My 15 month old was just diagnosed with a hydrocele. is there still a chance it will resolve without surgery? it seems to be getting smaller.

Watch and see: These can resolve on their own. They don't usually do any damage so watchful waiting while it decreases in size is definitely a good idea.

Probably not: Hydroceles in young babies often do not communicate with the abdominal cavity, & they usually resolve in the first few months of life. Hydroceles found after the first birthday connote communication with the abdominal cavity & usually do no resolve spontaneously. Surgery is usually needed. That said, one can watch a hydrocele for quite some time seeing what will happen without bad consequence.

Yes: New born hydroceles often resolve spontaneously. If it is getting noticeably smaller (even if slowly), is not varying in size throughout the day, is not associated with groin swelling and is asymptomatic, then continued observation is prudent. The srotum usually has a completely normal appearance after spontaneous resolution.