Traces: making sense of urodynamics testing--Part 5: evaluation of bladder filling/storage functions

Lower urinary tract function is characterized by two stages: bladder filling/ storage and micturition. Natural bladder filling tends to be slow, intermittent, and variable, while urodynamics testing employs a continuous, supraphysiologic fill rate. A clear understanding of the typical proportion between bladder storage and micturition is essential when urodynamics findings are interpreted within a clinical setting. When completing a filling cystometrogram, the urodynamics clinician must answer five essential questions to generate clinical meaningful results: bladder capacity, bladder wall compliance, competence of the urethral sphincter mechanism, sensations of bladder filling, and detrusor response to bladder filling/storage. While the emphasis of each question differs depending on the patient's lower urinary tract symptoms and specific questions posed by the referring physician, the combined answers to these questions form a comprehensive evaluation of lower urinary tract filling and storage functions. This article will address how the urodynamic clinician answers the first question, "What is the capacity of this bladder?"