What is the initial lab workup for a 12-year-old with near nightly nocturnal enuresis?

Initial Laboratory Workup for Nocturnal Enuresis in a 12-Year-Old

The initial laboratory workup for a 12-year-old with near nightly nocturnal enuresis should include urinalysis and possibly urine culture; more invasive tests are pursued only with specific indications from the history, physical examination, or positive urinalysis results. 1

Essential Laboratory Testing

• Urinalysis: Every enuretic child should have a screening urinalysis to rule out urinary tract infection and certain metabolic disorders 1

  • Clear urine on inspection, negative dipstick (for leukocyte esterase and nitrite), and negative microscopic examination have negative predictive values for urinary tract infection between 95% and 98% 1

• Urine Culture: Often sent simultaneously with urinalysis due to the logistic difficulty of obtaining a culture subsequent to the office visit and because no rapid method of urinalysis can exclude infection with 100% certainty 1

• First-morning Urine Specific Gravity: May be helpful in predicting who will respond to desmopressin acetate (DDAVP) treatment 1

  • Based on the lack of nighttime and early-morning surges in ADH secretion, early-morning unconcentrated urine (specific gravity of less than 1.015) has been proposed as useful in distinguishing enuretic and non-enuretic children 1
  • Some studies have found significantly lower morning urine specific gravity in children with enuresis compared with controls, while others have failed to find such a difference 1

When to Consider Additional Testing

More invasive tests are not routinely needed and should be pursued only with specific indications, including:

• Renal Ultrasound: Consider when history reveals continuous wetting, abnormal voiding pattern, or recurrent urinary tract infections 1

• Voiding Cystourethrogram: Consider when physical examination findings are concerning or urinalysis/culture results are positive 1

• Further Urologic Evaluation: Indicated for daytime wetting, abnormal voiding (unusual posturing, discomfort, straining, or poor urine stream), history of urinary tract infections, or evidence of infection on urinalysis or culture 1

Clinical Approach Algorithm

1. Obtain a 2-week baseline record of wet and dry nights before the initial evaluation 1

   • This serves as a standard against which the success of subsequent interventions can be gauged
   • Sometimes this baseline monitoring alone is associated with improvement

2. Perform urinalysis and possibly urine culture as the initial laboratory workup 1

3. Consider first-morning urine specific gravity to help predict response to desmopressin 1, 2

4. Evaluate for specific conditions that may require targeted testing:

   • Constipation or fecal impaction (may cause mechanical pressure on bladder) 1
   • Sleep apnea or upper airway obstruction (enlarged tonsils/adenoids) 1
   • Diabetes mellitus or diabetes insipidus (suggested by polyuria, polydipsia) 3
   • Neurological disorders (suggested by abnormal neurological examination) 3, 4

Common Pitfalls to Avoid

• Overinvestigation: Beyond urinalysis and possibly urine culture, more invasive tests are not routinely needed unless specific indications are present 1

• Underinvestigation: Failing to perform even basic urinalysis could miss treatable causes like urinary tract infection 1

• Ignoring psychosocial factors: Secondary enuresis (previously dry child who begins wetting) may be related to stress or trauma and requires different evaluation 1

• Overlooking medication side effects: Some medications can cause or exacerbate enuresis 1

• Punitive approaches: Ensuring parents understand the non-volitional nature of enuresis is crucial to avoid harmful punitive responses 1