Background: While NOTES promises incisionless access to the abdomen, for the foreseeable future laparoscopic entry will be via trocars. Understanding abdominal wall morphology is a key to optimal trocar placement, operative planning, and port design.
Methods: In a non-selected consecutive series of patients undergoing laparoscopic surgery of the foregut, colon, and solid organs, trocar location and abdominal wall thickness (AWT) under 12-15 mmHg of insufflation was measured. (Correlations are noted as *=p<.05)
Results: Data from 50 patients (mean age=51.3, range=18-77) with BMI average 29 (SD=6.0, range=17-46) are reported below. Averaged across all abdominal locations, BMI was predictive of AWT. However, the quality of this prediction varied across patient morphology, age, port location, and positioning. Morphology: In the non-obese population, BMI correlated well to AWT averaged across all abdominal locations (r=.53*), and at the epigastrum (r=.50), but less so in the obese population (r=.32, and r=.22).Age: Age also interacted with the strength of correlation, with BMI correlating more highly with AWT in those under age 55 overall and at the epigastrum (r=.73* and r=.63* respectively), compared to those aged over 55 (r=.56* and r=.37). Location: Umbilicus had the thinnest AWT, the lowest variability of all measured abdominal locations, and no significant correlation to BMI (r= -.37).Positioning: BMI is highly correlated with AWT when the patient is positioned laterally (r=.81*), compared to supine positions (r=.58*).Procedure: No interaction was found between the type of surgery and AWT.
Conclusions: In previous research we have shown that BMI correlates to AWT and that there are regional differences in the abdominal wall. This study, based on a larger sample, shows that there is a better correlation between BMI and AWT in the young and non-obese populations, and for patients positioned laterally. Data suggest that, because of decreased AWT and AWT-variability, coupled with AWT’s low correlation to BMI, placing a port at the umbilicus may be a useful strategy to minimize at-the-trocar wall thickness and AWT variability between patients.The data presented here may be useful in providing further refinement for the understanding of differences in AWT.