It depends on who (or what company) is running the Acute dialysis program at any given hospital.
No, you do not "need" med-surg, but a background in M/S or ER/ICU is looked on very favorably. It will help you in managing your patients in the acute setting, and integrating what you are doing (dialysis), with whatever acute illness it is your patient presents. It will also help you communicate with the different departments/RN's/docs, and you will be responsible for some medically complex patients. The more you know, the more it helps other people in the interdisciplinary team. And believe me, they will ask a LOT of questions. Best you are not standing there with a "duh" look on your face because you have no clue how to answer the hospitalist when they come into your dialysis room asking you about this and that dialysis issue as it pertains to their patient's illness. If you have a poor grasp of the big picture, you are going in with a limp.
In general, nurses are not beating down the door to get into acute dialysis. It's not as easy as it looks to master, and some folks are scared to work that independently, not to mention the on-call.
Once you've "got it" though, it becomes a very cool job, and dare I say...sometimes too easy. Sometimes not easy at all. I loved it.
But yes, you do need a good foundation in outpatient dialysis. Most companies will require at least six months in outpatient before they allow you to start training in acutes.
I don't know where you live, or how many inpatient/acute programs and outpatient clinics there are in your area. If you choose to work for an outpatient unit, choose a unit that also runs an acute program. Da Vita and Fresenius (FMC) have most of the market, and while I am no fan of either, if I were to pick one it would be Da Vita as they have a pretty good training program for new dialysis RN's, and they are known to treat their employees better than Fresenius.
So in a nutshell, my advice would be to stay at your current job for now, and start connecting with the dialysis programs/clinics in your area. If possible, make an appointment with a clinic or acute manager in your area to discuss your long range goals. Perhaps they can guide you to a training program. Start making connections.
Ditching your job right now would look bad, and quite frankly it will make you a much better Acute dialysis RN if you have M/S experience.