Size is no barrier: robot‐assisted partial nephrectomy in patients with a high body mass index

In the February edition of the BJUI, Malroc et al. 1 from the Cleveland Clinic presented their single centre series of partial nephrectomy (PN) in obese patients. Here they examined a large retrospective cohort of obese patients [body mass index (BMI) >30 kg/m2] undergoing PN over a 4-year period by either open (OPN) or robot-assisted (RAPN) approaches and compared the peri- and postoperative outcomes. The authors analysed their prospective database, excluding patients with comorbidities (Charlson Comorbidity Index >1) or a single kidney to isolate obesity in their analysis. They compared 177 RAPNs vs a smaller group of 60 OPNs, with selection based on surgeon preference for each technique. Not surprisingly on both uni- and multivariate analyses we see that the oncological outcomes are equivalent, whilst the intraoperative and postoperative outcomes favoured RAPN for operative time by 27 min (180 vs 207 min), intraoperative transfusion rates (10 vs 1%), postoperative complications (mainly minor Clavien–Dindo Grade I–II such as UTI, wound infection), and length of stay (LOS; 3 vs 4 days). There was also a shorter warm ischaemia time (WIT) for the RAPN cohort of 19.5 vs 27 min cold ischaemia in the OPN cohort, although there were no long-term differences in estimated GFR between the groups. Impressively there were no RAPN conversions to open but the OPN group had larger tumours at 2.8 vs 2.5 cm in diameter. This is a pertinent study as we are currently faced with an increasing incidence of global obesity in the small renal mass population. In addition, not only is the average BMI of the general population rising but the incidence of RCC is higher in obese patients 2. Obese patients present challenges in how we manage them, not only from a surgical and anaesthetic perspective but perioperatively given the associated comorbidities these patients increasingly have. Consistent with current UK and USA practice, as highlighted by the authors, RAPN is the predominant technique for nephron-sparing surgery, with firm evidence suggested by the recent meta-analysis by Shen et al. 3 demonstrating a lower incidence of complications and blood loss, and shorter LOS compared with the OPN technique. In contrast, the current study 1 attempts to evaluate obesity independently of comorbidities to better understand its relationship to intra- and postoperative outcomes; and hence identify the ideal approach for the obese patient. However, this limits the applicability of the study as they acknowledge that the generalisability is somewhat compromised, with a significant proportion of obese patients having covert or undiagnosed comorbidities. Common among this demographic is the metabolic syndrome, comprising obesity, hypertension, elevated fasting glucose, triglycerides and low high-density lipoproteins. This is an unfortunate clustering of medical conditions, thought to be a consequence of inappropriate energy utilisation. The incidence itself is alarming, but more concerning is the association with the significant conditions of cardiovascular disease and type 2 diabetes. Hence obesity cannot be considered in isolation amongst such significant pathologies. The outcomes of this study 1 reflect the limited findings in the literature to date observing clear benefits in the application of RAPN over OPN in obese patient cohorts. Contextualising this in the literature, the authors acknowledge the study by Webb et al. 4 confirming estimated blood loss and LOS advantages of RAPN over OPN. A variety of other small studies confirm similar operative time benefits with RAPN, and that obesity does not lead to an increased incidence of major morbidity; however, the risks do increase with increasing grade of obesity. There are several additional surgical considerations not mentioned in the study that support the use of RAPN in obese patients. Obese patients have the most to gain from minimally invasive surgery in terms of enhanced postoperative recovery, optimised pain management, improved mobility, reduced deep venous thrombosis incidence and wound complications that are facilitated by RAPN over OPN. Robotic surgery allows for a potentially faster procedure, less WIT and the ability to manage more complex tumours with higher nephrometry scores over laparoscopic PN and sometimes OPN. Despite initial challenging patient habitus often RAPN is very feasible once commenced, as the difficulty often depends on whether fat is visceral, subcutaneous or in fact adherent peri-renal fat. General adiposity often lends itself to clear dissection planes and efficient operating; however, the problem of ‘sticky’ fat is documented to make operating more challenging, and obesity is a clear predictive factor alongside gender, hypertension, and imaging findings 5. There is no longer term follow-up of the surgical wounds mentioned here but the significantly increased incidence of surgical wound pain, muscle bulging and incisional hernia is increased in the open loin approach. Not mentioned in this paper's discussion 1 is another interesting element of the obesity paradox 6. Various studies suggest that patients in the overweight and obese categories may do better than underweight, morbidly obese or even ‘normal’ weight patients due to physiological reserve. This has a firm base in cardiothoracic surgery, while there is increasing evidence in the general surgery and orthopaedic specialties, something highly relevant in a urological population that has an increasing BMI and incidence of RCC. Bariatric surgeons will often suggest rapid preoperative weight loss with agents such as OPTIFAST® (Nestlé Health Science, Gatwick, UK); the intention being increased liver mobility with decreased hepatic steatosis. This is not something we have used to date with adequate mobilisation usually possible; however, it could be used in patients with significant hepatic steatosis and difficult right upper pole lesions. With the inherent operative benefits of minimally invasive surgery lending themselves to the obese population, in addition to the postoperative advantages of reduced morbidity, it seems robotic surgery can be beneficial for all, especially patients who are overweight or obese. Malroc et al. 1 have confirmed that patient size certainly is not everything and confirmed the value of RAPN. This supports other evidence for RPN being the new ‘gold standard’ technique. None of the authors have anything to disclose.

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