Zac was twenty-three months of age and was brought to see the GP because of a bad nappy rash. He was not yet toilet trained. On examination, he was noted to have directly over the midline a very sacrococcygeal pit with a very narrow opening. This seemed unusual as it was so narrow and seemed deep. Zac walked well for his age and his milestones were all normal. He had had no obvious trouble at this stage with his bowels or bladder, given his age. The GP arranged an ultrasound that showed that the pit went down to the level of bone.
Advice was sort from a paediatric neurosurgeon who suggested that when Zac was old enough to co-operate, perhaps at age five, he should have an MRI scan of the region. If this were done now Zac would need a general anaesthetic as he would not be able to keep still. At this stage, there was no need for an X-ray as the information would come from the MRI scan and the management would not change in the meantime. Having said that, Zac’s parents were advised about abnormal neurological signs that could develop with the condition, although these were most unlikely to occur. More concerning was the risk of infection in the pit, and the parents were told to gently remove any fluff they saw around the entrance of it and not to probe or clean it.
Sacrococcygeal pits are found in 2-4% of newborns. The vast majority do not require investigation as they are shallow and clearly uncomplicated. There are often associated abnormalities such as hair tufts, hypo- or hyper pigmentation, haemangiomas, fatty masses and asymmetrical gluteal creases. A sacrococcygeal sinus (the bottom of the pit cannot be seen) is likely to be more serious as it may connect to the subarachnoid space. It should be noted that ultrasound may underdiagnose this severity of this condition. In addition to this, fibrolipomas are often found at the base of the sinus and may be associated with a low conus.
The management of the low conus when found in association with a fibrolipoma at the base of the pit is controversial. Some neurosurgeons suggest preventative surgery to avoid tethering during the growth spurt at puberty as the operation is generally considered safe and uncomplicated if done early.
There is also an increased incidence (13% approximately) of other congenital abnormalities in children born with intraspinal lesions in association with sacrococcygeal pits. These deformities are typically renal and urological. Conversely, intraspinal sacrococcygeal abnormalities are much more common (27%) when renal and urological abnormalities are identified. Skin lesions around sacrococcygeal pits correspond much less frequently with intraspinal involvement (6%).
In conclusion, the authors of this research suggested that potential complications from sacrococcygeal pits were more likely than currently thought. The risk factors for intraspinal involvement include deep pits, congenital abnormalities, and possibly asymmetrical gluteal folds (a marker for fibrolipomas in the region) and significant cutaneous abnormalities. They suggest a screening ultrasound if there is any doubt, and if this is equivocal or the patient is at high risk, an MRI scan should be arranged.
1. Harada A. Intraspinal lesions associated with sacrococcygeal dimples. J Neurosurg Pediatrics 14:81–86, 2014