3D reconstruction MSCT
Paediatric radiology
Case TypeAnatomy and Functional Imaging
Authors
Dr. Daniel Adri, Dra. Martina Aineseder, Dr. Marcelo Pietrani, Dra. Marina Ulla
Patient16 years, female
16-year-old female ventrolateral parapagus type conjoined twins (sharing the umbilical region) were referred to our institution with dysmenorrea since menarche. Pelvic magnetic resonance imaging (MRI) was performed to find a cause for pain, and computed tomography (CT) for pre-surgical anatomical demonstration.
Both patients had a completely separate cervical-dorsal-lumbar spine, a sacrum, and a fused iliac and pubic bone (Fig. 1, 2).
A fused liver with a single gallbladder was identified. Each twin had a kidney and a spleen (Fig. 3)
The twins had individual aortas, that continued as iliac arteries, which were divided into external iliac and hypogastric arteries. The external iliac artery continued as a femoral artery to supply each homolateral lower limb (Fig. 2)
A normally developed uterus and ovaries were identified, and behind the rectum, positioned between two lumbar columns, was a structure compatible with rudimentary vaginal canal and uterus, with hematic content in the endometrial cavity, and without a vulval opening. This was postulated as the cause of the dysmenorrhoea (Fig. 4-5).
Conjoined twins are a type of mono-zygotic twin in which the embryonic division fails during days 13 to 15 post-conception. [1, 2]
They are an infrequent event without an exact prevalence, but prevalence is reported to vary from 1 in 50000 to 1 in 100000, showing a higher incidence in females in Asia and Africa. [3, 4, 5]
The most widespread classification of conjoined twins is based on the place where they are united. To name the different types that exist, the Greek term 'pagus' is used, which means "something united". In most cases (40%), the twins are united by the chest area (thoracos). The least frequent are those that share the head: craniopagus (2%) [3] . When the union is not symmetrical, the term "heteropagus" is used, differentiating between the twin "host" and the "parasite", the former being the one that presents complete development, and the latter the one that does not possess vital capacity, depending exclusively on the first to subsist. [6, 7]
Although there is no imaging modality of choice, ultrasound is the first method by which prenatal diagnosis is reached, allowing a diagnosis from week 12, until the evaluation of visceral fusion from week 20 onward. In complex situations, the role of prenatal MRI is important. [3, 8]
As was shown in our case and regarding postnatal pre-surgical analysis, both CT and MRI have great advantages thanks to multiplanar and 3D reconstruction, tissue analysis and definition of the vasculature with the administration of intravenous contrast.
Surgery was performed identifying and removing an atrophic uterus and vaginal canal with an atretic hymen.
To complement the imaging analysis, 3D printing models are gaining in importance, demonstrating the exact size of vital organs and helping surgeons to understand spatial relationships. Currently, it performs 3 main functions: surgical planning, providing a specific simulacrum of the patient, and education. [1, 9]
TEACHING POINTS
1) Conjoined twins are rare.
2) Ultrasound is the most common modality used for diagnosis in the prenatal period.
3) CT scan and MRI are useful to demonstrate anatomy.
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URL: | https://eurorad.org/case/15786 |
DOI: | 10.1594/EURORAD/CASE.15786 |
ISSN: | 1563-4086 |
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