Brief Answer: Hi again Detailed Answer: Thanks for the query. This isn't indicating something serious but you should do basic urine analysis and creatinine/urea blood levels to verify is there uroinfection or kidney disorder. Also,you should do urologic ultrasound to rule out prostate enlargement and obstruction of ureter. Probably this is uroinfection which is commonly seen and it should be treated by antibiotics for 7-10 days. Red blister can be sign of such infection or it can be due o irritation, urethral injury by stone,herpes infection. rarely it can be sign of malignant process but this is the last thing to think of at this point. So just do tests I ve mentioned and follow the size of this blister. Meanwhile, drink plenty of fluids and uroprotective teas and avoid cold environment. Wish you good health. Feel free to ask. Regards

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