Sacral Dimple

A sacral dimple is located very close to the sacrum. The word “Sacrum” comes from the name of the bone at the end of the spine that is shaped like a triangle; the dimples are found over this bone. It occurs in about 4% of the population, and many of them are minor and not associated with any abnormality. However, some may be a sign of disease. They are common in newborn babies. An indentation, present at birth in the skin on the lower back, is called a sacral dimple. It is also known as pilonidal dimples, or sacrococcygeal or coccygeal dimples or pits. They are the most common anomaly detected during neonatal spinal examinations. In the majority of cases, they are a normal part of a healthy body.

Usually, they are located above the crease between your buttocks. Most are harmless and do not need any treatment; if the dimple is small or shallow, it is harmless. Sometimes, sacral dimples are a sign of birth defects involving the spinal cord or bones, hence, doctors pay close attention to sacral dimples. One such common birth defect is spina bifida occulta, which usually does not cause problems. In some cases, they indicate problems with the kidneys. The abnormalities or problems are detected by the pediatrician or by an obstetrician who delivers the child. With a few medical tests, these conditions can be ruled out.

Sacral dimples that have a tuft of hair, certain types of skin discoloration, or a skin tag are often a sign of an underlying abnormality of the spine; you may need an imaging test for this and your physician will give you treatment based on its cause.

Usually, the dimple looks like a small pit in the child’s lower back.

There may be certain appearances like swelling in the area, a birthmark, skin tags, or patch of hair. These appearances may trigger concern about accompanying birth defects.

Pilonidal disease may appear as:

• A pilonidal abscess: In this, the hair follicle becomes infected. In the fat tissue, pus is collected.
• A pilonidal cyst: If an abscess has persisted for a long time, a cyst or hole forms.
• A pilonidal sinus: A tract grows under the skin, and it may also grow deeper from the hair follicle.
• A small pore or pit in the skin that may contain dark spots or hair.

Normally, the dimples are less than 5mm in the midline and less than 25mm from the anus. They are found in up to 4% of the population and are a normal variant. However, if a dimple is greater than 5mm deep and large or located more than 25mm from the anal margin, it could be related to occult spinal dysraphism. The presence of lumbosacral lipomas, hairy patches, skin tags, or vascular lesions increases the risk of occult spinal dysraphism. Also, the risk increases with more than one cutaneous lesion overlying the spine.

Management

If the dimple is less than 5mm in the midline and less than 25mm from the anus and no other spinal abnormality is present, parents can be reassured that it is a normal variant and no further investigation is required.

If the dimple appears atypical (i.e., greater than 5mm and more than 25mm from the anal margin), the patient should undergo a spinal ultrasound scan.

If there is a hairy patch, skin tag, vascular lesion, or lumbrosacral lipoma present, the child should be referred for ultrasound spinal imaging. 

A pit or indentation in the skin on the lower back is the main symptom of sacral dimple.

A sacral dimple is located above the crease between the buttocks.

Dimples are small and shallow. There may be fluid draining from it and/or swelling and redness around it.

Sometimes, the signs and symptoms may also include:

• Bowel incontinence
• Numbness in the bladder
• Weakness in the legs

There is no known cause of sacral dimple because it is a congenital condition (present at birth).

Most of them are minor abnormalities that may occur during the baby’s growth in the womb. Rarely are they associated with any spinal abnormality.

Common causes are congenital pilonidal dimple and congenital dermal sinus.

If fluid is draining from the dimples or it is large and accompanied by swelling, discoloration, tenderness, or drainage, a doctor should be consulted. Sometimes, it may get infected and form a cyst. 

They may be evident when the child is physically examined by a pediatrician during post-natal checks.

The doctor will check:

• If there is a tuft of hair in the dimple
• The distance from the buttocks to the dimple; the lower the better
• The floor of the dimple covered with skin
• Any other problems like weak lower limbs

Making a diagnosis of sacral dimple is done by performing several tests.

Your child does not need to see a physician, but if you are bothered by it, you can visit the doctor and ask questions, such as:

• What is a sacral dimple? Does my child need any tests?
• Are there any treatments?
• Does it need special cleaning?
• Is this related to a more serious condition?

The doctor will obtain the child’s medical history and perform a physical examination. In most cases, the physician will comment that there is nothing to worry about; the child only has a pilonidal dimple. But in some rare cases, the following information may be asked:

• Any change in the appearance of the pilonidal dimple
• Any drainage from the dimple
• Any developing symptoms
• Any other symptoms present
• Numbness or loss of movement in the legs
• Any change in bladder control

Your doctor may recommend imaging tests if the sacral dimple has a skin tag, certain types of discoloration, or has a tuft of hair, as these may indicate spinal cord problems. Certain characteristics like a large, deep, unusual appearance or location of the sacral dimple may need further testing. Ultrasound and magnetic resonance imaging help rule out serious conditions.

Some tests include:

• Ultrasound: A noninvasive procedure that uses sound waves to produce images of the body. An ultrasound is one of the most commonly used modalities, especially in neonatal assessment. This is the first test performed to determine if the child has any deeper abnormality associated with a sacral dimple. It is done three or four months after birth. Further evaluation for diagnosis and treatment is needed if the test shows any birth defect associated with the sacral dimple.
• MRI, or magnetic resonance imaging: This offers more detailed images and uses radio waves to create cross-sectional images.

There is no treatment necessary for sacral dimples. Rarely, sacral dimples indicate a serious spine or spinal cord abnormality. 

Sacral dimples cannot be prevented because they are present at birth.

You can take some precautions to avoid complications, such as:

• Taking regular baths
• Keeping the dimple clean through good hygiene

There is no known homeopathic remedy for sacral dimple.

Lifestyle modifications are necessary in order to cope with sacral dimples.

Keep the dimples clean and free of debris, and take a bath every day.

Remove hair regularly to prevent infection.

For babies, apply a protective barrier diaper ointment to keep the stool out so it will not have a rash.

Contact the healthcare provider if there is a clear or pus-containing fluid draining from the dimple.

Normally, minor shallow sacral dimples do not have any complications.

However, when the child is much older, usually, the deeper pits or sinuses may become infected. An abscess or cyst may develop, known as a pilonidal cyst. The word “Pilonida” means “nest of hair.” This may be due to hair, oil secretion, a friction in the area, or the presence of bacteria, which may come from fecal matter. The doctor may recommend surgery to remove or drain the cyst.

There are several risks and complications associated with sacral dimples.

Some of the rare, underlying abnormalities of the spine associated with sacral dimple include:

• Spina bifida: Spina bifida occulta can occur if the spine does not close properly around the spinal cord, but the cord remains in the spinal canal. Usually, there are no symptoms, as it is a mild form of this disorder.
• Tethered cord syndrome: Normally, the spinal cord hangs freely within the spinal canal.  This disorder occurs when tissue attachments limit the movement of the spinal cord. Symptoms may include numbness or weakness in the legs, and bowel and bladder incontinence.

In about 3% of healthy babies, some type of abnormality in the sacral region is found. However, there are no known risk factors for minor sacral dimples. Certain factors like not having enough folic acid during pregnancy or the mother having diabetes may increase the risk of spinal abnormalities.

If the sacral dimple appears with certain types of skin discoloration, has a tuft of hair, or has a skin tag, there will be a higher risk of spinal problems.

Sacral dimples may occur in people who are obese, have experienced trauma or irritation in the area, excess body hair, sit for longer periods of time, or have hair that grows into the crease between the buttocks and wear tight clothes.