What is the most appropriate first step in evaluating a patient presenting with nocturnal enuresis, weight loss, and polydipsia?

Urine Dipstick Test is the Most Appropriate First Step

The most appropriate first step in evaluating a patient with bedwetting (nocturnal enuresis), weight loss, and polydipsia is urine dipstick testing (urinalysis), as this triad strongly suggests diabetes mellitus or other serious metabolic conditions that require immediate detection. 1

Clinical Reasoning

This presentation is a medical red flag requiring urgent evaluation:

• Weight loss combined with polydipsia and enuresis indicates potential diabetes mellitus or renal disease that must be ruled out immediately before considering primary enuresis 1
• The International Children's Continence Society explicitly states that glycosuria on dipstick testing mandates immediate exclusion of diabetes mellitus, and proteinuria in repeat samples should prompt investigations for kidney disease 1
• These symptoms represent "alarming features" that distinguish this from simple monosymptomatic enuresis 1

Diagnostic Algorithm

Step 1: Immediate Urine Dipstick Testing

• Test for glycosuria (diabetes mellitus) and proteinuria (kidney disease) 1
• This is the sole obligatory laboratory test for patients presenting with enuresis according to ICCS guidelines 1
• If glycosuria is present, diabetes mellitus must be immediately excluded 1
• If proteinuria is present in repeat samples, investigate for kidney disease 1

Step 2: Additional Baseline Investigations (if dipstick abnormal or high suspicion)

• Blood glucose/HbA1c to confirm diabetes mellitus 1
• Electrolytes and renal function to assess for kidney disease 1
• Frequency-volume chart for 2-3 days to document polyuria and detect polydipsia 1

Step 3: Targeted Evaluation Based on Initial Findings

• If diabetes mellitus confirmed: initiate appropriate diabetes management
• If kidney disease suspected: renal ultrasound and further nephrology workup 1
• If both negative but symptoms persist: consider diabetes insipidus or other causes of polyuria 1

Critical Distinctions

Why NOT renal ultrasound first:

• Ultrasound of kidneys and upper urinary tract is NOT warranted as a routine procedure in enuresis 1
• Imaging is only indicated after initial screening identifies specific risk factors (history of UTI, hematuria, urolithiasis, or renal insufficiency detected on initial testing) 1
• Starting with imaging misses the urgent need to detect diabetes mellitus, which requires immediate treatment 1

Common Pitfalls to Avoid

• Never dismiss the combination of weight loss, polydipsia, and enuresis as simple primary enuresis - this triad demands investigation for systemic disease 1
• Do not delay urine testing - glycosuria detection is time-sensitive for preventing diabetic complications 1
• Avoid ordering expensive imaging before basic screening tests - this wastes resources and delays diagnosis 1
• Remember that children with polyuria due to diabetes or kidney disease require further investigation, and desmopressin therapy may be dangerous in children with habitual polydipsia 1

Key Historical Features to Elicit

When taking the history, specifically ask about:

• Recent onset of fatigue or tiredness (suggests diabetes or kidney disease) 1
• Quantification of fluid intake using a bladder diary to distinguish pathologic polydipsia from normal intake 1
• Frequency of daytime voiding to assess for polyuria versus bladder dysfunction 1