General Practice 2022

Gêmeos siamese: what is são, why it happens and surgery

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Gêmeos siamese: what is são, why it happens and surgery
Gêmeos siamese: what is são, why it happens and surgery

Siamese twins are identical twins who were born together in one or several body regions, such as the head, back, trunk, hips or shoulders, for example, and may also share organs, such as the heart, lungs, intestines or brain.

The birth of conjoined twins, also called conjoined twins or xiphopagus twins, is rare, however, due to genetic factors, during the fertilization process, the embryo may not be separated in a timely manner, which takes to the birth of conjoined twins.

The detection of conjoined twins can be done, in some cases, during routine pregnancy tests, such as ultrasound, and treatment, when possible, is done through surgery.

Why it happens

The exact cause of conjoined twins is not fully known, however there are two theories of how conjoined twins form, and they include:

  • Theory of partial fission or division: is the most accepted theory in which it is believed that the separation of the embryonic layers of identical twins, which normally occurs after 8 to 12 days of fertilization does not occur at the right time. In the case of Siamese, this separation into two babies is done between 13 to 15 days after fertilization, being incomplete, causing the babies to be united in some part of the body;
  • Theory of fusion or junction: in this theory it is believed that after complete separation in two babies, the fetuses come back together in some part of the body.

In some cases, conjoined twins can be detected during pregnancy by performing routine ultrasounds. See the main tests performed during pregnancy.

What parts of the body can be joined together?

There are different parts of the body that can be shared by conjoined twins, which depend on the region where the twins are connected, such as:

  • Shoulder;
  • Head;
  • Waist, hip or pelvis;
  • Chest or belly;
  • Back or base of spine.

Furthermore, there are many cases where siblings share a single trunk and a single set of lower limbs, so there is a sharing of organs between them, such as the heart, brain, intestine and lung, depending on how the twins are linked to each other.

Is there any risk to one of the twins?

Depending on the organ that is shared, one of the twins can be harmed due to the greater use of the organ by the other. In order to prevent one of the twins from suffering consequences, surgery to separate the twins is recommended.

However, this is a delicate procedure and whose complexity varies according to the limb and organ shared by the babies.

How the surgery is performed

Surgical separation of conjoined twins is a complicated procedure in most cases, which needs to be carefully evaluated with the doctor, as this surgery is not always indicated. This is especially true of twins who are joined at the head or who share vital organs.

When approved, the surgery is usually quite time-consuming, and can last for more than 24 hours. And even during that time there is a high chance that one or both of the twins will not survive. Therefore, it is recommended that the surgery be performed by a medical team composed of several speci alties, such as a plastic surgeon, a cardiovascular surgeon and a pediatric surgeon, for example, in order to reduce the risks as much as possible.

Sharing of organs is more common in twins who are joined at the head and torso, however when there is sharing of kidneys, liver and intestines, separation can be a little easier.The big problem is that Siamese twins rarely share just one organ, which can make their separation even more difficult. In addition to sharing organs and being physically united, conjoined twins are emotionally connected and live a common life.

Is surgery always recommended?

Due to its high risks and complexity, surgery is not always recommended, especially in the case of sharing vital organs.

So, if surgery is not possible or if the family, or the twins themselves, choose not to have the surgery, the twins can remain together leading a relatively normal life once they get used to living together from birth, maintaining a good quality of life.

Possible risks and complications

The biggest risk of surgery for conjoined twins is death during or after the procedure. Depending on how the twins are conjoined, surgery can be high risk, especially if vital organs are shared, such as a heart or brain, for example.

In addition, the twin, when separated, may have some sequelae such as heart failure and neuronal changes that can result in changes or delay in development.

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