In a Simple CMG, if the first sensation is at 120 mL, a strong urge at 200 mL, and fullness at 250 mL with a steady rise in the syringe, what is the interpretation?

In a Simple CMG, if the first sensation is at 120 mL, a strong urge at 200 mL, and fullness at 250 mL with a steady rise in the syringe, what is the interpretation?

• A. Small bladder capacity with normal compliance
• B. Small bladder capacity with detrusor instability
• C. Large bladder capacity with normal compliance
• D. Large bladder capacity with detrusor instability

Answer: (B)

In this simple CMG pattern, the volumes at which sensations occur tell you about bladder capacity, and any involuntary contractions during filling point to detrusor instability. The first sensation at 120 mL is already a relatively low threshold, indicating a small bladder capacity. The strong urge at 200 mL reinforces this, as the detrusor is overactive enough to trigger a decisive urge well before reaching a normal or large capacity. Fullness at 250 mL confirms that the maximum tolerated volume for this filling is quite low. Detrusor instability is about involuntary detrusor contractions during filling that produce urgency and can limit capacity. In this scenario, the combination of early sensation, a marked urge at mid-filling, and a relatively low fullness volume fits with a bladder that is small and irritable—i.e., small capacity with detrusor instability. The pattern is not typical of normal compliance with a larger capacity, nor of a large-capacity bladder, so those options don’t fit as well.

In this simple CMG pattern, the volumes at which sensations occur tell you about bladder capacity, and any involuntary contractions during filling point to detrusor instability. The first sensation at 120 mL is already a relatively low threshold, indicating a small bladder capacity. The strong urge at 200 mL reinforces this, as the detrusor is overactive enough to trigger a decisive urge well before reaching a normal or large capacity. Fullness at 250 mL confirms that the maximum tolerated volume for this filling is quite low.

Detrusor instability is about involuntary detrusor contractions during filling that produce urgency and can limit capacity. In this scenario, the combination of early sensation, a marked urge at mid-filling, and a relatively low fullness volume fits with a bladder that is small and irritable—i.e., small capacity with detrusor instability. The pattern is not typical of normal compliance with a larger capacity, nor of a large-capacity bladder, so those options don’t fit as well.