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Clinical Obstetrics

Poster Session 3

(794) MRI After Ultrasound Consistent with Accreta Incorrectly Changes Diagnosis to Negative in up to One-Third

Wednesday, February 14, 2024
8:30 AM – 10:00 AM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective: Many studies have demonstrated similar sensitivity of MRI and ultrasound (US) for placenta accreta spectrum (PAS) detection; however, since all patients get an ultrasound, the relevant clinical question is not if MRI is more sensitive but whether it adds value to ultrasound in PAS diagnosis or management. Our goal was to evaluate the added value of obtaining an MRI after ultrasound in suspected PAS.

Study Design:

We reviewed 21 references from 2 recently published systematic reviews comparing the sensitivity and specificity of MRI and US in patients with clinical risk factors for PAS. Included studies reported, either directly or in a way that it could be mathematically derived, 1) # of patients with discordant or concordant MRI and US results and 2) pathologic presence or absence of PAS at delivery. Data were abstracted as follows: Discordant: 1) # MRI true positive(TP) /US false negative(FN), 2) # MRI true negative(TN) /US false positive(FP) , 3) # MRI FP / US TN, 4) # MRI FN / US TP). Concordant: 1)  # MRI TP/ US TP, 2) # MRI TN / US TN, 3) # MRI FP / US FP, 4) # MRI FN / US FN). We created pooled estimates for each category to estimate the added value of MRI under different scenarios.

Results: 460 patients with suspected PAS from 10 studies met inclusion criteria. 201 (43.6%) were US+ and 259 (56.4%) US(-) for PAS (Figure). MRI was concordant with US in 155 (77.1%) of US+ and 217 (83.7%) US(-) (Figure 1). In 46 US+ patients (22.9%), MRI was negative for PAS.  Of those US+/MRI-, MRI incorrectly changed the diagnosis to negative in 16 (34.7%), and correctly changed to negative in 30 (65.3%).  Of those US– /MRI+, MRI correctly changed the diagnosis to positive in 45.2% of cases and incorrectly confirmed the negative diagnosis in 23 (54.8%) of cases.

Conclusion:

Routinely obtaining an MRI after a positive US can lead to incorrectly changing the diagnosis to negative in up to 1/3 of patients. MRI thus may be best utilized in cases of negative ultrasound where PAS is strongly suspected or US imaging is suboptimal.