General

Synonym/Acronym:
Cystometrography (CMG), urodynamic testing of bladder function.

Rationale
To assess bladder function related to obstruction, neurogenic pathology, and infection including evaluation of surgical, and medical management.

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

• Normal filling pattern
• Normal sensory perception of bladder fullness, desire to void, and ability to inhibit urination; appropriate response to temperature (hot and cold)
• Normal bladder capacity: 250 to 450 mL. Bladder size and corresponding capacity vary with gender and age; in the pediatric patient, the normal bladder stretches to maximum capacity without an increase in pressure
• Amount of postvoid residual urine is less than 30 to 50 mL
• Normal functioning bladder pressure: 8 to 15 cm H₂O
• Normal bladder pressure increases 30 to 40 cm H₂O during voiding
• Normal detrusor pressure: Less than 10 cm H₂O
• Normal first urge to void: 175 to 250 mL; sensation of fullness and need to empty the bladder: 350 to 450 mL
• Urethral pressure that is higher than bladder pressure, ensuring continence.

Critical Findings and Potential Interventions
N/A