How to assess for neurogenic bladder in a patient with a Foley catheter (Foley catheter) using a bladder scan or ultrasound (US)?

From the Guidelines

Assessing for neurogenic bladder in a patient with an indwelling Foley catheter requires temporary catheter removal followed by bladder ultrasound or scan, as recommended by the most recent guidelines 1. To evaluate neurogenic bladder, first remove the Foley catheter and allow the bladder to fill naturally for 4-6 hours while monitoring for spontaneous voiding.

• Then perform a bladder ultrasound to evaluate post-void residual volume, bladder wall thickness, and detrusor activity.
• Significant post-void residual volumes (>100-150 mL) may suggest neurogenic bladder.
• Look for bladder wall thickening (>5 mm), which indicates chronic overdistension or detrusor hypertrophy.
• During the assessment, observe for uninhibited bladder contractions, which may indicate detrusor overactivity. This approach is necessary because an indwelling catheter prevents natural bladder filling and emptying, making direct assessment impossible while the catheter remains in place. The temporary removal allows for functional evaluation of the bladder's neurological control mechanisms, and it is also recommended to remove the Foley catheter as soon as possible to avoid increased risk of urinary tract infection, ideally within 48 hours 1. Coordinate with urodynamic studies for a comprehensive evaluation, as these provide detailed information about bladder pressure, compliance, and sphincter coordination. However, the most recent guideline from 2021 1 provides the best approach for diagnosis and evaluation of adult neurogenic lower urinary tract dysfunction.

From the Research

Assessing Neurogenic Bladder with a Foley Catheter

To assess for neurogenic bladder in a patient with a Foley catheter, a bladder scan or ultrasound (US) can be used. The following steps and considerations should be taken into account:

• The use of a 3D portable ultrasound device, such as the Verathon BladderScan BVI 9400, can provide a quick, safe, and non-invasive measurement of post-void residual urine volume (PVR) 2.
• The accuracy of ultrasound bladder scanners has been shown to be high, with a correlation coefficient of 0.89 between scan volume and catheter volume, and a specificity of 91.0% and negative predictive value of 93.1% in predicting a catheter volume of <100 ml 2.
• When using a bladder scan or ultrasound, it is essential to consider the patient's individual characteristics, such as age, body mass index, and parity, although these factors have not been shown to affect the accuracy of the measurement 2.
• The European Association of Urology (EAU) and the European Society for Paediatric Urology (ESPU) guidelines recommend a proactive approach to diagnosing and managing neurogenic bladder, including the use of urodynamic studies and clean intermittent catheterization (CIC) 3.
• In patients with neurogenic bladder, it is crucial to monitor and manage the condition to prevent severe complications, including renal damage, and to achieve continence and preserve the upper urinary tract 4, 5, 3.

Using a Bladder Scan or Ultrasound

The following points should be considered when using a bladder scan or ultrasound to assess for neurogenic bladder:

• The bladder scan or ultrasound should be performed promptly after voiding to ensure accurate measurement of PVR 2.
• The scan volume should be compared to the catheter volume to ensure accuracy and reliability 2.
• The use of a bladder scan or ultrasound can help identify patients who require re-catheterization or other interventions to manage their neurogenic bladder 2.
• The EAU/ESPU guidelines recommend regular follow-up, including ultrasound, bladder diary, urinalysis, and urodynamics, to monitor and manage neurogenic bladder in children and adolescents 3.