Polysplenia syndrome, also known as left isomerism, is a type of heterotaxy syndrome where there are multiple spleens congenitally as part of left-sided isomerism.

Epidemiology

Polysplenia is seen predominantly in female patients. It is usually diagnosed in childhood or adulthood, later than asplenia syndrome, since associated congenital heart diseases tend to be less severe than those encountered in the latter.

Associations

• congenital heart disease (>50%): especially non-cyanotic, and less complex/severe than in asplenia syndrome ³

  • abnormal pulmonary venous return (70%, PAPVR/TAPVR)

  • dextrocardia (37%)

• gastrointestinal

  • semi-annular pancreas / dorsal pancreatic agenesis ^4,6,8

  • midgut malrotation (80%) ^7,8

  • gallbladder agenesis (50%) and biliary atresia

  • mobile cecum

  • tracheo-esophageal fistula

  • absent C-loop of duodenum

• genitourinary

  • renal cyst

  • renal agenesis

  • ovarian cyst

• vascular

  • inferior vena cava anomalies ^7,8

    • ​intrahepatic IVC interruption with azygos/hemiazygos continuation

  • portal vein anomalies ^7,8

    • preduodenal portal vein

Clinical presentation

It is related to the associated pathology.

Pathology

Polysplenia results from failure of development of the usual left-right asymmetry of organs and consists of situs ambiguus, with features of bilateral left-sidedness.

Etiology

The exact cause of polysplenia is unknown. However, it is suggested that it is caused by various factors ¹⁰:

• embryogenic

• genetic

• teratogenic 

Radiographic features

General

• primary features:

  • presence of multiple splenules without a parent spleen

  • typically occurs on the left side, though it may be bilateral

  • commonly associated with inferior vena cava interruption, with azygos or hemiazygos continuation³

• additional characteristic features:

  • bilateral hyparterial bronchi

  • bilateral bilobed lungs

  • bilateral pulmonary arteries/left atria

  • midline liver

Treatment and prognosis

• overall mortality:

  • the condition carries a 75% mortality rate by age 5

• impact of congenital geart disease:

  • the presence of congenital heart diseases significantly increases the mortality rate

• 1-Year Mortality:

  • in polysplenia syndrome, the 1-year mortality rate is greater than 50%, as it is less commonly associated with congenital heart diseases¹¹

  • in comparison, right isomerism has a 1-year mortality rate of approximately 85%

See also

• asplenia syndrome

• heterotaxy syndrome

• situs classification

• isomerism