The causes of pain in groin and genital region could range from stones in the urinary tract
to involvement of nerves supplying these areas. Since he is on many medications and was a case of AML, so both possibilities have to be considered. The tests would involve scan of the pelvic region. lower part of the spinal cord
and spinal nerve
roots also have to scanned with MRI. You should take him to consult both urologist and neurologist
for further evaluation.