Bladder Scan Interpretation 💧
Guide for interpreting bladder scans and post-void residual volumes. Urinary retention assessment, catheter decision-making, and voiding dysfunction for NCHDs.
Bladder volume interpreter
Enter post-void residual (PVR) or bladder volume in ml, or tap a range — then review suggestions and escalation prompts.
Quick ranges
Enter a volume to see tailored suggestions.
Educational aid only. Bladder scan interpretation depends on timing (pre- vs post-void), technique, comorbidities, and local protocol. This does not replace clinical assessment, documentation, or senior review.
🧠 Definition & Purpose
- Bladder scan (ultrasound) measures bladder volume non-invasively.
- Used to assess post-void residual (PVR) urine, detect retention, and guide catheterisation decisions.
- Helps differentiate between urinary retention and low urine output due to other causes (e.g., dehydration, AKI).
📊 Interpreting Results
- Normal PVR: <50–100ml (age-dependent; older adults may have slightly higher).
- Borderline: 100–200ml — monitor, especially if symptomatic.
- Retention: >200ml — significant; >300ml usually requires intervention.
- Empty bladder: <50ml post-void suggests adequate voiding.
🔍 Clinical Interpretation by Volume
- <100ml: Normal/adequate emptying — continue monitoring if asymptomatic.
- 100–200ml: Mild retention — consider if patient symptomatic or at risk; may need repeat scan.
- 200–300ml: Moderate retention — usually warrants catheterisation if symptomatic or progressive.
- >300ml: Significant retention — catheterisation typically indicated, especially if painful or associated with complications.
📞 When to Request
- Low urine output without clear cause (e.g., not dehydrated, AKI unclear).
- Suspected urinary retention (e.g., patient unable to void, abdominal discomfort).
- Post-voiding to check residual volume.
- After catheter removal to confirm adequate voiding.
- Monitoring in at-risk patients (e.g., post-operative, neurological conditions, BPH).
🩺 Clinical Context Matters
- Symptomatic retention (pain, discomfort, palpable bladder) → act on lower volumes (e.g., >150ml).
- Asymptomatic with large PVR → assess risk factors and consider intervention based on patient factors.
- Acute retention vs chronic: Acute retention usually requires immediate catheterisation.
- Patient factors: Neurological disease, BPH, medications (e.g., anticholinergics) affect threshold for intervention.
💊 Management Based on Results
- PVR <100ml: Monitor; likely no intervention needed unless symptomatic.
- PVR 100–200ml: Repeat scan if symptomatic; consider intermittent catheterisation if progressive or bothersome.
- PVR 200–300ml: Usually catheterise (IDC or intermittent) if symptomatic or deteriorating.
- PVR >300ml: Catheterise — IDC often preferred for acute retention or if frequent scans needed.
- Always reassess: Repeat scan after catheterisation to confirm drainage, and after removal to ensure adequate voiding.
⚠️ Troubleshooting & Considerations
- False readings: Ensure proper technique (correct probe position, adequate gel, patient positioning).
- Obesity or abdominal distension: May affect accuracy; consider clinical context.
- Recent void: If patient voided just before scan, consider waiting 10–15 minutes for accurate residual.
- Haematuria or clots: May affect readings; use clinical judgement.
- Chronic retention: Patients with longstanding retention may tolerate higher volumes; assess symptoms and risks.
🚩 Red Flags Requiring Urgent Action
- Large volume (>500ml) with pain or palpable bladder → urgent catheterisation.
- Signs of urosepsis (fever, rigors, hypotension) with retention → catheterise, send cultures, consider antibiotics.
- Acute retention with inability to void → immediate intervention.
- Retention causing kidney injury or deteriorating renal function → urgent urology consult.
📝 Documentation
- Record: Volume (ml), timing relative to voiding, patient symptoms, clinical context.
- Note: Pre-void vs post-void, catheterisation decision and outcome.
- Follow-up: Repeat scan results if applicable.