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1998 PLENARY SESSION: IMAGING SYMPOSIUM |
1 From the Department of Radiology, University of Texas Medical School, 6431 Fannin St, MSB 2.132, Houston, TX 77030. From the Plenary Session, Friday Imaging Symposium: Acute Radiology—Where Minutes Count, at the 1998 RSNA scientific assembly. Received February 19, 1999; revision requested April 30 and received May 21; accepted May 21. Address reprint requests to S.M.G.
Index Terms: Fetus, death, 856.41 • Fetus, effects of irradiation on, 856.47 • Fetus, injuries, 856.41 • Pregnancy, 856.41 • Pregnancy, irradiation in, 856.47
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INTRODUCTION |
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 Top INTRODUCTION PREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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The cardinal principle in the management of trauma in pregnancy is that there can be no fetal survival without maternal survival. Therefore, stabilizing the mother's condition takes precedence over concerns about the fetus. The possible exception is third-trimester trauma in which the prognosis for maternal survival is poor. In this situation, immediate cesarean section may be necessary to save the fetus.
This article describes appropriate treatment of the severely traumatized pregnant patient and her fetus. It stresses the fact that immediate attention to the mother is required in cases of severe trauma in pregnancy. The specific topics discussed are prehospital management, potential effects of trauma, emergency department workup, diagnostic workup, and radiation exposure.
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PREHOSPITAL MANAGEMENT |
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TopINTRODUCTIONPREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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POTENTIAL EFFECTS OF TRAUMA |
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TopINTRODUCTIONPREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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Major injuries include shock, skull fracture, cerebral contusion, intracerebral hemorrhage, spinal column fracture or other injury, chest injury requiring a thoracotomy or tube thoracostomy, abdominal visceral or genitourinary injury requiring surgery, and pelvic fracture (5). Uterine rupture occurs in 0.6% of cases and is almost always secondary to major trauma; the rate of fetal death in this situation approaches 100% (1,7). Fetal survival has been achieved in a few cases with immediate surgery.
On arrival at the emergency department, the patient must be immediately assessed for a surgical emergency on the basis of clinical signs and symptoms. Maternal hypotension is especially worrisome because it directly affects the fetus as well. Rapid radiologic evaluation of the mother is essential. In cases of central nervous system injury, the stage of pregnancy does not appear to affect the severity of neurologic injuries in the mother. Intrathoracic injuries, which include rib fracture, pneumothorax, hydrothorax, lung contusion and collapse, and complete bronchial tear, should be investigated. The potential severity in relation to gestational age has not been well investigated. However, in regard to abdominal injuries in the mother, lacerations of the liver and spleen occur when the fetus is closer to term because the uterus is compressed by the rib cage (8). About 12 weeks after conception, pelvic trauma can be more severe due to displacement of the bladder by the uterus. With increasing gestational age, bleeding problems secondary to increased uterine flow and pelvic or venous engorgement (7) are additional potential concerns.
Maternal trauma may affect the fetus whether or not the trauma is limited to the abdomen. Of utmost importance is the fact that fetal death can occur with either minor or major trauma, and correlation with the extent of injury is not definitive. Such injuries as a minor slip or fall can lead to fetal death, usually due to incomplete or complete separation of the placenta. As a result, fetal monitoring—probably including fetal ultrasonography (US)—for bradycardia, tachycardia, and placental integrity is essential in the emergency department regardless of the severity of the injury. The following facts about the fetus in maternal trauma need to be considered:
1. The major cause of fetal death is maternal death. The fetal death rate approaches 80% in cases of maternal shock (5,8).
2. When the mother survives, the major cause of fetal death is complete (6%–66% of cases) or incomplete (30%–80% of cases) placental separation (1).
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EMERGENCY DEPARTMENT WORKUP |
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TopINTRODUCTIONPREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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First and foremost, the mother's condition must be stabilized. One should rapidly obtain a pertinent prenatal history (1), which should include whether the mother has noted fetal motion. According to the type of trauma, initial radiographs might include a bedside chest radiograph (Fig 2), an abdominal radiograph, and a lateral radiograph of the cervical spine (Table 1). If a perforated viscus is suspected, a left lateral decubitus radiograph of the abdomen can be obtained as well. Careful collimation and pelvic shielding should be used whenever possible. In critical cases, CT, especially spiral CT, is often used to rapidly provide the broadest diagnostic potential in the shortest time, especially in cases of head trauma. At one institution, CT is frequently the study of choice in severe abdominal trauma (6).
