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Phillip A. Low, M.D.
Tests and diagnosis (1)
- Tilt table test: Why is it performed?
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Question
Fainting during urination (micturition syncope): What causes it?
Last week, my husband got up and went to the bathroom to urinate and while there, he fainted. This is not the first time this has happened. His doctor suggested he might have something called micturition syncope. What causes this?
Answer
from Phillip A. Low, M.D.
Micturition (or post-micturition) syncope is fainting during or, more commonly, immediately after urination due to a severe drop in blood pressure. Micturition syncope is most common in older men and usually occurs at night after a deep sleep.
The exact cause of micturition syncope isn't fully understood. But it may be related to opening (vasodilation) of the blood vessels that occurs when getting up and standing at the toilet or that occurs at the rapid emptying of a full bladder. This is thought to result in a sudden drop in blood pressure.
Other factors that may play a role in micturition syncope include:
- Alcohol
- Hunger
- Fatigue
- Medical conditions, such as a respiratory infection
Micturition syncope is uncommon and should be evaluated by a doctor. Prevention of micturition syncope depends on recognizing the factors that contribute to micturition syncope and avoiding them. Sitting down to urinate also may treat the problem.
Next questionTilt table test: Why is it performed?
- Faintness and syncope. In: Ropper AH, et al. Adams and Victor's Principles of Neurology. 8th ed. New York, N.Y.: The McGraw-Hill Companies; 2005. http://www.accessmedicine.com/content.aspx?aID=969866. Accessed Feb. 24, 2009.
- Seizures and syncope. In: Aminoff MJ, et al. Clinical Neurology. 6th ed. New York, N.Y.: The McGraw-Hill Companies; 2005. http://www.accessmedicine.com/content.aspx?aID=2082869. Accessed Feb. 24, 2009.
- Olshansk B. Neurocardiogenic (vasovagal) syncope. http://www.uptodate.com/home/index.html. Accessed Feb. 24, 2009.
