Does Body Mass Index Impact the Performance of Robot-Assisted Intracorporeal Ileal Conduit?

Abstract

Background and Purpose:

Body mass index (BMI) has been shown to influence perioperative outcomes for patients undergoing open radical cystectomy and urinary diversion. The impact of BMI on robot-assisted intracorporeal ileal conduit has not been studied.

Patients and Methods:

All patients undergoing robot-assisted radical cystectomy (RARC) with ileal conduit at our institution were offered intracorporeal ileal conduit beginning May 2009. Fifty-six consecutive patients underwent robot-assisted radical cystectomy with intracorporeal ileal conduit from May of 2009 to July 2010. Patients were categorized into three groups based on BMI: Normal (BMI <25 kg/m²), overweight (BMI=25–29 kg/m²), and obese (BMI ≥30 kg/m²). The effect of BMI on intraoperative and postoperative outcomes was assessed by retrospective review of a comprehensive RARC quality assurance database.

Results:

Median age at cystectomy was 72 (range 42–87 y), and 75% of patients were male. Median follow-up for the entire cohort was 5 months (range 12 d–16 mos). Median BMI was 27 kg/m² (range 19–47 kg/m²), and 75% of patients were overweight or obese. Age, ASA score, and overall operative time were not significantly different among the normal, overweight, and obese patients. Median urinary diversion times were 95, 151, and 124 minutes for normal, overweight, and obese patients, respectively (P=0.13).

Conclusions:

Robot-assisted intracorporeal ileal conduit can be safely performed in all body mass indices. Further studies are needed to assess long-term conduit function and stomal complications.

Introduction

O besity has emerged as a significant healthcare problem in the United States that is associated with increased healthcare costs, higher risk of comborbid conditions, and premature death.¹ Data from the National Health and Nutrition Examination Surveys demonstrate that the prevalence of obesity for adults older than age 20 was 32% for men and 35% for women in 2008.²

The influence of body mass index (BMI) on surgical outcomes remains controversial.^3
–5 Large open radical cystectomy series have demonstrated increased blood loss, longer operative times, and complications for patients with elevated BMI.^6
–8 Robot-assisted radical cystectomy (RARC) with extracorporeal ileal conduit diversion has been shown to be an efficacious alternative to open radical cystectomy in overweight and obese patients.⁴

Preliminary reports of total intracorporeal robot-assisted ileal conduit are limited and have not evaluated the impact of BMI on perioperative outcomes.⁴ Theoretical concerns for intracorporeal urinary diversion in the overweight and obese populations include limited operative space within the insufflated abdomen, inability to mobilize bowel to traverse the abdominal wall, and increased anesthetic risk because of elevated ventilation pressures that are associated with longer operative times. The goal of this study was to assess the impact of BMI on robot-assisted intracorporeal urinary diversion.

Patients and Methods

All patients undergoing RARC with ileal conduit at our institution were offered intracorporeal ileal conduit from May 2009 to June 2010. After Institutional Review Board approval, demographic and perioperative information was collected as part of a quality assurance database from 56 consecutive patients who underwent RARC with intracorporeal ileal conduit. Our technique of robot-assisted intracorporeal ileal conduit has been described.⁹

Patients were categorized into three groups based on BMI: Normal (BMI <25 kg/m²), overweight (BMI=25–29 kg/m²), and obese (BMI ≥30 kg/m²). The effect of BMI on intraoperative and postoperative outcomes was assessed by retrospective review. Complications were graded according to the Memorial Sloan-Kettering Cancer Center modified Clavien system and were included if they occurred within 90 days of surgery.¹⁰ When more than one complication occurred, the complication with highest Clavien grade was used for analysis of severity.

Statistical analyses for comparing groups in regard to categorical variables were performed using the Fisher exact test. Continuous variables were analyzed using the Kruskal-Wallis nonparametric test. Values for continuous variables are given as median (range). Values for categorical data are specified as frequency (percent). Statistical analysis was performed using SAS statistical analysis software version 9.2 (SAS Institute Inc, Cary, NC). A nominal significance level of 0.05 was used.

Results

Median age at cystectomy was 72 years (range 42–87 y), and 75% of patients were male. Median BMI was 27 kg/m² (range 19–47 kg/m²), and 42 (75%) patients were categorized as obese or overweight (Table 1). Median follow-up for the cohort was 5 months (range 12 d–16 mos). Demographic and pathologic data are presented in Table 1. Mean lymph node yield was 25 (standard deviation±13), and 9 (16%) patients had positive lymph nodes. Nine (64%) patients in the normal weight group had a history of abdominal surgery compared with 11 (52%) and 14 (67%) in the overweight and obese groups, respectively.

Table 1.

Patient Demographics

	BMI
BMI	Normal (n=14) <25	Overweight (n=21) ≥25 – <30	Obese (n=21) ≥30	P value
Sex
Male	8	18	16	0.16
ASA score (%)
1–2	8 (62)	9 (43)	9 (45)	0.61
3–4	5 (38)	12 (57)	11 (55)
Previous surgery (%)	9 (64)	11 (52)	14 (67)	0.69

BMI=body mass index; ASA=American Society of Anesthesiologists.

Median overall operative time was 356 minutes and was not significantly different among the normal, overweight, and obese groups (P=0.2). Median urinary diversion time was 95, 151, and 124 minutes for normal, overweight, and obese groups, respectively (P=0.128). No procedure needed conversion to open ileal conduit. Median estimated blood loss was significantly higher in the overweight and obese group compared with normal weight patients (P=0.0002) (Table 2).

Table 2.

