What is the initial evaluation step for a boy with polydipsia (excessive thirst), polyuria (frequent urination), and nocturnal enuresis (night bed wetting)?

Initial Evaluation: Urine Dipstick Testing

The correct answer is A. Urine analysis—specifically an immediate urine dipstick test—which is the sole obligatory laboratory test for a child presenting with nocturnal enuresis, and becomes critically urgent when accompanied by polydipsia and polyuria, as these symptoms constitute red flags for diabetes mellitus or kidney disease. 1, 2, 3

Why Urinalysis First

The International Children's Continence Society guidelines explicitly state that urine dipstick testing is the only mandatory laboratory test in children with enuresis 1. This becomes even more critical in this clinical scenario because:

• Polydipsia and excessive thirst are red flag symptoms that signal potential diabetes mellitus or kidney disease requiring immediate metabolic investigation 2, 3
• Glycosuria on dipstick mandates immediate exclusion of diabetes mellitus and should prompt urgent blood glucose testing 2, 3
• The dipstick provides immediate point-of-care screening without delay, guiding whether urgent blood glucose testing is needed 2
• Proteinuria in repeat samples should prompt investigations for kidney disease 1, 4

Why Not the Other Options

B. FBS (Fasting Blood Sugar) or C. Random Blood Glucose

While blood glucose testing will ultimately be necessary if glycosuria is detected, starting with urinalysis is the correct sequence because:

• The dipstick can be performed immediately in the office without requiring the child to be fasting 2
• It screens for both diabetes (glycosuria) AND kidney disease (proteinuria) simultaneously 1, 4
• Guidelines specifically warn against delaying testing by ordering comprehensive metabolic panels first—the dipstick reveals whether urgent blood glucose testing is needed 3

D. Ultrasound

Routine ultrasound of the kidneys is not warranted in enuresis 1. The International Children's Continence Society explicitly states that imaging is only indicated after initial screening identifies specific risk factors such as history of UTI, hematuria, or renal insufficiency detected on initial testing 4. Ordering expensive imaging before basic screening tests wastes resources and delays diagnosis 4.

Critical Clinical Algorithm

Step 1: Perform immediate urine dipstick testing 1, 2, 3

Step 2: If glycosuria is present:

• Immediately exclude diabetes mellitus with blood glucose/HbA1c testing 3, 4
• This combination of nocturnal enuresis, polydipsia, and polyuria strongly suggests new-onset diabetes mellitus 5

Step 3: If proteinuria is present on repeat samples:

• Initiate investigations for kidney disease including electrolytes and renal function tests 4

Step 4: Complete a frequency-volume chart for 2-3 days to objectively document polyuria and fluid intake patterns 1, 2, 4

Important Pitfalls to Avoid

• Never attribute bedwetting to behavioral causes when accompanied by polydipsia and excessive thirst—these are red flag symptoms requiring metabolic investigation 2, 3
• Do not delay urine testing, as this can lead to delayed diagnosis and prevention of diabetic complications 4
• Consider diabetes insipidus if urine dipstick is negative for glucose but polyuria persists—first-morning urine specific gravity can help distinguish between different causes of polyuria 2, 6, 7
• Recent onset of fatigue or weight loss further suggests diabetes or kidney disease and makes urgent evaluation even more critical 1, 4