Just because you are old doesn't deny you the right to diagnosis and treatment. Chronological age is almost out of the equation in almost all medical specialities. It is the physiological age which defines what treatment a patient can undergo. But we have to respect the age too. Diagnosing is not an issue. But what treatment we should take for it should be well balanced taking the natural history of the diease diagnosed. If the diagnosed condition is not going to affect your overall survival without affecting your quality of life then a more conservative approach can be taken instead of hopping onto heroic actions / surgeries. You should not worry about the age as the reason for any neglect in medical care.
A ct scan of the abdomen and cystoscopy will diagnose most of the causes for urinary obstruction. If there is no anatomical( structural) obdtruction then urodynamic study is the next step which will define any neurological cause for urinary obstruction.
I hope this helps you.
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