Most sacral dimples are completely harmless. These small indentations near the base of the spine, found in roughly 2% to 7% of newborns, are one of the most common minor findings on a newborn exam and almost never signal an underlying problem. The vast majority need no imaging, no follow-up, and no treatment. But a small subset of sacral dimples look or feel different from the typical kind, and those differences matter because they can occasionally point to a hidden spinal abnormality that benefits from early detection.
What Counts as a Simple Sacral Dimple
Pediatricians divide sacral dimples into two categories: simple and atypical. A simple sacral dimple is a single, shallow pit sitting right on the midline, less than about 5 mm wide, and located within 2.5 cm of the anus. It has no drainage, no surrounding skin changes, and no other unusual marks nearby. When a dimple checks all of those boxes, the risk of a hidden spinal problem is extremely low.
An atypical dimple is anything that deviates from that profile. The features that move a dimple into the “atypical” column include being large, deep, located high on the back (farther from the anus), sitting off the midline, or appearing alongside other skin findings such as unusual hair patches, hemangiomas, skin tags, fatty lumps under the skin, or a deviated gluteal crease. Multiple dimples also raise concern. These atypical features are what prompt doctors to investigate further.
How Common Are Sacral Dimples, and How Often Is Something Actually Wrong
Sacral dimples are far more common than most parents realize. In a study of over a thousand healthy newborns, about 16% had some form of dimple in the lumbosacral or coccygeal region, and roughly a quarter had deviated or duplicated gluteal creases or lumbosacral hairiness. These minor skin findings are part of the normal range of newborn anatomy.1PubMed Central. A Cross-Sectional Assessment of Cutaneous Lumbosacral and Coccygeal Physical Examination Findings in a Healthy Newborn Population – Section: Results
The question parents really want answered is: how often does a sacral dimple actually mean something is wrong underneath? For simple dimples, the answer is rarely. An eight-year review of nearly 200 infants who had spinal ultrasounds for a simple sacral dimple found that only about 1% were diagnosed with any form of spinal dysraphism, and both of those cases were tethered cords.2PubMed Central. Evaluating the Diagnostic Utility of Spinal Ultrasound in Neonates With a Simple Sacral Dimple: An Eight-Year Retrospective Study – Section: RESULTS A separate large study of nearly 3,900 healthy infants with simple dimples found that only 0.13% ended up needing surgery, and the vast majority of initially “abnormal” ultrasound findings turned out to be clinically meaningless on follow-up imaging.3PubMed. The simple sacral dimple: diagnostic yield of ultrasound in neonates – Section: RESULTS
These numbers are important context. When a doctor points out a sacral dimple during a newborn exam, the statistical reality is heavily on your side.
The Warning Signs That Actually Matter
Knowing what to look for is more useful than worrying about the dimple itself. The physical characteristics that genuinely raise the odds of an underlying spinal abnormality are specific and identifiable.
A dimple that is deep enough that you cannot see the bottom is more concerning than a shallow one. In one MRI-based study, abnormalities beneath the skin were found in about 35% of infants with deep dimples compared to roughly 9% of those with shallow ones.4Journal of Neurosurgery: Pediatrics. Intraspinal lesions associated with sacrococcygeal dimples – Section: Results Depth is one of the stronger predictors.
Location matters too. A dimple sitting high on the lower back, well above the gluteal crease, is more suspicious than one nestled right near the tailbone. And a dimple sitting off to one side rather than centered on the midline deserves closer attention.
The biggest red flag is not the dimple alone but the company it keeps. When a dimple appears alongside other skin markers, the risk jumps considerably. A review of children with skin markers of hidden spinal problems found that when two or more different skin lesions appeared together, the rate of underlying spinal dysraphism was far higher than when a single lesion appeared in isolation.5JAMA Dermatology. Skin Markers of Occult Spinal Dysraphism in Children: A Review of 54 Cases – Section: Results The companion signs to watch for include:
- Hair tufts: A patch of thick hair growing over the lower spine, distinct from the fine body hair common in newborns.
- Hemangiomas: Red or purplish skin markings overlying the spine.
- Skin tags or fleshy bumps: Small protrusions near the dimple.
- Fatty lumps under the skin: A soft mass that you can feel beneath the surface.
- A deviated gluteal crease: The crease between the buttocks veering to one side rather than running straight.
- Drainage or discharge: Any fluid leaking from the dimple.
A simple dimple without any of these features sits in a fundamentally different risk category from a dimple with one or more of them. The atypical features, not the dimple by itself, are what drive the clinical concern.6PubMed Central. Sacral dimple: clinical perspectives of lesions hidden beneath the skin – Section: Diagnosis
What Could Be Hiding Underneath
The reason doctors pay attention to atypical sacral dimples is that the skin of the lower back develops in close coordination with the spinal cord during early pregnancy. The neural tube, which becomes the brain and spinal cord, closes during the first few weeks of gestation. The most caudal (lowest) part of the spinal cord forms through a slightly different process that continues into the second month of pregnancy. Because the skin and the spinal cord are developing side by side during this window, a disruption can leave both a visible mark on the skin and a hidden abnormality in the spine beneath it.
