Association between cesarean scar defect and adenomyosis in patients with abnormal uterine bleeding

Background: The prevalence of cesarean section (CS) has recently increased dramatically. Cesarean scar defect (CSD) is one of the most common complications of CS. This study aims to investigate and compare the depth and volume of the CSD in symptomatic patients with and without uterine adenomyosis. Methods: This retrospective case-control study was done from November 2020 to November 2022 at our referral women's hospital. The patients who underwent sonohysterography with a previous history of one or two CS for at least one year ago and chief complaints of abnormal uterine bleeding were included in our study. The patients with myometrial or endometrial pathology were excluded from the study. The symptomatic patients who met the inclusion criteria were divided into two groups: with adenomyosis (case) and without adenomyosis (control). The demographic data, medical history, and sonohysterography findings were obtained from the patient’s documents and archived images. In sonohysterography, CSD features, including the length, depth, width, volume, RMT (Remained Myometrial Thickness), AMT (Adjacent Myometrial Thickness), and RMT/AMT were measured. To analyze the variables, t-tests, and chi-square were used. Results: Among 310 symptomatic women with a history of previous cesarean section underwent sonohysterography, 160 patients met the inclusion criteria (case group with adenomyosis: 82 patients and control group without adenomyosis: 78 patients). The chief complaints were post-menstrual bleeding (43.8%), prolonged bleeding (34.3%), and intermenstrual bleeding (21.9%). In the case group, 25.6% had CSD with RMT<2mm, but in the control group (without adenomyosis), only 6.4% had RMT<2mm. CSD depth and volume were significantly larger in patients with underlying adenomyosis (P-value of 0.002 and 0.038, respectively). Also, the mean RMT and RMT/AMT ratio were significantly lower in the case group (P-values of 0.004 and 0.00, respectively). Conclusion: Our study demonstrated a strong association between the presence of adenomyosis and larger CSDs. To establish a causative relationship, we suggest a prospective cohort study to follow up the patients and compare the evolution of CSD in patients with and without adenomyosis.