into
of 200
before
the
performed the
right
atrium or superior vena cava via an antecubital or femoral vein, with a modified Seldinger technique, as a sterile procedure. Forty milliliters of nonionic iodinated contrast material (iohexol, Omnipaque [350 mg of iodine per milliterj; Nycomed, Oslo) was injected at a rate of 25 mL/sec for each acquisition. Patients
Abbreviations: dase, DSA
=
AAP = alanine aminopeptidigital subtraction angiography,
= v glutamyl transpeptidase, N-acetyl-3-D-glucosaminidase.
GGT
NAG
=
101
Resulis
of Mean
Urinary
Enzyme
Activity
from
Spot Urine
Samples
in 36 Patients Pati ents Who Underw
ent
Transplantation
Azathioprine Normal Serum Creatinine (n = 9)
Control Subjects (n
NAG
(U/mmol
urinary
Mean
7.00 7.80 10.40 7.80 8.00
132 1.00 1.68 1.02 1.46
10.65
1.33
12.30
1.21
11.20
9.21
2.02
18.48
7.78 10.52
1.09 0.99
15.05 10.46
2.13 1.07
12.30 10.20
1.45 1.91 1.11
0.63
10.50
1.34
5.52
1.42
7.86
1.09
6.30
1.74
3.56
2.59
331
0.46
1.12 0.58
3.24 5.47 4.09 3.60
0.56 0.34 0.80
3.10
4.60 4.08 8.16 5.28 4.00
1.40
3.98 3.43 3.38
0.86 0.49 0.89 0.73 0.46
0.77
5.96 3.32
0.49 0.40 1.18 0.44
1.62 1.93 3.69 1.72
0.17 0.26 0.55 0.21
1.31 1.50 2.69 2.29
0.25 0.21 0.42 0.72
1.81 2.04 4.98 4.02
0.34 0.27 0.34 1.10
1.53
0.18 3.87
1.02 100.2
0.21 6.63
1.88 180.4
0.15 21.9
1.33 128.9
0.42 17.2
3.77
=
standard
77.1
renal transplantation such injection of con-
trast
control
material.
The
2.77
patients
re-
ceived one to five injections (mean, three injections) of 40 mL of iohexol, depending on why they were undergoing DSA. Urine and blood samples were obtained immediately before and after DSA. Urine samples were also collected on the morning of the DSA
and
daily
for
2 more
days
at
intervals.
Nephrotoxicity
was
assessed
by
mea-
surement of the urinary activity of NAG, AAP, and GGT. NAG is a proximal renal tubular lysosomal enzyme, while AAP and GGT are present in the brush border cells of the proximal tubule. All of these enzymes have been shown to be sensitive markers of nephrotoxicity and have been used extensively in the clinical environment
to document
Laboratory Urine
damage
were as the
were
urine
stored
samples
analyzed final
Radiology
#{149}
Mean
SEM
Mean
All
Creatinine (n = 10)
Patients (n = 12)
SEM
Mean
SEM
Mean
SEM
8.30 5.25 8.70 17.15 9.90
2.12 2.62 3.39 13.2 2.40
31.46 27.51 40.98 36.41 30.78
3.73 3.71
27.60 23.80
5.95 5.56
4.66
35.60
8.11
8.45 4.75
33.20 27.30
7.54 7.80
2.18
0.52 0.65
3.72 3.16 2.82
0.71 0.71 0.79 0.06 0.03
specimen
1.09
1.49 1.69
0.19 0.17
1.35
1.15
331
0.47
2.91
0.54
2.75 2.55 1.35 110.5
2.76 2.40 0.07 636
used.
In all three assays, use of a small volume of sample relative to the volume of bufferreduced
to a minimum
any
in-
terference by inhibitors. It was therefore not necessary for the samples to undergo dialysis before measurement of enzyme activity. The concentration of nonionic at 4#{176}C prior from
a single
simultaneously had
been
as re-
ceived. Urinary NAG activity was measured by using an automated fluorometric procedure (14), with minor modifications (15). GGT activity was measured by using centrifugal analysis (Centrifichem 400; Union Carbide, Danbury, Conn) with kit reagents (catalog no. 543098; Boehringer Mannheim, Indianapolis, md).
