retrocop - // He went into the waiting room after surgery to lock the front door and saw a large rat crawling out the toilet bowl. Thereafter he was chasing round the house ensuring the toilet seats were down after use. //
It is not more likely that the rat was already in the house and simply fell into the bowl?
Toilet outlet pipes are an average of four inches wide, with a ninety-degree bend in them - it would take something pretty tempting to convince a rat to climb up one into a dwelling. I suggest that, in common with spiders, the rat simply got lost exploring the house, rather than being tempted up a sewage pipe.