My 8 Years Son Have Pass The Stool In Underwear

My 8 years son have pass the stool in underwear by doing byscocpy and berima test the nerve cell is absent at the end of rectum. He is healthy and good but pass the stool in underwear so please help about it we also concern on homeopathy doctor by taking medicine he pass the stool in toilet but when medicine is stopped again same condition is occurred so guide me about this