Conjoined Twins Clinical Presentation

Updated: May 08, 2018
  • Author: Khalid Kamal, MD, MBBS, FAAP, FCPS, MCPS; Chief Editor: Robert K Minkes, MD, PhD  more...
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Presentation

History and Physical Examination

Cephalothoracopagus twinning is characterized by the anterior union of the upper half of the body, with two faces angulated variably on a conjoined head. The anomaly is occasionally known as janiceps, named after the two-faced Roman god Janus. The prognosis is extremely poor because surgical separation is not an option, in that only a single brain and a single heart are present and the gastrointestinal (GI) tracts are fused. This malformation is extremely rare (see the image below).

Cephalothoracopagus twins. Cephalothoracopagus twins.

Craniopagus occurs in 2% of conjoined twins. In this variety, the twins have cranial fusion (see the images below). Stone and Goodrich subclassified craniopagus into four varieties, depending on whether a significantly shared dural venous sinus system (total vs partial) is present and on whether the intertwin longitudinal angulation is below 140º. [21]

Craniopagus twins. Craniopagus twins.
Craniopagus twins. Craniopagus twins.

Bicephalus or dicephalus means that two heads are present on a single trunk (see the images below).

This set of conjoined twins was a stillbirth. Pren This set of conjoined twins was a stillbirth. Prenatal ultrasonography failed to reveal the second head. An emergent cesarean section was performed after failure to progress.
This is an example of double-headed (bicephalus) c This is an example of double-headed (bicephalus) conjoined twins, a rare occurrence.

In omphalopagus, the anterior abdomens are united (see the image below). Omphalopagus (34%) is considered a subset of thoracoomphalopagus. Its incidence is usually added to that of thoracopagus (40%) to yield the overall incidence of thoracoomphalopagus (74%). Pure omphalopagus twins have no cardiac union.

Thoracoomphalopagus twins. Thoracoomphalopagus twins.

A case of thoracoomphalopagus twins, after separation, is shown below.

A case of thoracoomphalopagus twins, after separat A case of thoracoomphalopagus twins, after separation.

In the condition parapagus, (see the image below) or diprosopus, [22]  twins have lateral union of their trunks so that both faces are forward looking in the same plane.

Parapagus twins. Parapagus twins.

Pygopagus (see the image below) is the term used when the twins face in opposite directions. The sacra are fused, and the twins may share a portion of the spinal cord. In addition, the rectum and perineal structures are usually fused.

Pygopagus twins. Pygopagus twins.

In rachipagus (see the image below), the twins are joined back-to-back at any point, usually above the lumbar spine. They may have extensive vertebral fusion in the dorsal midline and may have meningocele, neural connection, or both. One of the embryos generally fails to survive, leaving some body part attached to the other twin's dorsal column. In these cases, rachipagus must be differentiated from fetus in feto (within a body cavity) and teratoma (no mature organ). [23]

Rachipagus twins. Rachipagus twins.

Thoracopagus is the most common variety, occurring in 40% of conjoined twins. The chests are joined, and the hearts are almost always fused in some way (see the images below). As noted above, thoracopagus is often combined with omphalopagus.

Conjoined twins unified at the thorax and abdomen. Conjoined twins unified at the thorax and abdomen.
Another view of the same set of twins as shown in Another view of the same set of twins as shown in the previous image.
A superior radiographic view of the same set of tw A superior radiographic view of the same set of twins as shown in the previous 2 images. The twins have 2 hearts that are not conjoined, making this a possible operation.
Esophagram showing union at the level of stomach. Esophagram showing union at the level of stomach.
Thoracoomphalopagus twins. Thoracoomphalopagus twins.
Thoracoomphalopagus twins. Thoracoomphalopagus twins.

In ischiopagus twins (see the image below), the lower abdomen and the pelves are fused. [24, 25]  The twins may have three legs (ie, tripus) or four (ie, tetrapus). The genitourinary system and the rectum are shared; the liver may also be fused.

Ischiopagus tetrapus twins. Ischiopagus tetrapus twins.