eMedicine Specialties > Radiology > Pediatrics

Situs Inversus

Author: Annamaria Wilhelm, MD, Staff Physician, Department of Radiology, Mayo Clinic
Coauthor(s): John M Holbert, MD, Professor, Department of Radiology, Scott and White Memorial Hospital and Clinic
Contributor Information and Disclosures

Updated: Feb 24, 2009

Introduction

Background

Marco Severino first recognized dextrocardia in 1643. More than a century later, Matthew Baillie described the complete mirror-image reversal of the thoracic and abdominal organs in situs inversus.

Schematic drawings illustrate the standard anatom...

Schematic drawings illustrate the standard anatomy of situs solitus (A) and the mirror image of situs inversus (B). The right lung (RL), left lung (LL), right atrium (RA), and left atrium (LA) are shown.

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Schematic drawings illustrate the standard anatom...

Schematic drawings illustrate the standard anatomy of situs solitus (A) and the mirror image of situs inversus (B). The right lung (RL), left lung (LL), right atrium (RA), and left atrium (LA) are shown.


For excellent patient education resources, visit eMedicine's Heart Center and Lung and Airway Center. Also, see eMedicine's patient education articles Tetralogy of Fallot and Heart and Lung Transplant.

Pathophysiology

Situs describes the position of the cardiac atria and viscera.1,2,3,4,5,6,7,8 Situs solitus is the normal position, and situs inversus is the mirror image of situs solitus (see Image 1). Cardiac situs is determined by the atrial location. In situs inversus, the morphologic right atrium is on the left, and the morphologic left atrium is on the right. The normal pulmonary anatomy is also reversed so that the left lung has 3 lobes and the right lung has 2 lobes. In addition, the liver and gallbladder are located on the left, whereas the spleen and stomach are located on the right. The remaining internal structures are also a mirror image of the normal.

Schematic drawings illustrate the standard anatom...

Schematic drawings illustrate the standard anatomy of situs solitus (A) and the mirror image of situs inversus (B). The right lung (RL), left lung (LL), right atrium (RA), and left atrium (LA) are shown.

[ CLOSE WINDOW ]
Schematic drawings illustrate the standard anatom...

Schematic drawings illustrate the standard anatomy of situs solitus (A) and the mirror image of situs inversus (B). The right lung (RL), left lung (LL), right atrium (RA), and left atrium (LA) are shown.


Situs inversus can be classified further into situs inversus with levocardia or situs inversus with dextrocardia.1,2,3,4,5,6,7,8 The classification of situs is independent of the cardiac apical position. The terms levocardia and dextrocardia indicate only the direction of the cardiac apex at birth; they do not imply the orientation of the cardiac chambers. In levocardia, the base-to-apex axis points to the left, and in dextrocardia, the axis is reversed. Isolated dextrocardia is also termed situs solitus with dextrocardia. The cardiac apex points to the right, but the viscera are otherwise in their usual positions. Situs inversus with dextrocardia is also termed situs inversus totalis because the cardiac position, as well as the atrial chambers and abdominal viscera, is a mirror image of the normal anatomy.

When situs cannot be determined, the patient has situs ambiguous or heterotaxy.1,2,3,4,5,6,7,8 In these patients, the liver may be midline, the spleen absent or multiple, the atrial morphology unclear, and the bowel malrotated. Often, normally unilateral structures are duplicated or absent. The 2 primary subtypes of situs ambiguous include the following1,2,3,4,5,6,7 : (1) right isomerism, or asplenia syndrome, and (2) left isomerism, or polysplenia syndrome.

In classic right isomerism, or asplenia, bilateral right-sidedness occurs. These patients have bilateral right atria, a centrally located liver, and an absent spleen, and both lungs have 3 lobes. The descending aorta and inferior vena cava are on the same side of the spine. In left isomerism, or polysplenia, bilateral left-sidedness occurs. These patients have bilateral left atria and multiple spleens, and both lungs have 2 lobes. Interruption of the inferior vena cava with azygous or hemiazygous continuation is often present.

The features of situs ambiguous are inconsistent; therefore, situs ambiguous cases are challenging and require thorough evaluation of the viscera.1,2,3,4,5,6,7,9 The location and relationships of the following should be reviewed carefully: abdominal viscera, hepatic veins, superior vena cava, inferior vena cava, coronary sinus, pulmonary veins, cardiac atria, atrioventricular connections and valves, cardiac ventricles, position of the cardiac apex, and aortic arch and great vessels.

Frequency

United States

Situs inversus is present in 0.01% of the population.

Mortality/Morbidity

Situs inversus totalis that is associated with primary ciliary dyskinesia is known as Kartagener syndrome.10,11,12,13,14 Patients with primary ciliary dyskinesia have repeated sinus and pulmonary infections.10,15,16 Frequent pulmonary infections often result in bronchiectasis, which predominantly affects the lower lungs.

