Causes of frequent urination: Is it overactive bladder syndrome?

causes of overactive bladder 1200400

Frequent urination, or urinary frequency, is the urge of having to pass urine very often (usually once every hour).1 It is difficult to define urinary frequency according to the number of episodes of urination as frequency can vary from person to person. It is very subjective, but usually you will know if you have urinary frequency, as it is a change from your normal pattern. Urinary frequency can be caused by a number of conditions, one of which is overactive bladder syndrome (OAB). But how can you tell if this may apply to you? And what should you do about it?

As a symptom of overactive bladder syndrome (OAB) urinary frequency may present with or without urinary incontinence (unintentional leakage of urine) and nocturia (the need to wake and urinate at night) if OAB is the cause.2 The combination of symptoms associated with this condition suggests that there is dysfunction of the lower urinary tract, which includes your bladder, pelvic floor muscles, urethra and corresponding nerves. OAB is thought to occur in the absence of any underlying conditions such as an infection.

An average person can put off urinating whilst the bladder collects urine (up to 50-200mls).3 The detrusor muscle (the muscle that makes up the bladder wall) is able to sense the amount of urine in the bladder, and contracts to release urine when a certain threshold is reached. When urine accumulates to a point of 500mls, the average person would feel a desperate urge to urinate. With OAB, this desperate urge to urinate occurs before this amount is reached.4

Although OAB is most common in women above 40years, it is not a disorder associated with old age as it also affects younger women. The prevalence of OAB in women is approximately 17%, making it a common condition.5 The prevalence does rise with age, reaching 31% in women over 65 years.6

Symptoms of OAB

Urgency is the predominant symptom of OAB. Urgency is the sudden desire to pass urine which cannot be deferred.7 The inhibition of the micturition reflex (when the bladder contracts and the urethral sphincter which holds urine relaxes to let urine out) is impaired in OAB, and so is the control of voiding. Thus those with OAB have a desperate urge to pass urine that cannot be stopped. Other symptoms include urge incontinence, which is the leakage of urine associated with urgency, and urinary frequency, due to the increased frequency of detrusor muscle contractions, which increases the amount of urination episodes.

Normally, our bladders can hold a good amount of urine before needing to urinate and so most people can sleep throughout the night without needing the toilet. As the threshold for passing urine has decreased, and detrusor muscle contractility (the ability to contract) has increased, people with OAB will get up at night to pass urine, resulting in nocturia.

What causes OAB?

Overactivity of the detrusor muscle is due to some sort of disruption to either the property, structure, or distribution of nerves to the detrusor muscle.8 There are a few theories as to the cause of OAB and its symptoms, which are detailed below.

Firstly, there is a complex interaction between the brain and nerves that supply the bladder. Normally the brain produces inhibitory signals to prevent urination or the micturition reflex. Damage to parts of the brain or spinal cord which carry these nerves to inhibit the reflex can cause OAB.9

Another theory states that partial loss of nerve supply of the bladder’s detrusor muscle causes increased excitability of the muscle. This causes the detrusor muscle to contract spontaneously, and more often, despite there being small amounts of urine in the bladder.10

Finally, an alternative theory includes the neurotransmitter acetylcholine (a chemical messenger that relays signals between nerve cells, and between nerve and muscle cells). Acetylcholine is the principal transmitter causing the detrusor muscle to contract and release urine. It is believed that in people with OAB, either a greater amount of acetylcholine is released during normal distension of the bladder, or the receptors of acetylcholine in the detrusor muscle are more sensitive.11 This causes hypercontractility of the bladder.

Treatment

There are three different treatment strategies when it comes to managing OAB. Firstly, lifestyle changes can help keep it under control. This includes keeping a bladder diary to help show you your urinary patterns, help your doctor diagnose OAB, and help you plan your day, for example managing water intake. Reducing, or stopping altogether, consumption of caffeine and alcohol (which are both diuretics) can help symptoms. If you are already on diuretic medication, speak to your doctor about how this can be tailored to your symptoms. Losing weight if you are overweight is also recommended, as is quitting smoking if you are a smoker.