Operative and Pathological Data

	BMI
BMI	Normal (n=14) <25	Overweight (n=21) ≥25 – <30	Obese (n=21) ≥30	P value
Diversion time (min)	95 (37–245)	151 (42–360)	124 (58–270)	0.13
Total operative time (min)	349 (233–410)	380 (246–510)	349 (255–564)	0.2
Blood loss (mL)	150 (50–400)	300 (100–3900)	500 (100–1700)	0.002
Pathologic stage
T₀ –T₁	4	6	9
T₂	3	6	2	0.34
T₃	6	9	7
T₄	0	0	3
Mean lymph node yield	22	23	29	0.36
Number of patients with positive lymph nodes	1	3	5	0.53

Data in parentheses represent ranges.

BMI=body mass index.

Length of stay and Clavien grade of complications were similar in all groups (P=0.51, P=0.08) (Table 3). The number of postoperative complications in each group was not significantly different (P=0.36). There were a total of 16 readmissions within 30 days with no difference between the three groups (P=0.86). Four (25%) patients were readmitted for ileus, four (25%) for pyleonephritis or pneumonia, three (19%) for dehydration, two (12.5%) for lymphocele, and one (6%) for diverticulitis (Table 3). One patient with a BMI of 34 kg/m² returned to the operating room within 30 days for a fascial dehiscence (site of specimen removal).

Table 3.

Postoperative Characteristics by Body Mass Index Group

	BMI
	Normal <25 kg/m² (n=14)	Overweight ≥25 – <30 kg/m² (n=21)	Obese ≥30 kg/m² (n=21)	P value
Complications	6 (43)	14 (67)	12 (57)	0.36
Clavien grade
1–2	3	12	6	0.087
≥3	2	2	6
Length of stay days	7 (5–18)	8 (6–17)	8.5 (5–43)	0.51
Readmission within 30 days	3 (23)	7 (33)	6 (32)	0.86

All data in parentheses represent percentages or ranges.

Discussion

Previous studies have shown that obesity is associated with greater perioperative risks after radical cystectomy.^6,8,11 Similar studies for patients undergoing laparoscopic radical prostatectomy have shown increased blood loss and operative times in patients with elevated BMI.^12
–14 Other reports have demonstrated no difference in outcomes for laparoscopic surgery in patients with elevated BMI.^15,16

Two large series directly evaluated the impact of obesity on open radical cystectomy outcomes. Chang and colleagues⁸ reported that overweight and obese patients had higher blood loss and longer operative times. Lee and associates⁶ reported an increased complication rate, operative time, and estimated blood loss in patients with an elevated BMI. In addition, Svatek and coworkers⁷ found that patients undergoing radical cystectomy with an elevated BMI were at an increased risk of postoperative paralytic ileus.

In our initial experience of 51 consecutive patients who underwent RARC and extracorporeal ileal conduit, we found no difference in operative time, blood loss, and complications rates between all BMI subgroups.⁴ Bladder extirpation was faster in patients with BMI >25, while extracorporeal diversion took longer in the overweight and obese groups. Obese patients in that series had decreased blood loss compared with normal weight patients.

The current series is the first to evaluate the influence of BMI on robot-assisted intracorporeal ileal conduit diversion after RARC. Unlike our previous study, BMI did not affect diversion time. In contrast, however, patients in the current series with BMI ≥30 kg/m² did have an increased blood loss (mean 500 mL). This was less than what was reported for obese patients in both large open series. The increased estimated blood loss in the elevated BMI groups may be explained by the increased presence of intra-abdominal fat and mesenteric fat. Another possible explanation is that the intracorporeal conduit is performed at the end of the operation and the respiratory effects of the extreme Trendelenburg position begin to affect patients who are overweight or obese to a greater degree. This may in turn lead to a decrease in pneumoperitoneum during this portion of the operation for overweight and obese patients, which leads to an increased risk of bleeding.

Similar to the open series, BMI was not associated with length of stay or severity of complications. In contrast to previous open series, however, the number of complications was similar in all BMI classes. While this study may be underpowered to detect a difference in reoperative risk, obesity has been shown in other studies to be a risk factor for dehiscence.¹⁷

Previous studies have demonstrated that obesity is a risk factor for stomal complications.^18
–20 Increased abdominal pressure and abdominal wall thickness are thought to contribute to the development of parastomal hernias, stomal stenosis, and stomal retraction. Kouba and colleagues²¹ reported an increased incidence of stomal complications in obese patients undergoing radical cystectomy with ileal conduit diversions. Of 137 patients, the incidence of stomal complications was 27.3% in obese patients and 16.4% in overweight patients compared with 4.1% in normal weight patients. The minimum follow-up time in that study was 12 months, and mean time to develop parastomal hernia was 8 months. There were no stomal complications in the current study; however, complication follow-up was limited to 90 days.

To our knowledge, no intracorporeal ileal conduit series evaluating the impact of BMI have been published. The current study has several limitations, including small sample size and the retrospective nature. As in some of the large open series, our institution is a tertiary referral center, and complications treated outside may be underreported. Also, long-term (>90 d) complications were not analyzed in this study. Finally, the outcomes from this series represent those of a single surgeon with fellowship training in robotic surgery and extensive previous robotic surgery experience. These results, as in large open series, therefore, may not be applicable to all urologists.

Conclusion

Robot-assisted intracorporeal ileal conduit can be performed safely in patients of all BMI indices. Further studies are needed to assess long-term conduit function and stomal complications.

Footnotes

Disclosure Statement

Dr. Guru is a board member with Simulated Surgical Systems. For all other authors, no competing financial interests exist.

Abbreviations

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