Thanks! Very well explained! I'm resting him even before the first visit to the Dr. This was due to overtrain a young kid while having a growth spurt. In the future will modify training accordingly.
A pars stress fracture is not uncommon in a young person who is actively engaged in sports which require repetitive movement involving bending and straightening of the spine.
The recommended treatment is bracing ( although some prefer no bracing and encourage muscle strengthening) and avoiding the specific movements that generated the stress response for 10-12 weeks.
It is possible that based on the findings on CT that a definite fracture event has not been identified, but the risk would appear higher if he continues to play sports without allowing sufficient rehab and strengthening the core muscles of the abdomen and lower back.
When the movement of rotation and extension can be performed without pain, slow return to sports activity can begin. Changes in how your son performs his hitting (ie don't switch-hit) may be appropriate to reduce the risk of recurrent injury/complications.
It would be beneficial to have a sports physiologist or sports medicine evaluation and participation in a supervised therapy program to improve his conditioning.