What is the initial evaluation for a pediatric patient, specifically a young boy, presenting with nocturnal enuresis (night bed wetting), polydipsia (excessive thirst), and increased fluid intake?

Initial Evaluation: Urinalysis (Option A) and FBS (Option B)

For a young boy presenting with nocturnal enuresis, polydipsia, and excessive fluid intake, urinalysis is the single most important initial test and should be performed immediately, followed by blood glucose testing (FBS) if glycosuria is detected or clinical suspicion for diabetes mellitus remains high. 1

Why Urinalysis First

• Urinalysis is the sole obligatory laboratory test recommended by the International Children's Continence Society for children with enuresis, specifically to screen for diabetes mellitus, urinary tract infection, and kidney disease 1

• Polydipsia and excessive thirst are red flag symptoms that mandate metabolic investigation rather than attributing bedwetting to behavioral causes 1

• Urine dipstick provides immediate point-of-care screening and can detect glycosuria, which would mandate urgent blood glucose testing to exclude diabetes mellitus 1

• The presence of glycosuria on dipstick requires immediate exclusion of diabetes mellitus and should prompt urgent blood glucose testing 1

The Critical Triad: Enuresis + Polydipsia + Polyuria

This clinical presentation raises serious concern for:

• Diabetes mellitus (most common and immediately life-threatening if undiagnosed) 2
• Diabetes insipidus (either central or nephrogenic) 2, 3
• Chronic kidney disease with impaired concentrating ability 2, 1

Why Not the Other Options Initially

• Urine culture (Option C): Should only be sent if urinalysis suggests infection (positive leukocyte esterase or nitrites) or if clinical suspicion remains high despite negative screening 1. A negative dipstick has 95-98% negative predictive value for UTI 1

• Ultrasound (Option D): Has no role in initial evaluation unless structural abnormalities are suspected based on history, physical examination, or urinalysis findings 1. This is not a first-line test for this presentation

Complete Initial Workup Algorithm

After urinalysis:

1. If glycosuria present: Immediately check blood glucose (FBS or random) and HbA1c 2

2. If proteinuria or hematuria present: Evaluate for kidney disease with serum creatinine and renal function tests 1

3. If pyuria or positive nitrites: Send urine culture and treat urinary tract infection 1

4. Additional baseline investigations recommended include: electrolytes/renal function, thyroid function, calcium, and HbA1c 2

Essential Complementary Evaluation

• Frequency-volume chart for 1-2 weeks to objectively document fluid intake and urine output patterns 1, 4

• First-morning urine specific gravity can help distinguish between different causes of polyuria 1

• Physical examination focusing on growth parameters, blood pressure, abdominal palpation for bladder distention, and neurologic assessment 1

Critical Pitfall to Avoid

Never dismiss nocturnal enuresis accompanied by polydipsia and excessive thirst as simple behavioral enuresis. These symptoms together represent a metabolic disorder until proven otherwise, and delaying diagnosis of diabetes mellitus can result in diabetic ketoacidosis with significant morbidity and mortality risk 1, 5. The case report of familial central diabetes insipidus initially presenting as nocturnal enuresis emphasizes that polyuria and polydipsia must be carefully evaluated 5.