Differences of alternative methods of measuring abdominal wall hernia defect size: a prospective observational study

Despite the importance of defect size, there are no standardized recommendations on how to measure ventral hernias. Our aims were to determine (1) if any significant differences existed between various methods of measuring ventral hernias and (2) the effect of these methods of measurement on selection of mesh size.

A prospective study of all patients enrolled in a randomized trial assessing laparoscopic ventral hernia repair at a single institution from 3/2015 to 7/2016 was eligible for inclusion. Abdominal wall hernia defect size was determined by multiplying defect length and width obtained separately using each of five methods: radiographic (CT), intraoperative with abdomen desufflated, intraoperative with abdomen insufflated to 15 mmHg (intra-abdominal aspect), intraoperative with abdomen insufflated to 15 mmHg (extra-abdominal aspect), and clinical. The primary outcome was intraclass correlation between the five different methods of measurement for each patient. Secondary outcome was changes in mesh selection assuming a 5 cm overlap in each direction.

Fifty patients met inclusion criteria for assessment. The five different measurement methods had an intraclass correlation for each patient of 0.533 (95% CI 0.373-0.697) (weak correlation) for length; 0.737 (95% CI 0.613-0.844) (moderate correlation) for width; and 0.684 (95% CI 0.544-0.810) (moderate correlation) for area. Different types of measurements affected mesh selection in up to 56% of cases.

Among five common methods of measuring abdominal wall hernia defect, sizes are only weakly to moderately correlated. Further studies are needed to determine which method results in optimally sized abdominal wall prostheses and superior ventral hernia repair.