The encryption and decryption functions return a varbinary(8000). Just use the + append operator and a WHILE loop. There are a few blogs worth checking out, especially the first one - it has an LOB encryption/decryption example:

http://blogs.msdn.com/yukondoit/archive/2005/11/24/496521.aspx

http://blogs.msdn.com/raulga/

http://blogs.msdn.com/sqlsecurity/