Learn Russian: Этот симптом показывает воспаление, значит, мы должны его лечить. - This symptom indicates inflammation, so we must treat it.

In this sentence, значит is not acting as the main verb 'it means'. Instead, it is a discourse marker (an introductory word) meaning 'so', 'therefore', or 'that means'. It introduces a logical conclusion based on the first clause and is typically set off by commas.

Could we use следовательно in place of значит here?

Yes, следовательно also means 'therefore' or 'consequently' and fits perfectly here. The difference is in the tone: значит is extremely common in everyday conversational Russian, while следовательно sounds more formal, scientific, or strictly logical.

Does the pronoun его refer to the symptom (симптом) or the inflammation (воспаление)?

Logically, it refers to воспаление (the inflammation), since you treat the underlying condition. Grammatically, его is the accusative form for both the neuter pronoun оно and the masculine pronoun он. A good refresher: even though an inanimate masculine noun like симптом doesn't change its ending in the accusative case, the pronoun replacing it still becomes его.

Could I use указывает на instead of показывает for 'indicates'?