from Randy: Keeping the same loan number is a function of your accounting practices and has nothing to do with whether or not a transaction would be considered a renewal or refinance. Since you don't provide in what context you are asking your question, the best thing to do would be to have this discussion with your legal counsel.
from Andy: I would add that to help you determine the difference between a refinance and a renewal, look to Reg Z § 1026.20. And I ditto the encouragement to consult counsel as there are varying opinions on the ability to renew a matured loan. Your current loan documents, state laws and the time frame since maturity may influence the decision.