Bodyweight, not age, determines oesophageal length and breaking strength in rats

Abstract Background/Purpose Delayed primary repair is still the method of choice in the management of long-gap oesophageal atresia in many centres, but the timing of anastomoses varies. Some assume the infant's bodyweight to be an important factor, whereas others prefer age. We therefore aimed to clarify whether age or bodyweight determined oesophageal length in a rodent model. Methods We explanted the oesophagi of 20 Sprague–Dawley rats, aged 15 to 444 days (n = two per time point), measured bodyweight, oesophageal length, weight, and linear breaking strength to measure tissue resilience. Univariate and multivariate regression analyses were conducted to determine the influence of age and bodyweight on oesophageal length and linear breaking strength. Results All parameters were highly correlated (R > 0.8), except for age and linear breaking strength (R = 0.65). Both age and bodyweight were univariate significant predictors of oesophageal length, weight, and linear breaking strength (p  2  = 0.9031]. This was also true for linear breaking strength (p = 0.0007 and p = 0.97, respectively) [adjusted R 2  = 0.71]. Moreover, the influence of age was negligible, as the adjusted R 2 and the regression coefficient of bodyweight and its 95% confidence interval were almost identical between univariate und multinomial regressions. Conclusions Only weight determines oesophageal length and tissue resilience in rodents, whereas age is irrelevant. If a similar relationship exists in humans, it may facilitate choosing the optimum time point for delayed primary anastomosis. Level of evidence IV – Experimental Paper.