Radiological imaging studies are needed for
follow-up and treatment decision of an aortic aneurysm, which is a disease with a high mortality rate.[5] These
radiological imaging modalities should be threedimensional
with a high spatial resolution and contrast
enhancement to be used in the decision making
of surgical or endovascular treatment methods. In
particular, the morphological eligibility criteria of the
aneurysms for EVAR procedure should be evaluated,
which has been increasingly preferred recently to
surgical procedures.
The CTA is a worldwide approved standard
method used in the planning and follow-up of
endovascular treatment.[1,2] It is well known that
contrast agents used in CTA are nephrotoxic and tend
to lead to CIN; therefore, morbidity and mortality
rates increase leading to longer hospitalization
duration and increased medical expenses.[6,7] Patients
with aortic aneurysms are more often elderly having
other comorbidities. Diabetes mellitus and renal
injury are the most common comorbidities in these
patients.[5]
The most important reason for CIN is impaired
kidney functions, and another significant risk factor
is the amount of contrast agent used.[3,4] Patients
with aortic aneurysms are exposed to large amounts
of contrast agent during treatment planning, during
EVAR, and during follow-up after EVAR. This
condition also carries a high risk for the development
of CIN in patients with CKD and aortic aneurysms.
Thus, alternative imaging methods to CTA are needed
to consider in these patients.
All these limitations led us to seek an easy
applicable, operator-independent technique which
can be used in CKD patients before and after EVAR
with a high resolution and sufficient anatomical
details and without aggravating the already impaired
renal functions or causing new renal injuries. In the
present study, we used the TA-CTA technique to
overcome these limitations. We obtained sufficient
IQS (mean: 3,495) from all 17 TA-CTA procedures.
None of the patients developed procedure-related
contrast material nephrotoxicity or complications. In
12 procedures, the mean creatinine levels on Days
2-5 after the procedure were lower than the baseline
levels, which can be related to the precautions taken
to decrease CIN, particularly adequate hydration
(saline, sodium bicarbonate infusions) before a after the procedures, erythropoietin treatment in
patients with renal anemia (hemoglobin values below
11 g/dL, erythrocyte suspension was replaced),
avoiding the unnecessary use of loop diuretics,
antibiotics and nonsteroidal anti-inflammatory drugs,
discontinuation of angiotensin-converting enzyme
inhibitors and/or angiotensin II receptor blockers
24 h before the procedure, preventing hypotension
and dehydration, and continuation of regular statin
use. There are many studies suggesting that, beside
the use of low-dose contrast material, hydration is
the most important measure in the protection from
CIN.[8] The comparison of baseline serum creatinine
and eGFR values with post-procedural short- and
long-term serum creatinine and eGFR values showed
a significant difference in favor of eGFR values only
between baseline and at Months 1-3.
To the best of our knowledge, there is no study
similar to ours concerning EVAR planning and
follow-up with the use of very low contrast material.
However, in a similar study including eight patients
with CKD, Isaacson et al.[9] reported that that low-dose
iodine TA-CTA was a feasible option for EVAR
planning. Also, Joshi et al.[10] used an intra-arterial
low-dose contrast agent with CTA in the evaluation of
pelvic blood vessels of patients with renal insufficiency undergoing percutaneous aortic valve replacement and
they mixed normal saline and 10 to 15 mL of contrast
agent with a ratio of 3:1 and 4:1 and, then, injected the
mixture through a pigtail catheter which was inserted
into the abdominal aorta at the infrarenal level. Prior
to the intraarterial CTA, they performed pelvic digital
subtraction angiography to ensure the catheter level.
The mean baseline eGFR values before the procedure
was 54.8±3.9 mL/min/1.73 m2. The authors conclude
that there was no significant difference in the eGFR
values before and 72 h after the procedure. In our
study, we successfully scanned a larger area with
the use of less contrast material (8 and 16 mL) after
we placed the flush catheter and also lowered the
additional contrast load by avoiding angiography.
