Title: The Added Diagnostic Value of Transvaginal Ultrasound to Transabdominal Ultrasound in Detection and Assessment of Placenta Previa
Authors: Ola Mohamed Darwish, Alaa Eldin Mohamed Mustafa
DOI: https://dx.doi.org/10.18535/jmscr/v6i1.01
Abstract
Aim: To evaluate the added diagnostic value of the transvaginal ultrasound (TVUS) to transabdominal ultrasound (TAUS) in the detection and evaluation of placenta praevia (PP).
Methods: This study was carried out on 46 pregnant women during the second trimester, the third trimester or both, over two year’s duration. The study group was divided into two main groups: a- The pathological group including 8 pregnant women who were diagnosed to have abnormal relation of their placentae to the internal os in the 2nd trimester. Only two of them were diagnosed to have PP in the third trimester and the remaining six were excluded from the study b- The control group which included 20 pregnant women who were diagnosed to have normal relation of their placentae to the internal os by both TAUS and TVUS. The findings of both techniques were compared with each other and with the operative results after cesarean sections (CS). Statistical analysis was carried out using Chi-square test, Fisher’s Exact or Monte Carlo correction & Student t-test.
Results: TAUS correctly diagnosed 12/12 (100%) cases of PP totalis, 2/2 cases of PP near totalis, 3/4 cases of PP marginalis. While it overestimated one case of PP marginalis as PP totalis, in addition to false positive diagnosis of PP in two cases who were falsely diagnosed as PP marginalis in one case and low lying placenta in another case. Both cases were diagnosed as normal by TVUS and operative room data. TAUS succeeded in negation of PP in all 20 (100%) control cases. It showed 100%, 90%, 90% and 100% sensitivity, specificity, positive predictive value and negative predictive values respectively. TVUS showed true positive diagnosis of PP in 100% of cases, and negated PP in all 20 control pregnant women (true negative diagnosis). It correctly excluded the false positive diagnosis in two cases as low lying placenta and PP marginalis suggested by TAUS. It also corrected another overestimated diagnosis of PP totalis in a case of PP marginalis by TAUS. It showed 100% diagnostic accuracy, sensitivity, specificity, positive predictive value & negative predictive value.
Conclusion: Diagnosis of PP should not be established except on the 3rd trimester. TAUS has higher incidence of false positive diagnosis of PP in comparison to TVUS. TVUS is a valuable procedure to compliment TAUS in the evaluation of patients with suspected PP.
Keywords: Transabdominal ultrasound, Transvaginal ultrasound, Placenta previa.
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