situs inversus

Situs Inversus

Definition

Situs inversus is a condition in which the organs of the chest and abdomen are arranged in a perfect mirror image reversal of the normal positioning.

Description

Normal human development results in an asymmetrical arrangement of the organs within the chest and abdomen. Typically, the heart lies on the left side of the body (levocardia), the liver and spleen lie on the right, and the lung on the left has two lobes while the lung on the right has three lobes. This normal arrangement is known as situs solitus.However, in about 1 in 8,500 people, the organs of the chest and abdomen are arranged in the exact opposite position: the heart is on the right (dextrocardia), as is the two-lobed lung, and the liver, spleen, and three-lobed lung are on the left. Yet because this arrangement, called situs inversus, is a perfect mirror image, the relationship between the organs is not changed, so functional problems rarely occur.

Causes and symptoms

Early in the normal development of an embryo, the tube-like structure that becomes the heart forms a loop toward the left, identifying the left/right axis along which the other organs should be positioned. Although the mechanism that causes the heart loop to go left is not fully understood, at least one gene has been identified to have a role in this process. However, it is thought that many factors may be involved in causing situs inversus. Rarely, situs inversus can run in families, but most often it is an isolated and accidental event occurring in an individual for the first time in the family.Most people with situs inversus have no medical symptoms or complications resulting from the condition. Although only 3-5% of people with situs inversus have any type of functional heart defect, this is higher than the rate of heart defects in the general population, which is less than 1%.It is estimated that about 25% of people with situs inversus have an underlying condition called primary ciliary dyskinesia (PCD). PCD, also known as Kartagener's syndrome, is characterized as situs inversus, chronic sinus infections, increased mucous secretions from the lungs, and increased susceptibility to respiratory infections. PCD is caused by a defect in the cilia that impairs their normal movements.

Diagnosis

Situs inversus should detected by a thorough physical examination. It is often picked up when a physician, using a stethoscope, hears otherwise normal heart sounds on the right side of the body instead of the left. To confirm the a suspected diagnosis of situs inversus, imaging studies such as MRI, CT, or ultrasound may be ordered, and a referral may be made to a cardiologist or internist for completeness. Imaging studies will also rule out the possibility of random arrangement of the organs, or heterotaxy, which has a much higher risk for serious medical complications.

Treatment

There is no treatment for situs inversus. In the unlikely case that a heart defect is present, it should be treated accordingly by a cardiologist.Individuals who have situs inversus should be sure to inform all physicians involved in their medical care. In addition to preventing unnecessary confusion, this will reduce the risk of missing a crucial diagnosis that presents with location-specific symptoms (such as appendicitis).

Alternative treatment

Not applicable.

Prognosis

The prognosis for an individual with situs inversus is good, and in the absence of a heart defect or other underlying diagnosis, life expectancy is normal.

Prevention

There is no known method of preventing situs inversus.

Resources

Periodicals

Ainsworth, Claire. "Left Right and Wrong." New Scientist 66, no. 2243 (June 17, 2000): 40-45.Janchar, T., Milzman, D., and Clement, M. "Situs Inversus: Emergency Evaluations of Atypical Presentations." American Journal of Emergency Medicine 18, no. 3 (May 2000): 349-50.Travis, John. "Twirl Those Organs into Place." Science News 156, no. 8 (21 August 1999): 124-125.

Organizations

American Heart Association. National Center. 7272 Greenville Avenue, Dallas, TX 75231-4596. (214) 373-6300. (800) 242-8721. 〈inquire@heart.org〉.NIH/National Heart, Lung and Blood Institute Information Center. P.O. Box 30105. Bethesda, MD 20824-0105. (301) 592-8573.

Key terms

Cilia — Tiny hairlike projections on certain cells within the body; cilia produce lashing or whipping movements to direct or cause motion of substances or fluids within the body.CT — A special technique that uses a computer to create a cross-sectional image of the body from a series of x rays.Gene — A single unit of genetic information, providing the body with instruction for a specific biological task.MRI — An imaging study that uses magnetic forces to produce an image of the body's internal structures.Ultrasound — An imaging study that uses high-frequency sound waves to form a visual image of the body's internal structures.

situs

[si´tus] (L.) site or position.situs inver´sus total or partial transposition of the body organs to the side opposite the normal.

si·tus in·ver·'sus

reversal of position or location. Synonym(s): situs transversus

situs inversus

(ĭn-vûr′səs)n. A congenital condition in which internal organs are transposed through the sagittal plane so that the heart, for example, is on the right side of the body.

situs inversus

A term referring to the completely incorrect (mirror-image) sidedness of structures, where morphologically right-sided structures are present on the left side of the body and morphologically left-sided structures on the right.

si·tus in·ver·sus

(sī'tŭs in-vĕr'sŭs) Reversal of position or location, referring particularly to left-right reversal of thoracic viscera.

situs inversus

An uncommon mirror-image reversal of the organs of the trunk. The heart points to the right, the LIVER and APPENDIX are on the left and the stomach and spleen on the right. Situs inversus is seldom of medical significance, but may confuse diagnosis until detected. See also DEXTROCARDIA.

