star trek - What illness did Scotty have that was treated by Dr. McCoy?

Admiral Kirk arrives aboard the Enterprise for an inspection of the training crew. While inspecting the crew as they stand in line. He comes to Scotty and says the following.

From The Script

                                       KIRK
                                 (continuing to Scotty)
                         Mr. Scott, you old space dog. You're
                         well?

                                       SCOTTY
                         I had me a wee bout -- but Dr. McCoy
                         pulled me through.

                                       KIRK
                         Oh? A wee bout of what, Mr. Scott?

               Uncomfortable, Scotty exchanges a glance with Bones --

                                       BONES
                         Shore leave, Admiral.

                                       KIRK
                         Ah.

I've have seen this film a number of times, and always wondered. What was wrong with Scotty. It's clear that he went to Dr. McCoy for treatment of something, but that it was a personal thing so McCoy says "Shore leave" to the Admiral.

I don't remember anything happening to Scotty in the first Star Trek film that could be related.