Featured Article by Rawan Adam
We look at the same diagram of the body everytime we study human biology. Every diagram you’ll ever see when studying anatomy follows the same structure, mapping out how the human body is structured internally. But what if we said this diagram doesn’t represent the entire human population?
What is Situs Inversus?
Situs Inversus, the full Latin name being Situs Inversus Viscerum, is a rare genetic condition, recurring in about 1 in 10,000 people and being more common in Males, in which the organs in your chest and/or abdomen are positioned in a mirror image of normal human anatomy. While the foetus is developing in the womb, almost all the thoracic organs develop in your body in a left-right formation. With Situs Inversus, the organs develop in a right-left formation. The word ‘Situs’ refers to the regular orientation of the organs in the chest and/or abdomen. In regular human anatomy, the orientation of the organs is called Situs Solitus. The replacement of the word Solitus with Inversus, refers to the orientation of the organs being the inverse, or reversed.
What causes this condition?
Situs Inversus is caused by a genetic mutation in one or more of several different genes. More than 100 genes have been linked to defects related to orientation in the body. These include: DNAH9, WDR16, MMP21, PKD1L1, CCDC11, NODAL, ANKS3, and NME7. It’s inherited in an autosomal recessive pattern, meaning both parents must have a mutated gene. For their children to inherit the condition. As well as inheriting the gene, Situs Inversus can be caused by risk factors in the parents, including a family history of cardiac defects, of noncardiac anomalies and diabetes in the mother. A specific but common risk factor is the use of cough suppressants during pregnancy; it’s known to contribute to the chances of your child developing PCD, a condition Situs Inversus is associated with.
How does it occur?
Situs Inversus commonly occurs alone and not as a direct cause and effect of another medical complication or condition. However, sometimes, it can occur with another birth defect, or as part of a medical condition or syndrome. For example, Situs Inversus is frequently seen as an effect of a condition called primary ciliary dyskinesia (PCD), also referred to as Kartagener Syndrome. PCD is a rare, inherited disorder that affects cilia, an adaptation that aids your body in the clearing of mucus, the movement of the egg to the uterus, and more. Situs inversus is also associated with dextrocardia (true mirror image) with only 3-5% incidence of congenital heart disease, most commonly transposition of the great vessels. Of these patients, 80% have a right-sided aortic arch. Situs inversus with laevocardia (which is much rarer: 0.00005%) congenital heart disease is found in 95% of patients. Up to 20% of patients with situs inversus can have Kartagener syndrome 3 which comprises a subgroup of primary ciliary dyskinesia. Rarely, Situs Inversus is associated with asplenia or polysplenia. Complete situs inversus is associated with the absence of inferior vena cava.
What are the different forms Situs Inversus comes in?
Dextrocardia and Levocardia are the two types of Situs Inversus. For any other abnormality in the left-right development of your organs, the term Situs Ambiguous is used. This occurs when several of your organs are in abnormal positions, and not in an easily defined pattern like Dextrocardia or Levocardia. Dextrocardia occurs when the apex (tip) of your heart points towards the right side of your chest. Your other organs are in the opposite direction as well. Levocardia occurs when the apex of your heart is pointing towards the left side as normal, but the other organs are flipped. Levocardia is rarer, and is commonly associated with other cardiac defects.
Patient experiences
Situs Inversus patients often share experiences of reversed films being ignored and dismissed as an error of the x-ray technician. It’s only when they visit the Doctor for unrelated problems that the possibility arises. Patients recall Doctors always getting excited over a patient with Situs Inversus being around, as medics may only come across one case of Situs Inversus once in their careers. Patients with Situs Inversus often wear MedicAlert bracelets, to notify emergency medical staff of their conidition. It serves the valuable purpose of preventing the possibility of having an operation on the wrong side in an emergency.
Conclusion
Since all the organs of a person with Situs Inversus assume the exact opposite location, in Levocardia at least, situs inversus does not affect a person’s overall health. A person with Situs Inversus can live a long, healthy life with little to no complications directly linked with the condition, and there have been very few patients who do suffer from complications. While situs inversus itself typically does not cause health problems, it is often associated with other conditions such as primary ciliary dyskinesia, which can lead to more significant health issues. Awareness and understanding of situs inversus are crucial for accurate diagnosis and management, particularly in scenarios involving surgical or clinical interventions where the reversal of organs can impact medical procedures. As research continues, the hope is to gain deeper insights into the genetic and developmental mechanisms underlying situs inversus totalis. This could potentially enhance our understanding of not only this condition but also the broader spectrum of developmental abnormalities. For those living with situs inversus totalis, advances in genetics and medicine promise better diagnostic and therapeutic strategies, ensuring they can maintain a high quality of life.
Citations:
Situs Inversus: Causes & Outlook.
Situs Inversus Totalis: A Clinical Review – PMC
Situs inversus | Radiology Reference Article | Radiopaedia.org
Astra Stem 
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