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unilateral leg swelling Post-Thrombotic-Syndrome

Unilateral leg swelling: Post-Thrombotic Syndrome vs Lymphedema

The main pathologies causing unilateral swollen legs are venous stasis (like Deep Vein Thrombosis (DVT) or venous insufficiency), lymphedema, malignancy, trauma and infections (like cellulitis). Unilateral swelling of the lower extremities should be categorized as Acute vs Chronic to facilitate diagnosis. Here I present two cases with a simplified approach to the diagnosis.

Case 1

78 Y-O man with left leg skin discolouration and thickening for many years. He also reported mild swelling and a “dull chronic ache” in his left leg, although he has gotten used to it. His signs and symptoms are chronic and were present for over ten years. As shown in the pictures below, hyperpigmentation, lipodermatosclerosis and eczema are mainly present on the left side, indicating “chronicity” and a “venous source” of his problem.

Questioning revealed a history of Deep Venous Thrombosis (DVT) 12 years prior to this presentation. At the time, he was hospitalized for one month and required full anticoagulation due to the severity of the thrombosis, as evident in the pictures below. He also had a few venous ulcers, which have healed.

Post-Thrombotic Syndrome (PTS) or Venous Stasis Syndrome (VSS) occurs in 30-40% after an episode of acute DVT to some degree. In about 4% of patients, the signs and symptoms could be severe. The symptoms usually occur within the first 6 months but can occur up to 2 years after the acute event. Developing PTS two years after the event, is highly unlikely. Some of the most common symptoms of PTS are as follows:

  • Chronic edema
  • Chronic pain
  • Skin discoloration (Hyperpigmentation)
  • Chronic diffuse ache
  • Skin dryness and eczema
  • Hardening of the skin (Lipodermatosclerosis)
  •  Skin ulcers
This case is a mild form of Post-Thrombotic Syndrome developed after an episode of DVT. The patient was not bothered by his symptoms as they were present for many years and were mostly mild in nature. As such, no specific therapy was required. However, this case serves as a reminder to keep Post-Thrombotic Syndrome in mind, in case of unilateral limb swelling and complaints. Specific enquiring about prior episodes of DVT, hospitalization or anticoagulation is required to reveal the history as patients usually forget about the episodes over time.

Case 2

The second case is a 75 Y-O man referred to investigate his swollen right leg. He was diagnosed with Neuroendocrine Tumor, requiring chemotherapy and surgery. However, his swollen right leg had raised the suspicion of Heart Failure. The pictures are shown below: (Click to enlarge)

As evident in the images, there are no signs of “venous stasis” in this case, i.e. no hyperpigmentation and no lipodermatosclerosis. An echocardiogram did not show any evidence of heart failure (even though heart failure does not cause unilateral leg edema). There was no lymphadenopathy or mass effect to explain his unilateral Lymphedema either. 

Further questioning revealed that he had had this unilateral leg swelling for over 40 years! The language barrier had confused his treating oncologists. At 30, he was involved in a severe motor vehicle accident causing multiple fractures in his right leg. His leg had to remain in a cast for nearly a year. After this event, his unilateral leg swelling slowly emerged and never resolved. This is a case of traumatic lymphadenopathy, which can only be diagnosed through thorough history taking and ruling out other sinister causes.


Both of these are cases of chronic unilateral swelling of the leg. However, there are a few crucial differences between the two. The first case shows significant skin thickening and hyperpigmentation, hallmarks of chronic venous stasis. In the second case, despite significant pitting edema, the skin texture has remained intact with no hyperpigmentation or lipodermatosclerosis. The crucial initial step in approaching unilateral leg swelling is to determine the chronicity

The usual causes of Acute unilateral leg edema are infectious (cellulitis) and vascular (Deep Venous Thrombosis) etiologies. A less common cause for acute unilateral leg swelling is cancer and the mass effect, usually due to compression of large femoral or iliac veins. Lymphoma is an example that can cause unilateral lower extremity edema and requires a high level of suspicion for prompt diagnosis.

Chronic causes of unilateral lower leg swelling include post-thrombotic syndrome and secondary (traumatic) Lymphedema. Traumatic Lymphedema is usually due to lymph node excision as part of cancer treatment. However, severe limb injuries can permanently damage the lymphatic system, leading to chronic Lymphedema.