Would an abdominal ultrasound (US) be reasonable in a male patient with urinary urgency and retention, negative urinalysis (UA) and normal laboratory results?

Abdominal Ultrasound for Male Patients with Urinary Urgency and Retention

Abdominal ultrasound is reasonable and appropriate in a male patient with urinary urgency and retention who has a negative urinalysis and normal laboratory results, as it can identify potential causes of obstruction and rule out significant pathology. 1

Rationale for Abdominal Ultrasound

Initial Assessment

• Post-void residual (PVR) measurement is a critical first step in evaluating urinary retention, with PVR >50-100ml suggesting significant retention 1
• Ultrasound provides a non-invasive method to:
  • Measure bladder volume and post-void residual
  • Assess the prostate size and morphology
  • Evaluate for hydronephrosis or other upper tract abnormalities
  • Rule out other pathologies that may cause or mimic urinary symptoms

Diagnostic Value

• Abdominal ultrasound can detect significant incidental findings in patients with lower urinary tract symptoms (LUTS):
  • Renal carcinomas (0.1%)
  • Abdominal aortic aneurysms (1.1%)
  • Urinary tract calculi (1.1%) 2
  • Prostatic abnormalities requiring further evaluation

Clinical Guidelines Support

• The American Urological Association recommends measuring PVR in patients with LUTS as a safety measure to rule out significant urinary retention both initially and during follow-up 3
• PVR measurement via ultrasound eliminates the risks of urinary tract infection and urethral trauma associated with catheterization 3

When to Consider Additional Testing

Urodynamic Studies

• Uroflow testing may be appropriate if voiding/emptying abnormalities are suspected, as recommended by the AUA 3
• Multi-channel filling cystometry should be considered when:
  • Diagnosis remains unclear after initial assessment
  • Detrusor overactivity is suspected
  • Invasive or irreversible treatments are being considered 3
• Pressure flow studies (PFS) should be performed when determining if urodynamic obstruction is present, particularly before invasive treatments 3

Other Imaging Considerations

• CT is generally not indicated as an initial test unless there is suspicion of urolithiasis or malignancy
• MRI is not appropriate in the initial evaluation of urinary retention 3

Important Clinical Pearls

• A single elevated PVR should not be used alone to make treatment decisions, as there can be significant variability 3
• PVR cannot differentiate between obstructive and non-obstructive conditions by itself 3
• Addressing constipation is essential, as treatment of constipation alone can improve bladder emptying in 66% of patients with increased PVR 1
• Consider neurological causes of retention, which require a focused neurological examination 1
• Case reports have documented rare but serious conditions presenting with urinary retention, including iliac artery aneurysms 4

Conclusion

Abdominal ultrasound provides valuable diagnostic information in male patients with urinary urgency and retention, offering a non-invasive method to assess bladder function, prostate abnormalities, and rule out other significant pathologies. The 6.6% incidence of detecting potentially serious conditions through ultrasound in patients with LUTS supports its use in the diagnostic algorithm 2.