• Journal of Korean Neurosurgical Society
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• v.64 no.3
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• pp.380-385
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• 2021

Caudal agenesis refers to the congenital malformation with the essential feature of the agenesis of the sacrococcygeal bone. It is associated with various types of spinal cord anomaly as well as with complex anomalies of genitourinary or gastrointestinal system. The wide spectrum of the disease can be attributed to its pathoembryological origin, the secondary neurulation. This review presents the definition, etiology, classification, and clinical features of the disease.

• Journal of Korean Neurosurgical Society
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• v.64 no.3
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• pp.386-405
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• 2021

Recent advancements in basic research on the process of secondary neurulation and increased clinical experience with caudal spinal anomalies with associated abnormalities in the surrounding and distal structures shed light on further understanding of the pathoembryogenesis of the lesions and led to the new classification of these dysraphic entities. We summarized the changing concepts of lesions developed from the disordered secondary neurulation shown during the last decade. In addition, we suggested our new pathoembryogenetic explanations for a few entities based on the literature and the data from our previous animal research. Disordered secondary neurulation at each phase of development may cause corresponding lesions, such as failed junction with the primary neural tube (junctional neural tube defect and segmental spinal dysgenesis), dysgenesis or duplication of the caudal cell mass associated with disturbed activity of caudal mesenchymal tissue (caudal agenesis and caudal duplication syndrome), failed ingression of the primitive streak to the caudal cell mass (myelomeningocele), focal limited dorsal neuro-cutaneous nondisjunction (limited dorsal myeloschisis and congenital dermal sinus), neuro-mesenchymal adhesion (lumbosacral lipomatous malformation), and regression failure spectrum of the medullary cord (thickened filum and filar cyst, low-lying conus, retained medullary cord, terminal myelocele and terminal myelocystocele). It seems that almost every anomalous entity of the primary neural tube may occur in the area of secondary neurulation. Furthermore, the close association with the activity of caudal mesenchymal tissue in secondary neurulation involves a wider range of surrounding structures than in primary neurulation. Although the majority of the data are from animals, not from humans and many theories are still conjectural, these changing concepts of normal and disordered secondary neurulation will provoke further advancements in our management strategies as well as in the pathoembryogenetic understanding of anomalous lesions in this area.

• Journal of Veterinary Clinics
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• v.41 no.1
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• pp.43-48
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• 2024

A two-year-old, intact female Golden Retriever had previously been diagnosed with a portosystemic shunt (PSS) during an ultrasonographic examination at a local animal hospital. The serum biochemistry revealed elevated liver enzymes and bile acid levels. The abdominal radiographic examination revealed mild serosal detail loss and microhepatica, while abdominal ultrasonography revealed mild ascites and high-velocity flow to the caudal vena cava (CVC) suspected as a PSS. The gallbladder was not observed within the hepatic parenchyma during ultrasonography. Computed tomography (CT) revealed an absent gallbladder and dilation of the common bile duct (CBD). Dilations of the gastroduodenal, splenic, colic and renal veins were also observed. A dilated left phrenico-abdominal vein that entered the CVC was previously misinterpreted as a PSS on the ultrasound examination. Based on the imaging examinations, the dog was diagnosed with congenital gallbladder agenesis associated CBD dilation.