Evaluation of preoperative ultrasound signs associated with bladder injury during complex Cesarean delivery: case-control study

OBJECTIVE

Intraoperative hemorrhage and peripartum hysterectomy are the main complications in patients presenting with a low-lying placenta or placenta previa undergoing repeat Cesarean delivery (CD). Patients with a high probability of placenta accreta spectrum (PAS) at birth also have a higher risk of intraoperative urologic injury. The aim of this study was to evaluate the ultrasound signs and intraoperative features associated with these injuries.

METHODS

This was a retrospective case-control study of consecutive singleton pregnancies included in a prospective cohort of patients with a history of at least one prior CD and diagnosed prenatally with an anterior low-lying placenta or placenta previa at 32-36 weeks' gestation. All patients underwent investigational preoperative transabdominal and transvaginal ultrasound examination within 48 h prior to delivery. Ultrasound anomalies of uterine contour and uteroplacental vascularity, and gross anomalies of the lower uterine segment (LUS) and surrounding pelvic tissue at delivery, were recorded using a standardized protocol, which included evaluation of the extent of uterine contour anomalies. The diagnosis of PAS was established when one or more placental lobules could not be separated digitally from the uterine wall at delivery or during the gross examination of the hysterectomy or partial myometrial resection specimens, and was confirmed by histopathology. Data were compared between cases complicated by intraoperative bladder injury and controls from the same cohort matched at a 1:3 ratio by parity and the number of prior CDs using conditional logistic regression.

RESULTS

There were 16 (9.4%) patients with an intraoperative bladder injury in a cohort of 170 managed by the same multidisciplinary team during the study period. There were no patients diagnosed with ureteric or bladder trigone damage. There were 14 (87.5%) patients with a bladder injury that had histopathologic evidence of PAS at birth, including 11 (68.8%) cases described on microscopic examination as placenta increta and three (18.8%) as placenta creta. There was a significant (P = 0.03) difference between cases and controls in the distribution of the intraoperative LUS vascularity, whereby the higher the number of enlarged vessels, the higher the odds of bladder injury. Multivariable regression analysis revealed that both gestational age at delivery and LUS remodeling on transabdominal ultrasound were associated with bladder injury. A longer gestational age was associated with lower risk of injury. A higher LUS remodeling grade on transabdominal ultrasound was associated with an increased risk of bladder injury. Patients with Grade-3 remodeling (involving > 50% of the LUS) had 9-times higher odds of a bladder injury compared to patients with Grade-1 remodeling (involving < 30% of the LUS).

CONCLUSIONS

Preoperative ultrasound examination is useful in the evaluation of the risk of intraoperative bladder injury in patients with a history of prior CD presenting with a low-lying placenta or placenta previa. The larger the remodeling of the LUS on transabdominal ultrasound, the higher the risk of adverse urologic events. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

The role of transvaginal ultrasound in the third-trimester evaluation of patients at high risk of placenta accreta spectrum at birth

BACKGROUND

Transvaginal ultrasound imaging has become an essential tool in the prenatal evaluation of the lower uterine segment and anatomy of the cervix, but there are only limited data on the role of transvaginal ultrasound in the management of patients at high risk of placenta accreta spectrum at birth.

OBJECTIVE

This study aimed to evaluate the role of transvaginal sonography in the third trimester of pregnancy in predicting outcomes in patients with a high probability of placenta accreta spectrum at birth.

STUDY DESIGN

This was a retrospective analysis of prospectively collected data of patients presenting with a singleton pregnancy and a history of at least 1 previous cesarean delivery and patients diagnosed prenatally with an anterior low-lying placenta or placenta previa delivered electively after 32 weeks of gestation. All patients had a least 1 detailed ultrasound examination, including transabdominal and transvaginal scans, within 2 weeks before delivery. Of note, 2 experienced operators, blinded to the clinical data, were asked to make a judgment on the likelihood of placenta accreta spectrum as a binary, low or high-probability of placenta accreta spectrum, and to predict the main surgical outcome (conservative vs peripartum hysterectomy). The diagnosis of accreta placentation was confirmed when one or more placental cotyledons could not be digitally separated from the uterine wall at delivery or during the gross examination of the hysterectomy or partial myometrial resection specimens.