102
SEM
A method for analysis of AAP activity (16) was adapted for the centrifugal analyzer. Twenty microliters of urine was diluted with 65 L of buffer (tromethamine [TRIS] hydrochloride, 59 mmol/L; pH, 7.8) and 250 L of alanine-4-nitro-analide hydrochloride (2.6 mmol/L in buffer) to give a final optimum substrate concentration of approximately 2 mmol/L. The reaction was carried out at 37#{176}C, and the optical density of the released p-nitroalanine was read at 405 nm. The enzyme activity in units per liter was calculated by using a factor of 1,776 to take into account the molar extraction of p-nitroanaline and the volume of urine and of buffer-substrate
substrate
(3-13).
Methods
The
patient soon
renal
samples
to assay.
Mean
High
Serum
2.34
4.36
0.51
4.93 9.10 5.93 4.69
0.67 1.17
0.64
5.98
0.64
4.95 10.43
9.26 6.04 188.1
4.00 4.50
0.60
8.20 5.47
0.57
4.38
0.99 0.95
5.21
0.71
0.96 1.80 1.03 1.12
1.60 1.47
4.32
1.75
9.15
2.23
1.80
8.14
1.02
5.26 175.20
2.42 2.02
38.3
25.1
of the mean.
error
who had undergone received only one
after
Patients (n = 14)
SEM
DSA
Note.-SEM
24-hour
Creatinine (n = 5)
Normal Serum Creatinine (n = 2)
creatinine)
Day 2 Day 3 Day 4 AAP (U/mmol of urinary creatinine) Before DSA After DSA Day 2 Day 3 Day 4 Serum creatinine (.tmol/L)
day
SEM
All
Mean
DSA
After
10)
High
Serum
of
urinary creatinine) Before DSA After DSA Day 2 Day 3 Day 4 GGT (U/mmol of Before
=
Cyclosporine
contrast
material
in the
urine,
after
a sin-
gle intravenous injection, was calculated. A quantity of contrast material was then added to one-half of a pre-DSA sample of urine to simulate a “physiologic” content of filtered contrast material. Both halves of the sample were then analyzed; no differences were found in the enzyme activities. It was therefore shown that contrast material present in the concentrations to be found in urine did not alter the assay results. Urine enzyme levels were expressed as
a ratio thereby
of urine creatinine concentration, compensating to some degree for variations in the rates of flow of urine (7,17). In this study all three enzymes were expressed in terms of level of urine creatinine, which was measured with a centrifugal
analyzer
by
using
the
standard
alka-
line picrate method. The baseline values were compared with established normal reference values for NAG ( < 10 U/mmol urinary creatinine), GGT ( < 5.9 U/mmol urinary creatinine), and AAP ( < 1.5 U/mmol urinary creatinine) (17).
RESULTS The Table.
results are summarized The data were analyzed
ing standard statistical are displayed in Figures baseline enzyme levels just above the reference
in the by us-
methods and 1-3. The were within ranges for
or
the 10 control patients (an older age group), for the nine transplantation patients who were treated with azathioprine and who had serum creatinine levels in the normal range (mean, 100.2 imol/L), and for the two transplantation patients who were treated with cyclosporine and who had serum creatinine levels in the normal range (mean, 110.5 p.mol/L). The baseline levels of NAG and AAP for patients who were treated with cyclosporine and who had elevated serum creatinine levels (mean, 188.1
April
1992
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values
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were the
had
serum
creatinine
of patients with elevated for all patients by group.
approximately
upper
limit
of normal.
levels serum Mean
activity
followed
the
pattern
183
Number
#{149}
1
120 i.mol/L levels ±
(normal).
