Plantar vein thrombosis and pulmonary embolism

Introduction

Plantar vein thrombosis is an unusual and under-diagnosed condition that affects the plantar deep venous system. ¹ Although duplex scanning allows excellent visibility of the plantar veins and is the most useful examination in the diagnosis of this condition, current ultrasound investigation protocols for deep venous thrombosis neglect this entity and it is not specifically mentioned in therapeutic guidelines or medical books. To our knowledge, there are only seven reports in the literature of 20 patients with plantar vein thrombosis detected with sonography without an associated pulmonary embolism.^2–8 We present a case report of a patient with a plantar vein thrombosis associated with pulmonary embolism.

Case report

A 45-year-old female patient presented with varicose vein disease was referred to our laboratory to undergo a duplex scanning study. She used hormone therapy for dysmenorrhea treatment and was awaiting a hysterectomy. She was otherwise healthy and did not have major medical problems, including any history of prior deep venous thrombosis, hypercoaguable state, family history, smoking, obesity, recent surgery or trauma as well as unusual stress of the foot. On examination, the calves demonstrated no evidence of edema or signs of inflammation. She complained of pain on palpation of the medial plantar region of the left foot associated with fatigue and shortness of breath for approximately five days.

Comprehensive duplex ultrasonography was performed to examine the deep veins of the entire both legs. The patient was lying in the supine position with the leg externally rotated and slightly flexed at the knee. She was examined from the inguinal ligament to the medial malleolus. The common femoral, femoral, popliteal, tibial posterior, peroneal, as well as veins of the gastrocnemius, and soleal plexus were examined. The compressibility of these veins was assessed at 3 cm intervals in the transverse plane. The duplex scan showed no signs of deep venous thrombosis in the femoro-popliteal and calf veins. There was no suggestion of proximal abnormalities including abnormal maximum venous outflow velocities or loss of phasicity with respiration at the femoral vein. The patient complained of foot pain, and the plantar veins were assessed by following the posterior tibial veins below the medial malleolus, at the medial side of the foot until the full extent of the lateral and medial plantar veins. Acute occlusive thrombus was found in the lateral plantar veins (Figure 1). The possibility of lung scintigraphy was discussed with the attending physician because of sonographic findings associated with the presence of fatigue. OPEN IN VIEWER

The patient was referred for a SPECT/CT. After inhalation of the radioaerosol (99mTc-phytate) and intravenous administration of the radiopharmaceutical (99mTc-MAA), planar images were obtained in several lung projections of interest and the acquisition of tomography (SPECT) during the infusion step. CT was performed in multislice helical gear 4 channels, with CT 5.0 mm, acquired with low dosage. The perfusion study demonstrated heterogeneous distribution of the radiopharmaceutical in the lung parenchyma, with hypoperfusion on the projection of the anterior segment of the right upper lobe and part of the lateral segment of the middle lobe, cuneiform aspect, with the base toward the pleural surface, which was most observable in coronal cuts. The inhalation study demonstrated the deposition pattern of a radioaerosol discordant perfusion study and findings consistent with the diagnosis of pulmonary thromboembolism (Figure 2). OPEN IN VIEWER

The patient was hospitalized for anticoagulant treatment and was discharged after seven days in good clinical condition. The standard pharmacological approach included initial intravenous unfractionated heparin (five days) followed by long-term oral treatment (six months) with warfarin with a standard INR goal of 2.0 to 3.0. After six months, the patient underwent repeat duplex scanning showing partial recanalization of the plantar vein thrombosis with associated insufficiency, demonstrated by pulsed Doppler as a retrograde flow with duration longer than one second after manual foot compression (Figure 3). There was no abnormality on other veins. The hematological tests workup showed no sign of hypercoaguable state. OPEN IN VIEWER

