Do women have smaller bladders than men?

Question

It is a common belief that women need to go to the bathroom more often than men because of the smaller size of their bladders.

Is this true? Are there more factors involved?

Answer 1

Anatomic bladder capacity is the maximum liquid volume that can fit inside the bladder [1]. While various sources [2, 3, 6] claim it is between 500 and 1000 ml none makes a comparison between men and women.

Functional bladder capacity is the urine volume that triggers micturition sensation [1]. And, yes, there are slight differences between men and women:

Fitzgerald, Stablein, and Brubaker (2002) evaluated voiding diaries in 300 women with differing racial and ethnic backgrounds, and reported that the median voided volume was 330 ml. Latini, Mueller, Lux, Fitzgerald, and Kreder (2004) analyzed multiple variables from voiding diaries in 284 men without bothersome lower urinary tract symptoms and found that the median voided volume was 382 ml. Van Doorn and associates (2011) evaluated voiding parameters in 1688 Dutch men and found a similar mean voided volume in adult men of 400 ml [1].

However, many factors influence this values:

Because functional bladder capacity represents the intravesical volume present when an individual makes a decision to urinate, it is prone to variability based on multiple factors, such as the magnitude of the desire to urinate and individual judgment based on considerations related to the availability of a toilet in the near future [1].

But not only these. Age also matters [4]:

All three groups reported that mean voided volumes tended to be small in older adults, although 24-hour volumes remained unchanged. Van Doorn and associates (2011) followed patients longitudinally over a period of 6.5 years and found that median voided volumes declined from 400 ml to a median value of 245 ml as men aged [1].

Overactive bladder is a condition that modifies functional bladder capacity and it is quite common amongst women:

At minimum, 11 to 16 million women in the United States cope on a daily basis with symptoms that include sudden strong urges to urinate, difficulty delaying voids, frequent trips to the bathroom, and in many cases involuntary loss of urine when urgency strikes. They may wear pads for accidents, plan ahead for access to bathrooms, and modify their social and work lives to accommodate their symptoms [5].

And there are other conditions more common in women which can make them go to the bathroom more often [7]:

• Urinary incontinence
• Stress incontinence
• Neurogenic bladder
• Flaccid bladder
• Spastic bladder
• Bladder stones
• Bladder extrophy
• Urinary retention
• Cystitis

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References:

1. Mikel Gray. Evaluation of Bladder Filling/Storage Functions. Urol Nurs. 2011;31(3):149-153. Available on Medscape.com. Accessed 11.07.2014
2. Wikipedia contributors, "Urinary bladder," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Urinary_bladder&oldid=612184165 (accessed July 11, 2014).
3. WebMD. Image Collection: Human Anatomy: The Bladder http://www.webmd.com/urinary-incontinence-oab/picture-of-the-bladder (accessed 11.07.2014)
4. Siroky MB. The aging bladder. Rev Urol. 2006;6 Suppl 1:S3-7. PubMed PMID: 16985852.
5. Hartmann KE, McPheeters ML, Biller DH, et al. Treatment of Overactive Bladder in Women. Rockville (MD): Agency for Healthcare Research and Quality (US); 2009 Aug. (Evidence Reports/Technology Assessments, No. 187.) Chapter 1, Introduction. Available from: http://www.ncbi.nlm.nih.gov/books/NBK32536/
6. Glenn Elert and his students. Volume of a Human Bladder. Available at http://hypertextbook.com/facts/2001/DanielShaw.shtml. Accessed 11.07.2014
7. (reviewed by) George Krucik. Body Maps: Bladder. Available at http://www.healthline.com/human-body-maps/bladder. Accessed 11.07.2014