Since 1991, when Clayman et al first reported laparoscopic nephrectomy [1], many investigations have shown the various advantages of the laparoscopic technique, such as decreased blood loss, rapid recovery, shorter hospital stay, less postoperative pain, and better cosmesis than with open nephrectomy [2,3]. Building on these gains, laparoscopic radical nephrectomy (LRN) is increasingly being performed at many centers and has become the standard technique for radical nephrectomies for T1 renal tumors (7 cm or less), except in favorable cases of nephron-sparing surgery [4,5]. Recently, laparoscopic surgery has also tended to be performed for larger renal masses (>7 cm) [6,7].

The Korean National Health and Nutrition Surveys reported an increase in the prevalence of obesity from 1995 to 2001, and the prevalence of obesity was 31.8% in 2005 [8]. As a result of this trend, laparoscopic surgery has been increasingly performed in obese patients. However, several previous studies reported that obesity is a potential risk factor for poor outcomes after laparoscopic surgery. Therefore, obesity was regarded to be a relative contraindication to laparoscopy [9,10]. Despite these suggestions, the use of laparoscopic surgery for surgical procedures has been rapidly growing and most of the literature now agrees that the laparoscopic approach is feasible and safe in obese patients.

Several recent studies have concerned the effect of obesity on the perioperative outcomes of LRN [9-15]. However, most studies were limited to T1 renal cell carcinoma (RCC). In the present study, we estimated the impact of obesity on LRN in T2 RCC as well as T1 RCC.

From January 2004 to March 2011, we retrospectively analyzed 266 patients who underwent LRN for T1 and T2 RCC. All LRN procedures were performed by a single experienced laparoscopic surgeon. All patients were divided into T1 and T2 groups. These two groups were then subdivided into obese and nonobese groups according to body mass index (BMI) on the basis of the Asia-Pacific criteria in the World Health Organization classification. Patients with a BMI of 25 kg/m² or greater were defined as the obese group and those with a BMI of less than 25 kg/m² were defined as the nonobese group. Patients' demographic parameters and perioperative surgical outcomes were compared between the obese and nonobese groups in the same stage group. The demographic parameters included age, BMI, gender, tumor size, and tumor laterality. To evaluate the operative outcomes, we compared operative time, actual blood loss (ABL) [16], transfusion rate, time to oral intake, hospital stay, and complication rate.

LRN was performed by the transperitoneal approach in all cases. Pneumoperitoneum was achieved by using a Veress needle, and 3 or 4 ports were placed depending on the case. After laterocolic incision and mobilization of the colon, the renal hilum was dissected in the standard fashion with adequate visualization of the renal vein and artery. We used 3 or 4, 10 or 15 mm Hem-o-Lok clips to control the renal artery. The renal vein was controlled by 3 or 4, 15 mm clips. Para-aortic or paracaval and hilar lymph node dissection (LND) were performed when an enlarged lymph node was found radiologically before surgery or grossly during the operation. We removed the kidney, which was surrounded by the perinephric fat and enveloped by Gerota's fascia, with or without a concomitant adrenalectomy. All of the specimens were removed intact without morcellation or fragmentation in an Endo Catch retrieval bag through a lower abdominal incision. An indwelling Jackson-Pratt drain was placed in the retroperitoneal space through a 5 mm port site in all of the patients.

Continuous variables were compared with an independent Student's t-test and categorical variables were assessed with the chi-square test. All p values were 2-sided, and p<0.05 was considered significant. Analyses were conducted by using SPSS ver. 12.0 (SPSS Inc., Chicago, IL, USA).

The non-obese T1 group and the obese T1 group included 135 and 60 patients, and the non-obese T2 group and the obese T2 group included 49 and 22 patients, respectively. There were no significant differences in age, sex, mean tumor size, or tumor laterality between the nonobese T1 and obese T1 groups or between the nonobese T2 and obese T2 groups.

