Plantar vein thrombosis masquerading as plantar fasciitis: A case report

Introduction

There is minimal research to guide clinicians in the treatment of a plantar vein thrombosis (PVT) despite thrombosis of the lower leg being well researched with clear guidelines for diagnosis and therapy. ¹ PVT is an uncommon venous disorder affecting the deep plantar veins whereby the affected foot presents with non-specific pain, swelling, and a heavy sensation. ² PVT may be an under-diagnosed cause of inferior heel pain.^3,4

Although it has been suggested that deep vein thrombosis (DVT) originates in the calf veins, it may arise in any part of the deep venous system, including the foot. ² This under-researched entity has important implications and the paucity of evidence requires consolidation to better inform on its diagnosis and management. Herein, a case of a 51-year old female presenting with a lateral plantar vein thrombosis presenting as chronic heel pain resistant to usual care is reported.

Case

A 51-year old female nurse was referred to our clinic reporting a two-week history of chronic left foot pain and swelling resistant to conservative care. She was healthy and without major medical problems, including no history of prior DVT, hyper-coagulable state, family history of DVT, recent surgery, trauma, or stress to the foot. She was not obese and was a non-smoker. Extended periods of weight-bearing exacerbated her pain. On examination, pain and inflammation was exhibited underlying the heel and plantar fascia in a similar presentation to chronic plantar fasciitis.

Ultrasound (US) was performed to assess the usual structures within the left foot. The plantar veins were examined by following the posterior tibial veins below the medial malleolus. The lateral plantar vein was non-compressible when compared to the contralateral foot.

Magnetic Resonance Imaging (MRI) (Figure 1) identified expansion of the lateral plantar vein just distal to the plantar fascia origin suspicious of thrombosis. A second US performed off-site showed no intra-lesional flow, whereas the contralateral foot showed normal compressible veins.

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Figure 1.

Magnetic Resonance Imaging (MRI) showing expansion of the lateral plantar vein.

Her symptoms disappeared following conservative therapy and non-steroidal anti-inflammatory drugs for two weeks. A follow-up compression ultrasound performed six weeks later showed no residual thrombus of the plantar veins.

Discussion

Statistically, plantar fasciitis is the most common cause of unilateral foot pain, with 10% of the population experiencing this pathology at least once. ⁴ On US, plantar fasciitis exhibits hypo-echogenicity and thickening of the fascia. ⁵ PVT may be a differential diagnosis, as it seems to be a frequently misdiagnosed condition in the clinical setting.

Less than 30 cases of PVT have been reported in the literature.^4,6,7 The average time between initial symptoms until diagnosis is 8.8 days.^8,9 Thomas & O’Dwyer ¹⁰ observed PVT formation in 10% of patients compared to 44% within the calf veins. They recommend the inclusion of at least one view of the foot veins in a standard phlebogram in patients suspected of having a DVT or PE.

Usually, PVT has traditional DVT risk factors, ⁴ yet physical strain to the sole of the foot may be a unique precipitating factor, as it may lead to micro-trauma of the plantar veins, activating the coagulation cascade. ⁹ Other causes include athletic activity, ⁴ immobilisation,^3,11 anticardiolipin antibody syndrome, ¹² prothrombin G20210A mutation, ¹³ paraneoplastic syndrome, ¹⁴ orthotics ¹⁵ and footwear. ¹⁶

When investigating for DVT, ultrasonography is useful,^{3,10–14,17,18} yet investigation of the foot veins is not routine. ⁴ US allows easy visibility of the plantar veins. ¹⁹ In 17 out of 19 cases recently reported,^3,6,11,12,14 diagnosis was made initially by US. US findings of PVT included hypo-echoic enlarged venous structures in the transverse plane and hypo-echoic enlarged veins in the longitudinal plane.^11–14 Magnetic resonance imaging (MRI) may also be of benefit in diagnosing PVT, as it can observe tissue oedema, enhancement of bordering soft tissue, and filling defects of the plantar veins. ¹³

No standardised therapy currently exists. Treatment with non-steroidal anti-inflammatory medication (NSAIDs) has been proposed. ⁶ Czihal et al. ⁹ treated patients with low-molecular weight heparin (LMWH) and knee-length compression stockings. Individuals whose thrombi extended to the calf veins were treated according to DVT guidelines for three months with LMWH overlapping with vitamin-K antagonists. Heparin therapy and elastic compression of the ankle has been trialled^11,14 and another patient was treated with rest, NSAIDS, and acetaminophen. ¹³ Karam et al. ⁴ recommended the use of anticoagulation therapy for a three-month period.

Pulmonary embolism (PE) is potentially lethal. Patients with pain and swelling of the foot with concomitant respiratory symptoms should undergo US examination and careful evaluation. ⁴ Whether PVT is a starting point of an ascending DVT has not been confirmed ⁹ and its relationship to pulmonary embolism (PE) is speculative. Currently, PVT appears to carry a low risk of symptomatic PE and post-thrombotic syndrome. ⁹

Conclusion

We report a case of a patient reporting chronic foot pain masquerading as plantar fasciitis. MRI and US identified expanded lateral plantar veins that were non-compressible. Symptoms resolved following two weeks of NSAID therapy. PVT may be an overlooked and under-diagnosed condition and a degree of suspicion should be maintained in patients presenting with spontaneous unilateral foot pain, especially when they report a ‘heavy’ sensation. Diagnosis can be made via US or MRI.