For a fluctuating painful lump on the buttock, what is the most appropriate initial intervention?

The most appropriate initial intervention for a fluctuating painful lump on the buttock is incision and drainage. This procedure is often necessary when dealing with a fluctuant abscess or similar collection of pus, particularly if the lump is painful and there is a suspicion of infection. Incision and drainage allows for the release of pus, which alleviates pressure and pain, facilitates healing, and can prevent the spread of infection.

Performing incision and drainage addresses the underlying issue directly by removing the infectious material, while other options may not be sufficient on their own. For instance, topical treatments like mupirocin ointment are primarily used for superficial skin infections and would not effectively treat an abscess that requires drainage. Systemic antibiotics might be necessary post-drainage if there is widespread infection, but they do not address the source of pain and fluctuation directly. Similarly, moist compresses can provide some symptomatic relief, but they won't resolve the fluctuating lump or the pain associated with it, and they may not be effective if a significant abscess is present. Thus, incision and drainage is the most direct and necessary first step in management.