Genital anomalies associated with unilateral renal agenesis are generally due to agenesis or hypoplasia of the entire urogenital ridge or distal mesonephric aberrations. However, renal adysplasia could also occur in association with anomalies of the ventral urogenital sinus. The patient presented didelphys uterus in the superior uterine segment, a septate cervix, and a simple vagina. After transvaginal puncture and injection of a contrast agent into the bulge observed in the right vaginal wall, a filled sac or cavity was detected, possibly a hemibladder. This structure continued upward with a possible dilated tortuous ureter that filled retrogradely. Magnetic resonance imaging also showed the presence of the right blind paravaginal sac. Right hemitrigone and ureteral orifice were absent in the cystourethroscopy. No right kidney was found, despite the use of multiple imaging techniques. Blind hemibladder, ectopic ureterocele, and Gartner's duct cyst seem to be a possible diagnosis associated to Müllerian malformations and supposed unilateral renal agenesis. Therefore, Müllerian anomalies without combined mesonephric alteration could be associated with conditions of the ventral urogenital sinus, including blind hemibladder or ectopic ureterocele with secondary renal dysplasia.