What is the clinical significance and management of a sacral dimple?

Sacral Dimple: Clinical Significance and Management

The critical distinction is location: dimples at or below the gluteal creft line are benign coccygeal dimples requiring no workup, while dimples above this line on the flat sacrum are pathologic lumbosacral dermal sinus tracts requiring imaging and surgical referral. 1

Location-Based Assessment Algorithm

Use an imaginary line drawn between the tops of the two forks of the gluteal cleft as your decision point:

• Dimples at or below this line = Normal coccygeal dimples (found in ~4% of the population) 1

  • No imaging needed 2
  • No further workup or treatment required 1, 2
  • These do NOT give rise to pilonidal disease 1

• Dimples above this line = Pathologic lumbosacral dermal sinus tracts (DSTs) 1

  • Occur in ~1 in 2,500 live births 1
  • Always require imaging and surgical evaluation 1, 2

Critical Pitfall to Avoid

Discard the outdated teaching about visualizing the "bottom" of the dimple. The presence or absence of a visible base has little to do with pathology—location along the craniocaudal axis is what matters. 1, 2

High-Risk Features Requiring Immediate Referral

Any sacral dimple with associated cutaneous findings mandates neurosurgical referral, regardless of location: 2, 3

• Vascular anomalies (capillary malformations, hemangiomas) 1, 3
• Tufts of hair emerging from or near the dimple 1, 3
• Skin tags 1, 3
• Subcutaneous masses or dermoid cysts 1, 3
• Deviated gluteal cleft 3

Imaging Protocol

For infants under 6 months with lumbosacral dimples or concerning features:

• First-line: Spinal ultrasonography 2

  • Safe, effective screening tool 4
  • Can identify echogenic filum terminale, filar cysts, low-lying conus 4, 5

• MRI indicated when: 2

  • Ultrasonography reveals abnormal findings
  • High suspicion despite normal ultrasound
  • Associated markers of dysraphism present
  • Bowel/bladder dysfunction or lower limb upper motor neuron signs

Clinical Significance: Why This Matters

Untreated pathologic DSTs can cause devastating complications: 1, 2, 3

1. CNS infection (meningitis or intraspinal abscess)—the most feared complication 1
2. Aseptic meningitis from epithelial cell desquamation 1
3. Spinal cord compression from dermoid/epidermoid cyst growth 1
4. Neurologic deterioration from cord tethering 1
5. Acute flaccid paralysis (rare but documented) 6

Infection is particularly problematic because it creates intradural scarring that makes subsequent surgical excision much more difficult and increases risk of additional neurologic deficits. 1

Management Summary

For coccygeal dimples (below gluteal line):

• Reassure parents—these are benign variants 1, 2
• No imaging or follow-up needed 2, 7

For lumbosacral dimples (above gluteal line) or any dimple with concerning features:

• Refer to pediatric neurosurgery 2, 3
• Obtain spinal ultrasound if infant <6 months 2
• Surgical correction is required for confirmed DSTs 1

Evidence Quality Note

While screening ultrasound in simple sacral dimples often reveals benign findings like filum terminale lipomas (16.7% incidence) 8 or filar cysts (10.6% incidence) 5, and the actual risk of significant spinal malformations requiring surgery is exceedingly low (0.13%) 7, the catastrophic nature of missed pathologic DSTs—particularly CNS infections—justifies the location-based screening approach recommended by the American Academy of Pediatrics. 1, 2, 3