Sudden fainting after urination may be caused by urinary syncope, or pheochromocytoma occurring in the bladder, combined with cerebrovascular disease. 1. Voiding syncope: the main manifestation is that after urination, there will be fainting and coma, the time is relatively short, for the loss of consciousness during the coma. This is mainly due to the bladder emptying moment so that the intra-abdominal pressure fell violently, reflexively caused a drop in blood pressure, and thus cerebral ischemia led to fainting. 2. Pheochromocytoma of the bladder: Pheochromocytoma can lead to a sharp rise in blood pressure, especially after urination, the bladder pressure drops suddenly, which will cause the pheochromocytoma to release a large amount of norepinephrine and epinephrine in a short period of time, so that the human body’s blood pressure increases rapidly, and in severe cases, it will lead to hypertensive crisis, thus fainting. In addition, it may also be a sudden attack of cerebrovascular disease during urination, such as transient ischemic attack, cerebral hemorrhage, etc. It is recommended that the patient actively consult a doctor for treatment. Sudden fainting after urination may have other causes, patients need to consult a doctor for examination and early treatment.