Situs inversus Dr praveena pulmonology- final year post graduate
Definiton History Types Cause Clinical features Diagnosis Treatment
Definition The term situs inversus is a short form of the latin phrase "situs inversus viscerum", meaning "inverted position of the internal organs
Situs inversus (also called situs transversus or oppositus) is a congenital condition in which the major visceral organs are reversed or mirrored from their normal positions. The normal arrangement of internal organs is known as situs solitus while situs inversus is generally the mirror image of situs solitus.
Situs inversus is found in about 0.01% [1] 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 abdominal organs. Most people with situs inversus are asymptomatic and silent and hence remain undiagnosed. Recent advances and technology in medicine has enabled to diagnose situs inversus very easily.
History Dextrocardia (the heart being located on the right side of the thorax) was first seen and drawn by Leonardo da Vinci in 1452 1519, and then recognised by Marco Aurelio Severino in 1643. However, situs inversus was first clearly described more than a century later by Matthew Baillier
In rarer cases such as situs ambiguus 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
Symptoms & signs In the absence of congenital heart defects,individuals with situs inversus are phenotypically normal, and can live 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 common transposition of the great vessels. The incidence of congenital heart disease is 95% in situs inversus with levocardia.
Cardiac orientation Relationship or axis of the base to the apex of heart (levocardia,dextrocardia,mesocardia) If the cardiac apex fails to shift,it may result in situs solitus with dextrocardia which is termed as dextorversion or situs inversus with levocardia called levoversion
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 or a bout of appendicitis. The condition may also be discovered during the administration of certain medicines or during tests such as a Barium meal or enema. The reversal of the organs may then lead to some confusion, as many signs and symptoms will be on the atypical 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 physicians before an examination, so the physician can redirect their search for heart sounds and other signs. Wearing a medical identification tag can help inform health care providers in the event the person is unable to communicate.
cause Situs inversus is generally an autosomal recessive genetic condition, although it can be X- linked or found in identical "mirror image" twins 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 embryos with PCD have a 50% chance of developing situs inversus.
SITUS INVERSUS WITH DEXTROCARDIA Incidence rate in general population is estimatedat 1/8000 to 1/25000 The heart and thoracic,abdominal viscera are mirror images of normal. The bronchi are inverted. The heart is right sided The right hemidiaphragm is lower than the left hemidiaphram. The descending aorta is on the right The ascending aorta,aortic knuckle,pulmonary trunk in their mirror image positions.
Situs solitus with dextrocardia The lungs and abdominal viscera are solitus. The heart is right thorax (dextrocardia) The ascending aorta,aortic knucle occupy their normal positions and the descending aorta runs its normal course along the left vertebral border. The major cardiac shadow lies to the right of midline (dextrocardia), the base to apex points to the right The right hemidiaphram is lower than the left hemidiaphragm
Situs inversus with levocardia The left hemidiaphragm is lower than the right hemidiaphragm because the apex is on the left Inversion of bronchi,coincides with inversion of atria and lungs The stomach is on right,and the liver is on left
Right isomerism Left isomerism Bilateral morphologic right atria Bilateral morphologic left atria Asplenia Bilateral bilobed lungs Bilateral trilobed lungs Interrupted inferior vena cava Symmetric liver Partial anomalous pulmonary venous return Total anomalous pulmonary venous return
Diagnosis History Clinical examination Radiology x-ray Ultrasound Contrast studies Ct scan MRI scan
Treatment No treatment required as the patient is otherwise healthy
Kartageners syndrome Autosomal recessive primary ciliary dyskinesia leading to impaired mucociliary clearance Incidence_ 1:12500-40000 Characterised by clinical triad of Situs inversus Chronic sinusitis Bronchiectasis Other features include nasal polyposis Infertility in males Subfertility in females
Congenital anamolies of lung Bronchopulmonary anomalies Combined lung & vascular anamolies Vascular anamolies Congenital bronchial atresia Congenital lobar emphysema Congenital cystic adenomatiod malformation Bronchogenic cysts Tracheal stenosis Hypogenetic lung (scimitar) syndrome Brochopulmonary sequestration Absence of main pulmonary artery Anomalous origin of the left pulmonary artery from the right Anomalous pulmonary venous drainage Pulmonary arteriovenous malformation Tracheal bronchus
Scimitar syndrome
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Azygos lobe Azygos lobe is a congenital variation of the right upper lobe. It is seen in 1% of the population. Embryologically, it arises from an anomalous lateral course of the azygos vein in a pleural septum within the apical segment of the right upper lobe or in other words an azygos lobe is formed when the right posterior cardinal vein, one of the precursors of the azygos vein, fails to migrate over the apex of the lung and penetrates it instead, carrying along two pleural layers that invaginates into the upper portion of the right upper lobe.
As it has no bronchi, veins and arteries of its own or corresponding alteration in the segmental architecture of the lung, so it is not a true (misnomer), or even accessory, pulmonary lobe, but rather an anatomically separated part of the upper lobe It is usually an incidental finding on chest x- ray or computed tomography and is as such not associated with any morbidity but can cause technical problems in thoracoscopic procedures.
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