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DIAGNOSTIC WORKUP |
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TopINTRODUCTIONPREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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When one is determining what diagnostic tests to perform and when, the following points should be considered (Table 2) (13):
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2. CT is an excellent rapid screening test if it is readily available. It is also more sensitive in diagnosis of injuries affecting certain organs (eg, the pancreas). Spiral CT is advantageous because it can scan a large volume in a short time. CT will not demonstrate fetal injury in general but will show uterine rupture, placental separation (partial or complete) (Fig 5), placental ischemia, occasional fetal injuries (Fig 6), and so on. It has been suggested that significant perfusion defects in the placenta at CT may be a significant negative prognosticator of fetal survival even if US scans appear normal (6) (Figs 7, 8). If significant abdominal injuries are suspected, we prefer use of CT after the minimal amount of initial radiography.
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4. If it is available and the patient is in reasonably stable condition, MR imaging is an excellent modality, especially for evaluating suspected neural injuries in the mother. However, with acute trauma, MR imaging may not be immediately available. In these situations, CT is usually more than adequate (Fig 9).
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In cases of upper quadrant and midabdominal injury, US or MR imaging might be the first modalities considered due to their nonionizing nature. However, the role of MR imaging in this setting has not been well investigated, and motion in the abdomen compromises the usefulness of this modality. If MR imaging is used, contrast material–enhanced studies should be avoided (15). For conventional CT of the upper abdomen, we suggest obtaining 10-mm-thick sections after oral and intravenous administration of contrast material (13). If spiral CT is available, we recommend a pitch of 1.0 and a 7-mm beam width. For CT of the midabdomen in early pregnancy, when the conceptus will not be directly irradiated, we suggest imaging in the nephrographic or corticomedullary phase followed by delayed imaging to exclude active bleeding. For later stages of pregnancy, we suggest only late-phase imaging with the same technique. Pelvic evaluation is performed to investigate peritoneal fluid or skeletal injuries. If CT of the pelvis is required, we suggest 7-mm-thick sections at a pitch of 1.5–1.8. If skeletal radiographs suggest that CT evaluation of complex bone injury is needed, the technique will be governed by the imaging detail required, but the examination should be confined to the appropriate area of interest.
In evaluation of the urinary tract, microscopic hematuria without accompanying signs of a major injury is usually benign and requires no further workup of the kidney or bladder. Patients with gross hematuria and a pelvic fracture are at risk for bladder rupture and require conventional cystography (CT cystography is not the preferred technique in pregnancy due to the increased radiation dose to the fetus). Cystography should involve filling the bladder with at least 300–350 mL of contrast material followed by acquisition of an anteroposterior radiograph of the abdomen. The bladder should be drained with a catheter, and an additional radiograph should be obtained (13). If the results of the study are not diagnostic, it should be repeated with inclusion of oblique radiographs. In cases of suspected kidney injury alone, acquisition of a single intravenous pyelogram may be adequate. If unilateral nonfunction is seen or the pyelogram is nondiagnostic, performance of CT is appropriate to diagnose renal artery thrombosis or a potential major renal injury. Patients with gross hematuria and hypotension or signs of major injury involving another organ system should be examined with CT so that the intraperitoneal organs can be evaluated as well as the kidneys.
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RADIATION EXPOSURE |
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TopINTRODUCTIONPREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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In lifesaving trauma care, one should not hesitate to perform needed diagnostic imaging in any female patient of childbearing age (~12–50 years). Any such patient must be considered pregnant until this hypothesis has been disproved. Appropriate questioning of the patient and laboratory tests (ie, pregnancy tests) should be performed if time permits. The following axioms are appropriate: "When a woman requires an emergency radiological examination there should be no hesitation to do the study" (16) and "If the study requires direct exposure to the conceptus and there are no satisfactory diagnostic alternatives, the radiologist should proceed and not hesitate to complete the procedure properly" (16).
The International Commission on Radiological Protection (17) has issued the following guidelines for radiologic examination of pregnant patients:
When pregnant women require . . . radiological examinations, in which the primary beam irradiates the foetus, care must be taken to ascertain that the examination is indeed indicated. Sometimes the risk of irradiating the foetus is much less than that of not making a necessary diagnosis. . . . In such cases, . . . minimize the number of views and . . . absorbed dose per view. However, these alterations of technique should not be done to the undue detriment of the diagnostic value.
