Caudal Dysplasia Health Article

Definition

Caudal dysplasia is a total or partial failure of development of the lower vertebrae, including the sacrum (tailbone), which results in associated abnormalities of the lower extremities (legs), spine, kidneys, gastrointestinal and genitourinary tracts.

Description

Caudal dysplasia is also known as sacral agenesis, sacral regression, caudal aplasia, caudal regression sequence, or sirenomelia. Caudal dysplasia results from a failure of the caudal or lower region of the spinal column to form correctly. This abnormal development of the lower spine causes a wide range, or spectrum, of other abnormalities. On the mild end of the spectrum, there may be a partial absence of the tailbone with no associated symptoms (sometimes picked up accidentally on x ray), and on the severe end of the spectrum, there can be complete absence of the kidneys, openings on the spinal cord, genitourinary, limb and bowel abnormalities. Some of these more serious abnormalities can be life-threatening. Most infants with caudal dysplasia fall in between the two ends of the spectrum. They may have kidney malformations, gastrointestinal malformations, spinal cord problems, heart abnormalities, and problems with their lower limbs.

Sirenomelia is a rare condition that was once thought to represent the most severe end of the caudal dysplasia sequence. Infants with sirenomelia may have complete fusion of the lower limbs, complete or partial renal agenesis, and severe bowel problems. There is often oligohydramnios, or a low amount of amniotic fluid, during pregnancy. Because of the severity of the defects in this condition, it is generally lethal. As of 2005, sirenomelia is now thought to be a separate syndrome.

Caudal dysplasia is caused by a problem with the formation of certain tissues early in pregnancy. The lower spine is usually completely formed by the seventh week of pregnancy. Caudal dysplasia is a primary defect of formation of the tissues that will become the sacrum, spinal cord, kidneys, and gastrointestinal system.