Discussion

To our knowledge, this is the first case to demonstrate an association among plantar vein thrombosis by sonography and pulmonary embolism. Although most studies suggest that venous thrombosis starts in the calf veins, it may arise in any part of the deep venous system, including the sole of the foot.^9,10 Isolated plantar vein thrombosis is a rare venous disorder that may present with pain and/or edema in this area. A high index of suspicion must be maintained for patients presenting with spontaneous unilateral foot pain. The diagnosis is usually simple and easy to make on duplex sonography. Although ultrasound is the principal method for diagnosing DVT, including the plantar veins in the investigative protocol is generally not a routine procedure. Foot vein assessment, particularly in those patients presenting with pain on the plantar side of the foot, could be introduced in duplex scanning protocols. ⁷

Pulmonary embolism remains a commonly underestimated and potentially lethal condition. It is estimated that only 11 to 25% of all pathological-anatomical proven emboli have a correct diagnosis during life. ¹¹ In fatal pulmonary embolism, the correct clinical diagnosis is made in 1/3 of patients. Less than 10% of all pulmonary embolism deaths occur in patients in whom treatment is initiated. The majority of deaths due to pulmonary embolism (90%) occur in undiagnosed and untreated patients. ¹² The correct diagnosis of DVT is important in the assessment of PE, and the improved diagnosis of DVT presents the greatest opportunities to prevent fatal pulmonary embolism. In patients presenting with respiratory symptoms, the finding of DVT augments the likelihood of diagnosing PE. ¹³

The mechanisms related to PE and plantar vein thrombosis are unrecognized. We hypothesized that people with plantar vein thrombosis who are not on anticoagulation could disrupt the thrombus proximally by repeated compression of the foot determined by the musculovenous foot pump action. The plantar venous plexus represents the most distal of the musculovenous pumps of the leg. Its function may be integral to venous outflow from the calf and priming of the more proximal calf muscle pump. Because it is compressed with a significant force during ambulation, the plantar plexus is able to overcome the pressure of the column of blood within the deep venous system of the calf. Additional mechanisms of compression may also cause ejection of blood from this plexus and from the deep veins of the calf. ⁷

Plantar veins are part of the distal deep venous system, and thrombus in these veins has the potential to propagate into the infrapopliteal veins. ⁷ Plantar vein thrombosis treatment has been controversial. Some authors use only nonsteroidal anti-inflammatory drugs (NSAIDs), while others have prescribed anticoagulation. In our series we have studied 11 patients; nine of them had pain at the foot region, followed by edema in eight. Plantar veins were exclusively affected in nine patients, with calf compromise in two, and one with great saphenous vein thrombosis. Treatment was initialized with NSAIDs in five and low-molecular-weight heparins in six of the patients, the treatment being a decision of the patient’s physician. In the follow-up, there was evidence of thrombosis extension in three patients, all of them developed calf pain and were taking NSAID to treatment. After six months, ultrasound evaluation showed signs of partial recanalization in nine and complete recanalization in two of them. Patients who developed thrombosis extension demonstrated mild calf swelling associated with posterior tibial vein and/or soleal vein reflux by duplex scanning. ⁷ Like others we believe that patients with symptomatic DVT or chest symptoms should be anticoagulated for three months and evaluated at the end of treatment.

The main reason of using SPECT/CT is that this modality was the one available in our institution at the moment of duplex scanning examination. Although we agree that computed tomography pulmonary angiography (CTPA) nowadays is the preferred modality in the diagnosis of pulmonary embolism, head-to-head studies consistently demonstrate that SPECT has a higher sensitivity, that CTPA has a higher specificity, and that the overall accuracy of each modality is similar. Otherwise, SPECT (with or without CT) has a lower radiation dose, fewer technically suboptimal studies, and no contrast-related complications. SPECT/CT offers the potential for a single imaging procedure yielding a high accuracy for the detection of PE that has the added benefit of being able to identify various other pulmonary conditions. The test selected should consider patient factors (including age, gender, renal function, diabetes, and coexisting lung disease) and institutional factors (availability and local expertise).^14,15

In conclusion, plantar vein thrombosis is rare and could be related with pulmonary embolism. Patients who present with pain and swelling of the foot should undergo ultrasound examination and careful evaluation for respiratory symptoms.