The International Commission on Radiological Protection (18,19) has also developed the following useful guidelines:
During the first 10 days following the onset of a menstrual period, there can be no risk to any conceptus, since no conception will have occurred. The risk to a child who had previously been irradiated in-utero during the remainder of a 4-week period following the onset of menstruation is likely to be so small that there need be no special limitation on exposures required within these 4 weeks. . . .
. . . exposure of the embryo in the first three weeks following conception is not likely to result in deterministic or stochastic effects in the liveborn child. A pregnant patient is likely to know, or at least suspect, that she is pregnant after one missed menstruation, so the necessary information on possible pregnancy can, and should, be obtained from the patient herself. If the most recent menstruation has been missed, and there is no other relevant information, the woman should be assumed to be pregnant.
The radiologist must direct the imaging sequence in light of the preceding information. In general, required radiography confined to portions of the body outside the abdomen may be performed during any stage of pregnancy. Abdominal shields for extraabdominal radiography may be used as supplemental protection. Even though its value is frequently negligible, this supplemental shielding protects against inadvertent direct pelvic exposure and frequently comforts the patient.
In pregnancy, low-dose radiology is defined as conventional radiography of the extremity, head, or thorax; CT of the head; MR imaging; and US. CT of the chest is considered low dose as long as the study is tailored to avoid direct exposure of the fetus. Such studies may be undertaken without anxiety if proper shielding and collimation are used. On the other hand, high-dose emergency radiology consists of such techniques as abdominal or pelvic radiography, special procedures, and CT of the abdomen. (Nuclear medicine studies, if desired, may deliver high or low doses depending on the radiopharmaceutical, the condition of the patient, and the amount of activity administered [16].)
Important guidelines include the following (16):
1. Properly performed radiologic studies expose the fetus to only low-dose radiation. The principal concern is when multiple higher-dose examinations involving the uterus (CT, angiography, etc) are performed.
2. Doses from angiography performed with collimated techniques and careful attention to minimizing beam-on time in fluoroscopy are usually below the threshold of concern.
3. CT, when properly performed with modern equipment, should be reasonably safe. The dose from CT becomes a more important issue when multiple passes through the fetus are involved.
4. Alternative imaging techniques should be carefully considered, or appropriate modifications of the already selected study should be made to lessen the fetal radiation dose.
5. The effect of contrast agents on the fetus is unknown, but no untoward effect has been recognized in rats and rabbits.
When the risk-benefit analysis is considered, the following concepts seem appropriate:
1. There is, at best, only a slight possibility of induced carcinogenesis in all stages of pregnancy (eg, roughly 0.2%–0.8% for pelvic CT delivering a 50-mGy dose to the conceptus) (20).
2. There is a slight possibility of fetal death during the first 2 weeks after conception secondary to diagnostic radiation exposure, but the risk is less than 1.0%, depending on the dose (21).
3. There is a risk of small head size 2–15 weeks after conception, but intellectual damage has not been demonstrated in the 8 weeks after conception and the degree of the decreased head size is not easily recognized, except in population studies (22).
4. A risk of malformation exists for weeks 2–15 after conception, but this risk appears to be very small for diagnostic radiology, with a probable threshold of more than 100 mGy (16).
5. Acquisition of a plain radiograph for diagnostic purposes typically exposes the fetus to less than 10 mGy (16).
6. Typical abdominal studies and abdominal fluoroscopy lead to a dose of about 1–50 mGy (16).
7. Pelvic CT, pelvic angiography, and pelvic fluoroscopy lead to an exposure of 10–50 mGy (16).
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SUMMARY |
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TopINTRODUCTIONPREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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After the emergency department workup and clinical stabilization of the mother and fetus, a diagnostic workup should be designed to evaluate the extent and severity of injuries. The radiation exposure to the fetus should be considered, but an expeditious, correct diagnosis is the most important issue. The possibility of deleterious radiation effects never outweighs fetal and maternal survival. Prompt, rapid assessment of the traumatized pregnant patient followed by US of the fetus is key to a successful maternal and fetal outcome.
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Acknowledgments |
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Footnotes |
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References |
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TopINTRODUCTIONPREHOSPITAL MANAGEMENTPOTENTIAL EFFECTS OF TRAUMAEMERGENCY DEPARTMENT WORKUPDIAGNOSTIC WORKUPRADIATION EXPOSURESUMMARYReferences |
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hours. (a) Immediate spiral CT scan shows a liver laceration (arrow). Bilateral fractures of the pelvis were also seen. (b) CT scan shows low CT numbers in a significant portion of the lateral aspect of the placenta (arrowhead). Fetal death was noted 2 hours later. Delivery was induced, and a dead fetus was delivered.
