Many studies have been performed to determine whether there is an actual presence of a VNO in adult human beings. Trotier et al. estimated that around 92% of their subjects that had no septal surgery had at least one intact VNO. Kjaer and Fisher Hansen, on the other hand, stated that VNO structure disappeared during fetal development as it does for some primates. However, Smith and Bhatnagar (2000) asserted that Kjaer and Fisher Hansen simply missed the structure in older fetuses. Won (2000) found evidence of a VNO in 13 of his 22 cadavers (59.1%) and in 22 of his 78 living patients (28.2%). In a study published in 2016, Stoyanov et al. found the organ to be present in 26.83% of the Bulgarian population, using retrospective analysis of nearly a thousand outpatient nasal endoscopies.