Historically, when RN was the standard treatment for kidney cancer, PN was performed only in the patient who had a tumor in a solitary kidney, a bilateral renal tumor, or renal function impairment [4,5]. The main purpose of PN for these patients was the preserving of renal function, even though it was not enough. PN for the patient with a normal contralateral kidney is based on the concept that it provides an advantage over RN in preventing chronic kidney disease (CKD) by preserving more nephron capital. The relationship between nephron mass reduction and accelerated kidney damage was reported in experimental models [6,7]. The clinical data also indicated that the independent predictor of postoperative renal function after PN was the amount of renal volume reduction or the percentage of resected renal parenchyma [8-10].

Patients with renal cell carcinoma (RCC) may have a risk for CKD because of the shared risk of hypertension, smoking, diabetes, and advancing age [11,12]. Leaving this relation aside, recent studies reported a higher incidence of CKD after RN than after PN. A study by the MSKCC group of renal cortical tumors (≤4 cm) demonstrated that the 3-year probability of freedom of new-onset mild CKD [glomerular filtration rate (GFR) <60 ml/min/1.73 m²] was 80% after PN and 35% after RN, and that of moderate CKD (GFR <45 ml/min/1.73 m²) was 95% after PN and 64% after RN. RN was an independent risk factor for patients developing new onset of mild and moderate CKD in the multivariable analysis (hazard ratio [HR]: 3.82; 95% CI: 2.75-5.32; p<0.0001) [13].

CKD is defined as either kidney damage for ≥3 months as confirmed by structural or functional abnormalities manifested by pathologic abnormalities or markers of kidney damage with or without decreased GFR, or a decrease in GFR <60 ml/min/1.73 m² for ≥3 months with or without kidney damage [14]. According to one study, CKD is an independent risk factor for the development of cardiovascular events, hospitalization, and death [15].

Comparing RN with PN concerning the association with an increase in cardiovascular events and mortality for patients over 66 years of age, RN was associated with an increased risk of overall mortality (HR: 1.38, p<0.01) and a 1.4 times greater number of cardiovascular events after surgery (p<0.05), although RN was not significantly associated with cardiovascular death (HR 0.95, p=0.84) [8]. Another study reported that PN had fewer adverse renal outcomes (16.4% vs. 21.8%; adjusted HR: 0.74; 95% CI: 0.58-0.94), including a trend toward less frequent receipt of dialysis services, dialysis access surgery, or renal transplantation than with RN. However, the likelihood of adverse cardiovascular outcomes did not differ by treatment [9].

The overall survival rate of RN is regarded to be lower than that of PN. A matched control study for age, year of surgery, tumor size, and Furman grade to assess the effect of nephrectomy type (RN vs. PN) on overall mortality showed that RN was associated with 1.19-fold (p=0.048) higher overall mortality rate [16]. Additionally, RN was significantly associated with death from any cause compared with PN, especially in patients under 65 years of age (relative risk: 2.16, p=0.02) (Table 1) [10].

The above studies suggest that PN is preferred for solitary small RCC or suspicious RCC. However, because these studies were retrospectively designed, there are some limitations. Selection bias in deciding on the surgery type could exist. The methods of measuring preoperative and postoperative renal impairment were diverse [estimated GFR (eGFR), serum creatinine, proteinuria, and event of visiting dialysis center]. A randomized controlled trial is required.

As imaging check-ups have become widespread, the incidence of benign tumors confirmed during the operation that had been suspected as RCC is also increasing. Despite thorough preoperative radiological evaluation, 11% to 25% of presumed RCC were revealed to be benign in recent studies [17,18]. No imaging feature available currently can accurately distinguish oncocytoma and small or lipid-poor angiomyolipoma from RCC. For these patients, PN is preferred to avoid useless nephrectomy and to preserve renal function.

Although LPN has proved to be a worthy alternative with similar oncological outcomes [3] with lower morbidity and faster postoperative recovery [2], much experience is required to perform the surgery for adequate WIT and to get those results. A new alternative is RPN. Since the Da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA, USA) was introduced, it has become widespread because of its shorter learning curve than the laparoscopic approach. Now, it is well established for performing radical prostatectomy. As experience is accumulated, the indication of robotic surgery is expanding to PN [49]. Generally, the indications for RPN are the same as for OPN and LPN [50]. Recently, the indications of RPN have also expanded to the multiple renal masses of hereditary kidney cancer patients [51] and the nononcologic field for pediatric RPN [52]. Technically, the transperitoneal approach is used in most RPN series and the retroperitoneal approach was recently introduced (Fig. 1). Hybrid laparoscopic-robotic technique was used in the earlier period. Recent series tend to be fully robotic [53]. Cabello et al describe their three-arm robotic technique with sliding-clip renorrhaphy [54]. The bedside assistant places a clip on the suture, which is then slid down by the console surgeon to obtain perfect tension. With this technique, the console surgeon can fully control the renorrhaphy and WIT can be shorter without knot tying [55]. RPN shows at least equal perioperative outcomes to LPN with shorter overall operative times and WIT as surgeons become more experienced. A positive surgical margin is rare (0-2.3%), and there has been only one reported recurrence following RPN [56,57]. Postoperative renal function and oncological outcomes of RPN are comparable with the LPN series [58]. In recent series, complication rates have ranged from 0% to 17% with rare instances of open conversions. The most common complication is urine leakage [56]. Furthermore, recent reports have suggested that robot assistance confers a particularly strong advantage when attempting to address larger, complex lesions, including those that are predominantly endophytic, centrally located, or directly abutting the hilum (Table 2) [56,59-61]. However, RPN still has limitations. Robotic surgery is more expensive than OPN and LPN in many countries because of the high cost of the Da Vinci robot and because the health care system does not cover it. Another limitation is the requirement for an experienced bedside assistant. Generally, the role of the assistant is important during hilar clamping and releasing with the bulldog clamp or laparoscopic Satinsky. Although efforts to control the hilum by the console surgeon have emerged, such as the use of a fourth arm, it is more difficult than the three-arm approach owing to the crowding of the instruments.

LESS surgery is one of the innovations of laparoscopic surgery. It can minimize patient discomfort and maximize the cosmetic benefit with one small incision. For a kidney tumor, PN can get the advantage because of small specimen differ from RN. The reported WIT of LESS PN was 11 to 29 minutes and that of hybrid robot-assisted LESS PN was 16 to 43 minutes [62,63]. Because most surgeons do not have much experience, keeping the WIT short can be a burden. For this reason, some surgeons perform LESS PN without ischemia [64,65]. Mean operative time was comparable to RPN [50,62-66]. The most common complication was bleeding requiring transfusion [62-66]. Oncological outcomes are promising until cases accumulate. Although the feasibility has been proved, LESS PN is indicated only for small, exophytic, and easily approachable tumors. Wider experience and longer follow-up are necessary to establish the role of this technique.