Situs inversus (also called situs transversus or oppositus) is a

congenital condition A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can r ...

in which the major

visceral organs In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...

are reversed or

mirrored ''Mirrored'' is the debut studio album by American experimental rock band Battles. It was released on May 14, 2007 in the United Kingdom, and on May 22, 2007 in the United States. ''Mirrored'' marked the first album in which the band incorporated ...

from their normal positions. The normal arrangement of internal organs is known as situs solitus. Although cardiac problems are more common, many people with situs inversus have no medical symptoms or complications resulting from the condition, and until the advent of modern medicine, it was usually undiagnosed. Situs inversus is found in about 0.01% of the population, or about 1 person in 10,000. In the most common situation, situs inversus totalis, it involves complete transposition (right to left reversal) of all of the

viscera In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...

. The heart is not in its usual position in the left chest, but is on the right, a condition known as

dextrocardia Dextrocardia (from Latin ''dextro'', meaning "right hand side," and Greek ''kardia'', meaning "heart") is a rare congenital condition in which the apex of the heart is located on the right side of the body, rather than the more typical placement t ...

(literally, "right-hearted"). Because the relationship between the organs is not changed, most people with situs inversus have no associated medical symptoms or complications. An uncommon form of situs inversus is

isolated levocardia Isolated levocardia (also known as situs inversus with levocardia) is a rare type of organ (anatomy), organs' situs inversus in which the heart is still in normal position but other abdominal viscera are transposed. Isolated levocardia may occur wi ...

, in which the position of the heart is not mirrored alongside the other organs. Isolated levocardia carries a risk of heart defects, and so patients with the condition may require surgery to correct them. In rarer cases such as

situs ambiguus Situs ambiguus is a rare congenital defect in which the major visceral Organ (anatomy), organs are distributed abnormally within the chest and abdomen. Clinically heterotaxy spectrum generally refers to any defect of Left-right asymmetry and arrang ...

or heterotaxy, situs cannot be determined. In these patients, the liver may be midline, the spleen absent or multiple, and the bowel malrotated. Often, structures are duplicated or absent altogether. This is more likely to cause medical problems than situs inversus totalis.

Signs and symptoms

In the absence of congenital heart defects, individuals with situs inversus are homeostatically normal, and can live standard healthy lives, without any complications related to their medical condition. There is a 5–10% prevalence of

congenital heart disease A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital heart defect is classed as a cardiovascular ...

in individuals with situs inversus totalis, most commonly

transposition of the great vessels Transposition of the great vessels (TGV) is a group of congenital heart defects involving an abnormal spatial arrangement of any of the great vessels: superior and/or inferior venae cavae, pulmonary artery, pulmonary veins, and aorta. Congenit ...

. The incidence of congenital heart disease is 95% in situs inversus with

levocardia Levocardia is where the heart is on the normal side of the body (the left), as opposed to dextrocardia, in which the heart is in the right side of the thoracic cavity. This can be associated with '' situs solitus'', where the remainder of the organ ...

. Many people with situs inversus totalis are unaware of their unusual anatomy until they seek medical attention for an unrelated condition, such as a

rib fracture A rib fracture is a break in a rib bone. This typically results in chest pain that is worse with inspiration. Bruising may occur at the site of the break. When several ribs are broken in several places a flail chest results. Potential complicatio ...

or a bout of

appendicitis Appendicitis is inflammation of the appendix. Symptoms commonly include right lower abdominal pain, nausea, vomiting, and decreased appetite. However, approximately 40% of people do not have these typical symptoms. Severe complications of a rup ...

. The condition may also be discovered during the administration of certain medicines or during tests such as a

barium meal An upper gastrointestinal series, also called a barium swallow, barium study, or barium meal, is a series of radiographs used to examine the gastrointestinal tract for abnormalities. A contrast medium, usually a radiocontrast agent such as ba ...

enema An enema, also known as a clyster, is an injection of fluid into the lower bowel by way of the rectum.Cullingworth, ''A Manual of Nursing, Medical and Surgical'':155 The word enema can also refer to the liquid injected, as well as to a device ...

. The reversal of the organs may then lead to some confusion, as many signs and symptoms will be on the atypical side. For example, if an individual with situs inversus develops

, they will present to the physician with lower left abdominal pain, since that is where their appendix lies.

