- Open Access
Prediction of the relationship of cesarean section scar niche and postmenstrual spotting: is there any relation?
Egyptian Journal of Radiology and Nuclear Medicine volume 53, Article number: 24 (2022)
Postmenstrual spotting has recently been related to a discontinuation of the myometrium at the site of a previous cesarean section called "CS scar niche". There was no consensus regarding the gold standard method for the assessment of the niche. Recently, Magnetic resonance imaging (MRI) has shown promise in the evaluation of the niche. Our study aims to assess the role of MRI in the evaluation of the CS scar niche characters and its association with post-menstrual spotting.
A total of 65 patients with CS niche were prospectively included in this study and subdivided into two groups, according to presence or absence of postmenstrual spotting (Group A; 34 patients with postmenstrual spotting and Group B; 31 patients without spotting). All patients were examined using a 1.5 T MRI unit. CS scar niche volume was significantly higher among women with post-menstrual spotting (0.57 ± 0.07 vs. 0.07 ± 0.05 (cm3); P < 0.001). Also, women with post-menstrual spotting have significantly higher scar length (9.38 ± 3.06 vs. 5.02 ± 2.10 (mm); P < 0.001), scar depth (6.95 ± 3.16 vs. 3.23 ± 0.99 (mm); P < 0.001), scar width (15.78 ± 3.94 vs. 9.87 ± 1.84 (mm); P < 0.001) in comparison to those without post-menstrual spotting.
Scar depth (> 7.4 mm) had 81% sensitivity and 97% specificity for prediction of post-menstrual spotting with overall accuracy was 88.7%. While scar width (> 12.8 mm) had 71% sensitivity and 97% specificity for prediction of post-menstrual spotting with overall accuracy was 83.3%. Scar volume (> 0.15 cm3) had 97% sensitivity and 100% specificity for prediction of post-menstrual spotting with overall accuracy was 98.4%.
MRI measures (CS scar volume, depth, and width) are predictors for postmenstrual spotting in patients with CS scar niche, and scar volume is the most powerful predictor.
Cesarean section (CS) is a vital procedure if performed for the correct reasons. However; increasing rates of CS were associated with a growing number of complications . Gynecological complaints like postmenstrual spotting, dysmenorrhea, chronic pelvic pain, and dyspareunia are frequently noticed after CS. These symptoms could be attributed to the incomplete uterine healing scar forming a CS scar niche or defect (CSD). That defect could be a reason for abnormal bleeding due to the recollection of menstrual blood in that defect resulting in postmenstrual spotting .
Abnormal uterine bleeding has been connected to the recollection of menstrual blood in that niche, which is periodically expelled after the end of menstruation, as well as the poor contractility of the myometrium around the scar bringing on postmenstrual spotting . In addition, the fibrotic tissue below the niche may hinder the flow of menstrual passage through the cervix . When the bloody fluid from the cesarean scar passes into the vagina it ends in abnormal bleeding but if it flows in the opposite direction toward the uterine cavity, it may result in implantation failure. The retention of blood in the uterine cavity may result in infertility via a mechanism resembling hydrosalpinx . The management of the CS scar niche (isthmoplasty) is done either hysteroscopically or by other surgical procedures . So proper assessment is mandatory before the decision of correction.
There is no consensus regarding the gold standard method for detection and measurement of the CS niche, however, morphological abnormalities in the CS can be assessed using transvaginal ultrasonography (TVUS), gel, or saline infusion sonohysterography, or hysteroscopy [7,8,9,10]. Although TVUS is the most used method for evaluation of the uterine wall, it is operator-dependent and allows evaluation of the scar in only one plane (midsagittal plane). Magnetic resonance imaging (MRI) is promising in the assessment of uterine scar thickness as it reduces the operator dependence with a superior multi-planar capability . Our study aimed to assess the role of MRI in the evaluation of the CS scar niche characters and its association with post-menstrual spotting.
