What is situs inversus?
Situs inversus is a genetic condition in
which the organs in the chest and abdomen are positioned in a mirror image from
their normal positions. For example, the left atrium of the heart and the left
lung are positioned on the body’s right side. In the abdominal cavity, the
liver is positioned mostly on the left side instead of the right. And the stomach
is on the right side of the body instead of the left.
Situs inversus is a very rare condition. According
to an article in the journal Heart Views, it occurs in an estimated 1 in
What are the causes of situs inversus?
Situs inversus is caused by an autosomal
recessive genetic condition. An unaffected carrier mother and an unaffected
carrier father have a 1 in 4 chance of having a child with situs inversus.
Because many genetic steps would have to come together to cause situs inversus,
the condition is rare.
The condition is also seen in “mirror image”
twins. This type of twins occurs when a fertilized embryo splits later than usual during pregnancy. Mirror image
twins can also be opposites in things like handedness, asymmetrical features,
and brain-hemisphere dominance.
What are the types of situs inversus?
Situs inversus has two main subtypes:
dextrocardia and levocardia. A person is said to have dextrocardia if the point
of the heart is on the right side. A person is said to have levocardia if the
heart is on the left side, yet the other organs are flipped.
Levocardia is rarer and often associated
with other cardiac abnormalities, according to an article in the Journal of Anatomy &
Another subtype is situs ambiguous. This
occurs when several organs are in abnormal positions, but not in an easily
What are the symptoms of situs inversus?
Because the organs can be functional in situs
inversus, it’s possible for a person to have no complications.
Other patients can experience cardiac
dysfunction or a lung condition called primary ciliary dyskinesia (PCD), which
causes mucus buildup in the lungs. This can lead to chronic bronchitis and
sinusitis. People with situs inversus and PCD are said to have Kartagener’s
How is situs inversus diagnosed?
A doctor can diagnose situs inversus by looking
at the organs via:
- CT scan
- MRI scan
Because the condition seldom causes symptoms
and is so rare, a person may not know they have it. And it may not be discovered until visiting a doctor for a different reason.
Another way situs inversus may be discovered
is when a doctor listens to a patient’s heartbeat. The heartbeat is typically
loudest at the lower point of the heart on a person’s left side.
But a person with situs inversus can have a
heart that points to the right, so the heartbeat would be loudest on that side.
Doctors can use imaging studies to determine
the exact type of situs inversus.
How is situs inversus treated?
For many patients, situs inversus doesn’t cause
any other symptoms. If a person with situs inversus does have complications
like a heart defect, a doctor will treat the symptoms. Surgery to reverse the organs’
positioning is usually not recommended.
Knowing if you have situs inversus is
important if you undergo another surgical procedure.
Situs inversus is a very rare birth defect in
which some organs are atypically placed. Sometimes there are no symptoms, and
in other cases, there are associated complications.
Often, the condition is discovered when the patient visits a doctor for completely different medical care. Treatment is
usually aimed at helping symptoms of a related complication like a heart
defect. Surgery to correct the organs’ positioning is usually not recommended.