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Page 8 of 19 Deivasigamani et al. Mini-invasive Surg 2023;7:9 https://dx.doi.org/10.20517/2574-1225.2022.99

compared to radical approaches [60,61] . The factors most predictive of complications after CA appear to be
tumor size and tumor location, with centrally located tumors and upper pole tumors at the highest risk for
complications [46,51,58] . Complications were associated with higher RENAL scores, and the (MC)2 score, which
includes myocardial infarction and diabetic patients, was found to be the best predictor of complications
after CA, with tumor size and location appearing to be the best tumor characteristics predicting
complications.

RENAL FUNCTIONAL OUTCOMES
The necessity to reduce renal function loss in order to minimize secondary morbidity and mortality drives
the pursuit of nephron-sparing therapies for SRMs, including PN, CA, and other ablative technologies.
Although these techniques are nephron-sparing because they are intended to avoid loss of the entire
affected kidney, there is, by necessity, some healthy renal tissue that is sacrificed in order to have a margin
around the renal mass to prevent the residual tumor from being left behind. CA is no exception to this
principle, as in any ablative modality, the healthy renal tissue needs to be treated around the SRM to ensure
complete tumor ablation. Because there is expected to be some cryoinjury to the renal tissue adjacent to the
SRM, this can cause a small but measurable decrease in renal function following the procedure.

LCA vs. PCA
LCA had no immediate postoperative changes, with a small decline in serum creatinine level two years
following the treatment as a measure of renal functional outcome [35,47] . Studies comparing estimated
glomerular filtration rate (eGFR) between patients undergoing laparoscopic or open CA found that
measured eGFR reduction was comparable in the two groups, with baseline eGFR being the only reliable
indicator of functional impairment occurring after CA; tumor size had no bearing in this situation with
rates of CKD stage progression were equal in the PCA and LCA cohorts [48,62] . Wehrenberg-Klee et al. found
no statistically significant change between mean baseline eGFR values before the start of treatment and the
values at one month (41.1 vs. 41.4 mL/min per 1.73 m ) and one year (42.1 vs. 44.4 mL/min per 1.73 m ) in
2
2
22 CKD patients who received PCA . Only one patient with stage III CKD had advanced to stage IV after
[63]
one year, while two patients had decreased renal function to stage V. GFR dropped by more than 25% in
five cases. During the follow-up period, none of these people required dialysis. Sriprasad et al. investigated
[64]
renal function loss following cryoablation of an SRM in solitary kidneys in 102 individuals . Data on renal
function, including eGFR and CKD classification, were collected both before and three months after the
operation. The preoperative mean eGFR was 55.0 mL/min/1.73 m2 (SD = 18.1), while the postoperative
mean eGFR noted was 51.8 mL/min/1.73 m (SD = 18.8). The difference was statistically significant (P =
2
2
0.004) at -3.1 mL/min/1.73 m (95%CI: -5.2 to -1.0) units. The difference in CKD stages before and after
LCA, on the other hand, was not statistically significant.

CA vs. PN
In a study by Mitchell et al. , neither the post-treatment eGFR (50.3 vs. 49.1) nor changes in the CKD stage
[65]
were different between PN and ablation procedures in individuals with a single kidney at three months. The
same study observed no significant difference between CA and RFA in terms of the percentage change in
eGFR. In a multi-institutional comparison of PN and CA, Mues et al. . found no differences in
[66]
postoperative eGFR alterations between the two methods.

In a meta-analysis study, Uhlig et al. . examined renal function between CA and PN in 6,618 patients.
[67]
Comparing PN with CA, there was no statistically significant difference in renal function (P = 0.921). After
controlling for tumor characteristics and complexity, the mean proportional fall in eGFR was higher in the
Robotic PN (RPN) as compared to the CA group (13% vs. 6%). The study revealed that the smaller tumor
[48]
size is predictive of better renal functional outcomes in patients with CA .