Objective
The objective of this study was to determine whether computed tomography (CT) is a reliable method of imaging to assess placental injury after acute trauma during pregnancy.
Study Design
This study was a retrospective review of digital CT images and electronically scanned charts of pregnant trauma patients identified from the hospital trauma registry list.
Results
Using delivery within 36 hours of trauma as the clinical marker for the occurrence of placental abruption, positive radiologic readings showed 86% sensitivity and 98% specificity. The overall accuracy was 96%.
Conclusion
Given that defined patterns on CT can be identified and those can be correlated to actual abruption, CT may be a reliable method for evaluation of placental abruption after maternal trauma, especially in the face of abdominal trauma. Our results show that CT has both good sensitivity and specificity identifying abruption and should be considered for use in the management in the pregnant patient after trauma.
Trauma has been reported to affect between 3% and 8% of pregnancies and is known to increase maternal and fetal morbidity and mortality. Placental abruption is present in up to 40% of women with severe maternal trauma and is clinically evident in 1-5% of women with minor trauma. When placental abruption occurs in the face of trauma during pregnancy, fetal and maternal life can be compromised.
Early and accurate diagnosis is imperative for fetal and maternal resuscitation. Usually evaluation for placenta disruption from the uterus is accomplished by ultrasound imaging; however, in a review of the literature, the sensitivity for ultrasound in diagnosing abruption is reported to be anywhere between 24% and 50%. Consequently, a negative scan does not rule out placental abruption.
In early abruption, which would generally be the time of evaluation after trauma, it was found that the area of abruption was hyperechoic to isoechoic compared with the placenta. Depending on the age of the abruption, the appearance on ultrasound can vary between hyperechoic, isoechoic, hypoechoic, or sonolucent, which may add to the difficulty in diagnosis in the trauma setting. Computed tomography (CT) is commonly used to diagnose nonobstetric injuries in traumas, although concerns regarding radiation exposure have limited this practice in the pregnant patient.
The American College of Obstetricians and Gynecologists guidelines discourage the use of multiple diagnostic radiology examinations while recognizing a cumulative amount of less than 5 rad has not been associated with adverse fetal effects. Moreover, according to the American College of Radiology, no single diagnostic X-ray procedure results in radiation exposure to a degree that would threaten the well-being of the developing preembryo, embryo, or fetus.
When CT is used in the evaluation of a pregnant trauma patient, the chest, abdomen, and pelvis may be scanned safely with a low-exposure technique, combined with nonionic iodinated contrast. Recognizing that CT imaging of the abdomen and pelvis is used with increasing frequency, we undertook a study to determine whether CT imaging is a reliable method in diagnosing placental abruption after trauma. In a recent study of CT evaluation of placental abruption, the authors found that true placental abruptions were large, contiguous, and retroplacental. The authors also noted that full-thickness areas of low enhancement that form acute angles with myometrium suggested abruption.
Materials and Methods
This study was a retrospective study of pregnant trauma patients. After receiving institutional review board approval on Oct. 8, 2008, a list of pregnant trauma patients from the trauma registry at Maricopa Medical Center in Phoenix, AZ, was obtained. We focused our study on patients who had abdominal CT imaging during an 18 month period.
A board-certified experienced radiologist (G.S.) with no knowledge of the clinical course reviewed the CT images, looking for placental disruption, identified by separation of the placenta from the uterus, retroplacental hematoma, and decreased percent enhancement of the placenta after trauma. Independently without seeing the CT scan or its report, an obstetrician (M.M., L.B.) reviewed the electronically scanned charts of these patients to evaluate for clinical evidence of abruption, using markers of vaginal bleeding, uterine pain, abnormal fetal heart rate tracings, contractions, and delivery. Those patients who had any of the previously listed markers that required delivery were considered potential abruption, abruption then being validated on examination of placenta at delivery.
The data were collected and recorded independently and then submitted to a member of the research department who then merged the data. Given the retrospective nature of this study, the clinicians actually caring for the patients did have access to the CT scan and its report.
Between May 2006 and November 2008, 61 pregnant trauma patients were evaluated by abdominal or pelvic CT imaging (GE 16 slice detector; GE, Waukesha, WI) at Maricopa Medical Center. All patients had intravenous contrast with iopamidol, a nonionic iodine-based contrast medium that is safety rated as category B. A low-exposure technique was not implemented because the intent of scan was not focused to a specific area of interest but a full abdomen to assess for internal injury.
The data collected were analyzed using the kappa coefficient, thus allowing measure of association between the radiologist’s judgments and the clinical course defining abruption but correcting for chance agreement. With respect to power analysis, if the CT images are not at all useful in detecting placental trauma, then we would expect that sensitivity and specificity to be 50% each. We took this as the null hypothesis.
Results
The cause of trauma was motor vehicle accident except in 4 cases of assault and 2 cases of pedestrian vehicle accident. The age range of our patient was 16-40 years with 49 of the 61 patients being under the age of 30 years. Delivery within 36 hours of trauma was used as the standard for the occurrence of placental trauma, this being validated by postdelivery comments in the patients’ record of the placenta for clots or pathology reports identifying abruption. Of the patients who delivered, all were victims of motor vehicle accidents: 4 were restrained and 3 were not.
Fifty-four patients did not deliver and 7 did deliver; 6 of these 7 had positive interpretations ( Table 1 ). Positive interpretations were retroplacental hematoma ( Figure 1 ), separation of placenta, or decreased placental enhancement ( Figure 2 ). We classified placental enhancement in 3 categories, greater than 50% enhancement was considered no abruption, 25-50% enhancement was considered equivocal, and less than 25% focal enhancement was the marker for placental abruption. The CT image representing the largest area of placenta was used in determining percentage of enhancement; this was typically of 1 slice, and a combination of axial, coronal, and sagittal views were used.
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