Lumbosacral MRI is the Most Appropriate Next Step
The combination of anuresis (inability to urinate) during day and night, chronic constipation, and a sacral dimple constitutes a red flag constellation requiring immediate lumbosacral MRI to exclude tethered cord syndrome or other occult spinal dysraphism before any symptomatic treatment is initiated. 1, 2
Why Imaging Takes Priority Over Symptomatic Treatment
The presence of a sacral dimple with bowel and bladder dysfunction mandates neurological investigation immediately, as this triad can indicate underlying spinal cord pathology that requires surgical intervention rather than medical management alone. 1, 2
Never assume a sacral dimple is benign when accompanied by bowel and bladder dysfunction—this combination requires definitive imaging regardless of whether focal neurological signs are detected on examination. 1
Treating constipation before excluding tethered cord could mask progressive neurological deterioration and delay potentially irreversible neurological damage. 1
If tethered cord is present, the constipation and urinary symptoms are neurogenic manifestations requiring neurosurgical intervention, not medical management of constipation alone. 1
Why MRI Rather Than Other Options
Lumbosacral MRI is the definitive imaging modality for school-age children with suspected spinal dysraphism, as it provides complete visualization of the spinal cord and surrounding structures. 1, 2
Spinal ultrasound is only useful in infants under 3-6 months before vertebral ossification obscures visualization—it is inadequate for older children. 1
While urinalysis is part of standard enuresis workup, it does not address the structural neurological concern raised by the sacral dimple and cannot exclude spinal dysraphism. 1, 3
The American Academy of Child and Adolescent Psychiatry explicitly states that examination of the back for sacral dimple or other suggestion of vertebral or spinal cord anomaly is essential in every enuretic child, and positive findings direct subsequent imaging. 4, 3
Critical Clinical Algorithm
Order lumbosacral MRI immediately if a sacral dimple is present with bowel/bladder dysfunction, regardless of whether focal neurological signs are detected on examination. 1, 2
Perform thorough neurological examination looking for lower limb weakness or asymmetry, abnormal deep tendon reflexes, gait abnormalities, foot deformities, and muscle tone abnormalities while arranging imaging. 1
Urinalysis can be performed concurrently but should not delay imaging. 2, 3
Expected Findings and Next Steps
If MRI reveals tethered cord, lipoma, or other spinal dysraphism, immediate neurosurgical consultation is mandatory. 2
Even with normal imaging, the severity of continuous day-and-night urinary symptoms combined with chronic constipation requires pediatric urology referral, not primary care management alone. 2
Critical Pitfalls to Avoid
Do not delay imaging to first attempt conservative management of constipation or enuresis, as progressive tethered cord can cause irreversible neurological damage. 1
Do not attribute continuous day-and-night wetting to behavioral causes when a sacral dimple is present—this combination mandates neurological investigation. 2
Do not rely on normal neurological examination alone to exclude spinal dysraphism, as subtle findings may be missed and MRI is required for definitive evaluation. 1
Answer: B. Lumbosacral MRI