Welcome to HCM.
Your husband needs to have a Colour Doppler study of the scrotum
to find out the cause.
It could be due to varicocele
( distended and turtuous veins), fluid collection (hydrocele
), epididymal cyst
, enlarged testis etc.
Only Colour Doppler can give a diagnosis with certainty about these conditions.
Wishing yourself and your husband all the best.