Double J tubes in the body may cause adverse reactions such as abnormal urine, back discomfort or symptoms of infection. 1. Abnormal urine: Usually one end of the double J-tube is located in the renal pelvis and the other end is located in the bladder, the double J-tube may irritate the mucosal tissue of the renal pelvis or bladder, and symptoms of hematuria may occur. If a large amount of activity also tends to cause dislodgement of the double J-tube, which may stimulate the triangle of the bladder and the neck, and symptoms of urinary urgency, frequent urination, pain in urination, and hematuria may occur. 2. Lumbar discomfort: usually patients are due to ureteral stenosis or stone surgery before placing the double J tube, which can play a role in supporting and drainage, if the patient holds back urine, resulting in drainage is not smooth, there may be lumbar soreness, lumbar pain. In addition, double J tube is usually placed in the ureter, because the ureter is movable, and its long time friction with the double J tube, also easy to lead to lumbar discomfort. 3. Symptoms of infection: In the case of friction and stimulation between the ureter and the double J tube, the mucous membrane may be damaged and symptoms of infection may occur, such as fever, low back pain, and so on, and even septicemia may occur if it is not treated in time. Patients should inform the doctor if they have any uncomfortable symptoms during the placement of double J tube and treat the symptoms promptly.