To solve the given problem, we need to understand the symptoms and radiographic findings and correlate them with the possible diagnoses. The problem statement describes a young male experiencing pain and swelling in the floor of the mouth that worsens during meals. The radiographic examination reveals a radiopaque mass in the submandibular salivary duct.
Let's analyze each of the given options:
- Antrolithiasis: Refers to the formation of calcified masses or concretions within the maxillary sinuses. This does not match our case as the symptoms and location are different.
- Rhinolithiasis: Characterized by the formation of stone (or calcified mass) within the nasal cavity. Again, this does not align with the presented condition.
- Sialolithiasis: This denotes the presence of a salivary stone or calculus within a salivary duct, commonly the submandibular duct. Symptoms include pain and swelling, particularly during meals due to increased salivary flow, attempting to dislodge the obstruction. This matches the case scenario perfectly.
- Sialometaplasia: It is a benign, inflammatory condition of the salivary gland that typically does not present with stone formation. Moreover, it would not show a radiopaque mass on imaging consistent with a calculus.
Therefore, the most likely diagnosis, considering the symptoms and radiographic evidence, is Sialolithiasis. This condition is characterized by the presence of salivary stones within the salivary glands or ducts, leading to blockages, especially noticeable during mealtimes when saliva production increases.