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 ambiguus 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 distension, 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. Causes
Situs ambiguus has been linked to family history of malformations  and maternal cocaine use, suggesting both genetic and environmental factors play a role. Several genes in the TGF-beta pathway, which controls left-right patterning of visceral organs across the body axis, have been indicated in sporadic and familial cases of atrial isomerism.
A ring chromosome is an aberrant chromosome whose ends have fused together to form a ring. Ring chromosomes were first discovered by Lilian Vaughan Morgan in 1926. A ring chromosome is denoted by the symbol r in human genetics and R in Drosophila genetics. Ring chromosomes may form in cells following genetic damage by mutagens like radiation, but they may also arise spontaneously during development. Formation
In order for a chromosome to form a ring, both ends of the chromosome are usually missing, enabling the broken ends to fuse together. In rare cases, the telomeres at the ends of a chromosome fuse without any loss of genetic material, which results in a normal phenotype.Complex rearrangements, including segmental microdeletions and microduplications, have been seen in numerous ring chromosomes, providing important clues regarding the mechanisms of their formation.Small supernumary rings can also form, resulting in a partial trisomy.Ring chromosomes are unstable during cell division and can form interlocking or fused rings. Associated syndromes
Human genetic disorders can be caused by ring chromosome formation. Although ring chromosomes are very rare, they have been found in all human chromosomes. Symptoms seen in patients carrying ring chromosomes are more likely to be caused by the deletion of genes in the telomeric regions of affected chromosomes, rather than by the formation of a ring structure itself. Almost all ring chromosome syndromes feature marked growth delay.Ring chromosomes can be inherited or sporadic. Mosaicism is common and affects the severity of the condition.