Introduction
In the normal human body, the organs in the chest and abdomen cavities have a specific location on the right and left sides; the heart, pancreas, and spleen are on the left side, and the liver is on the right. This arrangement is known as situs solitus. In some rare situations, the orientation of these organs can be completely flipped from the right to the left side, known as situs inversus. However, this may only be a significant problem in individuals if it is a part of a syndrome or affects other body parts. In heterotaxy syndrome, the arrangement of organs is mostly between situs solitus and situs inversus. This is known as situs ambiguity. Unlike situs inversus, heterotaxy syndrome can cause serious health problems. The severity of the condition varies among individuals and depends on the specific abnormalities involved.
What Is Heterotaxy Syndrome?
Heterotaxy syndrome, also known as visceral heterotaxy or isomerism, is a condition in which the internal organs of the body are arranged abnormally in the chest and abdomen. Heterotaxy is a Greek word in which heteros means other than and taxis means arrangement. The prevalence of this condition is estimated to be one in 10,000 births worldwide and accounts for about three percent of all congenital heart defects. People with this condition suffer from complex birth defects that affect the lungs, heart, spleen, liver, intestine, and other organs. However, severity varies among patients and also depends on the abnormalities present in the condition. Some individuals may have mild health problems, whereas, at the other end of the spectrum, heterotaxy may be severe and life-threatening, especially in infancy and childhood.
What Are the Types of Heterotaxy Syndrome?
The exact cause of heterotaxy syndrome is not completely understood. However, studies have reported that it may be due to genetic reasons or prenatal risk factors such as smoking, exposure to chemicals or toxins, or due to certain diseases. Heterotaxy syndrome of two types;
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Right Atrial Isomerism: This condition involves different heart defects, such as holes in the septum (the wall that divides the heart) or heart valve problems. The blood flow to the heart from the lungs is affected as it can be irregular. The spleen and the other organs may be missing or in the wrong place.
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Left Atrial Isomerism: Individuals suffering from this condition have structural defects in the heart or a problem with the heart’s conduction system involving heart block. It mainly occurs due to the inability of the upper and lower chambers of the heart to send or receive signals. Patients may have many small spleens, or it may be missing.
What Are the Complications Associated With Heterotaxy Syndrome?
Heterotaxy syndrome is usually diagnosed before birth or soon after birth. However, a routine ultrasound may also diagnose some cases later in life. Physical examination of the patient and imaging tests such as magnetic resonance imaging (MRI), computed tomography scan (CT scan), and echocardiogram can also help diagnose heterotaxy syndrome. Each patient with heterotaxy syndrome is unique, and the problems may differ. However, some of the complications associated with heterotaxy syndrome include:
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Gastrointestinal System: Biliary atresia and intestinal malrotation (twisting) can be seen in about 70 percent of patients with heterotaxy syndrome. Intestinal malrotation can cause bilious vomiting (vomiting of bile) and bloody diarrhea, suggesting an acute abdominal emergency. The gastrointestinal structural defects cause feeding difficulties, severe abdominal pain, and other symptoms. Dysfunction or malfunctioning of the liver can affect the digestion of food (biliary atresia), leading to indigestion problems. Heterotaxy syndrome can also increase the risk of gallstone formation, pancreatitis (inflammation of the pancreas), intestinal obstruction, and diabetes mellitus.
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Immunologic System: The absence or hypofunction of the spleen in patients with heterotaxy syndrome can make them susceptible to infections and sepsis (severe inflammatory response to infection). Studies have shown that the rate of infection in children with heterotaxy syndrome is higher as compared to normal children.
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Genitourinary System: The disorders include the absence of a kidney, a horseshoe-shaped kidney, a hypoplastic kidney (poorly developed kidney), and ureter abnormalities. These abnormalities may predispose the patients to frequent urinary tract infections or the development of nephrolithiasis (kidney stones). A unilateral kidney can also cause hypertension and decreased kidney function in the future.
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Respiratory System: A defect in the development of cilia due to abnormally positioned organs (ciliary dyskinesia) can cause respiratory complications in heterotaxy syndrome patients. This can lead to inadequate clearance of secretions, recurrent chest infections, and atelectasis (partial or complete collapse of the lung).
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Central Nervous System (CNS): The abnormalities of CNS in heterotaxy syndrome include hydrocephalus (accumulation of fluid in the brain cavity), meningomyelocele (malformation of the neural tube), absence of corpus callosum (the nerve fibers that connect the two halves of the brain), holoprosencephaly (abnormal development of the brain), and other brain anomalies.
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Cardiac Manifestations: These include abnormal positioning of the heart and blood vessels, blockage in the blood flow, structural defects, and irregular heartbeats. This also includes right or left isomerism and can be challenging to treat. Patients with left isomerism may have less severe malformations than people with right isomerism. Most of the cardiac complications of right isomerism are identified in infancy due to its severity.
How Is Heterotaxy Syndrome Managed?
Heterotaxy syndrome requires a compressive approach to the treatment, as each child has different needs. Some of the treatment measures include:
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Children with right atrial isomerism require a series of surgeries to improve the functioning of the heart and the circulatory system. A Fontan procedure is recommended in which a single chamber replaces the two ventricles or the heart's lower chambers to pump the blood to the other parts of the body.
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Children with left atrial isomerism are recommended cardiac catheterization or surgery to fix the holes in the heart or heart walls. Abnormalities in the heart rhythm can be treated with small electrical devices that regulate the heart rhythm, such as cardiac pacemakers or defibrillators.
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Medications are prescribed to lower blood pressure and reduce stress on the heart muscles.
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Surgery may also be required to treat malrotation of the intestines and prevent bowel obstruction.
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Regular antibiotic medications are recommended for patients with dysfunctional spleens to help them manage different infections.
Conclusion
Heterotaxy syndrome is a rare and complex condition in which the internal organs of the chest and abdomen demonstrate an abnormal arrangement on both the left and right sides of the body. The long-term outlook of the condition depends on when it is diagnosed, its severity, or the organs affected. However, the survival rates of patients with heterotaxy syndrome have increased due to recent improvements in healthcare technology. As the patients are at a higher risk of systemic diseases and infections, heart transplantation may be required later in life. However, individuals with this condition will require lifelong cardiac care and frequent monitoring to improve their quality of life.
