Conjoined Twins

  • Juan A. TovarEmail author
Living reference work entry

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Monozygotic, monochorionic, and isosexual twins united by a part of their anatomy are known as Conjoined Twins. This is a rare and fascinating malformation that represents one of the more complex challenges of pediatric surgery. The twins are classified into two main groups: asymmetric and symmetric. Asymmetric ones are acardius acephalus, fetus-in-fetu, or heteropagus twins. In all these, only one component, the autositus supplying circulation, is viable. Symmetric twins are designated craniopagus, thoracopagus, omphalopagus, rachiopagus, ischiopagus, pygopagus, or parapagus according to the location of the joining bridge. This can be large and often contains shared organs. The cardiovascular systems of both components of the set are communicated and the internal environment is also shared to a variable extent.

Mortality is high before and after birth because of frequent and severe associated malformations. Viability of separation is difficult to determine and requires sophisticated imaging studies. Separation not only involves lengthy and complex operations but also difficult ethical decisions with familial, medical, and even court participation.

Separation, when possible, requires various groups of specialists under a strong leadership. Bony parts, nervous system, hearts, great vessels, digestive and genitourinary organs, as well as the skin and musculoskeletal tissues have to be divided and reconstructed to achieve separation with preservation for each component of as much function as possible. Survival is nearly impossible when the hearts are united, but it is possible for one or both twins in all the other forms. Complications are frequent and long-term quality of life is often burdened by fecal and urinary incontinence or by abnormal limbs and genitalia that are the price to pay for separation.

The quality of a pediatric surgical group is heavily put to test by these cases that can only be managed when outstanding expertise is available in the various specialties involved.


Conjoined Twin Acardius Acephalus Heteropagus Parasitic Craniopagus Thoracopagus Omphalopagus Ischiopagus Pygopagus Parapagus Separation Ethics 


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© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Pediatric SurgeryHospital Universitario La Paz, Universidad Autonoma de MadridMadridSpain

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