LAUSR

Lee et al. addressed the clinical impact of split renal volume (SRV) calculated on the basis of the findings of computed tomography (CT) used to evaluate renal function in patients with renal cell cancer who underwent partial nephrectomy. Previous studies have shown the correlation between renal parenchymal volume determined by CT-based renal volumetry and loss of estimated glomerular filtration rate, and other studies of living kidney donors have compared the findings of CT-based renal volumetry and those of nuclear renal scans. On the basis of the results of these studies, the present study shows the possible usefulness of CT-based volumetry along with nuclear renal scans for estimating split renal functions after nephron-sparing surgery. The results of the present study show that renal parenchymal volume calculated on the basis of the findings of CT can be used for a postoperative functional assessment, the same as that of a nuclear renal scan. In real clinical practice, CT scans to examine for postoperative recurrence are routinely carried out to follow up patients who undergo partial nephrectomy, whereas nuclear renal scans are not always carried out routinely. Therefore, the message from the present study can be very beneficial and informative for many urological surgeons, because it might enable cost-effective follow up of renal function at the same time as the examination to evaluate the oncological outcome after partial nephrectomy. In the present study, renal cortical volume and SRV were measured on the basis of CT scans obtained 1 year or more after partial nephrectomy. This means that renal cortical volume and SRV measured by the proposed method represent renal function at relatively long-term periods rather than that in early periods. The usefulness of assessing renal function in long-term follow up is one of the most important points of this method. As shown in Table 1, of 51 patients enrolled in the present study, 10 had hypertension and nine had diabetes mellitus as comorbidities. These patients risk histological kidney damage. Besides these, many patients treated with partial nephrectomy might have some comorbidities, which can lead to histological chronic kidney injury. In addition, histories of recurrent pyelonephritis, smoking and medication might have some effect. Taking all this information into consideration, I am afraid that some patients might have a split renal function based on a nuclear renal scan that is not consistent with an SRV based on CT. The change of renal function after partial nephrectomy is often difficult to predict and complicated, although investigators have previously researched it because, for both surgeons and patients, many factors can affect renal function after surgery. For instance, each surgeon’s surgical skills and procedures, including tumor excision and renorrhaphy, are thought to be crucial factors associated with postoperative renal function. Although the present study focused on the usefulness of renal cortical volume and SRV, the clinicopathological factors associated with reducing the renal cortex after partial nephrectomy are also interesting. Further study with larger volumes is expected to clarify these points in the near future.