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Sacral dimples and pits

Checked: 20-08-2024 by Rob Adams Next Review: 19-08-2026

Overview

A sacral dimple or pit is an indentation in the lower back, present at birth in, but sometimes not noticed until the infant’s 8 week check. Most are blind ending, just above or within the crease of the buttocks, and do not require investigation or treatment (1). They are seen in about 3-8% of newborn babies (2).

The following advice has been developed in discussion with paediatricians and radiologists from Bristol Royal Hospital for Children and is appropriate for use across BNSSG (primary, community and secondary care).

Typical Dimples

Children with "typical dimples", specifically: those that are <5mm, and where the base of the dimple is visualised, and is situated </= 2.5cm from the anus, and is in the midline, and have normal neurology, do not require imaging or referral.

Atypical Dimples

Some children with atypical dimples may have an associated underlying neurological problem, for example spinal dysraphism and need further imaging or referral as detailed below.

Who to Refer

Indications for imaging or referral:

Cutaneous stigmata (e.g. hair tufts or haemangioma)
Neurological symptoms or signs.
Dimple or pit is >5mm in maximum diameter or >2.5cm from the anus.
Pits with a base not clearly visualised or appear in combination with other lesions

Up to 6 weeks of age - request USS

If one or more of the above criteria for referral are met then USS can be requested for babies up to a maximum of 6 weeks of age* . This should usually be arranged at the initial neonatal check (hospital or community). Refer via ICE marked urgent if picked up in the neonatal period - the radiologists will prioritise these referrals to try to ensure that they are seen before 6 weeks of age.

After 6 weeks of age - refer

USS is not appropriate after 6 weeks of age as it can't penetrate enough to rule out spinal cord abnormality. If a pit or dimple that meets the above criteria is picked up at a later stage (for example at 8 week check), please make a general paediatric referral via eRS where further imaging may be considered. Direct referrals from GPs for MRI cannot be made.

*Local paediatric radiologists advise that after 6 weeks, US can’t penetrate deep enough to rule out spinal cord abnormality due to ossification of posterior elements. Performing US after neonatal period can’t give information of spinal dysraphism and parents could leave with false reassurance that everything is normal.

What to do before referral

Information to collect and provide if referral is indicated (1):

Can the base of the dimple be visualised?
Is the dimple greater than 5mm in size?
How far above the anal margin is the dimple?
Are there associated skin changes, hairy patch, skin tag or fatty lump?
How many dimples are there?
Is the dimple outside the sacrococcygeal region?
Can the infant move their legs normally?
Are there any problems with urination or stooling?
If you are sending in a photograph, please ask the parents to place a tape measure next to the dimple/lesion to the position of the anus, so that the reader can estimate the distance from the anal margin

Advice and guidance

If there is uncertainty about the need for investigations or referral then please consider requesting Paediatric Advice and Guidance.

Please provide the information listed above and a photograph if possible.

Referral

If referral is indicated then please request general paediatrics via eRS.

In North Somerset, refer children to general paediatrics (Seashore) via eRS.

Resources

(1) Sacral Dimples: Advice for Referrers (scot.nhs.uk)

(2) Sacral dimples | Right Decisions (scot.nhs.uk)

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