RESULTS

A total of 111 patients were included in the study. Abnormal placental tissue attachment was found in 76 patients (68.5%) at birth, and histologic examination confirmed superficial villous attachment (creta) and deep villous attachment (increta) in 11 and 65 cases, respectively. Of note, 72 patients (64.9%) had a peripartum hysterectomy, including 13 cases with no evidence of placenta accreta spectrum at birth because of failure to reconstruct the lower uterine segment and/or excessive bleeding. There was a significant difference in the distribution of placental location (X2=12.66; P=.002) between transabdominal and transvaginal ultrasound examinations, but both ultrasound techniques had similar likelihood scores in identifying accreta placentation that was confirmed at birth. On transabdominal scan, only a high lacuna score was significantly associated (P=.02) with an increased chance of hysterectomy, whereas on transvaginal scan, significant associations were found between the need for hysterectomy and the thickness of the distal part of the lower uterine segment (P=.003), changes in the cervix structure (P=.01), cervix increased vascularity (P=.001), and the presence of placental lacunae (P=.005). The odds ratio for peripartum hysterectomy were 5.01 (95% confidence interval, 1.25-20.1) for a very thin (<1-mm) distal lower uterine segment and 5.62 (95% confidence interval, 1.41-22.5) for a lacuna score of 3+.

CONCLUSION

Transvaginal ultrasound examination contributes to both prenatal management and the prediction of surgical outcomes in patients with a history of previous cesarean delivery with and without ultrasound signs suggestive of placenta accreta spectrum. Transvaginal ultrasound examination of the lower uterine segment and cervix should be included in clinical protocols for the preoperative evaluation of patients at risk of complex cesarean delivery.

Assessment of ultrasound features of placenta accreta spectrum in women at high risk: association with outcome and interobserver concordance

OBJECTIVES

To evaluate the prenatal ultrasound features associated with operative complications and to assess the interobserver agreement of prenatal ultrasound assessment with histopathologic confirmation of placenta accreta spectrum (PAS) in a cohort of high-risk patients with detailed intraoperative and histopathologic data.

METHODS

This was a retrospective multicenter cohort study of patients at high risk of PAS referred for specialist perinatal care and management between January 2019 and May 2022. Deidentified ultrasound images were reviewed independently by two experienced operators blinded to clinical details, intraoperative features, outcome and histopathologic findings. The diagnosis of PAS was confirmed by failure of detachment of one or more placental cotyledons from the uterine wall at delivery, and the absence of decidua with distortion of the uteroplacental interface by fibrinoid deposition on histologic examination of the accretic areas obtained by guided sampling of partial myometrial resection or hysterectomy specimens. Patients were categorized as having a low or high likelihood of PAS at birth. Interobserver agreement of prenatal ultrasound assessment with histopathologic confirmation of PAS was assessed using the kappa statistic. Primary outcome was major operative morbidity (blood loss ≥ 2000 mL, unintentional injury to the viscera, admission to intensive care unit or death).

RESULTS

A total of 102 women at high risk of PAS were referred, of whom 66 had evidence of PAS at birth and 36 did not. When blinded to other clinical details, the examiners agreed on the low or high probability of PAS, according to ultrasound features, in 75/102 cases (73.5%). The kappa statistic was 0.47 (95% CI, 0.28-0.66), showing moderate agreement. Morbidity was twice as common with concordant prenatal diagnosis of PAS vs concordant diagnosis of not PAS. Concordant assessment of high probability of PAS was associated with the highest morbidity (66.6%) and a very high (97.6%) likelihood of histopathologic confirmation.

CONCLUSIONS

The probability of histopathologic confirmation is very high with concordant prenatal assessment suggestive of PAS. The interobserver agreement for preoperative assessment with histopathologic confirmation of PAS is only moderate. Morbidity is associated with both histopathologic diagnosis and concordant antenatal assessment of PAS. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Searching for placenta percreta: a prospective cohort and systematic review of case reports

BACKGROUND

Placenta percreta is described as the most severe grade of placenta accreta spectrum and accounts for a quarter of all cases of placenta accreta spectrum reported in the literature.

OBJECTIVE

We investigated the hypothesis that placenta percreta, which has been described clinically as placental tissue invading through the full thickness of the uterus, is a heterogeneous category with most cases owing to primary or secondary uterine abnormality rather than an abnormally invasive form of placentation.

