obesity has emerged as a major healthcare problem in the united states and a common comorbid factor in surgical patients . data from the two national health and nutrition examination surveys ( nhanes ) demonstrate that the prevalence of obesity increased from 15.1% in 1980 to 31.1% in 2002 among patients 20 to 74 years of age . elevated bmi has been thought to be associated with poorer surgical outcomes , especially after procedures of increased technical complexity . chang et al reported increased perioperative blood loss and prolonged operative times in patients with elevated bmi undergoing open radical cystectomy . in the current study , the affect of elevated bmi on intraoperative parameters and postoperative and pathologic outcomes was evaluated in 51 consecutive patients who underwent robot - assisted radical cystectomy . an institutional review board - approved retrospective chart analysis was performed of 51 consecutive patients who underwent robot - assisted radical cystectomy for carcinoma of the bladder from october 2005 to april 2007 . all patients were offered open radical cystectomy or robot - assisted radical cystectomy , and all chose the robotic procedure . data were collected prospectively using medical record committee - approved forms and entered into a database required as part of an institutional quality assurance initiative . appropriate patients were given the choice of orthotopic continent diversion , cutaneous continent diversion , and ileal conduit urinary diversion . all diversions were performed in extracorporeal fashion , except for one neobladder that was created robotically . patients were divided into 3 cohorts : normal weight ( bmi < 25 ) , overweight ( bmi=25 to 29 ) and obese ( bmi=30 to 39.9 ) for the purpose of comparison . the effect of bmi on preoperative variables , intraoperative parameters and early postoperative results was evaluated . fisher 's exact test was used to study the association between categorical variables and bmi group . secondary analyses , based on ungrouped bmi values , were performed using either the exact test corresponding to the spearman rank correlation or logistic regression depending on the nature of the outcome variables . mean bmi was 28 , and 71% of the patients were over - weight or obese . two patients were converted to an open cystectomy : one patient was unable to tolerate a steep trendelenberg position and one patient had a large posterior tumor extending into the rectum . three fourths of patients were male , and sex distribution was similar in each bmi group . age and asa scores were similar across groups with mean age 67 and mean asa score 2.3 ( table 1 ) . demographics / cohort characteristics * for numerical variables , statistics represent mean ( sd ) ; for categorical variables , statistics represent frequency ( relative frequency ) . the mean operative time for pelvic lymph node dissection was 44 minutes and was similar in all cohorts . blood loss varied among the 3 groups but did not correlate with bmi ( table 2 ) . intraoperative parameters * for numerical variables , statistics represent mean ( sd ) ; for categorical variables , statistics represent frequency ( relative frequency ) . statistics represent mean ( sd ) ; for categorical variables , statistics represent frequency ( relative frequency ) . twenty - one patients had organ - confined bladder cancer , 18 patients had tumor extending into perivesical adipose tissue , and 10 patients had tumor extending into surrounding organs . five positive surgical margins occurred in the overweight cohort , and one positive margin occurred in the obese cohort ( p=0.05 ) . two surgical margins were positive ( 11% ) in pt3 patients , and 4 ( 40% ) surgical margins were positive in pt4 patients . the greatest numbers of lymph nodes were extracted from obese patients , but no significant difference existed among the 3 groups . thirteen postoperative complications occurred ; 3 developed in the normal weight cohort , 6 in the overweight cohort , and 4 in the obese cohort ( p=0.77 ) . postoperative stay and complications dvt = deep venous thrombosis , uti = urinary tract infection , psbo = partial small bowel obstruction , sbo = small bowel obstruction , c. difficile = clostridium difficile obese patients have increased risk for multiple medical problems that can adversely affect surgical outcomes . in the common toxicity criteria for adverse events of the cancer therapy evaluation program , being overweight ( bmi>25 ) is graded as a moderate risk of an adverse event , obesity ( bmi=30 to 39.9 ) is graded as a severe risk , and morbid obesity ( bmi>40 ) is considered life threatening . obesity with or without comorbidities can lead to deranged cardiovascular physiology leading to eccentric left ventricular hypertrophy that significantly increases the risk for future perioperative cardiovascular events , such as acute myocardial ischemia , myocardial infarction , congestive heart failure , and sudden death . several series have reported an increased incidence of obesity in patients with pulmonary embolism