Hello! Thank you for the query. Most likely this issue is caused by increased venous pressure due to pushing on the stool. It can be a symptom of impeded blood flow in the pelvis area. Any tumor which compresses main vessels in the pelvis area can give such symptom. But I`m pretty sure other symptoms like bowels obstruction, pain, blood in stool, weakness wound be present much earlier. Sometimes such symptoms can appear due to varicocele. You may also have pain or discomfort in the testis and noodles like structures palpable. Hope this will help. Regards.