Evaluation of Embolic Source of Pulmonary Thromboembolism Using Lower Limb MR Venography

Abstract

MR venography (MRV) is useful for the diagnosis of deep venous thrombosis (DVT). We evaluated the lower extremity vein as the embolic source of pulmonary thromboembolism (PTE) using MRV. We also investigated the location of pulmonary emboli. Twenty-eight patients with PTE confirmed by enhanced chest CT underwent MRV of the lower extremity. 2D-TOF was used in the pelvis and thigh, and Gd-enhanced MRV with 3-phase dynamic study was used in the calf. The most proximal localization of DVT was evaluated, and the relationship between the proximal site of DVT and the severity of PTE was investigated. Thrombi in the lower extremity vein were found in 26 patients (93%). Thrombi were localized only in the calf in 13 patients (46%). Five patients (18%) had only intramuscular thrombi. In clinical cases, the source of pulmonary thromboembolism had been detected in only 50-70% of cases, because thrombi within the calf were not easily diagnosed. MRV was a very useful method to evaluate DVT. We could detect lower extremity thrombi in 93% patients with PTE by MRV. Especially, Gd-enhanced MRV was effective for the examination of the calf vein. Almost half of the patients had thrombi only in the calf. Severe PTE might occur in patients with only intramuscular vein thrombi. We emphasize the importance of the calf vein thrombi, especially the intramuscular vein. MRV is very useful to diagnose the source of PTE.