Differential Diagnosis for Infected Mass without Cyst Wall
- Single most likely diagnosis
- Abscess: The presence of a round, severely tender mass that resembles an infected cyst but lacks a cyst wall upon incision is highly suggestive of an abscess. An abscess is a collection of pus that has built up within the tissue of the body, indicating a local infection. The absence of a cyst wall is consistent with an abscess, as these are typically fluid-filled cavities without a distinct epithelial lining.
- Other Likely diagnoses
- Infected hematoma: This could present similarly to an abscess, with a palpable mass and severe tenderness, but would be filled with blood rather than pus. The lack of a cyst wall could be due to the hematoma not being encapsulated.
- Phlegmon: A phlegmon is an area of diffuse inflammation and infection within soft tissues, which could feel like a mass and be severely tender. It doesn't have a distinct wall like a cyst or abscess.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Necrotizing fasciitis: Although less common, this condition is a severe infection of the fascia, the tissue that covers muscles, nerves, fat, and blood vessels in the affected area. It can present with severe pain, swelling, and sometimes a mass, but lacks the distinct boundaries of a cyst. It's critical to consider this diagnosis due to its high mortality rate if not promptly treated.
- Gas gangrene: This is a potentially deadly condition caused by Clostridium perfringens infection, characterized by severe pain, swelling, and gas production in the tissues. The absence of a cyst wall and the presence of severe tenderness could be indicative of gas gangrene, especially if there's a history of trauma.
- Rare diagnoses
- Echinococcal cyst infection (hydatid cyst): Although rare in many parts of the world, an infected hydatid cyst could present as a tender mass without a clear cyst wall upon incision, especially if the cyst has ruptured or become secondarily infected.
- Tuberculous abscess: In areas where tuberculosis is common, a tuberculous abscess could present as a chronic, infected mass without a distinct cyst wall. This diagnosis would be considered based on the patient's exposure history and other clinical findings.