Congenital stenosis of vena cava is a congenital anomaly in which the superior vena cava or inferior vena cava has an aberrant interruption or coarctation.

In some cases, it can be asymptomatic, and in other cases it can lead to fluid accumulation and cardiopulmonary collapse.

There are a variety of clinical manifestations of situs ambiguous. Acute symptoms can be due to both cardiac and non-cardiac defects. Cyanosis or blue skin coloration, primarily affecting the lips and fingernails, can indicate a systemic or circulatory issue. Poor feeding, failure to thrive, and rapid shallow breathing may also be observed due to poor circulation. Upon examination, arrhythmia and heart murmur may raise further suspicion of a cardiac abnormality. Non-cardiac symptoms include impairments of the liver and gastrointestinal tract. Biliary atresia, or inflammation and destruction of the bile ducts, may lead to jaundice. Vomiting and swelling of the abdominal region are features that suggest improper positioning of the intestines. Poor positioning of the intestine also makes it more prone to blockage, which can result in numerous chronic health issues. Asplenia and polysplenia are also possible features of heterotaxy syndrome.

Due to abnormal cardiac development, patients with situs ambiguous usually develop right atrial isomerism consisting of 2 bilaterally paired right atria, or left atrial isomerism consisting of 2 bilaterally paired left atria. Clinical features and symptoms can vary dependent upon assignment of left versus right atrial isomerism. In either instance, the apex of the heart will be poorly positioned, which should alert a clinician of the likelihood of atrial isomerism. It is estimated that 5-10% of isomeric patients have mesocardia, in which the heart is positioned at the center of the thorax, 25-50% have dextrocardia, in which the apex of the heart is pointed toward the right side of the thorax, and 50 - 70% have levocardia, in which the apex of the heart is pointed toward the left side of the thorax.

In PLSVC, the left brachiocephalic vein does not develop fully and the left upper limb and head & neck drain into the right atrium via the coronary sinus.

The variation, in isolation, is considered benign, but is very frequently associated with cardiac abnormalities (e.g. ventricular septal defect, atrioventricular septal defect) that have a significant mortality and morbidity. It is more frequent in patients with congenital heart defects.

In anatomy, a persistent left superior vena cava (PLSVC) is the most common variation of the thoracic venous system, is prevalent in 0.3% of the population, and an embryologic remnant that results from a failure to involute.

Abdominal organs, including the liver, stomach, intestinal tract, and spleen may be randomly arranged throughout the left-right axis of the body. Distribution of these organs largely dictates treatment, clinical outcomes, and further evaluation.

The liver is typically symmetrical across the left-right axis in patients with situs ambiguous, which is abnormal. A majority of left atrial isomeric patients have defects throughout the biliary tree, which is responsible for bile production, even when the gall bladder is functional and morphologically normal. This biliary atresia can lead to acute problems such as nutrient malabsorption, pale stools, dark urine, and abdominal swelling. If this condition continues without proper treatment, cirrhosis and liver failure become a major concern. Biliary atresia is not usually observed in patients with right atrial isomerism.

Random positioning of the stomach is often one of the first signals of situs ambiguous upon examination. Malrotation of the entire intestinal tract, or improper folding and bulging of the stomach and intestines, results in bowel obstruction. This impairment leads to vomiting, abdominal distention, mucus and blood in the stool. Patients may also experience abdominal pain. Intestinal malrotation is more commonly identified in patients with right atrial isomerism than in those with left atrial isomerism.

Isomeric patients often experience disruptions to splenic development during embryogenesis, resulting in an overall lack a spleen (asplenia) or development of many spleens (polysplenia). Asplenia is most often observed in patients with right atrial isomerism. Polysplenia results in 90% of patients with left atrial isomerism. Although they have many spleens, each is usually ineffective resulting in functional asplenia. Rarely, left atrial isomeric patients have a single, normal, functional spleen. Patients lacking a functional spleen are in danger of sepsis and must be monitored.