The mean operative time was similar between the non-obese T1 and obese T1 groups (167.2 minutes vs. 170.5 minutes, p=0.610). Although blood loss and the transfusion rate were higher in the obese T1 group than in the non-obese T1 group, these differences were not significant (186.4 ml vs. 233.4 ml, p=0.125; 3.7% vs. 8.3%, p=0.176). Time to oral intake, hospital stay, and complication rate were also not significantly different between the obese T1 and nonobese T1 groups (Table 1).

The mean operative time was significantly different between the non-obese T2 and the obese T2 groups (200.7 minutes vs. 253.6 minutes, p<0.001). Blood loss and the transfusion rate were also higher in the obese T2 group than in the non-obese T2 group (220.5 ml vs. 313.5 ml, p=0.193; 20.4% vs. 27.3%, p=0.522); however, these differences were not significant. The complication rate was significantly higher in the obese T2 group than in the non-obese T2 group (10.2% vs. 31.8%, p=0.025). Time to oral intake and hospital stay were not significantly different between the obese T2 and the non-obese T2 groups (Table 2).

In a total of 266 patients, 29 complications (10.9%) occurred in our series. There was 1 case of open conversion in each group. Of 135 patients, 12 complications (8.9%; 1 pulmonary edema, 2 ileus, 9 chylous ascites) occurred in the non-obese T1 group, and of 60 patients, 5 complications (8.3%; 1 wound dehiscence, 1 pneumonia, 3 chylous ascites) occurred in the obese T1 group (p=0.899). Of 49 patients, 5 complications (10.2%; 1 ileus and 3 chylous ascites, 1 pneumothorax) occurred in the nonobese T2 group, and of 22 patients, 7 complications (31.8%, 1 pulmonary edema, 1 wound dehiscence, 2 ileus, and 3 chylous ascites) occurred in the obese T2 group (p=0.025). According to the complication classification system suggested by Clavien et al [17], 21 cases were grade I and 8 cases were grade II. There were no grade III or worse complications (Table 3).

Obesity is a major public health issue that affects more than 30% of Korean adults [8]. Many diseases, including diabetes, coronary artery disease, hypertension, breast cancer, colon cancer, and osteoarthritis, are associated with obesity [18]. Theoretically, obese patients with these comorbid conditions have an increased risk of poorer outcomes after surgical treatment. At the beginning of laparoscopic surgery, obesity was considered to result in much technical challenge owing to the difficulty of trocar insertion, inadequate insufflations, limited movement of the trocars, and a narrow working space [12]. Laparoscopic surgery in obese patients is also a challenge for anesthesiologists, and obesity may complicate respiratory and hemodynamic management [19]. To minimize pulmonary complications including atelectasis and pneumonia, preoxygenation and rapid sequence induction should be performed and spirometry should be initiated in the immediate postoperative period. We must carefully discuss with anesthesiologists the perioperative management of obese patients undergoing LRN. Therefore, in the mid 1990s, there was much controversy regarding whether the benefits of laparoscopy existed for obese patients. Mendoza et al reported that obese patients were more prone to complications (57% vs. 16%) and Gill et al noted that obese patients underwent more conversions to open surgery (35% vs. 6%) [10,20]. However, in the current era, most of the literature now agrees that the laparoscopic approach is feasible and safe in obese patients. Futiga et al reported no statistically significant difference in operation time, blood loss, conversion rate, complications, length of hospitalization, or time to ambulation in a study of 32 obese and 69 normal-weight patients undergoing LRN [12]. Doublet and Belair also found no significant difference in operative time or complications between obese and nonobese patients [21]. Miyake et al reported no significant differences in operative time, estimated blood loss during LRN, and the incidences of open conversion and postoperative complications between these two groups [22]. In an analysis of 26 open radical nephrectomies and 30 LRNs, Lee et al reported that LRN is effective for both obese and nonobese patients [15]. Moreover, several studies reported better outcomes of laparoscopic surgery in obese patients. Fazeli-Matin et al reported that laparoscopic renal and adrenal surgery in obese patients showed lower blood loss, quicker return of bowel function, less analgesic requirement, shorter convalescence, and reduced hospital stay [11]. Klingler et al suggested that obese patients benefit more from laparoscopy than do nonobese patients with respect to postoperative pain and morbidity but do not experience more complications [23]. However, most of those reports were mainly intended for small-sized RCC, and there have been few studies about the impact of obesity for larger tumors.

