MRI Signs Associated With Bladder Injury During Cesarean Delivery in Severe Placenta Accreta Spectrum Disorders

Background: Bladder injury during cesarean delivery (CD) in pregnant women with severe placenta accreta spectrum (PAS) disorders mostly occurs in the dissection of vesico-uterine space. Placental MRI may help to assess the risk of bladder injury preoperatively.

Purpose: To identify the high-risk MRI signs of bladder injury during CD in women with severe PAS.

Study type: Retrospective.

Subjects: One hundred sixty-seven women with surgically confirmed severe PAS, defined as to increta or percreta, who underwent planned CD and available placental MRI.

Field strength/sequence: 1.5 Tesla, half-Fourier single-shot turbo spin echo sequence and true fast imaging with steady state free precession sequence.

Assessment: Presence of following imaging features of the vesico-uterine region were independently evaluated by three radiologists (with 8, 8, and 15 years of experience, respectively): vesico-uterine space hypervascularity, vesico-uterine space without chemical shift line, bladder wall interruption with hyperintense nodularity, bladder tenting, and uterine-placental bulge.

Statistical tests: Univariable analyses (Chi-square or Fisher's exact test) and multivariable regression analyses were used. A P value <0.05 was considered significant.

Results: Thirty-three of the women (19.8%) experienced bladder injury during CD. MRI features were significantly more frequent in the bladder injury group compared with the no bladder injury group: 69.7% vs. 26.9% in vesico-uterine space hypervascularity, 57.6% vs. 21.6% in absent chemical shift line in the vesico-uterine space, 18.2% vs. 1.5% in bladder wall interruption with hyperintense nodularity, 39.4% vs. 14.9% in bladder tenting, and 78.8% vs. 39.6% in uterine-placental bulging. Vesico-uterine space hypervascularity, absent chemical shift line, and uterine-placental bulge were independently associated with the risk of bladder injury (odds ratios: 4.190, 3.555, and 3.569, respectively).

Data conclusion: Vesico-uterine space hypervascularity, vesico-uterine space without chemical shift line and uterine-placental bulge were associated with bladder injury during CD in women with severe PAS.

Plain language summary: Bladder injury is a serious complication of cesarean delivery in pregnant women with severe placenta accreta spectrum, frequently resulting in massive hemorrhage, bladder dysfunction and severe infection. Accurate prenatal assessment is important to minimize these adverse consequences. This study showed that MRI features, including vesico-uterine space hypervascularity, vesico-uterine space without chemical shift line and uterine-placental bulge, were independently associated with bladder injury. These high-risk MRI signs may serve as effective means for prenatal assessment of bladder injury. This study would broaden the application of MRI in severe placenta accreta spectrum.

Evidence level: 3 TECHNICAL EFFICACY: Stage 2.