单词	situs inversus
释义	situs inversus situs in·ver·sus S0439650 (ĭn-vûr′səs)n. A congenital condition in which internal organs are transposed through the sagittal plane so that the heart, for example, is on the right side of the body. [New Latin : Latin situs, location + Latin inversus, past participle of invertere, to invert.] situs inversus situs inversus [′sīd·əs in′vər·səs] (anatomy) Complete mirror-image inversion of the internal organs. situs inversus Situs Inversus Definition Situs inversus is a condition in which the organs of the chest and abdomen are arranged in a perfect mirror image reversal of the normal positioning. Description Normal human development results in an asymmetrical arrangement of the organs within the chest and abdomen. Typically, the heart lies on the left side of the body (levocardia), the liver and spleen lie on the right, and the lung on the left has two lobes while the lung on the right has three lobes. This normal arrangement is known as situs solitus.However, in about 1 in 8,500 people, the organs of the chest and abdomen are arranged in the exact opposite position: the heart is on the right (dextrocardia), as is the two-lobed lung, and the liver, spleen, and three-lobed lung are on the left. Yet because this arrangement, called situs inversus, is a perfect mirror image, the relationship between the organs is not changed, so functional problems rarely occur. Causes and symptoms Early in the normal development of an embryo, the tube-like structure that becomes the heart forms a loop toward the left, identifying the left/right axis along which the other organs should be positioned. Although the mechanism that causes the heart loop to go left is not fully understood, at least one gene has been identified to have a role in this process. However, it is thought that many factors may be involved in causing situs inversus. Rarely, situs inversus can run in families, but most often it is an isolated and accidental event occurring in an individual for the first time in the family.Most people with situs inversus have no medical symptoms or complications resulting from the condition. Although only 3-5% of people with situs inversus have any type of functional heart defect, this is higher than the rate of heart defects in the general population, which is less than 1%.It is estimated that about 25% of people with situs inversus have an underlying condition called primary ciliary dyskinesia (PCD). PCD, also known as Kartagener's syndrome, is characterized as situs inversus, chronic sinus infections, increased mucous secretions from the lungs, and increased susceptibility to respiratory infections. PCD is caused by a defect in the cilia that impairs their normal movements. Diagnosis Situs inversus should detected by a thorough physical examination. It is often picked up when a physician, using a stethoscope, hears otherwise normal heart sounds on the right side of the body instead of the left. To confirm the a suspected diagnosis of situs inversus, imaging studies such as MRI, CT, or ultrasound may be ordered, and a referral may be made to a cardiologist or internist for completeness. Imaging studies will also rule out the possibility of random arrangement of the organs, or heterotaxy, which has a much higher risk for serious medical complications. Treatment There is no treatment for situs inversus. In the unlikely case that a heart defect is present, it should be treated accordingly by a cardiologist.Individuals who have situs inversus should be sure to inform all physicians involved in their medical care. In addition to preventing unnecessary confusion, this will reduce the risk of missing a crucial diagnosis that presents with location-specific symptoms (such as appendicitis). Alternative treatment Not applicable. Prognosis The prognosis for an individual with situs inversus is good, and in the absence of a heart defect or other underlying diagnosis, life expectancy is normal. Prevention There is no known method of preventing situs inversus. Resources Periodicals Ainsworth, Claire. "Left Right and Wrong." New Scientist 66, no. 2243 (June 17, 2000): 40-45.Janchar, T., Milzman, D., and Clement, M. "Situs Inversus: Emergency Evaluations of Atypical Presentations." American Journal of Emergency Medicine 18, no. 3 (May 2000): 349-50.Travis, John. "Twirl Those Organs into Place." Science News 156, no. 8 (21 August 1999): 124-125. Organizations American Heart Association. National Center. 7272 Greenville Avenue, Dallas, TX 75231-4596. (214) 373-6300. (800) 242-8721. 〈inquire@heart.org〉.NIH/National Heart, Lung and Blood Institute Information Center. P.O. Box 30105. Bethesda, MD 20824-0105. (301) 592-8573. Key terms Cilia — Tiny hairlike projections on certain cells within the body; cilia produce lashing or whipping movements to direct or cause motion of substances or fluids within the body.CT — A special technique that uses a computer to create a cross-sectional image of the body from a series of x rays.Gene — A single unit of genetic information, providing the body with instruction for a specific biological task.MRI — An imaging study that uses magnetic forces to produce an image of the body's internal structures.Ultrasound — An imaging study that uses high-frequency sound waves to form a visual image of the body's internal structures. situs [si´tus] (L.) site or position.situs inver´sus total or partial transposition of the body organs to the side opposite the normal. si·tus in·ver·'sus reversal of position or location. Synonym(s): situs transversus situs inversus (ĭn-vûr′səs)n. A congenital condition in which internal organs are transposed through the sagittal plane so that the heart, for example, is on the right side of the body. situs inversus A term referring to the completely incorrect (mirror-image) sidedness of structures, where morphologically right-sided structures are present on the left side of the body and morphologically left-sided structures on the right. si·tus in·ver·sus (sī'tŭs in-vĕr'sŭs) Reversal of position or location, referring particularly to left-right reversal of thoracic viscera. situs inversus An uncommon mirror-image reversal of the organs of the trunk. The heart points to the right, the LIVER and APPENDIX are on the left and the stomach and spleen on the right. Situs inversus is seldom of medical significance, but may confuse diagnosis until detected. See also DEXTROCARDIA. LegalSeeSitusFinancialSeesitus
随便看	mandatory mandatory access control mandatory access control framework mandatory access control mechanism mandatory alcohol server training mandatory altitude mandatory and customary mandatory and customary benefits mandatory and statutory training mandatory annual audit requirement mandatory arbitration agreement mandatory army service mandatory assignment mandatory audit firm rotation mandatory authority mandatory breath mandatory broadcast zone mandatory building inspection mandatory code signing mandatory conscription mandatory continued legal education mandatory continuing airworthines information mandatory continuing dental education mandatory continuing education mandatory continuing education for psychologists

situs inversus

situs in·ver·sus

situs inversus

situs inversus

situs inversus

Situs Inversus

Definition

Description

Causes and symptoms

Diagnosis

Treatment

Alternative treatment

Prognosis

Prevention

Resources

Periodicals

Organizations

Key terms

situs

si·tus in·ver·'sus

situs inversus

situs inversus

si·tus in·ver·sus

situs inversus