The Isthmocele: A Comprehensive Review of Anatomical Defects and Fertility Implications

Isthmocele, also known as a uterine niche or cesarean scar defect, is a 1 to 2 mm defect in the anterior myometrium that appears as a hypoechoic triangle at the location of the lower segment caesarean section scar. The term is derived from the Greek words “isthmo” (uterine isthmus) and “cele” (cavity or pouch). The number of cases of isthmoceles varies significantly in the medical literature, with approximately 30% of afflicted women exhibiting symptoms. The Delphi consensus classified the disorder as Caesarean Scar Disorder (CSD), characterized as a uterine niche with at least one major symptom (postmenstrual spotting, discomfort during uterine bleeding, technical problems after embryo transfer) or two secondary symptoms (unexplained infertility and intrauterine fluid). Isthmocele is a serious iatrogenic condition of caesarean birth that might have long-term consequences for reproductive health. The pathophysiological pathways connecting isthmocele and infertility are diverse, comprising mechanical impediment, chronic inflammation, intrauterine fluid buildup, and disturbance of normal uterine contractility and receptivity. Diagnostic advances, such as upgraded ultrasonography methods and standardized criteria, have facilitated the identification and characterization of many abnormalities. Therapeutic options are evolving, with less invasive surgical procedures exhibiting excellent success in treating problems and restoring fertility. However, considerable knowledge gaps persist, and further research is needed to better understand the best surgical method for different defect shapes and long-term obstetric outcomes following surgical repair. The growing global caesarean rate ensures that isthmoceles will remain a major clinical problem in reproductive medicine.