<s>[INST] my dads lower legs are turning dark brown and are real tight. he just had heart surgery in Jan which was a valve replacement and a 5 bypass. He has dieabites but it is not very bad because he has lost weight. He is under a doctors care. Do you have any ideas on what this could be? [/INST] Hello, Probably he may developed deep vein thrombosis or cellulitis. So please get it done colour doppler of lower limbs and get treated accordingly. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr. Penchila Prasad Kandikattu </s>