The effect of abdominal pressure on urinary flow rate

We examined the effect of abdominal pressure on urinary flow rate and urethral closure pressure in 46 subjects, ranging in age from 26 to 82 years. An increase in urinary flow rate caused by abdominal straining was not found when organic obstruction was present in the prostatic urethra in men or the proximal urethra in women, or when dysuria is caused by the lowered detrusor pressure. An increase in urinary flow rate caused by straining was noted when anterior urethral stricture or stress incontinence was present. The increase in urinary flow rate owing to straining was undetermined in the control group. The urethral closure pressure on the anti-stress incontinence zone increased as a result of straining at the same time and to the same degree as did the intravesical pressure. When the anti-stress incontinence zone was subjected to transurethral resection for canal formation urination became possible as a result of straining. The patients who were able to urinate with straining sometimes suffered temporary stress incontinence. The degree of straining did not determine whether the patient could urinate with straining. Therefore, it was concluded that abdominal pressure should be excluded from intravesical pressure in performing several urodynamic studies on the lower urinary tract, such as pressure flow studies, and that it is important to have a sufficient canal formation in the anti-stress incontinence zone when urination with straining is expected when performing an operation on patients with urethral obstruction in the anti-stress incontinence zone.