Sacral dimples are minor congenital anomalies. They occur in 3-8% of children¹.

As an isolated abnormality, simple dimples or pits are not useful markers of occult spinal dysraphism (OSD). OSD is a wide-range of skin-coloured spinal column abnormalities. Most OSD is picked up antenatally on anomaly scan.

Sacral dimples are more likely to be associated with OSD if they are above the gluteal cleft.

The following features of dimples are associated with OSD. The infant should be referred for an outpatient ultrasound if two or more are present²:-

• Multiple dimples
• >5 mm diameter
• Base of dimple is not visible, despite thorough examination by a registrar (an otoscope may be helpful)
• Dimple is oriented cephalically (i.e. toward the head), not straight down (i.e. caudal)
• Other dermal abnormalities or masses (see below)
• Distance > 2.5 cm from anus
• Abnormal neurological examination

Other signs of OSD that warrant investigation are listed below. The infant should be referred for an outpatient ultrasound scan if the combination of a sacral dimple and any one of the following features are present:-

• Skin abnormalities (in the area of the dimple):-
  - Hypertrichosis (excessive hair)
  - Lipoma or other mass
  - Pigmented lesions
  - Skin tags or tail-like appendages
  - Vascular lesions - hemangioma, telangectasis
  - Signs of infection such as skin erythema or induration
• Anorectal abnormalities
• Aplasia cutis congenita (in any location)
• Orthopaedic:-
  - Congenital dislocation of the hip
  - Leg length discrepancies
  - Pes cavus
  - Scoliosis
  - Talipes

Please ensure that the ultrasound scan request states the feature that have triggered the referral.

There are some good pictures of various suspicious and reassuring dimples here³.

If OSD is suspected, the infant should have an ultrasound scan of the dimple(s) within 4 weeks. Please attempt to reassure the parents appropriately and try not to use the term spina bifida, as this may lead to unnecessary anxiety.

If you are the SHO or registrar requesting a scan, it is your responsibility to chase up the result and inform the parents of the result by telephone. Do not routinely bring the child back to clinic for the result.