A preureteric vena cava, also known as a retrocaval ureter, is a rare congenital malformation of the right human ureter, in which the ureter passes behind the inferior vena cava, causing compression possibly leading to hydronephrosis. The prevalence of this condition is approximately 1 per 1,000 persons, with males 2-3 times more likely than females to develop the condition. Symptoms often do not manifest until those with the condition are aged in their 20s or 30s.

Cor triatriatum (or triatrial heart) is a congenital heart defect where the left atrium (cor triatriatum sinistrum) or right atrium (cor triatriatum dextrum) is subdivided by a thin membrane, resulting in three atrial chambers (hence the name).

Cor triatriatum represents 0.1% of all congenital cardiac malformations and may be associated with other cardiac defects in as many as 50% of cases. The membrane may be complete or may contain one or more fenestrations of varying size.

Cor triatrium sinistrum is more common. In this defect there is typically a proximal chamber that receives the pulmonic veins and a distal (true) chamber located more anteriorly where it empties into the mitral valve. The membrane that separates the atrium into two parts varies significantly in size and shape. It may appear similar to a diaphragm or be funnel-shaped, bandlike, entirely intact (imperforate) or contain one or more openings (fenestrations) ranging from small, restrictive-type to large and widely open.

In the pediatric population, this anomaly may be associated with major congenital cardiac lesions such as tetralogy of Fallot, double outlet right ventricle, coarctation of the aorta, partial anomalous pulmonary venous connection, persistent left superior vena cava with unroofed coronary sinus, ventricular septal defect, atrioventricular septal (endocardial cushion) defect, and common atrioventricular canal. Rarely, asplenia or polysplenia has been reported in these patients.

In the adult, cor triatriatum is frequently an isolated finding.

Cor triatriatum dextrum is extremely rare and results from the complete persistence of the right sinus valve of the embryonic heart. The membrane divides the right atrium into a proximal (upper) and a distal (lower) chamber. The upper chamber receives the venous blood from both vena cavae and the lower chamber is in contact with the tricuspid valve and the right atrial appendage.

The natural history of this defect depends on the size of the communicating orifice between the upper and lower atrial chambers. If the communicating orifice is small, the patient is critically ill and may succumb at a young age (usually during infancy) to congestive heart failure and pulmonary edema. If the connection is larger, patients may present in childhood or young adulthood with a clinical picture similar to that of mitral stenosis. Cor triatriatum may also be an incidental finding when it is nonobstructive.

The disorder can be treated surgically by removing the membrane dividing the atrium.

At birth, the ductus arteriosus is still open, and there is higher than normal resistance to blood flow in the lungs. This allows for adequate oxygenation via mixing between the atria and a normal appearance at birth. When the ductus begins to close and pulmonary vascular resistance decreases, blood flow through the ductus is restricted and flow to the lungs is increased, reducing oxygen delivery to the systemic circulation. This results in cyanosis and respiratory distress which can progress to cardiogenic shock. The first symptoms are cyanosis that does not respond to oxygen administration or poor feeding. Peripheral pulses may be weak and extremities cool to the touch.

HLHS often co-occurs with low birth weight and premature birth.

In neonates with a small atrial septal defect, termed "restrictive", there is inadequate mixing of oxygenated and deoxygenated blood. These neonates quickly decompensate and develop acidosis and cyanosis.

On EKG, right axis deviation and right ventricular hypertrophy are common, but not indicative of HLHS. Chest x-ray may show a large heart (cardiomegaly) or increased pulmonary vasculature. Neonates with HLHS do not typically have a heart murmur, but in some cases, a pulmonary flow murmur or tricuspid regurgitation murmur may be audible.

Co-occurring tricuspid regurgitation or right ventricular dysfunction can cause hepatomegaly to develop.

IVCS presents with a wide variety of signs and symptoms, making it difficult to diagnose clinically.

- Edema of the lower extremities (peripheral edema), caused by an increase in the blood pressure in the veins.

- Tachycardia. This is caused by the decreased preload, causing the heart to increase its frequency.

- In pregnant women, signs of fetal hypoxia and distress may be seen in the cardiotocography. This is caused by decreased perfusion of the uterus, resulting in hypoxemia of the fetus.

