What is the most appropriate initial investigation for a pediatric patient presenting with enuresis (involuntary urination) and chronic constipation?

Most Appropriate Initial Investigation

For a pediatric patient presenting with daytime enuresis (3-4 times daily) and chronic constipation, urinalysis (Option B) is the mandatory first investigation, followed by physical examination to assess for fecal impaction and neurological red flags that would then prompt spinal imaging. 1, 2

Algorithmic Approach to Investigation

Step 1: Mandatory Initial Screening

• Every enuretic child must have a screening urinalysis as the first laboratory test 1, 2
• The dipstick should test for:
  • Leukocyte esterase (pyuria/inflammation)
  • Nitrites (bacterial infection)
  • Glucose (to exclude diabetes mellitus)
  • Protein (to rule out kidney disease) 2
• Most physicians send both urinalysis and urine culture simultaneously given the logistic difficulty of obtaining culture after the office visit 1

Step 2: Critical Physical Examination Findings

The physical examination must specifically assess for:

• Abdominal palpation for fecal impaction (directly relevant to the chronic constipation) 1
• Examination of the back for sacral dimple or other signs suggesting vertebral/spinal cord anomaly 1
• Neurologic examination to rule out subtle dysfunction 1

Step 3: When to Proceed to Advanced Imaging

MRI of the spine (Option A) becomes indicated only when:

• Physical examination reveals a sacral dimple or other signs of spinal dysraphism 1, 3
• The child has continuous wetting (day and night) rather than intermittent episodes 1, 3
• There are neurological findings on examination 1
• The combination of daytime symptoms, constipation, and sacral dimple represents a red flag for tethered cord 3

Kidney ultrasound (Option C) is reserved for:

• Recurrent urinary tract infections 1, 2
• Abnormal voiding patterns 1
• Positive findings on urinalysis or culture 1
• Not routinely indicated for simple enuresis cases 2

Critical Clinical Context

Why Urinalysis Takes Priority

• Daytime enuresis (3-4 times daily) represents non-monosymptomatic enuresis (NMNE), which requires more aggressive investigation than isolated nighttime wetting 1, 4
• The negative predictive value of clear urine with negative dipstick for UTI is 95-98% 1
• Glycosuria requires immediate exclusion of diabetes mellitus 2

The Constipation Connection

• Chronic constipation and enuresis frequently coexist and bladder/bowel function are closely interrelated 1, 5, 6
• Constipation must be addressed first, as it may be difficult to achieve dryness without treating the bowel dysfunction 1, 7
• However, fecal disimpaction alone will not resolve nocturnal enuresis, though it remains important to address 7
• Occult or semi-occult constipation can be detected in up to 98.8% of children with refractory enuresis when properly evaluated 6

Common Pitfalls to Avoid

• Do not skip urinalysis - it is the mandatory screening test before any treatment is initiated 1, 2
• Do not order MRI spine routinely - it is only indicated with specific red flags on history or physical examination 1, 3
• Do not order kidney ultrasound as initial investigation - it is not indicated for routine enuresis evaluation in simple cases 2
• Do not overlook the physical examination - findings of fecal impaction or sacral dimple will direct subsequent imaging 1
• Do not attribute continuous day-and-night wetting to behavioral causes when physical examination reveals concerning findings like sacral dimple 3