STUDY DESIGN

We have evaluated the agreement between the intraoperative findings using the International Federation of Gynecology and Obstetrics classification with the postoperative histopathology diagnosis in a prospective cohort of 101 consecutive singleton pregnancies presenting with a low-lying placenta or placenta previa, a history of at least 1 prior cesarean delivery and ultrasound signs suggestive of placenta accreta spectrum. Furthermore, a systematic literature review of case reports of placenta percreta, which included histopathologic findings and gross images, was performed.

RESULTS

Samples for histologic examination were available in 80 of 101 cases of the cohort, which were managed by hysterectomy or partial myometrial resection. Microscopic examination showed evidence of placenta accreta spectrum in 65 cases (creta, 9; increta, 56). Of 101 cases included in the cohort, 44 (43.5%) and 54 (53.5%) were graded as percreta by observer A and observer B, respectively. There was a moderate agreement between observers. Of note, 11 of 36 cases that showed no evidence of abnormal placental attachment at delivery and/or microscopic examination were classified as percreta by both observers. The systematic literature review identified 41 case reports of placenta percreta with microscopic images and presenting symptomatology, suggesting that most cases were the consequence of a uterine rupture. The microscopic descriptions were heterogeneous, and all descriptions demonstrated histology of placenta creta rather than percreta.

CONCLUSION

Our study supported the concept that placenta accreta is not an invasive disorder of placentation but the consequence of postoperative surgical remodeling or a preexisting uterine pathology and found no histologic evidence supporting the existence of a condition where the villous tissue penetrates the entire uterine wall, including the serosa and beyond.

Failure of placental detachment in accreta placentation is associated with excessive fibrinoid deposition at the utero-placental interface

BACKGROUND

The main histopathologic diagnostic criteria for the diagnosis of placenta accreta for more than 80 years has been the finding of a direct attachment of the villous tissue to the superficial myometrium or adjacent to myometrial fibers without interposing decidua. There have been very few detailed histopathologic studies in pregnancies complicated by placenta accreta spectrum disorders and our understanding of the pathophysiology of the condition remains limited.

OBJECTIVE

To prospectively evaluate the microscopic changes used in grading and to identify changes that might explain the abnormal placental tissue attachment.

STUDY DESIGN

A total of 40 consecutive cesarean delivery hysterectomy specimens for placenta previa accreta at 32 to 37 weeks of gestation with at least 1 histologic slide showing deeply implanted villi were analyzed. Prenatal ultrasound examination included placental location, myometrial thickness, subplacental vascularity and lacunae. Macroscopic changes of the lower segment were recorded during surgery and areas of abnormal placental adherence were sampled for histology. In addition, 7 hysterectomy specimens with placenta in-situ from the Boyd Collection at 20.5 to 32.5 weeks were used as controls.

RESULTS

All 40 patients had a history of at least 2 previous cesarean deliveries and presented with a mainly anterior placenta previa. Of note, 37 (92.5%) cases presented with increased subplacental vascularity, 31 (77.5%) cases with myometrial thinning and all with lacunae. Furthermore, 20 (50%) cases presented with subplacental hypervascularity, lacunae score of >3, and lacunae feeder vessels. Intraoperative findings included anterior lower segment wall increased vascularization in 36 (90.0%) cases and extended area of dehiscence in 18 (45.0%) cases. Immediate gross examination of hysterectomy specimens showed an abnormally attached areas involving up to 30% of the basal plate, starting at <2 cm from the dehiscence area in all cases. Histologic examination found deeply implanted villi in 86 (53.8%) samples with only 17 (10.6%) samples presenting with villous tissue reaching at least half the uterine wall thickness. There were no villi crossing the entire thickness of the uterine wall. There was microscopic evidence of myometrial scarification in all cases. Dense fibrinoid deposits, 0.5 to 2 mm thick, were found at the utero-placental interface in 119 (74.4%) of the 160 samples between the anchoring villi and the underlying uterine wall at the accreta areas and around all deeply implanted villi. In the control group, the Nitabuch stria and basal plate became discontinuous with advancing gestation and there was no evidence of fibrinoid deposition at these sites.

CONCLUSION

Samples from accreta areas at delivery present with a thick fibrinoid deposition at the utero-placental interface on microscopic examination independently of deeply implanted villous tissue in the sample. These changes are associated with distortion of the Nitabuch membrane and might explain the loss of parts of the physiological site of detachment of the placenta from the uterine wall in placenta accreta spectrum. These findings indicate that accreta placentation is more than direct attachment of the villous tissue to the superficial myometrium and support the concept that accreta villous tissue is not truly invasive.