For about 6 weeks, my 2 year old has had pain in his groin area, low back pain, and has a high fever that comes and goes. It is never under 103 when he has the fever, and it will linger for a day or two and then go away. There are no other symptoms affiliated with the fever. We have had blood work, urinalysis, and ultrasounds done. The only thing out of the ordinary is his spleen is slightly large, at 9.5cm. Any ideas what could be the cause. Any advice?