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Page 6 of 19 Deivasigamani et al. Mini-invasive Surg 2023;7:9 https://dx.doi.org/10.20517/2574-1225.2022.99

[16]
uncertainties and are not planned for treatment with CA do not require RTB . However, for patients who
are going to undergo CA, there is more consensus that RTB should be performed in order to help guide
follow-up, and percutaneous RTB can be performed at the time of CA prior to the ablation of the lesion. In
terms of RTB type, core needle biopsy (CNB) is preferred due to better diagnostic yield compared to fine
needle aspiration (FNA); a recent systematic review found CNB to have sensitivity and specificity of 99.1%
[29]
and 99.7%, whereas FNA had sensitivity and specificity of 93.2% and 89.8% . The reason RTB is important
for patients undergoing CA is that the histology and grade of the treated renal mass are crucial for defining
a postoperative surveillance plan following CA, as well as for assessing CA oncologic outcomes . Indeed,
[30]
benign masses account for 15-20% of SRMs [31,32] , and these lesions may not need further follow-up after an
[31]
ablative procedure . Thus, the Focal Therapy Society (FTS) recommends pre-ablation biopsy in all patients
undergoing CA, and if the initial biopsy prior to ablation was nondiagnostic, the panel advised a post-
[33]
ablation biopsy ; however, the diagnostic accuracy of RTB may be decreased following ablation .
[34]
COMPLICATIONS
The rate of complications with CA is relatively low, ranging from 7.8% to 20%, and most of the
complications are minor [35-38] . Generally, flank pain or paresthesia is reported as the most common
complication of PCA, with reported rates ranging from 4.3% to 8.3%, although several authors discount the
accounting of self-limited flank pain as a complication [39,40] . Post-ablation syndrome is characterized by fever
and flu-like symptoms following CA and occurs in a minority of patients, but a much larger proportion of
[41]
patients will experience some post-ablation flu-like symptoms, which are typically self-limited . Other rare
but potential complications include UTI, hematuria, hemorrhage, perinephric hematoma, nerve injury,
pneumothorax, and damage to the urinary collecting system, which can rarely lead to urinoma or ureteral
stricture [23,39,42-44] . In addition to the potential procedure-related complications, we must also consider device-
related complications, which might differ depending on the ablation approach used. In a review of the Food
and Drug Administration’s Manufacturer and User Facility Device Experience (MAUDE) database, the
authors found CA had a small number of device-related complications, including a small number of cases
that had to be aborted due to instrument/system malfunction and hemorrhage requiring an additional
procedure . Although some studies have attempted to compare complication rates between CA and PN or
[45]
between various techniques for TA, there have not been any head-to-head randomized comparisons, so all
such comparisons are inherently influenced by selection bias. Patients selected to undergo TA generally
have more comorbidities and risk factors, which can only partially be controlled for by attempts at patient
matching. Table 1 offers a comprehensive review of complications associated with CA.

Complications by tumor complexity scores
Various reports have tried to evaluate the utility of scoring systems to quantify the risk of complication
based on tumor complexity related to CA. Previously developed scoring systems for tumor complexity were
based on PN experiences and included the RENAL nephrometry score (Radius, Exophytic/endophytic,
Nearness to collecting system/sinus, Anterior/posterior, and Location relative to the polar line) and
PADUA score (Preoperative Aspects and Dimensions Used for Anatomical classification of renal tumors).
In studies of CA, the RENAL score was found to have some correlation with the incidence of
[57]
complication [38,50,56,57] , but the PADUA score was not predictive of the incidence of complication . An
ablation-specific renal tumor scoring system, the (MC)2 score (Maximum tumor diameter, Central tumor
location, prior Myocardial infarction, and Complicated diabetes mellitus), was initially proposed in 2014
[51]
because the factors that impact risks associated with treating a renal tumor from a surgical approach are not
necessarily the same factors that impact the risks associated with treating a renal tumor with ablation,
especially from a percutaneous approach. The (MC)2 score has been externally validated and has been
[58]
shown to outperform the RENAL nephrometry score in predicting the risk of complications following
PCA . An additional factor that increases the risk of complication for PCA, which is different from PN, is
[51]