The Shape of the Urine Stream — From Biophysics to Diagnostics

• Published in: PloS one Vol. 7; no. 10; p. e47133
• Main Authors: Wheeler, Andrew P. S., Morad, Samir, Buchholz, Noor, Knight, Martin M.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 16.10.2012; Public Library of Science (PLoS)
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Algorithms; Analysis; Biology; Biophysical Phenomena; Biophysics; Capillary flow; Capillary waves; Clinical trials; Computational fluid dynamics; Computer applications; Computer Simulation; Diagnostic software; Diagnostic systems; Engineering; Engineering schools; Flow velocity; Fluid dynamics; Fluid mechanics; Fluids; Humans; Hydrodynamics; Male; Materials science; Medicine; Middle Aged; Models, Theoretical; Patients; Physics; Prostate; Reynolds number; Surface tension; Urine; Urodynamics; Urology; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0047133

We develop a new computational model of capillary-waves in free-jet flows, and apply this to the problem of urological diagnosis in this first ever study of the biophysics behind the characteristic shape of the urine stream as it exits the urethral meatus. The computational fluid dynamics model is used to determine the shape of a liquid jet issuing from a non-axisymmetric orifice as it deforms under the action of surface tension. The computational results are verified with experimental modelling of the urine stream. We find that the shape of the stream can be used as an indicator of both the flow rate and orifice geometry. We performed volunteer trials which showed these fundamental correlations are also observed in vivo for male healthy volunteers and patients undergoing treatment for low flow rate. For healthy volunteers, self estimation of the flow shape provided an accurate estimation of peak flow rate (± 2%). However for the patients, the relationship between shape and flow rate suggested poor meatal opening during voiding. The results show that self measurement of the shape of the urine stream can be a useful diagnostic tool for medical practitioners since it provides a non-invasive method of measuring urine flow rate and urethral dilation.