Dogs anus looks strange

recently in the last 2 weeks or so, my 6 yr old male shih tzu has been farting a lot (not sure if it’s farts but the smell comes and goes suddenly) he’s been gassy (sounds from his stomach) and has been excessively licking his anus. He also started scooting on the ground (something he never used to do) we got him a haircut so I was able to get a clear view of his anus and it looks swollen. I will be taking him to the vet but I just want to make sure what this could be so I could ease his discomfort in the meantime attached is a picture

Hello - the gassiness could be related.  If he's not forming stools properly for example, he might not be emptying his anal glands correctly.  In a perfect situation, the poos push against the gland at the anus during deafecation, squeezing out a drop of anal gland juice as they pass.  But if the poo is too soft for example, or the neck of the anal gland gets inflamed therefore narrowed for skin-related reasons, or the anal glands are positioned differently in the patient, or there is an abnormality within the anus, or some combination, then the AGs may get full and then they itch.  Anal glands tend to become implicated in a viscious circle - they itch, so they're scratched, so they're inflamed, so they don't drain, so they itch.....    and are often linked to skin problems or diarrhoea or conformation of the bottom, so for many dogs it can become a regular thing.  Dogs also rub their bottoms if they are uncomfortable for other GI reasons, eg gas, exacerbating things further.  If this does turn out to be the anal glands, then it may be well worth having a chat with your vet.  If not the anal glands, rectal abnormalities, lumps and bumps, other skin disease, worms etc may turn out to be possibilities, so it is still worth havng them checked.

I wonder if a short term appropriate change in diet may help, or treatment for the skin, or some combination - but bottoms are very sensitive and can get worse quite quickly - not to mention all poo sliding over a potentially sensitve area - so usually I reccommend that people involve their vets early on.