Typically, patients with situs inversus have a normal life expectancy. In the rare instances of cardiac anomalies, life expectancy is reduced, depending on the severity of the defect.17 Patients with Kartagener syndrome have a normal life expectancy if the bronchiectasis is treated adequately.11

Race

No racial predilection exists for situs inversus.

Sex

The male-to-female incidence is 1:1.

Age

Situs abnormalities are congenital.

Presentation

Situs inversus occurs more commonly with dextrocardia.18 A 3-5% incidence of congenital heart disease is observed in situs inversus with dextrocardia, usually with transposition of the great vessels. Of these patients, 80% have a right-sided aortic arch. Situs inversus with levocardia is rare19 ; this condition occurs in 1 case per 22,000, and it is almost always associated with congenital heart disease.20,21,22,23,24,25  

Kartagener syndrome affects 20% of patients with situs inversus. Kartagener syndrome is a subgroup of disorders of primary ciliary dyskinesia in which the cilia have abnormal or no movement, most commonly because of absent or irregular dynein arms. The inheritance pattern of Kartagener syndrome is autosomal recessive with no male or female predominance.

Kartagener syndrome is typified by bronchiectasis, sinusitis, and situs inversus, but only 50% of patients with Kartagener syndrome have situs inversus.10,12,13,14 In addition to this classic triad of abnormalities, patients may also have nasal polyps, an impaired sense of smell, recurrent otitis media, hearing loss, chronic respiratory infections, obstructive lung disease, reduced fertility (females), and/or infertility (males).10,13 Each of these conditions is related to impaired cilia or flagella. Abnormal sperm motility makes affected males completely infertile. Although ciliary dyskinesia of the fallopian tubes impairs female fertility, the tubes are not obstructed, and women with Kartagener syndrome can conceive.

The recognition of situs inversus is important for preventing surgical mishaps that result from the failure to recognize reversed anatomy or an atypical history. For example, in a patient with situs inversus, cholecystitis typically causes left upper quadrant pain, and appendicitis causes left lower quadrant pain. A trauma patient with evidence of external trauma over the ninth to eleventh ribs on the right side is at risk for splenic injury. If surgery is planned on the basis of radiographic findings in a patient with situs inversus, the surgeon should pay careful attention to image labeling to avoid errors such as a right thoracotomy for a left lung nodule. 

Preferred Examination

Situs abnormalities may be recognized first by using radiography or ultrasonography.9,26,27,28,29 However, computed tomography (CT) scanning is the preferred examination for the definitive diagnosis of situs inversus with dextrocardia. CT scanning provides good anatomic detail for confirming visceral organ position, cardiac apical position, and great vessel branching. Magnetic resonance imaging (MRI) is usually reserved for difficult cases or for patients with associated cardiac anomalies.30,31

Limitations of Techniques

Most patients with situs inversus with levocardia require additional imaging to evaluate the associated cardiac anomalies. When radiation exposure is a concern, MRI or ultrasonography may be preferred.

Differential Diagnoses

Appendicitis: Surgical Perspective
Asplenia/Polysplenia
Congenital Coronary Abnormalities: Surgical Perspective
Sinusitis
Ventricular Septal Defect

Other Problems to Be Considered

Kartagener Syndrome

Heterotaxy (See also the eMedicine articles Heterotaxy, Asplenia and Heterotaxy, Polysplenia [in the Pediatrics section].)

Left isomerism (ie, Ivemark syndrome) (See also the eMedicine article Asplenia/Polysplenia.)

Right isomerism (ie, asplenia syndrome) (See also the eMedicine article Asplenia.)

Situs solitus

Transposition of the Great Arteries  (in the Pediatric section)

More on Situs Inversus

Overview: Situs Inversus
Imaging: Situs Inversus
Follow-up: Situs Inversus
Multimedia: Situs Inversus
References
Further Reading
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References

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  4. Hagler DJ, O'Leary PW. Cardiac malpositions and abnormalities of atrial and visceral situs. In: Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP, eds. Moss and Adams' Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Vol 2. 5th ed. Baltimore, Md: Williams & Wilkins; 1995:1307-36.

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  9. Lee SE, Kim HY, Jung SE, et al. Situs anomalies and gastrointestinal abnormalities. J Pediatr Surg. Jul 2006;41(7):1237-42. [Medline].

  10. Ortega HA, Vega Nde A, Santos BQ, Maia GT. [Primary ciliary dyskinesia: considerations regarding six cases of Kartagener syndrome.] [Portuguese, English]. J Bras Pneumol. Oct 2007;33(5):602-8. [Medline]. [Full Text].

  11. Holzmann D, Ott PM, Felix H. Diagnostic approach to primary ciliary dyskinesia: a review. Eur J Pediatr. Jan-Feb 2000;159(1-2):95-8. [Medline].

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  13. Schidlow DV. Primary ciliary dyskinesia (the immotile cilia syndrome). Ann Allergy. Dec 1994;73(6):457-68; quiz 468-70. [Medline].

