From the Guidelines
Diagnosing urinary retention requires a combination of clinical assessment, physical examination, and diagnostic tests, with post-void residual (PVR) measurement being the most important diagnostic test, as indicated by the most recent evidence 1. To diagnose urinary retention, the following steps should be taken:
- Obtain a detailed medical history focusing on urinary symptoms such as difficulty initiating urination, weak stream, incomplete emptying sensation, and lower abdominal discomfort.
- Perform a physical examination including abdominal palpation to check for a distended bladder and a digital rectal examination in men to assess prostate size, as recommended by the AUA guideline 1.
- Measure PVR volume using either bladder ultrasound (non-invasive) or catheterization, with a volume greater than 100-150 mL suggesting urinary retention.
- Additional diagnostic tests may include uroflowmetry to measure urine flow rate, with rates below 15 mL/second indicating possible obstruction, and urodynamic studies to evaluate bladder function and pressure in complex cases.
- Laboratory tests should include urinalysis to rule out infection and serum creatinine to assess kidney function, as well as prostate-specific antigen (PSA) testing in men over 50 to evaluate for prostate enlargement.
- Imaging studies such as ultrasound of the kidneys and bladder or cystoscopy may be needed to identify anatomical causes of obstruction, as indicated by the management of adult stroke rehabilitation care guideline 1. The most recent evidence suggests that a PVR volume greater than 500 cm3, as detected by a bladder scanner, is an indication for management of acute urinary retention, and treatment is recommended if asymptomatic or greater than 300 cm3 if symptomatic 1.
From the Research
Diagnosing Urinary Retention
To diagnose urinary retention, a thorough history, physical examination, and selected diagnostic testing should be performed 2. The evaluation should include:
- A detailed history of current prescription medications, over-the-counter medications, and herbal supplements 3
- A focused physical examination with neurologic evaluation 3
- Measurement of post-void residual (PVR) volume of urine 3, 4
- Use of bladder scanners, which can be an alternative to catheterization for measuring PVR, especially in postoperative patients 5
Diagnostic Criteria
There is no consensus on a PVR-based definition for acute urinary retention, but the American Urological Association recommends that chronic urinary retention be defined as a PVR volume greater than 300 mL measured on two separate occasions and persisting for at least six months 3. The use of bladder scanners can help determine the need for catheterization, with a scan volume of 300 mL or greater in symptomatic patients and 500 mL or greater in asymptomatic patients being appropriate for catheterization 4.
Diagnostic Tools
Bladder scanners, such as the 3D portable ultrasound device, can be used to evaluate PVR and have been shown to be accurate and reliable 5. The BladderScan BVI 9400 has been found to have a high correlation with urethral catheterization measurements, with a specificity of 91.0% and a negative predictive value of 93.1% in predicting a catheter volume of <100 ml 5.
Initial Management
Initial management of urinary retention involves assessment of urethral patency with prompt and complete bladder decompression by catheterization 2, 3. Suprapubic catheters may be preferred over urethral catheters for short-term management, as they can improve patient comfort and decrease bacteriuria and the need for recatheterization 2, 3.