During pregnancy, most venous thromboses are confined to the deep veins of the lower extremity. Approximately 70 percent of cases are located in the iliofemoral veins without involvement of the calf veins. Isolated iliac vein and calf vein thromboses occur in approximately 17 and 6 percent of cases, respectively (Chan, 2010). In contrast, in the general population, more than 80 percent of deep-vein thromboses involve calf veins, and iliofemoral or isolated iliac vein thromboses are uncommon (Huisman, 2015).
he signs and symptoms vary greatly and depend on the degree of occlusion and the intensity of the inlammatory response. Ginsberg and coworkers (1992) reported that 58 of 60 antepartum women-97 percent-had left leg thromboses. Blanco-Molina and coworkers (2007) reported left-leg involvement in 78 percent. Greer (2003) hypothesizes that this results from compression of the left iliac vein by the right iliac and ovarian artery, both of which cross the vein only on the left side. Yet, as described in Chapter 53 (p. 1026), the ureter is compressed more on the right side.
Classically, thrombosis involving the lower extremity is abrupt in onset, and there is pain and edema of the leg and thigh. The thrombus typically involves much of the deepvenous system to the iliofemoral region. Occasionally, relex arterial spasm causes a pale, cool extremity with diminished pulsations. Alternatively, there may be appreciable clot, yet little pain, heat, or swelling. Importantly, calf pain, either spontaneous or in response to squeezing or to Achilles tendon stretching-Homans sign-may be caused by a strained muscle or contusion. Between 30 and 60 percent of women with a confirmed lower-extremity acute deep-vein thrombosis have an asymptomatic pulmonary embolism (p. 1016).
Clinical diagnosis of deep-vein thrombosis is diicult, and in an earlier study of pregnant women, the clinical diagnosis was conirmed in only 10 percent (Hull, 1990). Another challenge is that many of the common diagnostic tests that have been investigated extensively in nonpregnant patients have not been validated appropriately in pregnancy (Huisman, 2015). Shown in Figure 52-2 is one diagnostic algorithm recommended by the American College of Chest Physicians that can be used for evaluation of pregnant women (Guyate, 2012). With a few modifications, we follow a similar evaluation at Parkland Hospital.
In pregnant women with suspected deep-vein thrombosis, the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists (2017) recommend compression ultrasonography of the proximal veins as the initial diagnostic test. According to the American College of Chest Physicians, this noninvasive technique is currently the most-used irst-line test to detect deep-vein thrombosis (Guyatt, 2012). The diagnosis is based on the noncompressibility and typical echoarchitecture of a thrombosed vein.
For nonpregnant patients with suspected thrombosis, the safety of withholding anticoagulation for 1 week has been established for those who have a compression ultrasound examination that is initially normal (Birdwell, 1998; Heijboer, 1993). Serial compression examinations are then performed because isolated undetected calf thromboses that ultimately extend into the proximal veins will do so within 1 to 2 weeks of presentation in approximately a fourth of patients.
Pregnant women with suspected
Negative, but isolated iliac vein thrombosis is suspecteda
Doppler ultrasound of iliac vein, or CT-or MR-imaging or venography