FIGURE 52-2 Algorithm for evaluation of suspected deep-vein thrombosis in pregnancy. CT = computed tomography; MR = magnetic resonance. aSigns and symptoms include swelling of the entire leg, with or without flank, buttock, or back pain. (Data from Guyatt GH,
Akl EA, Crowther M, et al: Executive summary: Antithrombotic therapy and prevention of thrombosis, 9th ed: American College ofChest Physicians evidence-based clinical practice guidelines, Chest. 2012 Feb;141(2 Suppl):7S-47S.)
In pregnant women, the important caveat is that normal findings with venous ultrasonography do not always exclude a pulmonary embolism. his is because the thrombosis may have already embolized or because it arose from iliac or other deeppelvic veins, which are less accessible to ultrasound evaluation (Goldhaber, 2004). As discussed, thrombosis associated with pulmonary embolism during pregnancy commonly originates in the iliac veins.
he results of two studies are helpful for evaluating the need for serial examinations in pregnant women suspected of having a deep-vein thrombosis but who have a negative initial compression ultrasound examination. The combined results are depicted in Figure 52-3. Chan and coworkers (20l3) studied 221 pregnant and postpartum women presenting with a suspected deep-vein thrombosis. The 205 women with a negative initial study result underwent serial testing, which was negative in all cases. Of these, one woman with normal serial testing had a pulmonary embolism 7 weeks later. Le Gal and colleagues (2012) studied 210 pregnant and postpartum women with a suspected deep-vein thrombosis. Of these, 177 women without a deep-vein thrombosis were not anticoagulated and did not undergo serial testing. Two had an objectively conirmed thrombosis diagnosed within 3 months. In sum, these preliminary data suggest that a negative single complete compression ultrasonography study may safely exclude the diagnosis of deep-vein thrombosis in most pregnant women.
This imaging technique allows excellent delineation ofanatomical detail above the inguinal ligament. Thus, in many cases, magnetic resonance (MR) imaging is immensely useful for diagnosis of iliofemoral and pelvic vein thrombosis. The venous system can also be reconstructed using MR venography (Chap. 46, p. 911). Erdman and associates (1990) reported that MR imaging was 100-percent sensitive and 90-percent speciic for detection of venographically proven deep-vein thrombosis in nonpregnant patients. Importantly, almost half of those without deep-vein thrombosis were found to have nonthrombotic conditions that included cellulitis, myositis, edema, hematomas, and supericial phlebitis.
halil and coworkers (2012) used MR venography to study the natural history ofpelvic vein thrombosis after vaginal delivery. Among the 30 asymptomatic patients who were all within four days of delivery, 30 percent had a deinitive thrombosis in either the iliac or ovarian veins, and another 37 percent had a suspected thrombosis. Our experiences with hundreds of postpartum MR scans do not support these findings. Thus, although the clinical significance of their findings is uncertain, it seems clear that some degree of pelvic vein intraluminal illing defect may be a normal inding.