Horse shoe kidney is a congenital ( by birth) anomaly . it's not a disease. So don't worry. There is no need to separate those kidneys. Although both kidneys are normal. There is no such surgery to separate those normal kidneys. You want to know impact of horse shoe kidney on your life. Although those kidneys are functioning normal , but some of disease reported to be more common in these variants like stones etc. But you should not worry about those things. One last thing is that whenever you develops any complaints like  flank pain , unexplained fever, burning micturition  consult with nephrologist or Urologist.