- Supine hypotensive syndrome

Inferior vena cava syndrome (IVCS) is a result of obstruction of the inferior vena cava. It can be caused by invasion or compression by a pathological process or by thrombosis in the vein itself. It can also occur during pregnancy.Pregnancy can lead to problems with blood return due to high venous pressure in the lower limbs, failure of blood return to the heart, decreased cardiac output due to obstructions in inferior vena cava, sudden rise in venous pressure which can lead to placental separation, and a decrease in renal function. All of these issues can arise from lying in the supine position during late pregnancy which can cause compression of the inferior vena cava. Symptoms of late pregnancy inferior vena cava syndrome consist of intense pain in the right hand side, muscle twitching, drop of blood pressure, and fluid retention.

A sinus venosus atrial septal defect is a type of atrial septal defect primarily associated with the sinus venosus.

They represent 5% of atrial septal defects.

They can occur near the superior vena cava or inferior vena cava, but the former are more common.

They can be associated with anomalous pulmonary venous connection.

Hypoplastic left heart syndrome (HLHS) is a rare congenital heart defect in which the left side of the heart is severely underdeveloped. It may affect the left ventricle, aorta, aortic valve, or mitral valve.

The anomalous venous return forms a curved shadow on chest x-ray such that it resembles a scimitar. This is called the Scimitar Sign. Associated abnormalities include right lung hypoplasia with associated dextroposition of the heart, pulmonary artery hypoplasia and pulmonary sequestration.Incidence is around 1 per 100,000 births.

Vein of Galen aneurysmal malformations (VGAM) and Vein of Galen aneurysmal dilations (VGAD) are the most frequent arteriovenous malformations in infants and fetuses. VGAM consist of a tangled mass of dilated vessels supplied by an enlarged artery. The malformation increases greatly in size with age, although the mechanism of the increase is unknown. Dilation of the great cerebral vein of Galen is a secondary result of the force of arterial blood either directly from an artery via an arteriovenous fistula or by way of a tributary vein that receives the blood directly from an artery. There is usually a venous anomaly downstream from the draining vein that, together with the high blood flow into the great cerebral vein of Galen causes its dilation. The right sided cardiac chambers and pulmonary arteries also develop mild to severe dilation.

The ostium secundum atrial septal defect is the most common type of atrial septal defect, and comprises 6–10% of all congenital heart diseases.

The secundum atrial septal defect usually arises from an enlarged foramen ovale, inadequate growth of the septum secundum, or excessive absorption of the septum primum. About 10 to 20% of individuals with ostium secundum ASDs also have mitral valve prolapse.

An ostium secundum ASD accompanied by an acquired mitral valve stenosis is called Lutembacher's syndrome.

Most individuals with an uncorrected secundum ASD do not have significant symptoms through early adulthood. More than 70% develop symptoms by about 40 years of age. Symptoms are typically decreased exercise tolerance, easy fatigability, palpitations, and syncope.

Complications of an uncorrected secundum ASD include pulmonary hypertension, right-sided heart failure, atrial fibrillation or flutter, stroke, and Eisenmenger's syndrome.

While pulmonary hypertension is unusual before 20 years of age, it is seen in 50% of individuals above the age of 40. Progression to Eisenmenger's syndrome occurs in 5 to 10% of individuals late in the disease process.

Scimitar syndrome, or congenital pulmonary venolobar syndrome, is a rare congenital heart defect characterized by anomalous venous return from the right lung (to the systemic venous drainage, rather than directly to the left atrium). This anomalous pulmonary venous return can be either partial (PAPVR) or total (TAPVR). The syndrome associated with PAPVR is more commonly known as "Scimitar syndrome" after the curvilinear pattern created on a chest radiograph by the pulmonary veins that drain to the inferior vena cava. This radiographic density often has the shape of a scimitar, a type of curved sword. The syndrome was first described by Catherine Neill in 1960.

Shortness of breath is the most common symptom, followed by face or arm swelling.

