Post-Void Residual Testing
Order a bladder ultrasound to measure post-void residual (PVR) volume – this is the preferred non-invasive method for evaluating incomplete bladder emptying in your patient with cystitis-like symptoms, negative culture, and normal imaging 1, 2.
Why Ultrasound Over Catheterization
Ultrasound bladder volume measurement is preferred to urethral catheterization for PVR assessment 2. While catheterization provides direct measurement, ultrasound is:
- Non-invasive and better tolerated by patients
- Avoids risk of introducing infection
- Can be repeated easily if needed
- Provides immediate results
The interval between voiding and PVR measurement should be kept short to ensure accuracy 2.
Clinical Context for Your Patient
The 2022 AUA IC/BPS guidelines specifically recommend evaluating for incomplete bladder emptying in all patients presenting with chronic bladder/pelvic symptoms 1. Your patient's presentation – cystitis symptoms with negative culture and normal CT – fits the IC/BPS evaluation pathway, making PVR assessment a standard part of the workup.
A brief neurological exam should accompany PVR testing to rule out occult neurologic problems that could explain retention 1.
Interpreting the Results
There is no universally accepted cutoff for abnormal PVR 2. However, recent evidence suggests:
- Large PVR (>200-300 mL) indicates marked bladder dysfunction 2
- The 95th percentile for normal adults is approximately 100 mL for men and 94 mL for women 3
- PVR increases with bladder volume and symptom severity (IPSS scores) 3
Important caveat: PVR alone does not diagnose specific conditions like bladder outlet obstruction and should be interpreted within the broader clinical picture 4, 2. It's most useful for monitoring treatment response rather than making initial diagnoses 4.
What NOT to Order Routinely
Do not order cystoscopy or additional imaging at this stage. Recent evidence shows that routine cystoscopy and ultrasound in women with recurrent UTI-like symptoms yield few abnormalities and add unnecessary costs 5. Cystoscopy is only indicated if you suspect Hunner lesions (a specific IC/BPS phenotype) or need to rule out bladder cancer, stones, or foreign bodies 1.