Background: Vesicouterine fistula (VUF) is a rare complication after cesarean section. It is challenging to diagnose VUF correctly. Case presentation: A 34-year-old woman complained of recurrent hematuria and urinary tract infection for more than 4 years after cesarean delivery, mostly during menstruation, without vaginal leakage and with a normal menstrual cycle. Conventional transabdominal ultrasound showed no abnormal findings in bilateral kidneys and ureters, bladder and uterus, and transvaginal ultrasound showed that the scar at the lower part of the anterior uterine wall was closely adhered to the posterior wall of the bladder. Considering that the patient had hematuria but no vaginal leakage, we assumed that the fistula was flowing unidirectionally from the uterine cavity to the bladder cavity. Therefore, we chose to inject SonoVue (ultrasound contrast agent) into the uterine cavity rather than into the bladder. After intrauterine injection of SonoVue, the ultrasound contrast agent was seen flowing from the uterine cavity into the bladder cavity through the fistula, showing a hyperechoic fistula between the posterior wall of the bladder and the uterine wall, confirming the diagnosis of VUF. The accuracy of this diagnosis was then further confirmed by both MRI and cystoscopy. Conclusions: