Sacral dimples are small clefts at the base of the spine. They are relatively common in newborn babies and do not usually indicate problems.

In rare cases, people may experience symptoms later in life. In this article, learn about the possible complications of sacral dimples.

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Sacral dimples are common in newborn babies.

A sacral dimple is a small dimple or cleft at the base of the spinal cord. It is found in the small of the back, near the tailbone, which is also known as the sacrum.

It is a congenital condition, meaning a person is born with it. Sacral dimples are sometimes known as pilonidal dimples. Often, they will be discovered when a doctor first examines an infant.

Sacral dimples are relatively common in healthy, newborn babies and do not normally signal a concern. They are seen in around 2-4 percent of births, although the cause of them is unknown.

In most cases, sacral dimples are simply signs of minor abnormalities as the baby grows inside the womb. In rare cases, they can indicate a deeper spinal abnormality.

They can also be present in later life and not cause problems.

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A sacral dimple is a congenital condition that appears in the lower back.

A sacral dimple will appear as a small dimple or pit in the lower back. It is usually very shallow, and the bottom can be seen easily. A sacral dimple may be located in the crease between the buttocks.

However, some attributes can signal further defects, and they will need to be examined with an ultrasound. These include:

  • swelling in the area
  • skin tags
  • a birthmark in the area
  • a patch of hair by the dimple
  • a fatty lump
  • a dimple larger or deeper than 5 millimeters (mm)
  • discoloration
  • tenderness

A sacral dimple can also form in children or adults. Although the exact cause is unknown, it is believed it happens when loose hairs push into the skin.

Some circumstances are known to increase the risk of a sacral dimple occurring. These include:

  • obesity
  • being between the age 15 and 40 years
  • having an above-average amount of body hair
  • having coarse or curly body hair
  • a previous injury to the area
  • family history of the condition
  • having a job that involves driving or sitting for long periods

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Minor sacral dimples have no known risk factors.
Image credit: The Korean Neurosurgical Society

Sacral dimples that are minor and shallow usually have no complications, and there are no known risk factors. These dimples do not require any treatment.

However, deeper pits that continue inside the body can link directly to the spinal cord or the colon. This can also cause a chronic rash. In these cases, the dimple needs to be closed.

Deeper pits can often become infected, and an abscess or cyst may develop. Often this type of growth does not happen until the person is in their teens.

There is no known link between the presence of a sacral dimple and spinal dysraphism or incomplete fusion of the spine or spinal cord.

If there is concern that the sacral dimple is a sign of an underlying problem, then an ultrasound assessing the spinal canal is often the first test to be done. It is usually carried out within 3 or 4 months after the child is born.

If testing shows a birth problem related to a sacral dimple, then the baby may undergo further evaluation and diagnosis for treatment. This can include magnetic resonance imaging (MRI).

Sometimes large or deep sacral dimples are a sign of a birth defect involving the spinal cord or the spinal bones. The most common of these is spina bifida occulta, when there is a small irregularity in one of the vertebrae.

People concerned about a sacral dimple should contact their doctor if they notice any of the following:

  • drainage of pus
  • redness
  • swelling
  • tenderness

A doctor will look at a person's medical history and do a physical examination before deciding the best action to take.

Tethered cord syndrome

A sacral dimple can also indicate an underlying problem known as tethered cord syndrome. This is a fixation of the spinal cord that limits a person's movement.

In a child, this can mean increased tension on the spinal cord as they grow, which can lead to several neurological problems. In most cases, the individual will experience problems in childhood, but they may not appear until adulthood.

Symptoms of this syndrome include:

  • lower back pain
  • leg pain or numbness
  • leg weakness
  • difficulty walking
  • foot or spinal deformities
  • high-arched feet and hammertoes

In most cases, tethered cord syndrome will be diagnosed using either an MRI or computed tomography (CT) scan. In some cases, electromyography will be used to assess nerve function as well.

Surgical treatment will be used to untether the spinal cord. The type of surgery will depend on individual cases, symptoms, and circumstances.

Most sacral dimples are completely harmless and do not require treatment. However, in newborn babies, a doctor will examine the infant for any signs that may indicate a birth irregularity.

Those concerned about developing a sacral dimple later in life can help limit the risk by keeping the area clean and dry and maintaining a healthy weight.

If an infection does occur, it will be treated with antibiotics. If there is an abscess, a minor operation may be needed to drain the pus.

The sacral dimple may have to be surgically removed if infections keep occurring. This solution can be carried out in three different ways, depending on the symptoms:

  • cutting the dimple out and packing it daily with dressing until it heals
  • closing the dimple with a flap of skin and stitching
  • scraping it out and filling it with a special glue