Urine Output Assessment for 29-Year-Old Male, 42 kg
This patient's 12-hour urine output of 1200 mL (100 mL/hour or 2400 mL/24 hours) is within normal limits and does not indicate polyuria. 1, 2
Normal Urine Output Parameters
- Normal adult urine output ranges from approximately 800–2000 mL per 24 hours, with guidelines suggesting a target of approximately 1 liter per 24 hours for healthy individuals 2
- Polyuria is defined as urine output exceeding 3 liters per 24 hours in adults, which is the standard diagnostic threshold 1, 2, 3, 4
- This patient's extrapolated 24-hour output of 2400 mL falls well below the 3000 mL polyuria threshold 1, 2
Weight-Based Considerations
- For a 42 kg adult, the hourly output of 100 mL/hour translates to approximately 2.4 mL/kg/hour, which is substantially above the oliguria threshold of <0.5 mL/kg/hour 5
- The patient's output demonstrates adequate kidney perfusion and function, as it exceeds oliguria thresholds by nearly 5-fold 5
Clinical Context
This output is reassuring and indicates normal renal function. The key distinction is:
- Oliguria (<0.5 mL/kg/hour for ≥6 hours, or <400 mL/day in a 70 kg adult) would be concerning 5
- Anuria (<100 mL per 24 hours) would be critical 6, 5
- Polyuria (>3000 mL per 24 hours) would warrant investigation 1, 2, 3
Important Caveats
- A single 12-hour measurement should not be used to definitively diagnose polyuria; the definition requires measurement over a full 24-hour period 1
- If there are concerns about abnormal urine patterns, a 3-day frequency-volume chart documenting both number of voids and individual void volumes is the gold standard diagnostic tool to distinguish polyuria from other conditions like nocturnal polyuria or urinary frequency 1, 2
- Do not confuse hourly urine output rates (which assess kidney function) with single void volumes (which reflect bladder capacity and voiding habits) 5