Polysplenia is a rare heterotaxy disorder with a reported incidence of 1 per 250 000 live births. Various studies have attempted to classify the broad spectrum of anomalies into asplenia and polysplenia [1
]. Classical polysplenia results in hyparterial bronchi (both main bronchi are below the pulmonary arteries) and bilobed lungs. Asplenia results in trilobed lungs and eparterial bronchi (both main bronchi are located superior to the main pulmonary arteries).
The precise aetiology of polysplenia is unknown. Embryonic, genetic and teratogenic components have all been implicated as causative factors in polysplenia [2
]. Although polysplenia syndrome has a wide range of abnormalities, there is no single pathognomic abnormality that characterises this rare entity. The range of anomalies include multiple spleens of equal volume, visceral heterotaxia, right-sided stomach, a left-sided or large midline liver, malrotation of the intestine, a short pancreas and IVC anomalies [3
Polysplenia has been described mainly in childhood owing to critical anatomic malformations related to cardiac defects or biliary atresia. Only those with mild anatomical abnormalities survive into adulthood. Symptomatic polysplenia in adults is often caused by abnormal biliary and pancreatic duct drainage, cholecystisis and bowel obstruction [4
]. Polysplenia is usually an incidental finding on abdominal ultrasound or CT performed for other causes.
In our patient there were multiple small spleens along the greater curvature of the stomach, a midline liver and bilateral hyparterial bronchi. We also noted dorsal pancreatic agenesis and a preduodenal portal vein.
Anomalies of the pancreas have been described in polysplenia syndrome [1
]. Normal pancreas formation occurs from fusion of ventral and dorsal pancreatic buds. The ventral pancreatic bud gives rise to the uncinate process and the head, while the dorsal pancreatic bud gives rise to the body and tail. The development of both dorsal pancreatic bud and spleen occur in the dorsal mesogastrium. Consequently, anomalies in both these organs can be expected in patients with polysplenia syndrome [5
Clinical significance of dorsal pancreatic agenesis is the development of pancreatitis owing to poor drainage from the remnant ventral duct. CT demonstration of a short pancreas is not synonymous with agenesis and is a pitfall well avoided. Fat replacement in the distal pancreas can mimic agenesis. Similarly partial vs complete dorsal duct agenesis can only be differentiated by pancreatic duct studies using either MRCP or endoscopic retrograde cholangiopancreatography.
Presence of preduodenal portal vein was seen in 12 out of 15 patients in 1 large review [6
]. First described by Knight in 1921, the preduodenal portal vein is a congenital anomaly that involves the portal vein passing in front of the duodenum [6
]. Preduodenal portal vein can be associated with duodenal atresia, stenosis, annular pancreas and malrotation. Surgery may be required for these conditions. A preduodenal portal vein anomaly occurs owing to loss of vitelline veins in their cranial and middle communication during 9 mm stage of embryonic development. In normal development, the loss of caudal and cranial communications result in the development of a normal ‘S’ shaped portal vein.
We postulate that formation of calculus was caused by stasis of bile in the CBD owing to distal compression of the CBD by the preduodenal portal vein. Similar opinion was also expressed by Seo et al [7
]. When surgery is required care should be exercised in patients with preduodenal portal vein. Lack of awareness may lead to unwanted ramifications such as severe haemorrhage and other complications related to portal vein ligation.