To determine whether the development of a hydronephrosis-like pathology in Tspan7 transgenic mice is due to spontaneous development in inbred mice or depends on an additional developmental component due to genetic engineering, we calculated the odds ratio (OR) by comparing the incidence of mice with both large kidneys and a small liver between Tspan7 transgenic and intact mouse groups. This evidence concerns the gene TSPAN7 and hydronephrosis.