Asplenia and Polysplenia

 Absent spleen in virtually all patients


image Congenital heart disease in ∼ 100% of patients

image Bilateral trilobed lungs

image Malrotation in most patients

image Aorta and inferior vena cava (IVC) are frequently ipsilateral (usually right side)


• Polysplenia (PSP) syndrome: Left isomerism or bilateral left-sidedness
image Usually multiple spleens, but may have single normal spleen
– Isolated reversal of splenic position (in right abdomen) common

image Increased risk of complex cardiac anomalies, although less common with PSP than ASP

image IVC interruption with azygos continuation very common

image Bilateral bilobed lungs

image Truncated/short pancreas or agenesis of dorsal pancreas
– Increased incidence of diabetes and pancreatitis

image Intestinal malrotation is seen in most patients

image Liver often midline with range of biliary abnormalities

image Aorta usually located to left of midline




TOP DIFFERENTIAL DIAGNOSES




• Splenosis

• Accessory spleen

• Splenectomy


CLINICAL ISSUES




• ASP: Newborn or infant presentation due to cardiac disease with poor prognosis and early mortality
image ↑ risk of sepsis due to lack of spleen

• PSP: Infant or adult presentation with better prognosis due to lesser incidence of cardiac disease

image
(Left) Coronal volume-rendered CECT in a patient with polysplenia (PSP) syndrome demonstrates multiple spleens image in the left upper quadrant. The multiple spleens in PSP are typically in the left abdomen, but can rarely be on the right.


image
(Right) Axial CECT in the same patient demonstrates a markedly dilated azygous vein image.

image
(Left) Axial CECT in the same patient again demonstrates multiple spleens image and a dilated azygous vein image to the right of the aorta. Azygous continuation of the inferior vena cava (IVC) is a very common abnormality in PSP syndrome.


image
(Right) Axial CECT in the same patient demonstrates malrotation of the bowel, with the small bowel abnormally located in the right abdomen and the entirety of the colon in the left abdomen. Malrotation is quite common with both asplenia (ASP) and PSP syndromes.


TERMINOLOGY


Abbreviations




• Asplenia (ASP), polysplenia (PSP)


Synonyms




• Heterotaxy syndromes

• ASP: Asplenia syndrome, Ivemark syndrome, bilateral right-sidedness

• PSP: Polysplenia syndrome, bilateral left-sidedness


Definitions




• Complex inherited syndromes associated with absence (ASP) or multiplicity (PSP) of spleens, as well as many other anomalies


Associated Syndromes




• Heterotaxy: Abnormal embryologic placement of thoracoabdominal structures across right-left axis of body

• Situs solitus: Normal placement of thoracoabdominal organs in right-left axis

• Situs inversus: Reversal of normal positions of thoracoabdominal organs across right-left axis (mirror-image of situs solitus)
image Can be subdivided into situs inversus with dextrocardia or levocardia

• Situs ambiguus (heterotaxy syndrome): Abnormal placement of thoracoabdominal structures without situs inversus
image Situs ambiguus with polysplenia: Left isomerism or bilateral left-sidedness

image Situs ambiguus with asplenia: Right isomerism or bilateral right-sidedness


IMAGING


General Features




• Best diagnostic clue
image ASP: Absence of spleen, abdominal aorta and inferior vena cava (IVC) on same side (usually right), and bilateral distribution of right-sided viscera

image PSP: Multiple small spleens, intrahepatic interruption of IVC with continuation of azygos vein, bilateral distribution of left-sided viscera

• Morphology

• PSP
image Number of spleens varies from 2 to 16

• Key concepts
image ASP syndrome: Right isomerism or bilateral right-sidedness
– Situs ambiguus and bilateral right-sidedness; no fixed set of findings, abnormalities exist across a spectrum
image May be associated with situs solitus or situs inversus

– Spleen
image Absent spleen in virtually all patients

– Cardiovascular
image Congenital heart disease in ∼ 100% of patients

image Total anomalous pulmonary venous return (almost 100%), endocardial cushion defect (85%), single ventricle (51%), transposition of great vessels (58%), pulmonary stenosis or atresia (70%), dextrocardia (42%), mesocardia, ventricular septal defect, single atrioventricular valve, bilateral superior vena cava (SVC)

image Aorta and IVC are frequently ipsilateral (usually right side)

– Pulmonary
image Abnormal distribution of lobes with bilateral trilobed lungs

– Gastrointestinal
image Malrotation in most patients with ASP

image Other associations: Imperforate anus, ectopic liver, annular pancreas, esophageal varices, gallbladder agenesis, Hirschsprung disease, and duplication or hypoplasia of stomach

– Genitourinary
image Horseshoe kidney, bilobed urinary bladder, hydroureter, double collecting system, cystic kidney

– Miscellaneous
image Cleft palate, cleft lip, fused or horseshoe adrenal gland, absent left adrenal gland, scoliosis, bicornuate uterus, single umbilical artery, lumbar myelomeningocele

image PSP syndrome: Left isomerism or bilateral left-sidedness
– Situs ambiguus and bilateral left-sidedness: No fixed set of findings and abnormalities exist across a spectrum
image May be associated with situs solitus or situs inversus

– Spleen
image Usually multiple spleens in left upper quadrant, but some cases may have single normal spleen

image Isolated reversal of splenic position (in right abdomen) common

– Cardiovascular
image Increased risk of complex cardiac anomalies, although less common with PSP than with ASP, accounting for better long-term survival

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Nov 16, 2016 | Posted by in GASTROINTESTINAL IMAGING | Comments Off on Asplenia and Polysplenia
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