Intestinal malrotation Intestinal malrotation is a congenital anomaly of rotation of the midgut. It occurs during the first trimester as the fetal gut undergoes a complex series of growth and development. Malrotation can lead to a dangerous complication called volvulus ...

can also cause the appendix to be on the left side. 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

doctor Doctor or The Doctor may refer to: Personal titles * Doctor (title), the holder of an accredited academic degree * A medical practitioner, including: ** Physician ** Surgeon ** Dentist ** Veterinary physician ** Optometrist *Other roles ** ...

s before an examination, so the doctor can redirect their search for

heart sound Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. Specifically, the sounds reflect the turbulence created when the heart valves snap shut. In cardiac auscultation, an examiner may use a stet ...

s and other signs. Wearing a

medical identification tag A medical identification tag is a small emblem or tag worn on a bracelet, neck chain, or on the clothing bearing a message that the wearer has an important medical condition that might require immediate attention. For emergency medical providers ...

can help inform health care providers in the event the person is unable to communicate. Situs inversus also complicates

organ transplantation Organ transplantation is a medical procedure in which an organ (anatomy), organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. The donor and recipient may be at the same location, or organ ...

operations as donor organs will more likely come from situs solitus (normal) donors. As hearts and livers are

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...

, geometric problems arise placing an organ into a cavity shaped in the mirror image. For example, a person who requires a heart transplant needs all their

great vessels Great vessels are the large vessels that bring blood to and from the heart. These are: *Superior vena cava *Inferior vena cava *Pulmonary arteries * Pulmonary veins *Aorta Transposition of the great vessels is a group of congenital heart defec ...

reattached to the donor heart. However, the orientation of these vessels in a person with situs inversus is reversed, necessitating steps so that the blood vessels join properly.

Cause

Situs inversus is generally an

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

genetic condition, although it can be

X-linked Sex linked describes the sex-specific patterns of inheritance and presentation when a gene mutation (allele) is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). In humans, these are termed X-linked recessive, ...

or found in identical "mirror image" twins. About 25% of individuals with situs inversus have an underlying condition known as

primary ciliary dyskinesia Primary ciliary dyskinesia (PCD) is a rare, autosomal recessive genetic ciliopathy, that causes defects in the action of cilia lining the upper and lower respiratory tract, sinuses, Eustachian tube, middle ear, Fallopian tube, and flagella of ...

(PCD). PCD is a dysfunction of the

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

that occurs during early

embryonic development An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

. Normally functioning cilia determine the position of the internal organs during early development, and so embryos with PCD have a 50% chance of developing situs inversus. If they do, they are said to have

Kartagener syndrome Primary ciliary dyskinesia (PCD) is a rare, autosomal recessive genetic ciliopathy, that causes defects in the action of cilia lining the upper and lower respiratory tract, sinuses, Eustachian tube, middle ear, Fallopian tube, and flagella of ...

, characterized by the triad of situs inversus, chronic

sinusitis Sinusitis, also known as rhinosinusitis, is inflammation of the mucous membranes that line the sinuses resulting in symptoms that may include thick nasal mucus, a plugged nose, and facial pain. Other signs and symptoms may include fever, head ...

, and bronchiectasis. Cilia are also responsible for clearing mucus from the lung, and the dysfunction causes increased susceptibility to lung infections. Kartagener syndrome can also manifest with male infertility as functional cilia are required for proper sperm flagella function.

Effect on anatomy

The condition affects all major structures within the

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

and

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

. Generally, the organs are simply transposed through the

sagittal plane The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divid ...

. The heart is located on the right side of the thorax, the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

and

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

on the right side of the abdomen and the

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

and

gall bladder In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath the liver, although ...

on the left side. The heart's normal right atrium occurs on the left, and the left atrium is on the right. The lung anatomy is reversed and the left lung has three lobes while the right lung has two lobes. The intestines and other internal structures are also reversed from the normal, and the

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

s, and

lymphatics The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...

are also transposed. If the heart is swapped to the right side of the thorax, it is known as "situs inversus with

" or "situs inversus totalis". If the heart remains on the normal left side of the thorax, a much rarer condition (1 in 2,000,000 of the general population), it is known as "situs inversus with

" or "situs inversus incompletus". Situs inversus of the optic disc may occur unilaterally or bilaterally, associated with reduced

binocularity In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an ...

and stereoacuity resembling monofixation syndrome. It is characterized by emergence of the retinal vessels in an anomalous direction (from the nasal rather than the temporal aspect) with dysversion (tilt) of the optic disc. Situs inversus does not appear to significantly affect rates of

handedness In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to it being stronger, faster or more Fine motor skill, dextrous. The other hand, comparatively often the weaker, less dextrous or sim ...

