Department of Medicine University of Hong Kong Queen Mary Hospital Hong Kong, China
Sir,
We read with interest the article by Patil et al. [1] reporting on the use of helical CT angiography in evaluating living renal donors (LRD). We have previously compared the accuracy of helical CT angiography with conventional renal arteriography in the evaluation of Chinese LRD subjects, and found a much lower incidence of multiple renal arteries (11% vs 25.5%) with equal distribution on each side [2]. In the report by Patil et al. [1], the apparently higher incidence of multiple vessels in the left kidney (31% vs 20% on the right) could well be due to sheer chance, noting the lack of statistical data, and that another report [3] on Caucasoid subjects showed no side preference for the occurrence of multiple renal arteries.
Apart from delineation of vascular anatomy to decide which kidney is most amenable to harvesting and transplantation, another value of subjecting potential LRD to angiography is to diagnose unsuspected renal vascular and parenchymal diseases. While we agree that helical CT may have its limitation in detecting fibromuscular dysplasia, we wish to point out that it may be superior in diagnosing solitary ostial renal artery stenosis that may be totally missed by conventional arteriography [2]. This is because CT eliminates catheter-related error, which invariably occurs with selective renal arteriography, especially when there is a low clinical index of suspicion, such as in the pre-operative work up of normotensive LRD candidates.
While it is true that CT angiography involves a larger amount of radiocontrast than conventional arteriography, we do not agree that there is an increased risk of nephrotoxicity with the former. The smaller contrast volume injected directly into the renal arteries during conventional arteriography may have similar, if not higher, nephrotoxic potential due to its higher local concentration within the kidney than the larger volume used intravenously during CT angiography. In our cohort, serum creatinine levels were unchanged after either radiographic investigation [2]. Another advantage of CT over invasive angiography not mentioned by the authors is that total radiation exposure, particularly to staff, is conceivably much lower.
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