There are reports showing considerable morphological abnormalities in the lumbosacral region, which are usually caused by certain diseases or simply by anatomical variations. It is possible that if a caudal block is performed in patients with these anatomical abnormalities it will either fail or another unexpected difficult situation will result. However, there is no case report regarding such issues. We experienced two cases of an unexpected dural puncture during a trial of caudal block, and one case in whom the dural puncture would most likely have been caused by a trial of caudal block. The dural punture was caused by morphological abnormalities in the lumbosacral region i.e., diffuse ectasia of the lumbosacral dura and a posterior sacral meningocele with an enlargement of the lumbosacral canal. The dural termination was located more distally in the potential dural puncture case than in the normal cases.