(>
standard
120
error
(b, c) Curves
p.mol/L)
and
of the mean
show
(c) com-
are plotted.
of the
Several icity
mechanisms
secondary
of nephrotox-
to administration
Figure
3.
urinary
Graphs
depict
GGT before
levels
DSA and
of activity
of
immediately
after DSA and at 24, 48, and 72 hours after DSA. (a) Curves show the responses of patients in the three groups who had serum creatinine levels below 120 imol/L (normal). (b, c) Curves show (b) responses of patients with elevated serum creatinine levels ( > 120 p.mol/L) and (c) composite values for all patients by group. Mean values ± standard error of the mean are plotted.
increased more than levels of either GGT or NAG. Since AAP is localized superficially in the brush border membrane, it may be released more
DISCUSSION
The
control group, albeit at a higher level. Thus in all patients, irrespective of their serum creatinine status, urinary enzyme activity returned to the preDSA baseline levels. Volume
below creatinine values
three
baseline levels of NAG and AAP for the patients who were treated with azathioprine and who had elevated serum creatinine levels (mean, 170.1 p.mol/L) were just above the reference ranges. The urinary enzyme activity in all groups rose within 24 hours of DSA and returned to pre-DSA levels within 72 hours; the predominant effect was on the level of AAP. Patients who had undergone renal transplantation and who had normal creatinine levels had levels of enzymuria similar to those of the control group. Most of the abnormal elevation in enzyme levels was seen in patients with high initial serum creatinine levels. It should be noted, however, that even in these compromised patients, the pattern of enzyme
L4()
Tim.
C.
1, 2. (1) Graphs depict levels of activity of urinary NAG before DSA and immediately after DSA and at 24, 48, and 72 hours after DSA. (a) Curves show the responses of patients in the three groups who had serum creatinine levels below 120 imol/L (normal). (b, c) Curves show (b) responses of patients with elevated serum creatinine levels ( > 120 p.mol/L) and (c) composite values for all patients by group. Mean values ± standard error of the mean are plotted. (2) Graphs depict levels of activity of urinary AAP before DSA and immediately after DSA and at 24, 48, and 72 hours after DSA. (a) Curves show the responses of patients in the
groups
F5
DSAPsst’DSA24s.,.4l,s72sss
Time
2c.
(b) responses
,,
Sample
Figures
three
S
2
of
easily
than
which
enzymes
nal damage instead of 32-microgIobulin, a low-molecular-weight protein, because of the greater stability of the enzymes. Measurement of urinary
gested that the enzyme release was part of a diuretic phase response (12). In four patients studied more recently, levels of AAP were found to be higher at 12 hours than at 24 hours
NAG
after
activity
used
as markers
of re-
is a well-established
NAG,
membrane
is integrated
into
were
the
GGT,
iodinated contrast material have been proposed (18). These include glomerular injury, as evidenced by nonspecific proteinuria, and tubular injury, reflected by increased activity of tubule-specific enzymes in the urine. In our study, levels of specific urinary
which
Burchardt tients
phritis, crease
itself
(3,11),
is a lysosomal
et al, when with
acute
found in AAP
administration
DSA,
studying
or chronic
papyelone-
a four- to fivefold excretion after of diatrizoate
which
or
enzyme.
would
inand
sug-
be in keeping
means of detecting and monitoring renal damage (3-10). The activity in the urine of both GGT and AAP, two proximal tubular brush border en-
with this hypothesis. The minor changes seen in the level of AAP in the control group and in the azathioprime-treated transplantation group
zymes,
may,
has
also
been
shown
to be in-
creased with renal damage, and measurement of their levels can be used for monitoring nephrotoxicity (11-13). Endogenous renal GGT is a sensitive indicator of renal ischemic injury and renal homograft rejection in humans (13). In our series, levels of AAP
therefore,
be the
result
of in-
creased fluid intake (as part of the preparation for the procedure) rather than of direct tubular cell damage, especially since there was no significant rise in NAG or GGT activity (which would be considered an mdication of nephrotoxicity). Radiology
103
#{149}
The enzyme levels of all patients with a normal serum creatinine value behaved in a comparable fashion. In
In this study of the effects of nonionic iodinated contrast material on the kidney as evaluated on the
those
basis
of urinary
tion,
the
patients
with
elevated
serum
creatinine levels, findings were interesting in the patients treated with cyclosporine compared with findings in the patients treated with azathioprime: Not only did the patients treated with cyclosporine have higher baseline levels of enzyme activity, but they
also
had
the
greatest
response
to
the administration of nonionic contrast medium. This difference in enzyme activity might be explained by the fact that transplantation had been performed more recently in the group receiving cyclosporine (mean, 3 months) than in the group receiving azathioprine (mean, 5.5 years); hence, there was a difference in the duration of immunosuppressive therapy. However, there is evidence that patients treated with cyclosporine tend to have higher serum creatinine levels than patients treated with azathioprine and steroids (19). This was also observed in our study: Patients treated with azathioprine had a mean serum
creatinine
level
icily, an
with
normal
serum
104
Radiology
#{149}
abnormally
creatinine
in
with who
10.
