DOES SAMPLE SIZE AFFECT ANATOMICAL VARIATION REPORTS? CASE STUDY: ACCESSORY RENAL ARTERIES

Knowledge of variations in vascularization is essential for surgical procedures. Each kidney is normally supplied by a single artery arising from the abdominal aorta. Previous work indicates that an additional artery may supply the kidney in 9-76% of cases. We present a cadaveric study on incidence of accessory renal arteries, highlighting how sample size may affect variation in the reported incidence across studies. We hypothesize that the wide range of reported incidences may be skewed by small sample sizes. We propose a minimum required sample size for investigating the incidence of anatomical variations. Presence/absence and location of accessory renal arteries was recorded using a standardized data sheet by 1st year students from the Texas College of Osteopathic Medicine. Cadavers (n=34) observed for this study were acquired through the UNTHSC Willed Body Program. Z-score and chi-square tests were employed to compare results to previous work. Of the 34 cadavers examined, 12 (35%) had accessory renal arteries. A similar incidence (30%) is reported by Bergman et al. (2014) based on 45 studies they compiled. However, a methodologically similar study by Saritha et al. (2013) reported a much lower incidence of 12%. We hypothesize that Saritha et al.’s results are divergent from this study despite similar methodologies because of a smaller sample size (n=25). This may guide us towards a better understanding of what constitutes a representative sample in studies of anatomical variation, and propose that samples larger than 30 individuals are required to accurately reflect population-level incidence of anatomical variations.