The umbrella term for these hidden abnormalities is occult spinal dysraphism. “Occult” means it is not visible from the outside; “dysraphism” means the structures along the midline did not fully close or separate properly. The most common finding is a tethered cord, where the bottom of the spinal cord is anchored lower than it should be instead of floating freely within the spinal canal. Other findings include fatty tissue attached to the filum terminale (the thin thread at the end of the spinal cord), a low-lying conus (the tip of the spinal cord sitting too low), and dermal sinus tracts, which are tunnel-like connections between the skin surface and the deeper spinal structures.
When imaging is performed on infants who have atypical skin findings, the detection rate of occult spinal dysraphism is higher than many parents expect. In one large series of babies imaged with MRI for various skin markers, about 23% had some form of underlying abnormality. Among those with an isolated midline dimple specifically, the rate was around 20%. The majority of these were relatively mild findings such as a fatty filum or a low-lying conus, but about a fifth were more complex lesions.7Journal of Neurosurgery: Pediatrics. Use of magnetic resonance imaging to detect occult spinal dysraphism in infants – Section: RESULTS
Why Dermal Sinus Tracts Get Special Attention
Among the possible findings, dermal sinus tracts are the ones doctors worry about most urgently. A dermal sinus tract is a narrow channel that extends from the skin surface inward toward the spinal canal. Not every pit on the skin is a sinus tract, but the distinction matters because a true sinus tract can serve as a pathway for bacteria to reach the central nervous system. In a series of patients with confirmed dorsal dermal sinus tracts, some presented with meningitis and spinal abscesses.8PubMed Central. Spinal dorsal dermal sinus tract: An experience of 21 cases – Section: Results
This is why a dimple that has any discharge, redness, or swelling around it warrants prompt medical evaluation rather than a wait-and-see approach. Early surgical excision of a confirmed dermal sinus tract and its track, along with untethering of the cord if needed, is recommended to prevent these infections.9Interdisciplinary Neurosurgery. Complicated congenital dermal sinus: Diagnosis and management
Imaging and Timing
When a doctor does want a closer look, the first-line imaging tool in young infants is spinal ultrasound. It is painless, quick, and does not require sedation. Ultrasound works well in the first few months of life because a baby’s spinal bones have not yet fully ossified, so sound waves can pass through and create a clear picture of the spinal cord and surrounding structures.
There is a catch with timing, though. Very early scans, within the first few weeks after birth, can produce confusing results because the normal anatomy is still settling into its final position. Research suggests that waiting until the baby is past about 31 days old, with a corrected gestational age beyond roughly 42.5 weeks, gives more reliable results and reduces the chance of a false alarm that leads to unnecessary follow-up imaging or parental anxiety.10PubMed. Optimal Timing of Spinal Ultrasound Evaluations for Sacral Dimples in Neonates: Earlier May Not Be Better – Section: CONCLUSIONS On the other end, the window for reliable ultrasound closes as the baby grows. By about four to five months, the bones have hardened enough that it becomes difficult to accurately see the spinal cord’s position, and MRI becomes the imaging tool of choice.11PubMed Central. Outcome of ultrasonographic imaging in infants with sacral dimple – Section: Results
MRI provides a more detailed picture and is necessary when ultrasound findings are abnormal or when the baby is too old for ultrasound to be reliable. The trade-off is that MRI in very young infants typically requires sedation or general anesthesia to keep the baby still, which adds its own small set of risks. When ultrasound shows abnormalities such as a thickened filum, a low conus, or the presence of an intrathecal mass, MRI is used to confirm and characterize the finding before any surgical decisions are made.12PubMed. Occult spinal dysraphisms in newborns with skin markers: role of ultrasonography and magnetic resonance imaging – Section: RESULTS
Should Every Sacral Dimple Be Scanned
This is one of the more debated questions in pediatric practice, and the evidence has shifted the consensus in recent years. Some hospitals and clinics historically ordered spinal ultrasounds for every sacral dimple, including simple ones. But a growing body of research suggests this approach generates more anxiety and cost than clinical benefit.
A review pooling data from over 5,000 patients with simple sacral dimples found that the rate of abnormal ultrasound findings was about 3.4%, which is actually comparable to or lower than the rate found in children without sacral dimples. Most of the abnormal findings were clinically insignificant. The authors concluded that simple sacral dimples do not predict underlying spinal cord malformations and that routine ultrasound screening should not be performed for them.13PubMed. Spine ultrasounds should not be routinely performed for patients with simple sacral dimples – Section: CONCLUSION
Other researchers have similarly argued that screening ultrasounds for simple sacral dimples lead to unnecessary healthcare costs and stress on families without meaningfully improving outcomes.14PubMed. Screening for Spinal Dysraphisms in Newborns With Sacral Dimples The practical takeaway is that a truly simple dimple, one that meets all the criteria for size, depth, location, and absence of other skin findings, does not automatically need imaging. A careful physical exam by the pediatrician is often sufficient.