This cross-sectional study included patients who attended the gynecological outpatient clinic at our institution hospital in the period between February 2019 and October 2020. The inclusion criteria were (a) patients in the child-bearing period after at least 6 months from last cesarean section age ranged between 20 and 45 years, and (b) having CS scar niche diagnosed by TVUS; defined as any anechoic area at the site of CS scar with a depth of at least 1 mm. The exclusion criteria were (a) Pregnant women (b) patients with adenomyosis, uterine fibroids, or uterine congenital anomalies (c) patients with intrauterine devices, (d) patients with a bleeding tendency and (e) patients with any contraindication to MRI.
A total of 65 patients who fulfilled the inclusion criteria were included in the study and then grouped according to the presence of postmenstrual spotting into Group A (34 patients with spotting) and Group B (31 patients without spotting).
Sample size calculation
It was calculated using EPI info7, (considering the postmenstrual spotting was reported in (28.9%) women with a niche, compared to (6.9%) without a niche, with a two-sided confidence level of 95%, power 80%, the minimum calculated total sample size was 60 with 1:1 group ratio (30 cases in each group). The sample was raised by 20% to compensate for dropouts. After applying the eligibility criteria, the final sample was 65 patients Group A (n = 34 patients) and Group B (n = 31 patients).
History of postmenstrual spotting, its duration in days. Postmenstrual spotting was defined as more than 2 days of brownish discharge at the end of menstruation with a total length of menstruation (including spotting) of more than 7 days, or inter menstrual bleeding which starts within 5 days after the end of menstruation . The patients were examined using trans vaginal ultrasound (GE B6 system, GE Healthcare) with an empty bladder using standard procedures. We evaluated the cesarean scars. On the midsagittal view, the scar was identified as a discontinuity in the architecture of the uterus and appeared as a hypoechoic line. A niche was defined as any anechoic area at the site of the cesarean scar with a depth of at least 1 mm .
Pelvic MRI technique
MRI was done using a 1.5 T imaging unit (Magnetom Sempra, Siemens, Erlangen, Germany). Patients were imaged in a supine position with moderately full urinary bladder. A localizer rapidly acquired coronal images of the entire pelvis was obtained to optimize the positioning of the multi-coil array over the area of interest.
Multiplanar Sagittal, coronal, and axial T2-weighted images were obtained to provide excellent contrast resolution for the depiction of the uterine, and cervical zonal anatomy with TR 4000 ms, TE 90 ms, 4 mm slice thickness, 1500 flip angle, and 260 × 270 mm field of view. The duration of the complete examination was about 20–25 min.
Different characters of the scar niche were evaluated as follow: The length (distance of CS niche along the long axis of the uterus in mm), width (distance of CS niche from right to left at axial images in mm), depth (vertical distance between the base and apex of CS niche in mm), and shape of the scar (droplet, semicircular, triangular, and irregular) (Fig. 1). The minimal residual myometrial thickness (RMT) at the site of the CS scar was measured from the uterine cavity to the uterine serosa in mm and compared to the myometrial thickness of the posterior uterine wall. CSD volume was assumed as a cuboid and calculated by multiplication of thickness, width, and length in cm3 .
Data was collected and analyzed using SPSS (Statistical Package for Social Science, version 20, IBM, and Armonk, New York). Continuous data were expressed in form of mean ± SD or median (range) while nominal data were expressed in form of frequency (percentage). Test of normality was performed for the main quantitative variables using Shapiro-Kolmogorov test, yielded non-significant results, indicating normality of these variables. Chi2-test was used to compare the nominal data of different groups in the study while the student t-test was used to compare the mean of different two groups. Correlation between the duration of spotting with radiological data of the scar was determined by the Pearson correlation.
Multivariate regression analysis was used to evaluate different predictors of spotting in women with CS scar. Also, the diagnostic accuracy of these predictors was assessed by the ROC curve. The level of confidence was kept at 95% and hence, the p-value was significant if < 0.05. Inter-rater reliability as regards the CS scar niche volume was estimated by calculating the intra-class correlation coefficient (ICC) based on a mean rating (K = 3), absolute agreement, two ways mixed–effect model. The level of confidence was kept at 95% and hence, the P-value was significant if < 0.05.
