Everything about Situs Inversus totally explained
Situs inversus (also called
situs transversus) is a
congenital condition in which the major
visceral
organs are reversed or
mirrored from their normal positions. The normal arrangement is known as
situs solitus. In other rare cases, in a condition known as
situs ambiguus or
heterotaxy, situs can't be determined.
The term
situs inversus is a short form of the
Latin phrase "
situs inversus viscerum," meaning "inverted position of the internal organs."
Dextrocardia (the
heart being located on the right side of the
thorax) was first recognised by
Marco Severino in 1643. However, situs inversus was first described more than a century later by
Matthew Baillie.
The prevalence of situs inversus varies among different populations but is less than 1 in 10,000 people.
Effect on anatomy
The condition affects all major structures within the
thorax and
abdomen. Generally, the organs are simply transposed through the
sagittal plane. The heart is located on the right side of the thorax, the
stomach and
spleen on the right side of the abdomen and the
liver and
gall bladder on the left side. The left lung is trilobed and the right lung bilobed, and
blood vessels,
nerves,
lymphatics and the
intestines are also transposed.
If the heart is swapped to the right side of the thorax, it's known as
situs inversus with dextrocardia or
situs inversus totalis. If the heart remains in the normal left side of the thorax, a much rarer condition (1 in 22,000 of the general population), it's known as
situs inversus with levocardia or
situs inversus incompletus. Situs inversus with levocardia, or dextrocardia without situs inversus, present much higher rates of congenital defects than situs inversus with dextrocardia.
Significance
Situs inversus is generally an
autosomal recessive genetic condition, although it can be
X-linked or found in identical "mirror"
twins.
In the absence of congenital heart defects, individuals with situs inversus are
phenotypically unimpaired, and can lead normal healthy lives, without any complications related to their medical condition. There is a 5-10% prevalence of
congenital heart disease in individuals with situs inversus totalis, most commonly
transposition of the great vessels. The incidence of congenital heart disease is 95% in situs inversus with levocardia.
Many people with situs inversus totalis are unaware of their unusual anatomy until they seek medical attention for an unrelated condition. The reversal of the organs may then lead to some confusion, as many signs and symptoms will be on the 'wrong' side. For example, if an individual with situs inversus develops
appendicitis, that'll present to the physician with left lower abdominal pain, since that's where their appendix lies. Thus, in the event of a medical problem, the knowledge that the individual has situs inversus can expedite diagnosis. People with this rare condition should inform their
physicians before an examination, so they may redirect their search for
heart sounds and other
signs.
Situs inversus also complicates
organ transplantation operations as donor organs will almost certainly come from situs solitus donors. As hearts and livers are
chiral, geometric problems arise placing an organ into a cavity shaped in the mirror image. For example, a person with situs inversus who requires a heart transplant needs all the vessels to the transplant donor heart reattached to their existing ones. However, the orientation of these vessels in a person with situs inversus is reversed, necessitating steps so that the blood vessels join properly.
Kartagener syndrome
About 25% of individuals with situs inversus have an underlying condition known as
primary ciliary dyskinesia (PCD). PCD is a dysfunction of the
cilia that manifests itself during the embryologic phase of development. Normally-functioning cilia determine the position of the internal organs during early
embryological development, and so individuals with PCD have a 50% chance of developing situs inversus. If they do, they're said to have Kartagener syndrome, characterized by the triad of situs inversus, chronic
sinusitis, and
bronchiectasis. Cilia are also responsible for clearing
mucus from the lung, and the dysfunction causes increased susceptibility to lung infections.
Notable persons with situs inversus
Notable individuals with documented cases of situs inversus include:
- Randy Foye, an American basketball player for the NBA's Minnesota Timberwolves. He has suffered no discernible complications, and the condition isn't expected to jeopardize his career as a professional athlete.
- Catherine O'Hara, the Canadian comedic actress has said in interviews that her organs are reversed and her heart is on the right side of her chest.
- Donny Osmond, whose appendicitis was initially dismissed as a less serious condition because nobody realized he'd situs inversus. It was discovered when he was taken to hospital when on tour with his family in England.
- Enrique Iglesias, the Spanish singer told the press that he was born with situs inversus.
Fictional characters with situs inversus
In the Ian Fleming novel Dr. No, Julius No explains to James Bond that he once survived a murder attempt because his heart is located on his right side, which his would-be-killers didn't know when they stabbed the spot on the left where the heart of a normal human being would be.
Souther, from the anime/manga Fist of the North Star, has situs inversus totalis, making him immune to standard pressure-points martial arts.
In the webcomic It's Walky!, anyone who goes through the Martian resurrection process ends up being completely reversed, with their organs mirrored within their bodies and their primary hand becoming the opposite of what it had been before. This process happens to several major characters throughout the comic's run.
In the WB series Jack & Jill, Simon Rex played a young man with situs inversus.
Fortune, from . Revolver Ocelot points this out when he shoots Fortune on the left side of her chest, then remembers and states that her heart was on the right side.
In Margaret Mahy's novel The Tricksters, the character Hadfield is said to be an exact mirror image of his otherwise identical twin Felix, including having his vital organs in mirror-image layout.
In the Lord Peter Wimsey short story The Image in the Mirror by Dorothy Sayers, a character with reversed organs has long been haunted by dreams of a doppelgänger and by fears that he himself might be only the reflection of someone else.Further Information
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