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is a swelling in scrotum
and the muscle twitching is all over the body they do not have any relation.If the varicocele is small and not giving you pain or discomfort regularly then you need not worry right now but if you have pain and swelling and is big and disturbing then you will have to get treated/operated.
As for the twitching and pain it may be due to stress;fatigue;or even deficiency of vitamins;minerals or electrolytes.Presently just drink enough water and if possible 2-3 glasses of water with electral powder and coconut water;also you can start a multivitamin
and you should feel better and if not you need to consult a doctor for examination and treatment.