That said, there is legitimate gray area. Not every dimple fits neatly into “simple” or “clearly atypical.” If your pediatrician is uncertain about the depth of the dimple or whether a subtle skin change qualifies as a cutaneous stigma, ordering an ultrasound as a precaution is reasonable. The issue is not that ultrasound is harmful; it is that routine blanket screening of all simple dimples generates a cascade of follow-up that is rarely productive.
When Something Is Found and Surgery Is Needed
If imaging reveals a tethered cord, a dermal sinus tract, or another structural abnormality, the usual recommendation is surgical correction. The goal of surgery for a tethered cord is to release the cord so that it can move freely within the spinal canal. For a dermal sinus tract, the goal is to remove the tract entirely, eliminating both the infection risk and any tethering it causes.
Timing of surgery is a balancing act. For dermal sinus tracts, early intervention is generally preferred to avoid the risk of infection. However, a study of 52 children undergoing prophylactic removal of dermal sinus tracts found that operating before six months of age was associated with a higher complication rate compared to waiting slightly longer. The presence of associated spinal lipomas also influenced long-term outcomes.15PubMed. The importance of timing: evaluating the optimal age for surgical intervention in asymptomatic dermal sinus tracts – Section: CONCLUSIONS Surgeons weigh the urgency of preventing infection against the technical challenges of operating on a very small infant.
For tethered cords without a sinus tract, the decision depends on whether the child has symptoms. Some children with mild tethering are followed clinically rather than operated on immediately. When surgery does happen, earlier intervention before neurological damage accumulates tends to produce better results. Studies of tethered cord surgery outcomes have found that a shorter time from symptom onset to surgery and evidence of the cord rising to a more normal position after the procedure are associated with a more favorable prognosis.16PubMed. Long-term outcomes of surgical treatment for tethered cord syndrome
Tethered Cord Symptoms to Watch for as a Child Grows
Even if a sacral dimple was evaluated and appeared benign in infancy, it is worth knowing the symptoms of tethered cord syndrome, because in rare cases the condition develops or becomes apparent later in childhood. As a child grows, a tethered cord gets progressively stretched, which can damage the lower spinal cord over time.
The symptoms tend to appear gradually and can include leg weakness or clumsiness, back or leg pain, changes in gait, foot deformities such as high arches or curled toes, and problems with bladder or bowel control. Bladder dysfunction is one of the most common and sometimes the earliest sign. Research in adults with tethered cord syndrome has found that bladder problems were confirmed in the vast majority of patients, with impaired bladder muscle function being the predominant finding.17PubMed. Bladder dysfunction secondary to tethered cord syndrome in adults: is it curable?
In children, new-onset bedwetting after a period of dryness, difficulty with toilet training that seems disproportionate to age, or recurrent urinary tract infections without an obvious cause can all be subtle clues. Scoliosis is another presentation. If a child who had a sacral dimple noted at birth develops any of these symptoms, the dimple becomes relevant history worth mentioning to the doctor.
Surgical Outcomes and Long-Term Follow-Up
When surgery is performed for conditions like tethered cord or syringomyelia associated with closed spinal dysraphism, outcomes vary. In a study of children who had surgery for syringomyelia linked to closed spinal dysraphism, about a third showed improvement in at least one symptom, roughly a third remained stable, and a smaller group either stayed symptom-free or developed new or worsening symptoms over time.18PubMed. Syringomyelia in children with closed spinal dysraphism: long-term outcomes after surgical intervention – Section: RESULTS
One consistent finding across studies is that severe bladder dysfunction, once established, tends to be difficult to fully reverse even with successful surgery. This is one of the strongest arguments for early detection and intervention before irreversible nerve damage occurs. It is also why children who have undergone tethered cord surgery or who are being watched for possible tethering benefit from coordinated follow-up involving multiple specialties, including neurosurgery, urology, and orthopedics.19PubMed Central. Multidisciplinary Management of Tethered Spinal Cord Syndrome in Children: Operationalizing an Outpatient Patient-Centered Workflow – Section: CONCLUSION
What to Do as a Parent
If your newborn has a sacral dimple, the first and most important thing is the pediatrician’s physical exam. They are checking the features described above: size, depth, location relative to the anus, midline position, and the presence or absence of any accompanying skin findings. If the dimple is simple by every criterion, it is very likely that nothing more needs to be done.
If the doctor recommends an ultrasound, the ideal window is roughly one to four months of age. Going in during those first few days of life may not give the clearest picture, and waiting too long means ultrasound loses its usefulness and MRI becomes necessary. The ultrasound itself is a quick, painless scan that your baby can sleep through.
If you notice anything new around the dimple over time, such as redness, swelling, drainage, or a growing lump, bring it to your pediatrician’s attention promptly. And as your child grows, keep an eye on motor milestones, walking patterns, and toilet training progress. Delays or regressions in any of these are worth discussing with the doctor, especially in a child who had an atypical sacral dimple or borderline findings on early imaging. The vast majority of sacral dimples will never cause a problem, but knowing what to watch for puts you in the best position to act early in the rare case that something does develop.