Ten year old with one undescended testacle, what are the health implications?

Increased risk: Boys with undescended testicles are at risk for hormone problems (although unlikely with normally descended testicle on other side), fertility with increase risk of decreased sperm count, and testicular cancer (slightly higher risk than general population). You should have him evaluated by a urologist.

Position dependent: Undescended testes located within abdominal cavity have 25% lifetime risk of developing cancer. Lower udt is toward scrotum lower the risk. Similarly a udt should be brought down as soon after 6-months-of-age as possible to maximize fertility potential of that testis. The longer a testis remains undescended greater the chance of worse future sperm production. Rare 2ndary ascent testes are > normal.