EP26.03: Isthmocele diagnosis: the optimal timing for detection

The term isthmocele refers to a iatrogenic uterine defect in the site of the scar from a previous Caesarean section or other isthmic tract surgery. Multiple Caesarean sections, maternal obesity, diabetes and retroverted uteri have been related to the typical disruption of the myometrium of the scar. A correct diagnosis is fundamental since isthmocele has been associated with several gynecological and obstetric complications. Embryo implantation was demonstrated to be compromised. Scar pregnancy risk, placenta accrete spectrum disorders and uterine rupture in subsequent pregnancies results more frequent. Transvaginal ultrasonography (TVU) should be considered the first choice for the diagnosis. Isthmocele appears as a triangular anechoic indentation communicating with the endometrial cavity within the myometrium of the lower uterine segment. The exact timing for a diagnostic ultrasound has not been clearly defined. Several studied performed diagnostic procedures during the follicular phase of the menstrual cycle. This case series presents the diagnostic path of seven patients who were referred to our centre and subsequently diagnosed with isthmocele. Five of our patients were diagnosed with isthmocele after the first Caesarean section, the remaining two were diagnosed after the second Caesarean section. All the patients underwent multiple TVU throughout the menstrual cycle. Isthmoceles varied from 15 x 6 mm to 10 x 8 mm in size. Vascularisation was clearly detected in two of the total cases. Comparing the uterine images through the different phases, the diagnosis of the isthmocele was clearer when the TVU was performed in the secretive phase of the menstruation. In the second half of the menstrual cycle, the endometrium is uniformly echogenic due to mucus and glycogen in the endometrial cells. Moreover, the endometrial thickness and the enhancement of echoes allow a better visualisation of a uterine niche facilitating the isthmocele evaluation.