Secondly, physiotherapy, which includes behavioural therapy to retrain the bladder called ‘bladder drill’ can be used to treat OAB.12 Bladder drill involves recognition of the signs of increased contractility of the bladder, inhibiting the urge, delaying urination and then reinforcement of these steps. Behavioural therapy has proven to be effective in the short term in more than 50% of patients. However long term results show a reduction in effectiveness.13 Bladder training is normally first line treatment and is offered for a minimum of 6 weeks. Pelvic floor physiotherapy can also help with treating OAB.

Finally, medication or surgical treatment can both be used to treat OAB, with the latter being a last resort.

What are the some of the other causes of urinary frequency besides OAB?

Urinary frequency can be caused by disorders affecting any part of the urinary system including the kidneys, ureters, bladder and urethra. Again, simple lifestyle factors can cause urinary frequency, including excess water intake, excess caffeine intake, anxiety, and habit.

Certain conditions can cause inflammation of of the urinary tract, which causes frequency. These include urinary tract infections, which show symptoms such as painful urination, increased frequency, fever, pelvic pain, vomiting, and occasionally back pain when spread to the kidneys occur.

Urinary stones can also cause frequency, as well as being a risk factor for infection. Most people with stones do not know they have them until they present with recurrent infections, severe infection of the kidney, or when they pass them, which can be very painful.

Some conditions that affect the brain and spinal cord can affect the nerves supplying the bladder. This can affect the contractility of the detrusor muscle as well as the threshold for urination. Conditions include multiple sclerosis, stroke, dementia, and Parkinson’s. In these conditions, frequency occurs after the insult, and while frequency can be seen in these conditions it is not the principal symptom for diagnosis.

Increased frequency can also be found in endocrine conditions such as diabetes, and in diabetes mellitus is also associated with excessive thirst, nocturia, hunger, and weight loss.

Finally, disorders of the structure of the urinary system could cause urinary frequency, and anatomical causes also include pelvic masses such as fibroids, which can compress on the bladder causing it to be irritable.

Any sudden changes in urinary patterns warrant a trip to your doctor, and it is likely to be an infection. If not, excluding infection will aid your doctor in starting investigations to find the cause of your urinary frequency.

References

  1. K. Wrenn, ‘Chapter 181 Dysuria, Frequency, and Urgency’, Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edn, Boston, Butterworths, 1990.
  2. S. Srikrishna et al., ‘Management of overactive bladder syndrome’, Postgraduate Medical Journal, vol. 83, no. 981, 2007, pp. 481-486.
  3. C. Peng, ‘Overactive bladder syndrome’, 2016, [available online], http://hsajb.moh.gov.my/versibaru/uploads/farmasi/Buletin%20Penawar%20Jabatan%20Farmasi%20HSAJB%20Bil%203.2016.pdf, (accessed 27 July 2017).
  4. Ibid.
  5. S. Srikrishna, ‘Management of overactive bladder syndrome’, 2007, pp.481-486.
  6. Ibid.
  7. R. Foon, ‘The overactive bladder’, Therapeutic Advances in Urology, vol. 2, no. 4, 2010, pp. 147-155.
  8. C. Chapple et al., ‘The role of urinary urgency and its measurement in the overactive bladder symptom syndrome: current concepts and future prospects’, British Journal of Urology International, vol. 95, no. 3, 2005, pp. 335-40.
  9. A. Wein & R. Rackley, ‘Overactive bladder: A better understanding of pathophysiology, diagnosis and management’, The Journal of Urology, vol. 175, 2006, pp. S5-S10.
  10. Ibid.
  11. Ibid.
  12. S. Srikrishna, ‘Management of overactive bladder syndrome’, 2007, pp.481-486.
  13. J. Wyndaele, ‘The overactive bladder’, British Journal of Urology International, vol. 88, no. 2, 2001, pp. 135-140.

Dr Shreya Patel MBBS MSc BSc DFSRH

Shreya is a London-based doctor specialising in Obstetrics and Gynaecology. Her passion in global and public health, family planning, and reproductive rights led her to pursue a masters in Public Health at Harvard. She is a strong believer that women should have easily accessible, accurate information about their health, to enable them to make decisions about their health that are right for them.

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