how do you know if your body is not absorbing fat

[justwondered]

My 18 year old son has been complaining for some months now (and has seen doctor) about this persistent hyperhydrosis (excess perspiration) problem.  He says it affects him that when he sits down and stands up the chair and his clothes are soaking wet.  He feels that some fluid is leaking from his anus.  Naturally this is very embarrassing for him.  The doctor gave him Odaban an Aluminium based product to prevent excess perspiration.  Trouble is now I do wonder if he could indeed have something more serious.  He has always suffered from stomach pains and was admitted to hospital but nothing was found.  He drinks water, he drinks orange juice, he is tending to stay away from caffeine drinks i.e. coca cola.  Other than this problem he appears to be a healthy young man.  He is meticulously hygeinic and it makes him worry, therefore, making the problem seem worse.  I do not know how to check what is coming out, if indeed anything is coming out of his anus.  Have thought about him putting sanitary protection down there so we can monitor this.  Have this feeling gall bladder and fat absorption could be a possible factor.  Any suggestions gratefully appreciated.  Many thanks.