Do you have any real knowledge of these matters by virtue of an unrestricted license to practice medicine or other relevant education, training, or experience? If not, so what that you "can't think of a medical problem that would cause someone to spontaneously need to urgently go to the bathroom"?
A truly comprehensive medical assessment includes a "review of systems" (ROS), which is in effect a broad, systematic inventory of symptoms looking for problems that might be overlooked if all that was asked about was what was foremost on the patient's mind at the time. A reasonably thorough inventory would include whether or not if the individual experiences urinary frequency and/or urgency, along with other genito-urinary syptoms, e.g., painful or burning urination (dysuria), trouble initiating urination, incontinence, blood in urine, etc.
I don't think anyone should be required to carry with them a doctor's letter attesting to medical reasons why they might not be able to wait an excessively long time before using a lavatory to relieve themselves. Nor, do I think under other than exceptional circumstances passengers should have to endure very long waits (>20-30 minutes?) to use a lavatory.
see...
Frequent urination means needing to urinate more often than usual.
Urgent urination is a sudden, compelling urge to urinate, along with discomfort in your bladder.
A frequent need to urinate at night is called nocturia. Most people can sleep for 6 to 8 hours without having to urinate. Middle aged and older men often wake to urinate once in the early morning hours.
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Together, frequent and urgent urination are classic signs of a urinary tract infection. Since inflammation reduces the bladder's capacity to hold urine, even small amounts of urine cause discomfort.
Diabetes, pregnancy, and prostate problems are other common causes of these symptoms.
Other causes include:
* Interstitial cystitis
* Medicines such as diuretics
* Overactive bladder syndrome
* Prostatitis
* Stroke and other neurological diseases
* Urinary incontinence
Less common causes:
* Bladder cancer
* Bladder dysfunction
* Radiation therapy
http://www.nlm.nih.gov/medlineplus/e...cle/003140.htm