Why does sp_rename not affect the output of sp_helptext? create procedure Eg_Proce
as
begin
select * from po;
end

go

exec sp_rename 'Eg_Proce','Example_Procedure'


After renaming procedure

sp_helptext 'Example_Procedure'


The definition of the procedure is not updated

create procedure Eg_Proce  
as  
begin  
select * from po;  
end
Don't know why but it is kind of documented.

sp_rename (Transact-SQL)


  Renaming a stored procedure, function, view, or trigger will not
  change the name of the corresponding object name in the definition
  column of the sys.sql_modules catalog view.


sys.sql_modules is a view that uses the base table sys.sysschobjs. sp_helptext uses the view syscomments that in turn uses the base table sys.sysschobjs.