Choosing Between Two Column Values To Return As Single Column Value

I'm working on a social network where I store my friend GUIDs in a table with the following structure:
user1_guid       user2_guid
I am trying to write a query to return a single list of all a users' friends in a single column.  Depending on who initiates the friendship, a users' guid value can be in either of the two columns.  Here is the crazy sql I have come up with to give what I want, but I'm sure there's a better way...  Any ideas?SELECT DISTINCT UserId
FROM espace_ProfileProperty
WHERE (UserId IN
(SELECT CAST(REPLACE(CAST(user1_guid AS VarChar(36)) + CAST(user2_guid AS VarChar(36)), @userGuid, '') AS uniqueidentifier) AS UserId
FROM espace_UserConnection
WHERE (user1_guid = @userGuid) OR
(user2_guid = @userGuid))) AND (UserId IN
(SELECT UserId
FROM espace_ProfileProperty))