Quantification of urethral function based on Griffiths' model of flow through elastic tubes

Griffiths' model of flow‐through elastic tubes makes it possible to relate the elastic properties of the flow‐controlling zone to the pressure/flow relation of the urethra. In this work the pressure function p(A) = P mo + K n A n , where A is cross‐sectional area, P mo the minimal opening pressure, and K n and n parameters describing urethral distensibility, describes the elastic properties of the flow‐controlling zone. By curve‐fitting in the pressure/flow plot, the three parameters p mo , K n , and n can be estimated analytically. Using this model it is possible to identify three different biomechanical changes that may cause obstruction. First, p mo may be elevated. Second, the urethra can be distended to a certain area only, corresponding to high values of K n and n. Third, the urethra can be distended but a higher‐than‐normal pressure increase above P mo is needed, K n is high, and n is low. With this model it is possible to quantify urethral function for both scientific and clinical purposes.