Blood in the urine of seventy-something elderly may be caused by kidney stones, urinary tract infection, cystitis and other reasons. 1. Kidney stones: if the patient is affected by metabolic changes in the body, urinary tract obstruction, drugs and other factors, it will lead to the seventy-something old man with blood in the urine, and the common symptoms include hematuria, pain, nausea, vomiting and so on. 2. Urinary tract infection: when infected by bacteria, fungi, viruses and other infections, it may lead to the seventy-something old man to have blood in the urine, while the patient may have lumbar pain, frequent urination, urinary urgency, urinary pain and other uncomfortable symptoms. 3. Cystitis: This disease is mainly caused by a variety of pathogens invading the human body through different ways, and growing and reproducing in it, leading to the phenomenon of blood in the urine of patients, which is mainly manifested as abnormal urination, abnormal urine, perineal pain and so on. There are many other causes of blood in the urine, it is recommended that patients consult a doctor in a timely manner, under the diagnosis of the doctor, according to the condition, to take treatment, and pay attention to local hygiene in life, so as not to aggravate the infection.