You’d be able to see flystrike esp when you wash him and pat him dry.

He could have a urinary tract infection. The leg thing sounds like urine scalding or urine burn, and that’s a result of leaking/dribbling urine or sitting in his own urine. You can put ointment on the irritated area, fex diaper rash cream or bag balm, to make him more comfy. You need a vet to prescribe antibiotics for him.

You can also add a little bit of cranberry juice to his water (just check so he drinks it, some buns won’t drink water that has sth mixed in it), some UTI buns seem to experience relief from an addition of cranberry juice.

What caused it is difficult to say, of course. It is bacterial, but these bacteria are everywhere. Buns are sensitive to stress and being in a new environment without his family is stressful. Stress challenges the immune defense and pathogens can sieze the opportunity. That’s nobody’s fault, of course.

I agree with Bam. Give your bunny a sniff test – do you smell urine? The missing fur is probably not chewed off, but it fell off from the urine scald. This can happen quickly. Wet skin = fur loss. You’ll need to bath your bunny, keep him clean and dry. Even frequent baths, which are important to keep the urine off his skin (urine burns and causes ulcers), can cause fur loss. So after you bath him – be sure to dry him completely. Easier said than done… bunnies don’t dry easily.
He needs to see a vet to get tested for UTI. Cranberry juice is great. I use Oxbow urinary health support tablets – it lists how much cranberry is in the tablet, and use the same amount of that ingredient, in his treats. I’m drawing a blank and forgetting the name of the ingredient – I do that because I don’t know the amount of it in the liquid cranberry juice, and I don’t want him having all that natural sugar.
Baby diaper rash cream will work for his skin. I use sudocrem for my bunny. He is incontinent and it took me a while to figure out a routine to keep him dry. He is in a diaper 24/7. No hole cut in the tail, but I cut around the leg of the diaper so it fits nicely over his hips. I change it every 3-5 hours. If your bunny has a UTI, antibiotics will fix it real quickly. Kidney stones/crystals could also be a culprit, and a sonogram should pick those up. Another culprit could be EC, but your vet should check for a UTI first. Flystrike can indeed cause enough damage to result in incontinence. But with a thorough “pat down”, you’ll be able to feel the characteristic lump of the larvae. It takes weeks for the lump to be noticeable, so if your bunny did have flystrike, he would have gotten it before that trip. Since he was outside – and you don’t know exactly when the urinary problem began, keep checking him every day for the next 4 weeks for lumps. Check everywhere. Don’t just look – but feel his skin for lumps. If you feel a lump, check for a hold in the middle of the lump. Another early tell tale before the lump appears, is a pinhole in he fur, with a pinhole in the skin.
Hopefully it is just a UTI and he recovers fully.

While you are waiting on his recovery – you need to figure out how to keep him dry. Is he sitting in his urine after peeing? How is his gait and posture? Can he lift his butt to avoid peeing on himself? Does he lean to one side and pee on the inside of his legs?

How much does he weigh? Has he lost weight? You might want to try diapering him.
Corn starch/baby powder are also used to help keep bunnies dry. If I’m in a hurry, and the wet spot is small, I powder my bunny, put him back in a diaper, and bath him when I get back. The powder absorbs the urine. It’s not ideal, but it works if you don’t have a whole lot of time to wash/dry him. Diaper rash cream (I like Sudocrem) works really well. If he can reach the area to groom, use a zinc free cream. Lancelot can’t reach it, so it doesn’t matter what cream I use. If you can’t get hold of a zinc free cream – then diaper him. The cream makes the diaper waterproof – bad. Pee runs around in the diaper and contacts skin. So rub it gently into the skin so you aren’t leaving globs of cream on the diaper.

The increased water consumption could relate to a kidney/urinary tract infection, or EC.

Please keep us updated.

No – washing him is good! you want to wash the pee off. Just be sure to dry him. I wash Lancelot every weekend, and inbetween if he needs it. You DO want to wash the pee off. Just dry him properly afterwards. To help drying, I trim his fur. Lancelot is quite used to the process – I flip him over and cut cut cut. Less fur to be wet = easier to dry.
Don’t just hope he feels better – get him to a vet. It won’t resolve on it’s own.

Yes I use pet store pet shampoo for “critters”. It cleans really well. Doesn’t burn. But I also have Chlorhexadine shampoo which is an antibacterial shampoo. It requires a 5 minute soak before washing. so I sit his but in the sink with 2-3 inches of warm water with chlorhexadine. I just sit there with him and pet him for 5 minutes while he soaks in it. I put a rag in the sink for grip (a cut to size rubber mat would work too), and it doubles to catch the hair and poop (yes he might poop in the water) from going down the drain. Then I hold him in my arms and gently rub circles with either my fingers, or a cotton ball. I don’t use a wash cloth on his skin because I think it would be abrasive. The regular pet shampoo cleans really nicely, and the chlorhexadine has the antibacterial properties. So I use the antibacterial for after a pee, and the regular after the chlorhexadine – to get rid of the pee stain on his white fur.
To dry – I pat down with a towel, cut fur – I cur fur every single time I bath him, and for the pocket where his privates meet his belly – I crumple up paper towel pieces and put them in that pocket one at a time to soak up moisture. Then I break out the hair dryer. I bought a cheap hair dryer solely for his baths. I don’t’ use a hair dryer myself. I would never own one if it weren’t for him. Use the hair dryer on low heat, hold it 12-18 inches away, keep waving your hands under it so you are aware of the temp that he is receiving.
You can go ahead and use the pet shampoo. What brand is it?

BTW cutting his fur does absolute wonders for helping the drying go quicker. Whether you cut it wet or dry – use round-nosed scissors incase he jerks and you accidentally poke him. Cut as close to the skin as you can. The area that you are cutting – gently pull the skin tight if you know what I mean – so you know that you are cutting fur, and not skin folds! You’d be surprised at how many skin folds there are down there. I cut from mid thigh all the way down. Everything. the fur on his tail, all around his privates (go carefully there – plenty of skin folds), his belly (really furry), and the area above his tail.

If you find that he is leaning or not lifting his butt, then you will find yourself in a cycle of him peeing on himself, you washing him. Many times a day. Not good either. If that happens, you might want to consider diapering him.

You might find it at a pharmacy? I bought it on Amazon. The Petsmart shampoo should be fine. It does smell good. I like to use it on him before a vet visit! The correct spelling is Chlorhexidine. Petsmart doesn’t have it.

I’ll look up the link.

Here it is. Chlorhexidine Pet Shampoo. https://www.amazon.com/Davis-Chlorhexidine-Pet-Shampoo-12-Ounce/dp/B0078LOU3W/ref=sr_1_20?ie=UTF8&qid=1494445529&sr=8-20&keywords=chlorhexidine

Regarding chlorhexidine, some buns are hypersensitive. I’d start with very little on a small part of the skin:
http://www.medirabbit.com/EN/Skin_diseases/Chemical/Chlorhexidine_en.pdf

Good to know.

But I must add, chlorhexidine for bunny wound care is mentioned in lots and lots of places, incl Medirabbit, that has good bunny info, so I would assume rabbits as a rule tolerate it. It just came across this article a week or so ago and was quite dismayed, so I just wanted to mention it.

As for cranberry, I remembered our member Mikey had success with cranberry extract in water. It wouldn’t add sugar. Mikey’s vet also recommended daily drops or daily dried cranberry (the health-food kind that doesn’t have sugar) after the UTI. Here’s a (rather long) thread about Mikey and bunny Bombur, who had a rather bad spell of UTI in Nov 2016: https://binkybunny.com/FORUM/tabid/54/aft/150839/afpg/2/Default.aspx