Impact of Body Habitus on Single-Site Laparoscopic Appendectomy for Nonperforated Appendicitis: Subset Analysis from a Prospective,Randomized Trial

Introduction

We have irreversibly crossed into the minimally invasive era. As we continue to push toward minimizing the impact of operations with single-site laparoscopic techniques, we must carefully acquire data to identify patient benefits and quantify the degree of these advantages. We recently conducted a large prospective, randomized trial with 360 children that demonstrated longer operative time, increased hospital charges, more total doses of analgesics, and higher surgeon-rated difficulty with single-site laparoscopic appendectomy versus the standard three-port approach. ¹ However, the raw difference in operative time was only 5 minutes, and length of convalescence was identical. Because the approaches are similar in objective results when compiling the results from the entire population, the question becomes which patients are more likely to derive benefit from a single-site approach and which patients may be better served with a three-port approach. Therefore, we performed subset analysis of the trial data to determine the effect of body habitus on these outcome variables.

Subjects and Methods

A thorough description of the methods of the trial has been reported. ¹ In brief, after approval from the Internal Review Board (IRB protocol number 09 07-133) children under 18 years of age who required appendectomy for nonperforated appendicitis ² were consented to either undergo single-site laparoscopic appendectomy or standard three-port approach. The study was registered with clinicaltrials.gov at the inception of enrollment. Utilizing a power of 0.90 and α of 0.05, a sample size of 360 patients was established. Surgical difficulty was subjectively estimated on a 5-point scale, where 1 is most simple and 5 is most difficult. This estimation was agreed upon by the two surgeons performing the procedures.

In this study, body mass index (BMI) was calculated and plotted on standard growth curves for age and gender for each patient. BMI percentile was then determined. Standard definitions for overweight (85–95th percentile) and obesity (>95th percentile) were used. ³ We compared normal with overweight and normal with obese patients within both the three-port group and the single-site group. We also compared the single-site results with three-port results within each body habitus classification. Continuous variables were compared using unpaired, two-tailed Student's t test. Discrete variables were analyzed with the chi-square test with Yates's correction where appropriate. Significance was defined as a P value of ≤.05.

Resuults

Patient demographics are shown in Table 1. There were no differences in age or gender when comparing the overweight or obese patients in either group with those with normal BMI percentiles.

Operative data are shown in Table 2. Body habitus had no effect on surgical difficulty in either group. Within the three-port group, there was no difference in operating time related to body habitus. Operative time was identical between normal and overweight patients with the use of the single-incision technique. However, the use of single-site laparoscopy significantly increased operative time for obese patients. Rate of wound infection was nearly identical for each weight class within the three-port group. Obese patients in the single-site group tended to have a higher rate of wound infection, but this did not reach significance. The patient who developed a postoperative abscess was of normal weight and had undergone three-port appendectomy. Length of stay after the operation, doses of narcotics, and hospital charges did not differ among the three weight classes in the three-port group. The use of single-site laparoscopy significantly increased postoperative length of stay, doses of narcotics administered, and subsequent hospital charges in the obese patients.

The results of single-site compared with three-port laparoscopy within each body habitus classification can be seen comparing the numbers from the top portion of Table 2 with the corresponding column and row of the bottom portion. These comparisons showed that the single-site technique significantly increased operating time for normal weight patients by 4 minutes (P=.004) and obese patients by 16 minutes (P=.006) when compared with the three-port technique. There were no differences for overweight patients (P=.44). We saw no difference in hospital charges between the three-port and single-site groups for normal weight and overweight patients (P=.13 and .20, respectively). However, obese patients incurred significantly higher hospital charges when undergoing single-site appendectomy (P=.04). With the single-site approach, length of stay after operation was lengthened by 3.5 hours in the overweight group (P=.04) but was unchanged in the normal and obese patients (P=.59 and .14, respectively). Higher ratings for surgical difficulty were given with the single-site approach for the normal (P=.002), overweight (P=.006), and obese (P=.014) patients. There were no differences for rate of wound infection or doses of narcotics administered postoperatively between the groups for any of the three weight classes.

