An artificial model system for testing the effect of outflow obstruction on the ability of the patient to efficiently void and empty his bladder may be of benefit in future stydies. 
A simple test to objectively measure it in adult males will be an added tool in the armamentarium of urologists to estimate the power reserve of the bladder in patients suffering from outflow resistance. A predictive value of the voiding reserve would be of value in patients with BPH, Diabetic cystopathy, neurogenic bladder, and before Bottox injection

Thirty adult male volunteers < 40 years old were subjected to this study. Exclusion criteria were patients with known symptomatic or radiologic infra vesical obstruction and/or Maximum flow rate < 15ml/sec or significant post void residual.
All subjects were asked to undergo initial uroflowmetry. They were later asked to void into a uroflowmeter through a condom catheter fitted to the penis and the outflow tube guided urine into a vertical height of 40 cm above the level of the symphysis pubis. Urine was directed to fall into a uroflowmeter. Mean Maximum flow rates were compared for each subject with his own maximum flow rate as control. Post voiding residual was assessed after each uroflowmetry study. Again, results were compared to initial recorded residual value.

All subjects were able to continue the study without technical difficulty or complications. All results associated with straining were discarded. The test was repeated twice when candidates were feeling discomfort during voiding. After regular uroflowmetry,  Qmax ranged between 16 and 38 with a mean of 26.7 ml/sec. The candidates later voided into the resistance model. Qmax decreased to 18.1ml/sec at 40 cm height. PVR slightly increased to a mean of 46 ml at the 40 cm height. 76% of volunteers had PVR < 50 ml at 40 cm height resistance.

The use of tube height resistance test is simple, feasible, non-invasive, cheap with no apparent difficulty or complications. The main pitfall of the test is avoiding candidate straining during voids. Assessment of Voiding reserve would help urologists to predict outcome of outflow obstruction and guide their patients for ideal management. Further evaluation of such model is still required to improve its utility in the hand of urologists.

This new model for testing outflow resistance in normal volunteers to evaluate the effect on the voiding flow and post voiding residual is simple and informative. Further evaluation and modifications may still be required to improve its results.