Risk Factors For Renal Function Impairment Following Radiofrequency Ablation Of Renal Tumors Ⅲ

DISCUSSION 

RFA has emerged as an alternative treatment to partial nephrectomy for patients with small renal tumors (T1a) and can also be performed in larger tumors (T1b) (29-32). RFA has been regarded as having long-term oncologic outcomes comparable to that of partial nephrectomy. Given the comparable and favorable survival outcomes of each treatment, significant measures are often taken for renal function preservation (14). Many studies reported better renal function outcomes after RFA than after partial nephrectomy among patients with solitary kidneys (15, 16). Except for patients with solitary kidneys, the changes in renal function after performing each of the treatments remain unclear. The European Association of Urology, the National Comprehensive Cancer Network, and the American Urological Association do not have a firm suggestion for the treatment of choice based on renal function impact. Many studies evaluated continuous renal function tests, showing no significant differences between RFA and partial nephrectomy (17-21). However, some studies reported that RFA might protect renal function better when compared to partial nephrectomy (11, 22, 23). 

Organic Herbs For Renel Function Impairment

In univariable and multivariable logistic regression analysis, renal function impairment was positively associated with solitary kidney, CKD stage 3, and pyeloureteral injury. Better renal function outcome was reported following RFA compared to partial nephrectomy in patients with solitary kidneys (15, 16); however, solitary kidney by itself was independently associated with CKD development (33). Among the nine patients with solitary kidney, impaired renal function was reported in five. Two of them had preexisting stage 3 CKD, and the other two had a history of colon cancer surgery at an advanced age (over 70 years old). Lucas et al. (34) reported a significant decrease in renal function of patients with preoperative CKD stage  3 who had undergone partial nephrectomy compared to RFA. Wehrenberg-Klee et al. (10) demonstrated that RFA of renal tumors did not affect the renal function of patients with pre-existing CKD over stage 3. However, this study (10) showed that 7 of 48 patients had more than a 25% decrease in the eGFRs. In the present study, five of seven patients with pre-existing 

Fig. 2. Repeated-measures ANOVA to evaluate the interaction between risk factors and renal function inpairs. Visual analog scales for renal function outcomes (SCr and eGFR) are shown for with or without a single kidney, CKD, and pyeloureteral injury at various times. A-F. As time passed, SCr (A, C, E) and eGFR (B, D, F) showed statistically significant changes. There was a difference in overall change over time between with and without a solitary kidney, CKD stage 3, and pleasureliteral injury. CKD = chronic kidney disease, eGFR = estimated glomerular filtration rates, mo = month, RFA = radio freequency ablation, SCr = serum creatinine, wk = week, yr = year

CKD stage 3 showed decreased renal function outcome. Among them, four patients' condition worsened from CKD stage 3 to stage 4, and one patient from CKD stage 3a to stage 3b. Eight hydronephroses were detected on the follow-up CT scans. Three patients showed renal function impairment and the other five patients showed renal function preservation. Radiological interventions were performed in two of them; however, continuous ureteropelvic junction strictures were detected on follow-up CT along with worsened renal function. The two cases had tumors in the medial portion of the kidney and proximity to the collecting system. Before RFA, the SCr levels and eGFRs of the two patients were 0.73, 0.8 mg/ dL, and 115, 90.6 mL/min/1.73 m2, respectively. Post-RFA, the SCr levels increased to 1.24, 1.22 mg/dL, and eGFRs decreased to 69.2, and 64.8 mL/min/1.73 m2, respectively; these were measured at 4 months after RFA just before the interventional procedure for the ureteropelvic junction stricture. Although the tumor location did not show statistically significant results, the medial portion of the lower pole may be a significant predictor of ureteropelvic junction injury (12, 23, 35). The renal mass arising from the medial portion of the lower pole can be located closer to the ureter; hence the operator should perform an RFA carefully, considering invasive or non-invasive prevention methods such as hydro dissection, levering electrode, preprocedural ureter catheterization, or position change. The other case who had impaired renal function showed continuous mild hydronephrosis on follow-up CT scans. Radiological intervention was not performed. Before RFA, the SCr levels and eGFRs were 1.12 mg/dL and 68.1 mL/min/1.73 m2. The SCr level increased to 1.61 mg/dL and eGFRs decreased to 32 mL/min/1.73 m2 after a year. Five patients without decreased renal function showed mild Caliectasis on follow-up CT scans. There was no need to take further treatment about mild caliectasis.

There were certain limitations to our study. First, this study was conducted using a retrospective method. Hence, selection bias for the study population may be inevitable. Second, the small sample size in this study may lead to a less reliable conclusion. Third, we set the criteria for a significant decrease in renal function as a 0.3 mg/dL increase in SCr level without proven evidence. Partial nephrectomy may cause significant morbidity and mortality in patients with major comorbidities. RFA may be an alternative in not only poor surgical candidates but also healthy patients unwilling to undergo surgery. Among the medical conditions present before RFA, solitary kidney, and CKD over stage 3 may be considered risk factors for impaired renal function. Post-procedural pyeloureteral injury may also be considered a risk factor. High-risk comorbidities may require great care to avoid aggravating remnant renal function.

Author Contributions 

Conceptualization, all authors; data curation, P.I.C., K.D.W.; formal analysis, all authors; funding accquistion, Y.S.K.; investigation, P.I.C., K.D.W.; methodology, all authors; project administration, Y.S.K.; resources, P.I.C., K.D.W.; supervision, Y.S.K.; validation, Y.S.K., K.D.W.; visualization, P.I.C., K.D.W.; writing-original draft, all authors; and writing-review & editing, all authors. 

Conflicts of Interest Seong Kuk Yoon has been a Section Editor of the Journal of the Korean Society of Radiology since 2014; however, he was not involved in the peer reviewer selection, evaluation, or decision process of this article. Otherwise, no other potential conflicts of interest relevant to this article were reported.

Funding This work was supported by the Dong-A University research fund. 

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