DOI:10.2214/AJR.06.1509
AJR 2007; 188:W493
© American Roentgen Ray Society
Reply
Çetin Atasoy and
Elif Özyürek
Ankara University Medical School, Ibn-i Sina Hospital, Ankara,
Turkey
WEB—This is a Web exclusive article.
We thank Drs. Covey and Brown for their interest in our article,
"Prevalence and Types of Main and Right Portal Vein Branching Variations
on MDCT" [1]. We would
like to address their concerns regarding the similarity between our findings
and their findings.
We are astonished at how the authors found the results of the two studies
"similar." When one reads and compares the two articles with
modest care, he or she will quickly grasp the major differences in the
methodology used and, perhaps more important, the results reached.
Unlike the study of Covey et al.
[2], we evaluated separately
the variations involving the main portal vein ramification and right portal
vein ramification. In the Results section, we presented our findings
separately. To summarize, 34.5% of our patients showed variations only in the
main portal vein ramification. This is higher than most of the former studies,
including that of Covey et al.
[2], in which the relevant
figure is 22% (the sum of 9% with type 2 variation and 13% with type 3
variation, as presented in Table 1 of their study). More specifically,
although 9.5% of our patients had type 2 main portal vein anatomy, similar to
the 9% in the older study, 23.5% had type 3 anatomy, very much different from
the 13% reported by Covey et al. When we total the frequencies of type 2 and
type 3 anatomy in our study and their study, we find 33% and 22%,
respectively. If these figures are similar, then Drs. Covey and Brown are
right in their arguments.
Drs. Covey and Brown must have failed to recognize the separate
presentation of right portal vein branching variations in our study. Briefly,
22 of 131 patients with type 1 main portal vein anatomy had variant right
portal vein branching, which was 11% of the total study group. If we add this
11% to the 34.5% of patients with variant main portal vein branching, we reach
45.5%, which is also quite different from the 35% reported by Covey et al.
[2]. The types of variations
involving the right portal vein branch are also different in the two studies,
but a detailed discussion of these variations is beyond the scope of this
letter.
We believe these major differences might have resulted from the different
methodology used in the two studies. We evaluated the thin overlapping axial
sections obtained with a helical MDCT scanner and 3D reconstructions. In their
article, Covey et al. [2] have
already admitted that the study was potentially limited by its retrospective
nature and the use of thick nonoverlapping 7-mm axial slices that did not
allow 3D reformatting. Notwithstanding this admission, Drs. Covey and Brown,
in their letter, appear to ignore the potential benefit of 3D images in the
detection of subtle variations or the differentiation of those variations from
each other. Although the different genetic backgrounds of the two populations
may have had an effect, we believe the differences might also have resulted
from the 3D reconstructions routinely obtained in our study.
Finally, we apologize for not including their valuable study in our
reference list and thank the authors for giving us this opportunity to reveal
the striking disparity between the two studies.
References
- Atasoy Ç, Özyürek E. Prevalence and types of main
and right portal vein branching variations on MDCT.
AJR 2006; 187:676
-681[Abstract/Free Full Text]
- Covey AM, Brody LA, Getrajdman GI, Sofocleous CT, Brown KT.
Incidence, patterns, and clinical relevance of variant portal vein branching.
AJR 2004; 183:1055
-1064[Abstract/Free Full Text]
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