Caudal Regression Sequence, 12+6 wks

Lech Dudarewicz, Agnieszka Gach
Department of Genetics, Polish Mother's Memorial Hospital, Lodz, Poland; 2 - Medical Genetics Department - Institute of Mother and Child, Warsaw, Poland

Posting Dates: Sep 20, 2025 - Sep 29, 2025
Video 1 © 2025 Dudarewicz
Video 2 © 2025 Dudarewicz
Video 3 © 2025 Dudarewicz
Video 4 © 2025 Dudarewicz
Video 5 © 2025 Dudarewicz
Video 6 © 2025 Dudarewicz
Video 7 © 2025 Dudarewicz

View the Answer Hide the Answer

Answer

Ultrasound Findings (12+6 weeks):

Trunk shortening relative to limbs, with overall disproportion. CRL eqivalent to 12+4 wks, BPD corresponding to 12+6 wks

Juxtaposed iliac bones, abnormally close together in the axial plane.

Sacrum was not not visualized; the lower spine ended abruptly and had irregular caudal tapering, suggesting agenesis (Tortori-Donati et al., 2011).

The anus was visualized in the transverse plane and there was no dilation of the rectum or distal colon, which would likely be apparent at this gestational age in the case of anal atresia (Sepulveda et al., 2002).

non-visualization of nasal bones echo

Lateral neck cyst.

These findings are highly suggestive of caudal regression syndrome (CRS), a rare congenital disorder characterized by developmental failure of the caudal part of the spine and associated structures. CRS encompasses a broad spectrum of severity, ranging from isolated sacral agenesis to complete lumbosacral agenesis with lower limb anomalies and genitourinary or gastrointestinal involvement (Duhamel, 1961; Barkovich, 2018).

Discussion and Differential Diagnosis:

At this gestational age, CRS can be suspected by detailed evaluation of:

Truncal - head and limb disproportion

Early sacral non-visualization

Pelvic bone orientation anf juxtaposition

Associated findings such as imperforate anus, lower limb abnormalities, or bladder anomalies (not seen in this case)

Unossified nasal ridge and lateral neck cyst are not typically associated with CRS and probably represent incidental co-findings.

a-CGH microarray obtained by CVS rendered normal result

📚 Selected References

Tortori-Donati P, et al. Neuroradiology of the Spine. Springer, 2011. (Caudal regression overview)

Duhamel B. From caudal regression to sirenomelia. Teratology. 1961;4(4):277–88.

Sepulveda W, et al. Prenatal sonographic diagnosis of caudal regression syndrome in the first trimester. J Ultrasound Med. 2002;21(8):885–9.

Barkovich AJ. Pediatric Neuroimaging. 6th ed. Lippincott Williams & Wilkins; 2018.

Discussion Board

Start a discussion about this case

We appreciate your patience as we review all submitted answers. Check back soon to see if you were correct!

Add to Favorites Favorite

Menu