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Letters to the Editor |
Department of Radiology II, University Hospital Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria, e-mail: ferdinand.frauscher@uibk.ac.at
Editor:
I read with interest the article by Dr Rouvière and colleagues in the December 1999 issue of Radiology (1) on the subject of preoperative assessment of ureteropelvic junction (UPJ) obstruction with helical computed tomographic (CT) angiography compared with intraarterial angiography.
In this study, helical CT demonstrated a sensitivity of 100% and a specificity of 96.6% for the depiction of crossing arteries when its findings were compared with those of digital subtraction angiography (DSA). Dr Rouvière and colleagues concluded that helical CT seems suitable to replace intraarterial DSA.
I agree with Dr Rouvière and colleagues that the use of noninvasive imaging will help in the selection of appropriate therapeutic strategies (ie, open or laparoscopic pyeloplasty vs endopyelotomy), and I would like to address an additional option.
Dr Rouvière and colleagues failed to discuss the value of color Doppler imaging for the detection of crossing vessels. We examined 29 patients with UPJ obstruction; crossing vessels were detected with contrast material–enhanced color Doppler imaging in 22 patients and with laparoscopy in 23 patients (2). Color Doppler imaging yielded a sensitivity of 96% and a specificity of 100%. Kil et al (3) examined 22 patients with UPJ obstruction and reported a sensitivity of 92% and a specificity of 100% with color Doppler ultrasonography (US) in the detection of crossing vessels.
These results clearly demonstrate that color Doppler imaging is a valuable tool for the detection of crossing vessels at the UPJ, and this imaging modality has shown a sensitivity and specificity equal to those of helical CT. In contrast to CT, color Doppler imaging has the benefit of being a nonradiating, noninvasive, and relatively inexpensive imaging modality.
According to Van Cangh et al (4), recognition of crossing vessels is the most important prognostic factor for success with endopyelotomy. Therefore, it is my opinion that adult patients who have UPJ obstruction should undergo imaging for the evaluation of crossing vessels.
At our institution, we have considerable experience with DSA, helical CT, endoluminal US, and color Doppler imaging. On the basis of this experience, we recommend the use of nonenhanced color Doppler imaging as the primary imaging modality, and if vessels are detected, no further work-up is needed. If no vessels are found, contrast enhancement should be performed. I believe that the use of helical CT should be reserved for cases where enhanced color Doppler imaging findings remain inconclusive.
REFERENCES
and
Xavier Martin, MD,
Departments of Radiology* and Urology, Pavillons P-V, Edouard Herriot Hospital, 5 place d’Arsonval, 69437 Lyon cedex 03, France, e-mail: olivier.rouviere@netcourrier.com
We thank Dr Frauscher for his comments. We agree that color Doppler imaging may be a potential tool for use in the detection of crossing vessels. The recent findings by Dr Frauscher and colleagues (1) demonstrate that color Doppler US performed by an experienced operator could be highly accurate in the depiction of crossing vessels. Moreover, compared with other imaging techniques (helical CT, endoluminal US, DSA), color Doppler imaging has the benefit of being a noninvasive and nonradiating modality. However, the use of color Doppler imaging as a first-line imaging modality in preoperative assessment of UPJ obstruction requires a couple of comments.
First, the strategy proposed by Dr Frauscher and colleagues (1) is cost-effective only if color Doppler imaging findings do not remain inconclusive frequently. It is important to distinguish the arteries crossing immediately adjacent to the UPJ (which are a relative contraindication to endopyelotomy [2]) and the arteries and veins passing within 1–2 cm of the UPJ (which are not a contraindication to endopyelotomy but may be damaged during the procedure [3]).
An accessory renal artery crosses the UPJ in only 11%–39% of patients with UPJ obstruction (2,4–8), whereas vessels that pass within 1–2 cm of the UPJ can be found in up to 75%–80% of patients with UPJ obstruction (3,9). It is not clear whether Dr Frauscher and colleagues (1) focused only on truly crossing vessels or on all the vessels passing near the UPJ. It also remains unclear whether color Doppler imaging allows sufficient delineation of the UPJ and the proximal ureter to discriminate truly crossing vessels from vessels passing near the UPJ. This is an important issue since it could allow a better understanding of what should be considered an inconclusive result of color Doppler imaging. (Is the result inconclusive only when the operator believes that the examination is incomplete? Or, when the UPJ cannot be confidently delineated? Or, should helical CT be performed routinely when no crossing vessel is seen at enhanced color Doppler imaging?) The answer to these questions would allow a better appreciation of the potential cost savings induced by the use of color Doppler imaging as a first-line imaging modality.
Second, color Doppler imaging is in current use as a screening method for many vascular diseases, but its acceptance by referring physicians as the sole preoperative imaging modality may cause problems. At our institution, helical CT has been easily accepted by referring urologists as a replacement for DSA in the preoperative management of UPJ obstruction. One of the reasons for this acceptance is that helical CT provides understandable images that clearly depict crossing vessels. When they perform endopyelotomy, urologists prefer to see on transverse CT images the exact location of vessels that may be damaged during the procedure. We are not sure that color Doppler imaging would have been so easily accepted and that urologists would have relied on the sole sonographer’s report to choose the surgical technique or the exact location of the endoscopic incision.
REFERENCES
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