Precise urodynamic assessment of anatomic urethral obstruction in boys

Repeated pressure/flow studies of micturition, with and without a thick catheter in the urethra, together with an on‐line plot of detrusor pressure against flow rate, enable real anatomic urethral obstruction to be distinguished from (possibly artifactual) functional effects and often allow a urodynamic caliber to be assigned to any anatomic narrowing in the urethra. Results from 103 boys aged 3–15 years without overt neurologic abnormality are reported. It is shown how the presence of a thick urethral catheter enhances the sensitivity to anatomic obstruction, and urodynamic criteria for recognizing such obstruction are set up. Although clinically diagnosed abnormalities such as meatal stenosis are often urodynamically obstructive, 40% of obstructions diagnosed on nonurodynamic grounds were ruled out urodynamically. The overall incidence of urodynamically demonstrated anatomic obstruction in this selected material was 19%.