"Niche" a divertuculum of the myometrial cesarean section scar - etiology, diagnostics and symptoms

Niche, a newly described in the Polish literature complication of a cesarean section, is defined as a triangular anechoic deficient scar of the uterine myometrium, localized in the site of the scar after the incision of a typically performed low-transverse cesarean delivery. The aim of the paper is to provide an overview of the available literature on the diagnosis and symptoms of niche. Diagnostic evaluation of a niche comprises of visual diagnostic methods: transvaginal ultrasonography to localize the cesarean scar and contrast-enhanced sonography as the method of choice for measuring the depth of the niche, residual myometrial thickness, and total myometrial thickness. The niche development mechanism remains to be fully elucidated. It is believed to be a coincidence of many factors, including the closure technique, development of the lower uterine segment, location of the incision, and wound healing. The symptoms related to the presence of a niche are: abnormal uterine bleeding, lower abdominal pain, infertility, urination problems, and obstetrical complications which may be life-threatening for both, the woman and the fetus. The suggested correlation between the niche and the complications in future pregnancies, e.g. uterine rupture and implantation of the gestational sack in the site of the diverticulum, remains unexplained.