Initial Evaluation: Urine Dipstick Test for Diabetes Mellitus
The correct answer is A. Urine analysis (specifically urine dipstick test), which is the sole obligatory laboratory test and must be performed immediately to exclude diabetes mellitus in this child presenting with nocturnal enuresis, polydipsia, and polyuria. 1, 2
Clinical Reasoning
This child presents with a classic triad that raises immediate concern for diabetes mellitus:
- Nocturnal enuresis (new-onset bedwetting)
- Polydipsia (always thirsty)
- Polyuria (drinks a lot, implying excessive urine production)
The International Children's Continence Society explicitly states that glycosuria on dipstick mandates immediate exclusion of diabetes mellitus and should prompt urgent blood glucose testing. 2 The guidelines emphasize that "children with kidney disease or diabetes must be detected" as a primary goal of the initial evaluation. 3
Why Urine Dipstick First
- A urine dipstick test is the sole obligatory laboratory test in children with monosymptomatic enuresis. 3, 1
- Glycosuria detected on dipstick means diabetes mellitus must be immediately excluded. 1, 2
- The test can be performed immediately in the office without delay, potentially revealing a life-threatening condition. 2
- Polydipsia signals that children with polyuria due to diabetes or kidney disease obviously need further investigation. 2
Why Not the Other Options
B. FBS (Fasting Blood Sugar): While ultimately necessary if glycosuria is detected, the urine dipstick should be performed first as it is the recommended initial screening test and can be done immediately. 1, 2
C. Urine culture: This would be indicated if there were signs of urinary tract infection, but the presentation of polydipsia and polyuria points toward a metabolic disorder rather than infection. 3
D. Ultrasound: Routine ultrasound of the kidneys and upper urinary tract is not warranted in monosymptomatic enuresis and would not detect diabetes mellitus. 3
Critical Safety Considerations
- Do not delay testing by ordering comprehensive metabolic panels or scheduling follow-up appointments first—the dipstick can be done immediately. 2
- Do not attribute bedwetting to behavioral causes when accompanied by polydipsia—these are red flag symptoms requiring metabolic investigation. 2
- If proteinuria is detected on repeat samples (rather than glycosuria), this should prompt investigations for kidney disease. 1
Next Steps After Urine Dipstick
If the dipstick shows glycosuria, proceed immediately to blood glucose testing to confirm diabetes mellitus. 1, 2
If the dipstick is negative for glucose and protein, then complete a frequency-volume chart (bladder diary) for at least 2 days of measured intake/output and 1 week of wet/dry nights to objectively document the polyuria pattern. 1