Discussion

Laparoscopy rapidly gained popularity over the open approach for a variety of operations prior to the presence of prospective comparative data. After two decades since the introduction of laparoscopy for appendicitis we now have an abundance of data demonstrating the advantages.^4–12 As we progress toward more minimally invasive operations, we should use sound data to document their relative efficacy. ¹³ It would be ideal to also identify which patients benefit from the technology and which do not. This subset analysis demonstrates that obese patients undergoing single-site laparoscopic appendectomy experience longer operative times, need more postoperative narcotics, and have higher hospital charges. A previous smaller retrospective series suggested no differences in operating time or length of stay between obese and normal-weight children undergoing single-site laparoscopic appendectomy. ¹⁴ However, this large prospective dataset shows that not only does the single-site procedure require a more operating time when used on obese patients, but these patients suffer more postoperative pain. This might be expected as the umbilical incision and exposure to the fascia are more cumbersome with the single-site approach when the abdominal wall is thick. The thickness of the abdominal wall adds difficulty in bringing the appendix up when the extracorporeal method is used. Perhaps more impressive is the fact that obesity had no effect on these variables when three-port appendectomy was performed. This is because the umbilical port placement is similar, and the placement of the other ports is not influenced by the thickness of the abdominal wall. Laparoscopy has been reported as the approach of choice for morbidly obese patients with acute appendicitis compared with open appendectomy.^15,16 The usefulness of the three-port laparoscopic appendectomy in obese patients is clearly shown here where body habitus had no influence on the three-port results for which the same cannot be expected for the open procedure and was not replicated herein for the single-site approach.

The majority of the existing data regarding outcomes after single-site laparoscopic appendectomy come from retrospective and observational studies. By design, these studies are limited by selection bias, and conclusions about appropriate patient selection for a given operation are difficult. Mixed results for the effect of single-site laparoscopic appendectomy on operating time have been shown.^17–20 Our study was intentionally overpowered by traditional definitions with a power of 0.9, which is why the difference in operating time was highly significant despite only being 5 minutes longer for single-site appendectomy. ¹ The clinical relevance of this difference can be debated. A separate prospective comparison suggested similar findings with increased operating time of 9 minutes without statistical significance. ²¹ However, a third prospective study recently published showed no difference in operating time. ²² The latter two studies used a different technique and had overall longer operating times for both approaches. In this study, using the single-site operation increased operating time by only 4 minutes compared with the three-port technique in normal patients but increased operating time by 16 minutes in obese patients. Given the operation averages 30 minutes with the three-port approach across all levels of body habitus, this difference is clearly relevant.

Previous case series have been unable to define the rate of wound infection after single-site appendectomy.^23,24 Although we previously reported no difference in the rate of wound infection between the two approaches, ¹ the data presented here show a tendency for higher rates of surgical site infection in obese patients undergoing the single-site approach. Although this did not reach significance, the sevenfold increase over patients of normal weight is clinically worrisome and may serve as further deterrent to perform the operation in this patient population.

Previous studies have suggested increased postoperative pain and higher total doses of postoperative narcotics with single-site laparoscopic appendectomy.^1,19 Here we demonstrate that more doses of postoperative narcotics were required for adequate pain control in obese but not overweight patients undergoing single-site laparoscopic appendectomy. Again, this outcome was not seen with the three-port technique, suggesting that obese children are more affected by the longer umbilical incision and dissection than overweight and normal-weight individuals. Increased postoperative pain spills down to contribute to the longer length of stay for obese patients undergoing the single-site approach.

Finally, most single-site laparoscopic surgeons understand that we may incur some compromises for the advantage of a better cosmetic outcome. The importance of removing two 5-mm incisions becomes questionable in the obese population, who have an inherent abdominal cosmetic compromise, and the 5-mm incisions can be place invisibly under the belly fold. If the cosmetic advantage becomes less important or nonexistent in obese patients, then we must consider the objective detriments uncovered here. Therefore, we do not recommend the single-site approach for appendectomy in obese patients.