11.
duced
even
by
a rise
in those high
concentration.
baseline
by aminoglycosides
2.
3.
4.
5.
of transient
Meaney TF, GallagherJH. Use of digital subtraction angiography to assess function. In: Price RR, Rollo FD, Monahan WG, James AE, eds. Digital radiography: a focus on clinical utility. New York: Grune & Stratton, 1982; 235-243. Meaney TF, Weinstein MA, Buonocore E, et al. Digital subtraction angiography of the human cardiovascular system. AIR 1980; 135:1155-1160. Hartmann HG, Braedel HE, Jutzler GA. Detection of renal tubular lesions after abdominal aortography and selective arteriography by quantitative measurements of brush border enzymes in the urine. Nephron 1985; 39:95-101. Skovgaard N, Holm J, Hemmingsen L, Skaarup P. Urinary protein excretion following intravenously administered ionic and non-ionic contrast media in man. Acta Radiol 1989; 30:517-519. Severini G, Aliberti LM. Variation of unnary enzymes N-acetyl-beta-glucosaminidase, alanine-amino-peptidase, and lysozyme in patients receiving radio-contrast
agents. 6.
creatinine 7.
of 8.
Clin Biochem
1987; 20:339-341.
Price RG. Urinary enzymes, nephrotoxicity and renal disease. Toxicology 1982; 23: 99-134. Wellwood JM, Ellis BG, Price RG, Hammond K, Thompson AE, Jones NF. Urinary N-acetyl-beta-D-glucosaminidase activities in patients with renal disease. Br MedJ 1975; 139:408-411. Kunin CM, Chesney RW, Craig WA, England AC, DeAngelis C. Enzymuria as a
studies
in human
kid-
14.
a sensitive 1.
and disease:
jury in experimental animals and renal homograft rejection in man. Ann R Coll Sung EngI 1975; 57:248-261. Tucker SM, Boyd PJR, Thompson AE, Price
with serum
#{149}
injury
13.
12.
in urinary
patients
of renal
neys. In: Fillastre JP, ed. Nephrotoxicity: interaction of drugs with membrane systems mitochondnia-lysosomes. New York: Masson, 1978; 167-174. Burchardt U, Haschen RJ, Krosch H. Clinical usefulness of enzyme determinations in urine. In: Dubach UC, Schmidt U, eds. Diagnostic significance of enzymes and proteins in urine. Bern: Huber, 1979; 106112. Ward J. Gamma-glutamyl-transpeptidase,
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rise in urine enzyme activity after administration of nonionic contrast material was similar to the pattern of patients
rise
in a transplanted result in nephrotox-
as measured
enzymes,
of 170.12
levels who had undergone transplantation. This same pattern was also seen in healthy subjects in our series, which is in keeping with the results other authors (20).
9.
activ-
high serum creatinine levels were treated with cyclosporine. The level of NAG was least affected, and in all cases the enzyme changes were transient, returning to baseline levels within 72 hours. These data lead us to conclude that DSA performed with a
ture and function kidney does not
Despite the higher mean age of the control patients (55 years) and the increased dose of contrast material pattern
concentra-
enzyme
ity was small, except for the AAP in the group of patients
rial.
the
enzyme
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single intravenous injection of contrast material to examine renal struc-
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Sweny P, HopperJ, Gross M, Varghese Z. Nephrotoxicity of cyclosponine A. Lancet 1981; 1:663. Khoury GA, HopperJC, Varghese Z, et al. Nephrotoxicity of ionic and non-ionic con-
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