The mean age of women with post-menstrual spotting was 32 ± 5.75 years (ranged from 25 to 45 years) while the mean age of women without post-menstrual bleeding was 32.12 ± 5.34 years (ranged from 25 to 43 years) (Fig. 2).
Cesarean scar niche features on MRI
About half of (n = 16) women without post-menstrual spotting had a droplet shape of the CS scar niche while 18 patients (53%) of women with post-menstrual spotting have semi-circular CS scar (P = 0.02). Women without post-menstrual spotting have significantly lower scar length (5.02 ± 2.10 vs. 9.38 ± 3.06 (mm); P < 0.001), scar depth (3.23 ± 0.99 vs. 6.95 ± 3.16 (mm); P < 0.001), scar width (9.87 ± 1.84 vs. 15.78 ± 3.94 (mm); P < 0.001) in comparison to those with post-menstrual spotting (Figs. 3, 4).
CS scar niche volume was significantly higher among women with post-menstrual spotting (0.57 ± 0.07 vs. 0.07 ± 0.05 (cm3); P < 0.001). Women with post-menstrual spotting had significantly lower minimal residual myometrial thickness (mean ± SD = 2.58 ± 1.30 vs. 6.26 ± 3.97 (mm); (Median (IQR) = 2 (1) vs. 6.5 (2); P < 0.001) and significantly higher relative change percentage in the residual myometrial thickness (79.84 ± 9.24 vs. 57.26 ± 10.84 (%); P < 0.001) in comparison to those without post-menstrual spotting (Fig. 5).
Correlation of postmenstrual spotting duration with the radiological evaluation of the scar nich
Table 1 showed that the duration of post-menstrual bleeding had positive significant correlation with the scar depth (r = 0.41, P < 0.001), scar width (r = 0.51, P < 0.001), scar volume (r = 0.49, P < 0.001).
Multivariate regression analysis of the CSD features and their diagnostic accuracy
Table 2 demonstrated the presence of a statistically significant association of scar depth, scar width, and scar volume for the prediction of post-menstrual spotting. The scar depth (> 7.4 mm) had 81% sensitivity and 97% specificity with 88.7% overall accuracy while scar width (> 12.8 mm) had 71% sensitivity and 97% specificity with 83.3%overall accuracy and scar volume (> 0.15 cm3) had 97% sensitivity and 100% specificity with 98.4%overall accuracy (Fig. 6).
There was an excellent agreement between observers regarding (scar volume) with ICC = 0.97 (95% CI = 0.94–0.99) for women with postmenstrual spotting and ICC = 0.99 (95% CI = 0.96–0.99) for women without spotting.
MRI is a non-invasive method for the assessment of CS scar niche, scar volume, depth, and width represent good predictors of the development of post menstrual spotting.
Multiple previous studies reported that there is a relationship between CS scar niche and multiple gynecological symptoms [7, 10, 12,13,14,15]. The most common complaints related to CSD are prolonged menstrual bleeding and postmenstrual spotting (in up to three-quarters of women with CSD), followed by pelvic pain (39.6%), dysmenorrhea (53.1%), dyspareunia (18.3%), and secondary infertility . The retention of the blood products inside the defect and poor contractility of the uterine wall related to decreased myometrial thickness and fibrosis explained the relation between cesarean scar defects and postmenstrual spotting .
MRI can easily define CSD and can also be reviewed retrospectively. Tang et al., has compared the use of TVUS with MRI and concluded that MRI is better than TVUS for the measurement of CSD which may help to improve the therapeutic strategy for CSD. Measurements by MRI showed a better prediction of the clinical symptoms of CSD, and more reflective of the severity of clinical manifestations . However, MRI was not commonly used for CSD imaging due to its relatively high cost .
Multiple previous studies have postulated that there is a relation between CSD volume, residual adjacent myometrial thickness, and development of postmenstrual spotting based on the transvaginal ultrasound as a diagnostic method [7, 10, 16,17,18], however, a limited number of studies utilized MRI as a method for the evaluation of the CS scar defects [10, 14, 15].