. Based on a 2004 study documenting situs inversus in individuals with

, the proportion of right-handedness among those with situs inversus did not differ significantly from that of those with situs solitus.

Diagnosis

Diagnosis of situs inversus can be made using imaging techniques such as

x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...

, CT scan, and

magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...

(MRI). Any potential treatment for situs inversus would involve a complete and highly invasive surgical rearrangement of the internal viscera of the patient. Such a procedure is unnecessary, given that situs inversus rarely causes any additional symptoms. No treatment, medical or surgical, is prescribed for situs inversus patients, with medical professionals instead treating any other symptoms the patient may have with awareness of the unique anatomy of the patient.

Epidemiology

Situs inversus is very rare, affecting 0.01% of the population. This is equivalent to 1 in 10,000 people.

History

Dextrocardia Dextrocardia (from Latin ''dextro'', meaning "right hand side," and Greek ''kardia'', meaning "heart") is a rare congenital condition in which the apex of the heart is located on the right side of the body, rather than the more typical placement t ...

(the

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

being located on the right side of the

) was seen and drawn by

Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 14522 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, Drawing, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially res ...

, and then recognised by Marco Aurelio Severino in 1643. Situs inversus was first described more than a century later by

Matthew Baillie Matthew Baillie FRS (27 October 1761 – 23 September 1823) was a British physician and pathologist, credited with first identifying transposition of the great vessels (TGV) and situs inversus. Early life and education He was born in the mans ...

Etymology

The term ''situs inversus'' is a short form of the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

phrase ''situs inversus viscerum'', meaning "inverted position of the internal organs".

Notable cases

Notable individuals with documented cases of situs inversus include: *

Enrique Iglesias Enrique Miguel Iglesias Preysler (; (born 8 May 1975) is a Spanish singer and songwriter. He started his recording career in the mid-1990s on the Mexican indie label Fonovisa and became the bestselling Spanish-language act of the decade. By the ...

, a Spanish singer, songwriter, actor and record producer. * Catherine O'Hara, Canadian-American actress, writer and comedian. *

Randy Foye Randy Foye (born September 24, 1983) is an American former professional basketball player. He played collegiately at Villanova University. He was selected seventh overall in the 2006 NBA draft by the Boston Celtics, but was immediately traded to ...

, an American

basketball Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular Basketball court, court, compete with the primary objective of #Shooting, shooting a basketball (ball), basketball (appr ...

player in the

NBA The National Basketball Association (NBA) is a professional basketball league in North America. The league is composed of 30 teams (29 in the United States and 1 in Canada) and is one of the major professional sports leagues in the United St ...

. He has suffered no discernible complications, and the condition is not expected to affect his career as a professional athlete, as all his organs are in reverse. * Ginggaew Lorsoongnern, a Thai convict executed by firing squad. Her condition was discovered after she was shot in the left side of her chest and survived. After waking up in the morgue she was taken back and executed. * Tim Miller, director of the Ashtanga Yoga Center in Carlsbad, California. * Rose Marie Bentley, a Molalla, Oregon woman who unknowingly had the rare variant situs inversus with

, and lived to 99 years without any complications. She donated her body to

Oregon Health & Science University Oregon Health & Science University (OHSU) is a public research university focusing primarily on health sciences with a main campus, including two hospitals, in Portland, Oregon. The institution was founded in 1887 as the University of Oregon Medi ...

, where her condition was discovered during an anatomy class after students noticed the unusual arrangement of her heart's blood vessels, prompting further investigation of the cadaver.

Notes

References

External links

*
Chest X-ray & CT scan
Radiology Teaching File {{DEFAULTSORT:Situs inversus Autosomal recessive disorders Motor skills Rare diseases Congenital disorders