With the development of laparoscopic technique, the indications for LRN are expanding to encompass increasingly larger tumors. However, large tumors often result in several problems for LRN, including decreased working space, difficulty with maintenance of operator orientation, incidence of significant parasitic vessels, and difficult specimen removal, and are often combined with enlarged lymph nodes. Therefore, large tumors entail technical concerns even in the hands of experienced laparoscopic surgeons. Obesity also adds technical challenge to laparoscopic surgery. These challenges include inadequate insufflation of the peritoneal cavity, difficulty of trocar insertion, maintenance of pneumoperitoneum, and restrictive visualization due to limited exposure. Moreover, obese patients usually have a thicker abdominal wall that may result in limited movement of the trocars and decreased sensitivity felt by the surgeon. Obesity also induces more visceral fat, which has more parasitic vessels and consequently has more potential for bleeding in the operation field with impairment of the visual field. On the other hand, laparoscopic surgery in obese patients has several potential advantages. Compared with open surgery, laparoscopic surgery can minimize skin incision, and this minimal incision can prevent the risk of wound complications. In addition, laparoscopic surgery can reduce abdominal wall incision and closing time and may decrease the entire operative time. Reduction of operative time may reduce complications related to the patient's general condition caused by prolonged anesthesia.

In our study, we found that obesity had no significant effect on operative outcomes if the tumor size was smaller than 7 cm. Blood loss, the transfusion rate, operation time, time to oral intake, hospital stay, and the complication rate were not significantly different. However, in cases of larger tumors (>7 cm), we found that the operation time and complication rate were significantly increased in the obese group. This may have been because of the narrower working space and increased visceral fat. In the case of small tumors, although the working space may be decreased in obese patients, if we approach transperitoneally, enough working space can usually be secured. However, in the case of larger tumors, because of the volume effect of the tumor, more time can be taken for the dissection of the perirenal space as well as hilar dissection. Moreover, larger tumors may have a greater chance of being accompanied by enlarged lymph nodes irrespective of lymph node invasion. Therefore, when we undertake LRN in T2 obese patients, the lymphatic channels can be easily injured during hilar, paraaortic, or paracaval dissection owing to the increased visceral fat tissue.

For other consideration of our results, we suggest that the surgeon's skill plays a major role in the perioperative outcomes of LRN in obese patients. The experienced laparoscopic surgeon may overcome the difficulties of surgery in obese patients if the tumor size is small. However, the obese T2 RCC patients in our study showed a significant increase in operation times (200.7 vs. 253.6 minutes, respectively, p<0.001) and complication rates (10.2% vs. 31.8%, p=0.025) compared with nonobese T2 RCC patients. In T2 RCC patients, who have larger tumors than T1 RCC patients, even experienced laparoscopic surgeons can be affected by obesity in the patient. Therefore, we suggest that obesity may be an important factor that negatively influences operative outcomes of LRN for T2 RCC patients. As a result, we should pay more attention if we are planning to perform LRN on T2 RCC in obese patients.

The limitations of our study were that it had a retrospective design and did not involve comparisons with open surgery. We need to compare laparoscopic and open surgery in obese T2 RCC patients. However, our data were enough to evaluate the surgical outcomes of LRN related to obesity, and the surgical techniques were standardized. Moreover, it is significant that this report is the first about the impact of obesity on LRN of large RCC in Korea.

Our results suggest that LRN can be safely performed in Korean patients with T1 RCC regardless of obesity. However, in T2 RCC patients, LRN may become more difficult with increasing BMI considering the longer operation time as well as the higher complication rate. In conclusion, we suggest that LRN in obese patients with T2 RCC must be considered carefully.