Bij de Vate et al., reported that the semicircular scar defect shape is the most prevalent . In this study, the most prevalent shape was droplet followed by semicircular defect shape in 43% and 40% of patients respectively. However, post menstrual spotting was significantly related to semicircular scar defect shape than other shapes which may be related to the higher volume of the defect in semicircular scar shape.
Previous studies concluded that residual myometrial thickness (RMT) at the cesarean section scar is one of the major parameters correlated with menstrual bleeding. They defined large niches as those with a residual myometrium thickness of < 50% of that of the adjacent myometrium. Reduced myometrial thickness in combination with lower contractility because of fibrosis would induce the development of postmenstrual spotting. Also, these publications reported required residual myometrium of 2–3 mm for hysteroscopic niche resection, given the risk of perforation and/or bladder injury [7, 10, 14, 18]. In the present study, women with post-menstrual spotting had significantly lower RMT than those without post-menstrual spotting. However, RMT was insignificantly correlated with the duration of postmenstrual spotting.
He et al., used posterior wall thickness at the same level of scar center to represent anterior wall thickness before the prior cesarean section because the normal anterior and posterior uterine wall thickness is similar to one another in the normal woman . In the current study, the relative reduction in anterior wall myometrial thickness at the scar area in comparison to the posterior uterine wall was significantly higher in women with post-menstrual spotting with an average reduction of 79% in comparison to 57% without postmenstrual spotting.
Additionally, several previous studies concluded that postmenstrual spotting is related to niche volume [7, 10, 14]. The current work was in agreement with them regarding this point, also CSD volume (> 0.15 cm3) is the most important predictor for the development of postmenstrual spotting. with 97% sensitivity and about 100% specificity and 98.4% overall accuracy. In this study, scar depth and width represent other predictors for the development of postmenstrual spotting. These three parameters (depth, width, and volume) have a significant relationship with the duration of postmenstrual spotting as the increase in the defect depth, width and volume were accompanied by an increase in the duration of the postmenstrual spotting.
Limitations of this study included the cross-sectional nature of the study that jeopardize the external validity of the study and the possibility of selection bias in the control group i.e., women without postmenstrual bleeding as they are not selected from the normal population but women attending the gynecological outpatient clinic.
MRI is a reliable non-invasive method for the assessment of CS scar defects. MRI measures (CSD volume, depth, and width) are good predictor factors for postmenstrual spotting in those patients with scar volume is the most powerful predictor factor. Further multicenter comparative and validating studies against other diagnostic methods such as Ultrasound are recommended.
Availability of data and materials
Available on request with the corresponding author.
Cesarean section scar defect
Magnetic resonance imaging
Residual myometrial thickness
Antila-Långsjö RM, Mäenpää JU, Huhtala HS, Tomás EI, Staff SM (2018) Cesarean scar defect: a prospective study on risk factors. Am J Obstet Gynecol 219(5):458.e1-458.e8
Vervoort AJMW, Uittenbogaard LB, Hehenkamp WJK, Brölmann HAM, Mol BWJ, Huirne JAF (2015) Why do niches develop in Caesarean uterine scars? Hypotheses on the aetiology of niche development. Hum Reprod 30(12):2695–2702
Fabres C, Arriagada P, Fernández C, MacKenna A, Zegers F, Fernández E (2005) Surgical treatment and follow-up of women with intermenstrual bleeding due to cesarean section scar defect. J Minim Invasive Gynecol 12(1):25–28
Thurmond AS, Harvey WJ, Smith SA (1999) Cesarean section scar as a cause of abnormal vaginal bleeding: diagnosis by sonohysterography. J Ultrasound Med 18(1):13–16
