Micturition Syncope

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Syncope results from a reduction of cerebral blood flow. There are many triggers for syncope -  eg, coughing and defecation. Micturition syncope occurs when there is temporary loss of consciousness during or after urinating.

Syncope itself is a very common symptom, said to occur in 40% of the population at some time in life, with neurally mediated syncope being the most common type. There are no recent figures for the incidence of micturition syncope specifically. It is more common in males. Peak age of presentation is 30-49 years.

It occurs most often after ingestion of alcohol.

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  • Micturition syncope is a neurally mediated syncope, one of a number of "situational syncopes", others including defecation syncope and cough syncope.
  • The underlying cause of micturition syncope is thought to be related to vasovagal syncope with hypotension and possibly bradycardia.[3] This may involve postural hypotension and increased vagal tone as a result from straining (Valsalva manoeuvre).
  • However, the trigger of the vasovagal response is unclear. It has been hypothesised that the bladder becomes hyper-reflexic. This is supported by spinal cord injury patients who develop hypotension and syncope when intermittent urinary catheterisation is performed.[4]
  • The risk of developing hypotension is enhanced by any hypotensive medication - eg, alpha-blockers and even antidepressants.
  • Excess ethanol intake and excess warmth are also precipitating factors for micturition syncope. Again it is thought that these contribute to hypotension.
  • Research in patients with multiple system atrophy (MSA), who have frequent pre-syncope and syncope on micturition, reported that during bladder filling they experienced a slight rise in blood pressure with no change in heart rate (both increased in controls).[5] This is thought to result from activation of the sympathetic nervous system. In controls, at the beginning of micturition this sympathetic activity increased with a further rise in blood pressure and heart rate. Following this, there is a decrease in blood pressure and heart rate (back to baseline). Patients with MSA showed a similar pattern but with less of an increase in blood pressure at the beginning of urination, followed by a fall during micturition. However, the fall is more marked and the duration is longer in MSA. These changes are similar to those seen in neurally mediated syncope.

A person with micturition syncope describes feeling dizzy or light-headed, or having short-lived loss of consciousness when passing urine or straight afterwards. A collateral history is vital.

Syncope does not occur at every episode of micturition. It tends to occur when there are other factors contributing, such as drowsiness, alcohol or dehydration. It is more common when getting up in the night to pass urine.

Other causes of syncope:

These are mostly directed towards excluding other more sinister causes - eg, ECG, Holter monitoring and lying and standing blood pressures. Tilt table testing can be used to determine the extent of the autonomic instability. Often the diagnosis may be made with a careful history, examination and normal ECG.

Management on the whole involves identifying triggering factors and trying to avoid them, and taking safety measures to avoid injury should syncope occur.

  • Advise men to urinate in the sitting position.
  • Isometric exercises to improve circulation can be done prior to getting out of bed to pass urine, or should the warning symptoms be felt.
  • Avoid trigger factors such as alcohol, exhaustion and dehydration where possible.
  • Safety measures - eg, standing up slowly from a lying position, keeping the bathroom door open, moving sharp objects away.
  • Stop any precipitating medications - eg, antihypertensive medication (if possible - especially alpha-blockers) and antidepressants with hypotensive side-effects.
  • Fludrocortisone has been used and enhances blood pressure on standing.
  • Botulinum A toxin injections have been injected into the detrusor muscle of the bladder of patients with spinal cord injuries with some success.[4]

Further reading & references

  1. Parry SW, Tan MP; An approach to the evaluation and management of syncope in adults. BMJ. 2010 Feb 19;340:c880. doi: 10.1136/bmj.c880.
  2. Bae MH, Kang JK, Kim NY, et al; Clinical characteristics of defecation and micturition syncope compared with common vasovagal syncope. Pacing Clin Electrophysiol. 2012 Mar;35(3):341-7. doi: 10.1111/j.1540-8159.2011.03290.x. Epub 2011 Dec 21.
  3. Wieling W, Thijs RD, van Dijk N, et al; Symptoms and signs of syncope: a review of the link between physiology and clinical clues. Brain. 2009 Jul 8.
  4. Previnaire JG, Soler JM; Micturition syncope following intermittent catheterisation in a tetraplegic patient. Spinal Cord. 2006 Nov;44(11):695-6. Epub 2006 Feb 7.
  5. Uchiyama T, Sakakibara R, Asahina M, et al; Post-micturitional hypotension in patients with multiple system atrophy. J Neurol Neurosurg Psychiatry. 2005 Feb;76(2):186-90.
  6. da Silva RM; Syncope: epidemiology, etiology, and prognosis. Front Physiol. 2014 Dec 8;5:471. doi: 10.3389/fphys.2014.00471. eCollection 2014.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Gurvinder Rull
Current Version:
Peer Reviewer:
Prof Cathy Jackson
Document ID:
2455 (v24)
Last Checked:
Next Review:

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