Differential Diagnosis
- Single most likely diagnosis
- Postoperative seroma or hematoma: The patient has undergone multiple debridements and has evidence of postsurgical changes, including surgical drains and a multilobulated intramuscular hematoma with contrast extravasation. The presence of a low-density fluid collection within the superficial vastus medialis and unorganized subcutaneous and subfascial fluid throughout the right lower extremity also supports this diagnosis.
- Other Likely diagnoses
- Residual or recurrent necrotizing fasciitis: Although the patient has shown clinical improvement, the presence of punctate foci of gas and unorganized subcutaneous and subfascial fluid raises the possibility of residual or recurrent infection.
- Abscess formation: The low-density fluid collection within the superficial vastus medialis could represent an abscess, especially if it is surrounded by a rim of enhancement on the CT scan.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Arteriovenous fistula (AVF) or pseudoaneurysm: The punctate focus of contrast extravasation within the hematoma raises the possibility of a vascular injury, such as an AVF or pseudoaneurysm, which could lead to significant bleeding or other complications if not addressed.
- Compartment syndrome: The presence of a large hematoma and unorganized fluid throughout the lower extremity could lead to increased pressure within the compartments, resulting in compartment syndrome, which is a medical emergency.
- Rare diagnoses
- Soft tissue sarcoma: Although rare, soft tissue sarcomas can present as a mass or fluid collection in the soft tissues, and the patient's history of trauma and surgery could potentially mask the symptoms of a underlying malignancy.
- Pyomyositis: This is a rare infection of the skeletal muscle that can present as a fluid collection or abscess within the muscle, and could be considered in the differential diagnosis, especially if the patient has a history of immunocompromised state or other risk factors.