What are the next steps for a patient with abnormal findings on an Ultrasound (U/S) flow study in urology?

Next Steps After Abnormal Urologic Ultrasound with Flow Study

For patients with abnormal findings on urologic ultrasound with flow study, the next step should be pressure-flow studies (urodynamics) to distinguish between bladder outlet obstruction and detrusor underactivity, particularly when invasive treatments are being considered. 1

Evaluation Algorithm Following Abnormal U/S Flow Study

Initial Assessment

• Review specific abnormal findings from the ultrasound and flow study:
  • Maximum flow rate (Qmax) - critical parameter
  • Post-void residual (PVR) volume
  • Prostate size, shape, and configuration (if visualized)
  • Presence of hydronephrosis or other upper tract abnormalities

Decision Pathway Based on Flow Study Results

If Qmax < 10 ml/second:

• Bladder outlet obstruction (BOO) is likely 1
• Pressure-flow studies may not be necessary before proceeding to treatment 1
• Consider:
  • Prostate size assessment via transrectal or transabdominal ultrasound
  • PSA testing if not already done

If Qmax > 10 ml/second with abnormal findings:

• Pressure-flow studies are strongly recommended before any invasive therapy 1
• This is the only definitive method to distinguish between:
  • Bladder outlet obstruction
  • Detrusor underactivity
  • Combined conditions 1

Additional Testing Based on Clinical Scenario

1. For suspected storage symptoms/overactive bladder:

   • Multi-channel filling cystometry to evaluate for detrusor overactivity 1
   • Frequency-volume chart documentation 1
   • Validated symptom questionnaires 1

2. For suspected anatomical issues:

   • Prostate imaging with transrectal ultrasound if PSA is elevated 1
   • Endoscopic evaluation if specific anatomical configuration will affect treatment selection 1

3. For suspected upper tract involvement:

   • Upper tract imaging (ultrasound or excretory urography) if patient has:
     • History of urinary tract infection
     • Hematuria
     • History of urolithiasis
     • Renal insufficiency
     • Recent onset nocturnal enuresis 1

Treatment Decision Making

Treatment decisions should be based on urodynamic findings:

• If obstruction is confirmed: Proceed with appropriate interventional therapy 1

  • Consider anatomical characteristics of prostate for treatment selection
  • Options may include α-blockers, 5α-reductase inhibitors, or surgical intervention

• If no obstruction is found: Patient should be informed about potentially higher failure rates with interventional therapy 1

  • Consider alternative diagnoses and treatments

• If mixed conditions are found: (e.g., BOO with detrusor overactivity)

  • Treat the primary condition first
  • Reassess after initial treatment 1

Important Considerations

• PVR measurements may have significant variability - decisions should not be based on a single measurement 1
• At least two flow rate measurements should be obtained, ideally with voided volumes >150 ml 1
• For male infants with hydronephrosis, fluoroscopic voiding cystourethrography (VCUG) is recommended to evaluate for vesicoureteral reflux and posterior urethral valves 1
• Pressure-flow studies are the gold standard for diagnosing bladder outlet obstruction in men and should be performed before invasive or irreversible treatments 1

By following this structured approach after an abnormal ultrasound with flow study, clinicians can accurately diagnose the underlying condition and select the most appropriate treatment to improve morbidity, mortality, and quality of life outcomes.