Uterine niche after cesarean section: a review of diagnostic methods

The consequence of each cesarean section is the uterine scar formation. In some patients, uterine scar after cesarean section heals incompletely and as a result, the uterine niche is formed. Most of the small niches are asymptomatic, but the large cesarean scar niches in nonpregnant women may cause a cesarean scar syndrome, which manifest itself as abnormal uterine bleeding, dysmenorrhea and secondary infertility. Among pregnant women, the presence of large niches may be associated with potentially life-threatening consequences, such as cesarean scar dehiscence and uterine rupture, placenta accreta spectrum disorders, placenta previa, cesarean scar pregnancy. Due to the possibility of dangerous consequences related to the occurrence of a uterine niche, in recent years many studies have focused on the term of cesarean scar niche, its risk factors, diagnostic methods and treatment options. Uterine niche can be examined using two- or three-dimensional transvaginal ultrasonography, as well as two- and three-dimensional sonohysterography, hysterosalpingography, hysteroscopy or magnetic resonance imaging. However, neither of the above diagnostic method is considered as the "gold standard". There are no unambiguous guidelines on some aspect concerning the diagnosis of cesarean scar niche. The aim of this study is to analyze and describe the diagnostic methods of cesarean section niche.