Following are frequent symptoms:

- Difficulty breathing

- Headache

- Facial swelling

- Venous distention in the neck and distended veins in the upper chest and arms

- Upper limb edema

- Lightheadedness

- Cough

- Edema (swelling) of the neck, called the "collar of Stokes"

- Pemberton's sign

Superior vena cava syndrome usually presents more gradually with an increase in symptoms over time as malignancies increase in size or invasiveness.

Signs and symptoms of mitral stenosis include the following:

- Heart failure symptoms, such as dyspnea on exertion, orthopnea and paroxysmal nocturnal dyspnea (PND)

- Palpitations

- Chest pain

- Hemoptysis

- Thromboembolism in later stages when the left atrial volume is increased (i.e., dilation). The latter leads to increase risk of atrial fibrillation, which increases the risk of blood stasis (motionless). This increases the risk of coagulation.

- Ascites and edema and hepatomegaly (if right-side heart failure develops)

Fatigue and weakness increase with exercise and pregnancy.

Tracheal agenesis is a rare birth defect with a prevalence of less than 1 in 50,000, in which the trachea fails to develop. The defect is normally fatal, although occasional cases have been reported of long-term survival following surgical intervention.

There are three main types of tracheal agenesis, designated Types I, II and III.

In 2013, a case was reported of a South Korean child with tracheal agenesis who had been successfully treated after having been kept alive in an intensive care unit for the first two and a half years of her life. She then had an artificially created trachea implanted that had been created by tissue engineering using her own stem cells. The patient however later died from complications.

Anomalous pulmonary venous connection (or anomalous pulmonary venous drainage or anomalous pulmonary venous return) is a congenital defect of the pulmonary veins.

"Total anomalous pulmonary venous connection", also known as "total anomalous pulmonary venous drainage" and "total anomalous pulmonary venous return", is a rare cyanotic congenital heart defect in which all four pulmonary veins are malpositioned and make anomalous connections to the systemic venous circulation. (Normally, pulmonary veins return oxygenated blood from the lungs to the left atrium where it can then be pumped to the rest of the body). A patent foramen ovale, patent ductui arteriosa or an atrial septal defect "must" be present, or else the condition is fatal due to a lack of systemic blood flow.

In some cases, it can be detected prenatally.

There are four variants: Supracardiac (50%): blood drains to one of the innominate veins (brachiocephalic veins) or the superior vena cava; Cardiac (20%), where blood drains into coronary sinus or directly into right atrium; Infradiaphragmatic (20%), where blood drains into portal or hepatic veins; and a mixed (10%) variant.

TAPVC can occur with "obstruction", which occurs when the anomalous vein enters a vessel at an acute angle and can cause pulmonary venous hypertension and cyanosis because blood cannot enter the new vein as easily.

Common symptoms include a grayish-blue (cyanosis) coloration to the skin, lips, fingernails and other parts of the body. Other pronounced symptoms can be rapid/difficulty breathing, poor feeding, cold hands or feet, or being inactive and drowsy. "In a baby with hypoplastic left heart syndrome, if the natural connections between the heart's left and right sides (foramen oval and ductus arteriosus) are allowed to close, he or she may go into shock." Signs of shock can include cool or clammy skin, a weak or rapid pulse, and dilated pupils.

Hypoplastic right heart syndrome is a congenital heart defect in which the right atrium and right ventricle are underdeveloped. This defect causes inadequate blood flow to the lungs and thus, a blue or cyanotic infant.[3]

In medicine, agenesis () refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue. Many forms of agenesis are referred to by individual names, depending on the organ affected:

- Agenesis of the corpus callosum - failure of the Corpus callosum to develop

- Renal agenesis - failure of one or both of the kidneys to develop

- Phocomelia - failure of the arms or legs to develop

- Penile agenesis - failure of penis to develop

- Müllerian agenesis - failure of the uterus and part of the vagina to develop

- Agenesis of the gallbladder - failure of the Gallbladder to develop. A person may not realize they have this condition unless they undergo surgery or medical imaging, since the gallbladder is neither externally visible nor essential.