Do not worry about those medical certificates. They can produce a single medical citatation which says that B/L varicocele causes impotence.
Try to trap them at Cross examination, which should be effectively prepared. U may plead following points:
Whether she found u impotent from the very begining? If so, why it took 3 long years fro her to complaint.
If it devloped later on & they produce varicocele certificate of a later date, u may take it as an acquired disease which is easily curable & I got it treated on so & so date.
............... Actually they have to PROVE IMPOTENCE MEDICALLY & NOT VARICOCELE.
............... At the maximum, varicocele may be a cause of impotence, BUT WHERE IS THE IMPOTENCE AT ALL????
U must be sure that u dont have ;-)
Medical science can easily tell if somebody in impotent or not!