What is the Difference Between Pannus and Thrombus?

06/04/2025 • Giovanni Medeiros

The main difference between pannus and thrombus lies in their formation, composition, and location. Here are the key differences:

  1. Formation: Pannus is a more chronic process associated with the ingrowth of tissue, causing obstruction. In contrast, thrombus formation is a result of blood clotting, which can lead to obstruction in blood flow.
  2. Composition: Pannus is composed of fibrous tissue that grows over the prosthetic valve, while thrombus is a blood clot that forms on the valve surface.
  3. Location: Pannus formation is more common in the aortic position (70% vs. 21%), whereas thrombi can form in various locations, such as the left atrium in prosthetic mitral valves.
  4. Size: Thrombi are usually larger than pannuses, with a total length of 2.8±2.47 cm vs. 1.17±0.43 cm. Thrombi often extend into the left atrium, particularly in prosthetic mitral valves.
  5. Ultrasound Intensity: The ultrasound intensity of the mass is an important parameter that differentiates thrombus from pannus. Thrombi appear as a soft mass on the valve in 92% of cases, while 29% of pannuses have a soft echo density. The ultrasound video intensity ratio, derived as the video intensity of the mass to that of the prosthetic valve, is lower in the thrombus group (0.46±0.14 vs. 0.71±0.17).

Accurately distinguishing between thrombus and pannus is essential for proper diagnosis and treatment, as their management and implications are different.

Comparative Table: Pannus vs Thrombus

Here is a table comparing the differences between pannus and thrombus:

Feature Pannus Thrombus
Definition Pannus is a type of extra growth in the joints. A thrombus is a blood clot that forms in the blood vessels.
Formation Pannus is a chronic process. Thrombus formation is a normal process that can occur in response to injury or certain medical conditions.
Location Pannus typically forms in the joints, such as knees, wrists, and thumbs. Thrombus can form in blood vessels, potentially obstructing blood flow.
Diagnosis Pannus can be diagnosed through physical examination and imaging tests like X-rays, MRI, and CT scans. Thrombus can be diagnosed through physical examination and imaging tests, such as ultrasound, CT scans, and MRI.
Treatment Treatment options for pannus formation include medications like non-steroidal anti-inflammatory drugs, disease-modifying antirheumatic drugs (DMARDs), corticosteroids, and biologics, as well as surgical intervention. Treatment options for thrombus include blood-thinning medications, such as anticoagulants, antiplatelet drugs, and thrombolytic drugs, as well as surgery in some cases.

Note that both pannus and thrombus can cause serious life-threatening complications and can form due to autoimmune conditions. Additionally, both can be diagnosed through physical examination and imaging tests and may sometimes require surgical intervention.

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