Tanimura S, Funamoto H, Hosono T, Shitano Y, Nakashima M, Ametani Y et al (1999) New diagnostic criteria and operative strategy for cesarean scar syndrome: Endoscopic repair for secondary infertility caused by cesarean scar defect. J Obstet Gynaecol Res 41(9):1363–1369
Satpathy G, Kumar I, Matah M, Verma A (2018) Comparative accuracy of magnetic resonance morphometry and sonography in assessment of post-cesarean uterine scar. Indian J Radiol Imaging 28(2):169–174
Bij De Vaate AJM, Brölmann HAM, Van Der Voet LF, Van Der Slikke JW, Veersema S, Huirne JAF (2011) Ultrasound evaluation of the Cesarean scar: relation between a niche and postmenstrual spotting. Ultrasound Obstet Gynecol 37(1):93–99
Anter M, Gad M, Fahmy E, Al-Halaby A (2021) Endo-vaginal ultrasound versus hysterosalpingography in evaluation of Cesarean scar. Egypt J Hosp Med 82:773–777
Rosa F, Perugin G, Schettini D, Romano N, Romeo S, Podestà R et al (2019) Imaging findings of cesarean delivery complications: cesarean scar disease and much more. Insights Imaging 10(1):98
Tang X, Wang J, Du Y, Xie M, Zhang H, Xu H et al (2019) Caesarean scar defect: risk factors and comparison of evaluation efficacy between transvaginal sonography and magnetic resonance imaging. Eur J Obstet Gynecol Reprod Biol 242:1–6
Exhibit S, Ding N, Qi Y, He Y, Xue HD, Jin Z (2017) Morphological description of uterine scar one year after cesarean section by T2 3D SPACE 3. 0T MR.1-12. Chin J Acad Radiol 3:162–168
Florio P, Filippeschi M, Moncini I, Marra E, Franchini M, Gubbini G (2012) Hysteroscopic treatment of the cesarean-induced isthmocele in restoring infertility. Curr Opin Obstet Gynecol 24(3):180–186
Iannone P, Nencini G, Bonaccorsi G, Martinello R, Pontrelli G, Scioscia M et al (2019) Isthmocele: from risk factors to management. Rev Bras Ginecol e Obstet 41(1):44–52
Yao M, Wang W, Zhou J, Sun M, Zhu J, Chen P et al (2017) Cesarean section scar diverticulum evaluation by saline contrast-enhanced magnetic resonance imaging: the relationship between variable parameters and longer menstrual bleeding. J Obstet Gynaecol Res 43(4):696–704
Wong WSF, Fung WT (2018) Magnetic resonance imaging in the evaluation of cesarean scar defect. Gynecol Minim Invasive Ther 7(3):104
Naji O, Abdallah Y, Bij De Vaate AJ, Smith A, Pexsters A, Stalder C et al (2012) Standardized approach for imaging and measuring Cesarean section scars using ultrasonography. Ultrasound Obstet Gynecol 39(3):252–259
Vikhareva Osser O, Jokubkiene L, Valentin L (2010) Cesarean section scar defects: agreement between transvaginal sonographic findings with and without saline contrast enhancement. Ultrasound Obstet Gynecol 35(1):75–83
Van Der Voet LF, Bij De Vaate AM, Veersema S, Brölmann HAM, Huirne JAF (2014) Long-term complications of caesarean section the niche in the scar: a prospective cohort study on niche prevalence and its relation to abnormal uterine bleeding. BJOG An Int J Obstet Gynaecol 121(2):236–244
He YL, Ding N, Li Y, Li Z, Xiang Y, Jin ZY et al (2016) Cyclic changes of the junctional zone on 3 T MRI images in young and middle-aged females during the menstrual cycle. Clin Radiol 71(4):341–348
No funding was received for this study. The patients were exempted from fees of MRI for research purposes.
Ethics approval and consent to participate
The study was conducted after approval of the Ethical Committee of Faculty of Medicine, (Approval Number 17100784) and after clinical trial approval (NCT03911622). Informed written consent was obtained from each participant.
Consent for publication
All patients included in this study gave a written informed consent to publish the data contained in this study.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Bandry, K.W., Abou-Taleb, H., Seifeldein, G.S. et al. Prediction of the relationship of cesarean section scar niche and postmenstrual spotting: is there any relation?. Egypt J Radiol Nucl Med 53, 24 (2022). https://doi.org/10.1186/s43055-022-00699-y
- Cesarean section scar niche
- Postmenstrual spotting
- Cesarean section scar volume