Furthermore, the mean baseline eGFR value in our
patient group was 32.2 mL/min/1.73 m2, indicating a
much lower value.
For the thoracoabdominal and abdominal
TA-CTA, we used 16 mL and 8 mL of contrast agent,
respectively. There was no statistically significant
difference in the renal functions or the IQS between
the two doses. However, the non-significant difference
between 8 mL and 16 mL contrast agent can be
attributed to the length of the area scanned. The
non-significant difference on renal functions between
the two doses suggests that 16 mL of contrast agent
can be safely used in TA-CTA with a better image
quality.
The insufficient amount of contrast used in the
detection of type 2 endoleak caused by retrograde
reflux after EVAR in control patients may be a
limitation to the present study. To eliminate this
deficit, we performed additional CDUS on the control
group after EVAR. Type 2 endoleak was detected in
only one patient by CDUS. The endoleak detected on
CDUS was also clearly visible on TA-CTA (Figure 3).
Figure 3: An example for type 2 endoleak and IQS 4.
TA-CTA and CDUS images performed on an 80-year-old
man with an abdominal aortic aneurysm and chronic kidney
disease after EVAR. (a-c) Type 2 endoleak can be seen easily
in both of axial images, CDUS images, and its spectral
analysis. (d) Distal branches of visceral arteries and femoral
arteries are seen, as well as aorta on the axial and volume
rendered images.
TA-CTA: Transarterial computed tomography angiography; EVAR:
Endovascular aortic aneurysm repair; CDUS: Color Doppler ultrasound.
In general, the amount of contrast agent used
during EVAR is very high. It would be appropriate
to lower the use of contrast during imaging methods
and to use techniques that would lower the amount of
contrast used during procedures in CKD patients, as
in our study. For this purpose, among the endovascular
abdominal aortic repair methods, stenting and renal
artery catheterization technique with carbon dioxide
(CO2) has come to the forefront.[11] The CO2 is
a gas with negative contrast features. Aortic stent
procedure with CO2 is a safe and successful method.
Due to the low contrast resolution of CO2, special
post-processing software and automatic gas injectors
providing continuous gas infusion are necessary.[12]
Aortic stent procedure takes longer; therefore, the
amount of radiation received increases. The most
important theoretical risks are stroke and ischemia
of the spinal cord in supradiaphragmatic use.[13] In
addition to being an inexpensive negative contrast
material, there is no CO2 tube regulator system for
pressure regulation during injection in Turkey and,
therefore, its use is not widespread in our country.
In a study conducted by Canyigit et al.,[14] the renal
artery catheterization technique was used in 16 patients
with impaired renal functions, and no significant
difference was found in the serum creatinine and
eGFR values before and 72 h after the procedure. The
technique is based on catheterization of the renal artery
with Simmons catheter without the use of contrast and
the renal artery level is localized without the use of
aortography. Thus, the use of high amount of contrast material for the detection of renal artery level during
EVAR and the repeated use of aortographies for
distance determination while first placing the stent is
not required. In the aforementioned study, the lowest
possible amount of contrast material was used and
the procedure was completed. The risk of CIN was
minimized by intravenous hydration before and after
the procedure. Of note, in CKD patients with aortic
aneurysms, the use of lowest possible contrast dose is
of utmost importance during diagnosis, treatment, and
follow-up to minimize the risk of CIN.
Main limitation in our study was the low number
of patients.
In conclusion, the TA-CTA obtained with
diluted low-dose contrast material in CKD patients
with an aortic aneurysm is an invasive, but safe
and easy-to-use method which provides sufficient
anatomical details without causing CIN risk. Further
large-scale, prospective studies are needed to confirm
these findings.
Declaration of conflicting interests
The authors declared no conflicts of interest with respect
to the authorship and/or publication of this article.
Funding
The authors received no financial support for the research
and/or authorship of this article.