Cesarean Scar Defect

Published on 10/03/2015 by admin

Filed under Obstetrics & Gynecology

Last modified 22/04/2025

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Cesarean Scar Defect

Synonyms/Description

Uterine dehiscence

Etiology

Cesarean sections (C-sections) are performed in the United States at the rate of 20% to 50% of deliveries depending on clinical environment and demographics. The C-section scar is readily visible sonographically in the nonpregnant uterus as a focal narrowing of the anterior lower uterine segment, which becomes more pronounced with increasing number of prior sections. There is often a small myometrial discontinuity within the scar, seen as a triangular fluid collection or “niche,” likely representing menstrual blood that pools within the defect. Many patients who have had C-sections complain of intermittent intermenstrual or prolonged menstrual bleeding. Uppal and colleagues reported that among 71 patients with a history of C-section, 29 (40%) had a sonographically visible fluid-filled defect in the hysterotomy incision, and the presence of such a defect was significantly associated with prolonged periods or intermenstrual spotting. The incidence of abnormal bleeding was more frequent in patients with larger defects, and the size of the defect or niche was directly related to the number of prior C-sections. Wang and colleagues studied 207 patients with C-section scars and also found that those who had multiple C-sections had larger myometrial defects (width and depth) compared with those with only one prior C-section. Patients with retroflexed uteri also had wider defects than those whose uterus was anteflexed.
The myometrial thickness at the C-section scar becomes thinner as the number of C-sections increases; however, there is no established norm for this measurement. The presence of a C-section scar defect and the size of this myometrial niche seem to be better predictors of abnormal bleeding and even risk of uterine dehiscence in subsequent pregnancies.

Ultrasound Findings

The C-section scar defect is a wedge-shaped cystic or hypoechoic area in the anterior lower uterine segment myometrium, directly above the level of the cervix.
Saline distention of the cavity during a sonohysterogram can further delineate the scar defect, if clinically indicated. This more clearly shows the diverticulum-like outpouching of the endometrial cavity into the thinned, scarred myometrium.
Occasionally if the patient has had a classical C-section, a vertical scar can be seen on the front of the uterus, puckering the length of the body of the uterus (see Figure C2-3).
Rarely the C-section scar can dehisce, resulting in a myometrial defect, bulging anteriorly under the bladder. This cystic mass typically has low-level echoes consistent with unclotted blood that has accumulated during menses (see Figure C2-2).

Differential Diagnosis

The appearance of a C-section scar defect is characteristic and unmistakable. If the scar has ballooned anteriorly and caused a cystic mass in the lower uterine segment, the lesion could be confused with a degenerating fibroid or even a lesion involving the floor of the bladder such as an endometrioma. Most cases of C-section scar defects do not present a diagnostic dilemma.

Clinical Aspects and Recommendations

The presence of a fluid collection in the scar defect is an important finding that may explain abnormal uterine bleeding in some patients. It has also been associated with dysmenorrhea as well as infertility. At this point, most of the research is still focused on the prevalence and conditions associated with C-section scar defects. There are some reports of surgical repair of the defects resulting in improved fertility and resolution of prolonged or intermenstrual bleeding. Given that this is a relatively new, although rapidly increasing diagnostic entity, there are as of yet no standard recommendations.

Figures

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Figure C2-1 Longitudinal view of the normal uterus of a patient with a C-section scar defect. A small amount of fluid outlines the C-section scar defect (arrow) in the anterior lower uterine segment where the C-section scar is located. The niche is formed by the puckering of the anterior wall of the uterus, just above the cervix.

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Figure C2-2 Large rounded area of dehiscence of a C-section scar ballooning anteriorly and indenting the bladder. A and B, Two-dimensional views of the lower uterine segment taken obliquely, showing the mass-like defect between the cervix and bladder. The defect (calipers) is filled with low-level echoes indicating unclotted blood. Note the proximity of the defect to the bladder. C, A 3-D longitudinal view of the anterior aspect of the uterus, showing the defect (arrows) originating from the lower uterine segment and bulging anteriorly at the level of the C-section scar.

 

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Figure C2-3 Classical C-section scar in a pregnant patient. A, Note the puckering of the anterior surface of the entire uterus (arrows). B, A 3-D multiplanar reconstruction of the uterus showing the linear vertical scar in three orientations (arrows).

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Figure C2-4 Dehiscence of the C-section scar in a pregnant patient with one prior section. The membranes are seen herniating through the defect in the lower uterine segment (arrows).

 

Suggested Reading

Bujold E., Jastrow N., Simoneau J., Brunet S., Gauthier R.J. Prediction of complete uterine rupture by sonographic evaluation of the lower uterine segment. Am J Obstet Gynecol. 2009;201:320.

Jastrow N., Chaillet N., Roberge S., Morency A.M., Lacasse Y., Bujold E. Sonographic lower uterine segment thickness and risk of uterine scar defect: a systematic review. J Obstet Gynaecol Can. 2010;32:321–327.

Monteagudo A., Carreno C., Timor-Tritsch I.E. Saline infusion sonohysterography in nonpregnant women with previous cesarean delivery: the “niche” in the scar. J Ultrasound Med. 2001;20:1105–1115.

Naji O., Abdallah Y., Bij De Vaate A.J., Smith A., Pexsters A., Stalder C., Mcindoe A., Ghaem-Maghami S. Standardized approach for imaging and measuring Cesarean section scars using ultrasonography. Ultrasound Obstet Gynecol. 2012;39:252–259.

Uppal T., Lanzarone V., Mongelli M. Sonographically detected caesarean section scar defects and menstrual irregularity. J Obstet Gynaecol. 2011;31:413–416.

Vikhareva Osser O., Jokubkiene L., Valentin L. High prevalence of defects in Cesarean section scars at transvaginal ultrasound examination. Ultrasound Obstet Gynecol. 2009;34:90–97.

Vikhareva Osser O., Jokubkiene L., Valentin L. Cesarean section scar defects: agreement between transvaginal sonographic findings with and without saline contrast enhancement. Ultrasound Obstet Gynecol. 2010;35:75–83.

Vikhareva Osser O., Valentin L. Clinical importance of appearance of cesarean hysterotomy scar at transvaginal ultrasonography in nonpregnant women. Obstet Gynecol. 2011;117:525–532.

Wang C.B., Chiu W.W.C., Lee C.Y., Sun Y.L., Lin Y.H., Tseng C.J. Cesarean scar defect: correlation between Cesarean section number, defect size, clinical symptoms and uterine position. Ultrasound Obstet Gynecol. 2009;34:85–89.

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