  14. Yarnal JR, Golish JA, Ahmad M, Tomashefski JF. The immotile cilia syndrome: explanation for many a clinical mystery. Postgrad Med. Feb 1982;71(2):195-7, 200-2, 209-11 passim. [Medline].

  15. Jain K, Padley SP, Goldstraw EJ, et al. Primary ciliary dyskinesia in the paediatric population: range and severity of radiological findings in a cohort of patients receiving tertiary care. Clin Radiol. Oct 2007;62(10):986-93. [Medline].

  16. Kennedy MP, Omran H, Leigh MW, et al. Congenital heart disease and other heterotaxic defects in a large cohort of patients with primary ciliary dyskinesia. Circulation. Jun 5 2007;115(22):2814-21. [Medline].

  17. Bohun CM, Potts JE, Casey BM, Sandor GG. A population-based study of cardiac malformations and outcomes associated with dextrocardia. Am J Cardiol. Jul 15 2007;100(2):305-9. [Medline].

  18. Maldjian PD, Saric M. Approach to dextrocardia in adults: review. AJR Am J Roentgenol. Jun 2007;188(6 suppl):S39-49; quiz S35-8. [Medline].

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  24. Van Mierop LH, Eisen S, Schiebler GL. The radiographic appearance of the tracheobronchial tree as an indicator of visceral situs. Am J Cardiol. Oct 1970;26(4):432-5. [Medline].

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  30. Bartram U, Fischer G, Kramer HH. Congenitally interrupted inferior vena cava without other features of the heterotaxy syndrome: report of 5 cases and characterization of a rare entity. Pediatr Dev Pathol. Mar 22 2007;1 [epub ahead of print]. [Medline].

  31. Yoo SJ, Kim YM, Choe YH. Magnetic resonance imaging of complex congenital heart disease. Int J Card Imaging. Apr 1999;15(2):151-60. [Medline].

  32. Kouwenhoven JW, Bartels LW, Vincken KL, et al. The relation between organ anatomy and pre-existent vertebral rotation in the normal spine: magnetic resonance imaging study in humans with situs inversus totalis. Spine. May 1 2007;32(10):1123-8. [Medline].

  33. Sirin BH, Kurdal AT, Iskesen I. Congenitally corrected transposition of the great arteries plus dextrocardia operated with an unusual operative technique. Thorac Cardiovasc Surg. Sep 2008;56(6):367-9. [Medline].

  34. Rossman CM, Newhouse MT. Primary ciliary dyskinesia: evaluation and management. Pediatr Pulmonol. 1988;5(1):36-50. [Medline].

  35. Tan SY, Rosenthal J, Zhao XQ, et al. Heterotaxy and complex structural heart defects in a mutant mouse model of primary ciliary dyskinesia. J Clin Invest. Nov 21 2007;epub ahead of print. [Medline]. [Full Text].

  36. Winer-Muram HT, Tonkin IL. The spectrum of heterotaxic syndromes. Radiol Clin North Am. Nov 1989;27(6):1147-70. [Medline].

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Keywords

situs inversus, situs inversus totalis, situs inversus with dextrocardia, situs inversus with levocardia, mirror image of situs solitus, mirror-image organs, situs solitus, situs ambiguous/ambiguus, Kartagener syndrome, Kartagener's syndrome, primary ciliary dysplasia, PCD, primary ciliary diskinesia

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Contributor Information and Disclosures

Author

Annamaria Wilhelm, MD, Staff Physician, Department of Radiology, Mayo Clinic
Annamaria Wilhelm, MD is a member of the following medical societies: American College of Radiology
Disclosure: Nothing to disclose.

Coauthor(s)

John M Holbert, MD, Professor, Department of Radiology, Scott and White Memorial Hospital and Clinic
John M Holbert, MD is a member of the following medical societies: American College of Chest Physicians, American College of Radiology, American Roentgen Ray Society, and Radiological Society of North America
Disclosure: Amirsys Royalty Other

Medical Editor

Henrique M Lederman, MD, PhD, Consulting Staff, Department of Radiology, LeBonheur Children's Medical Center and St Jude Children's Research Hospital; Professor of Radiology and Pediatric Radiology, Chief, Division of Diagnostic Imaging in Pediatrics, Federal University of Sao Paulo, Brazil
Henrique M Lederman, MD, PhD is a member of the following medical societies: Society for Pediatric Radiology
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Marta Hernanz-Schulman, MD, FAAP, Professor, Radiology, Radiological Sciences, and Pediatrics, Director, Department of Pediatric Radiology, Radiologist-in-Chief, Director, Department of Diagnostic Imaging, Vanderbilt University Medical Center, Vanderbilt Children's Hospital
Marta Hernanz-Schulman, MD, FAAP is a member of the following medical societies: American Institute of Ultrasound in Medicine and American Roentgen Ray Society
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

John Karani, MBBS, FRCR, Consulting Staff, Department of Radiology, King's College Hospital, London
Disclosure: Nothing to disclose.

 
 
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