and deep venous thrombosis . increased incidence of bodily infections , including wound infections , numerous investigators have reported on the affect of an elevated bmi on various minimally invasive surgical procedures . singh et al reported increased blood loss and operative times during laparoscopic prostatectomy in patients with elevated bmi . mikhail et al reported similar findings in a study of 150 patients who underwent robotic prostatectomy . dominguez et al revealed longer operative times and higher blood loss in patients with elevated bmi during laparoscopic splenectomy . however , other investigators did not find a significant difference in outcomes when operating on overweight or obese patients . colombo et al demonstrated that bmi had no significant impact on outcomes after laparoscopic nephrectomy . robot - assisted prostatectomy data from the australian institute of robotic surgery suggest that vesicourethral anastomotic times were greater in obese patients , but the overall operative times were similar regardless of bmi . furthermore , the overall complication rates from the australian series were similar during the immediate postoperative period . boczko et al reported similar findings in 375 patients who underwent robot - assisted radical prostatectomy . chang et al reported that overweight and obese patients had elevated blood loss and longer operative times during open radical cystectomy . in their series lee et al reported increased blood loss , prolonged operative times , and increased complication rates in patients with elevated bmi in their open radical cystectomy series . the current series is the first to evaluate the effect of bmi on robot - assisted radical cystectomy . unlike the results reported by chang et al and lee et al , operative time , blood loss , and the complication rate did not significantly differ among the 3 cohorts in our series , demonstrating the decreased impact of elevated bmi on the performance of robot - assisted radical cystectomy . robot - assisted bladder extirpation was quicker in patients with bmi greater than 25 , while extracorporeal urinary diversion took longer in obese and overweight patients ( p>0.05 ) . the only adverse affect of elevated bmi was an increase in the rate of positive surgical margins ( p=0.05 ) . all positive margins occurred in patients with pt3 or pt4 disease and 4 of the 6 patients with positive margins had nodal metastasis . the positive margin rate of 21% in patients with bulky tumors ( pt34 ) was higher than the 12% positive margin rate for bulky disease noted by herr et al . hafron et al demonstrated that while soft tissue margins impact overall survival , no significant difference in disease - specific survival or overall survival was seen in obese , overweight , and normal weight patient populations . however , to our knowledge , no large robot - assisted radical cystectomy series have been published to date . another limitation is the retrospective nature of our study and the lack of a prospective , randomized comparison with open radical cystectomy . the analysis was performed retrospectively , but the data were collected prospectively as part of an institutional quality assurance initiative . robotic - assisted radical cystectomy can be considered in patients with elevated bmi because complication rates , operative times , and blood loss were similar in patients from the average , overweight , and obese bmi categories . our data suggest that wider surgical excision is needed in patients with elevated bmi to decrease the risk of a positive surgical margin . department of health and human services , centers for disease control and prevention , 19992002 .
background and objectives : obesity is a major comorbidity in the western world and influences outcomes of patient care . a minimally invasive approach towards radical cystectomy has been increasing in popularity . 
 we sought to determine the influence of body mass index ( bmi ) on robot - assisted radical cystectomy.methods:fifty-one consecutive patients underwent robot - assisted radical cystectomy for bladder cancer from october 2005 to april 2007 and were categorized into 3 groups based on their weight : normal ( bmi < 25 ) , over - weight ( bmi=25 to 29 ) and obese ( bmi= 30 to 39.9 ) . 
 effect of bmi on intraoperative , pathologic , and postoperative outcomes was assessed by retrospective review of the robot - assisted radical cystectomy database.results:mean bmi was 28.0 , and 71% of the patients were overweight or obese . 
 bmi did not correlate with age , sex , or american society of anesthesiologists ( asa ) score . 
 overweight and obese patients had similar operative times and estimated blood loss compared with patients with normal bmi . 
 overweight and obese patients with bulky disease ( pt34 ) had significantly higher rates of positive surgical margins ( p=0.05 ) . 
 complication rates were similar.conclusion:robotic-assisted radical cystectomy can be considered for patients of all body mass indices . 
 wider excision should be performed in patients with higher bmi .