Asplenia and Polysplenia

Published on 18/07/2015 by admin

Filed under Radiology

Last modified 22/04/2025

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 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
image Transposition of great vessels (13%), double outlet right ventricle (13%), pulmonary valvular stenosis (23%), subaortic stenosis, or atresia
image IVC interruption with azygos vein continuation is 2nd most common abnormality (65%) after multiple spleens
image Aorta usually located to left of midline
– Pulmonary

image Abnormal distribution of lobes with bilateral bilobed lungs
image Only seen in 55% of patients
– Gastrointestinal

image Truncated/short pancreas or agenesis of dorsal pancreas with increased incidence of diabetes and pancreatitis
image Intestinal malrotation seen in most patients with PSP and may range from nonrotation to complete malrotation
image Liver often midline with range of biliary tree abnormalities (absent gallbladder, biliary atresia)
image Isolated reversal of stomach position common
image Other associations: Esophageal or duodenal atresia, tracheoesophageal fistula, semiannular pancreas, gastric duplication, short bowel
– Genitourinary

image Renal agenesis, renal and ovarian cysts

Radiographic Findings

• Radiography

image ASP

– Situs ambiguus, situs solitus, or situs inversus
– Spleen: No distinct visible splenic contour
– Liver: Symmetric and midline in its position
– Stomach: Right, left, or central in position
– Malrotation of bowel
– Heart: Mesocardia or dextrocardia
– Right-sided bronchial pattern and minor fissure may be seen bilaterally
– Superior mediastinal widening (due to bilateral SVC)
– Both pulmonary arteries anterior to trachea on lateral chest film
– Bronchography: Bilateral eparterial bronchi on frontal view (pulmonary arteries inferior to bronchi)
image PSP

– Frontal view: Paratracheal soft tissue prominence (dilated azygos/hemiazygos) mimicking mass
– Chest lateral view: Both pulmonary arteries posterior to trachea and absence of IVC shadow

CT Findings

• ASP

image Absence of spleen
image Situs abnormalities: Liver, gallbladder, stomach, bowel, heart, trilobed lungs
image IVC and abdominal aorta lie on same side of spine (usually on right side with aorta lying posteriorly)

– Virtually pathognomonic feature of ASP
• PSP

image Multiple splenules in right or left upper quadrants

– ± asymmetric liver and midgut malrotation
– ± abdominal situs solitus or situs inversus
image Enlarged azygos or hemiazygos vein with azygous continuation of IVC

– Absence of IVC between renal and hepatic veins with independent drainage of hepatic veins into right atrium

Angiographic Findings

• Conventional

image ASP

– Splenic artery absent; entire celiac axis may arise from superior mesenteric artery
– IVC and abdominal aorta lie on same side (usually right): Virtually pathognomonic feature of ASP
image PSP

– Multiple spleens and common splenic-celiac artery
– Variations in course of IVC: Absence of intrahepatic segment of IVC, crossover of IVC in front of aorta

Nuclear Medicine Findings

• ASP

image Tc-99m sulfur colloid or Tc-99m tagged RBC scan can confirm absence of spleen
• PSP

image Tc-99m labeled heat-damaged RBC scan most sensitive test for detecting splenic tissue
image Hepatobiliary imaging

– Differentiate hepatic from splenic tissue
– Presence and position of gallbladder

Imaging Recommendations

• Best imaging tool

image CECT or MR can demonstrate position and number of spleen(s), as well as other visceral organ abnormalities associated with heterotaxy syndromes

DIFFERENTIAL DIAGNOSIS

Splenosis

• Scattered splenic tissue throughout abdomen usually seen in setting of traumatic splenectomy
• Multiple small implants ranging in size from few mm to few cm; should enhance similarly to normal splenic tissue
• No other associated anomalies

Accessory Spleen

• Normal embryologic variant usually found near splenic hilum along course of splenic vessels
• Identical to normal splenic tissue on any phase of enhancement
• No other associated anomalies

Splenectomy

• No splenic visualization after surgical splenectomy
• No other associated anomalies

PATHOLOGY

General Features

• Etiology

image Uncertain etiology, but may be associated with gene mutations (CFC1 gene, SHROOM3 gene, etc.)

– Altered timing in development of embryonic body curvature leads to visceroatrial situs abnormalities

image ASP: Delayed embryonic body curvature
image PSP: Accelerated embryonic body curvature
– Pressure of adjacent structures may interfere with splenic blood supply leading to development of ASP/PSP
• Associated abnormalities

image Pulmonary, cardiovascular, gastrointestinal, genitourinary, and miscellaneous anomalies

Gross Pathologic & Surgical Features

• ASP: Congenital absence of spleen
• PSP: Multiple splenic tissues in upper quadrants

Microscopic Features

• ASP: Heinz or Howell-Jolly bodies in circulating RBCs (indicates functional ASP)

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image ASP

– Most commonly present with cardiopulmonary disease (83%), including cyanosis as neonates or in infancy
– Patients are prone to overwhelming sepsis (especially postoperatively) due to lack of spleen
– Bowel obstruction (17%) due to malrotation
image PSP

– 10-15% may not present clinically until adulthood
– Often present with cardiac disease, including heart murmur, congestive heart failure, occasional cyanosis, heart block
– Jaundice due to biliary atresia or other biliary abnormalities
– Abdominal pain related to bowel obstruction or intestinal ischemia related to malrotation

Demographics

• Age

image ASP: Newborn or infant presentation
image PSP: Infant or adult
• Gender

image ASP: M > F (2:1)
image PSP: F > M
• Epidemiology

image ASP: 1 in 40,000 live births
image Heterotaxia syndromes: 1 in 10,000

Natural History & Prognosis

• ASP: Very poor prognosis

image Mortality rate: Prognosis depends on extent of cardiac abnormalities, but only 20% survive to age of 16
• Polysplenia: Fair prognosis, better than asplenia

image Mortality rate: 50-60% mortality in 1st year, 25% of patients live up to 5 years, and 10% survive to mid adolescence

Treatment

• ASP: Prophylactic antibiotics (not needed in PSP)
• Surgical correction of cardiac disease or malrotation in either ASP or PSP

DIAGNOSTIC CHECKLIST

Image Interpretation Pearls

• Left liver lobe can simulate spleen on US leading to missed diagnosis of ASP
• Differentiate PSP from accessory spleens and splenosis
image
(Left) Axial CECT in a patient with PSP syndrome demonstrates multiple spleens image located in the right upper quadrant and situs inversus. Note the reversed positions of the liver and stomach.

image
(Right) Axial CECT in the same patient demonstrates an abnormal right-sided stomach image. Note that the IVC image is normally located on the right. The majority of the small bowel is on one side of the abdomen, in keeping with malrotation.
image
(Left) Axial CECT in a patient with PSP syndrome shows dextrocardia and a left-sided IVC image.

image
(Right) Axial CECT in the same patient shows complete abdominal situs inversus with an otherwise normal-appearing stomach image and liver on the right-hand side. Note the left-sided IVC image.
image
(Left) Axial CECT in the same patient shows multiple splenules image in the right upper quadrant along with abdominal situs inversus.

image
(Right) Axial CECT in the same patient shows multiple spleens image, situs inversus, and cystic disease of the kidneys image. This patient was 35 years old (patients with PSP are much more likely to reach adulthood than ASP).
image
Axial CECT in a patient with ASP shows midline enlarged (congested) liver and right-sided stomach image. Extensive cardiac anomalies were also noted (not shown).

image
Axial CECT in a patient with ASP shows a left-sided IVC image.
image
Axial NECT in a patient with PSP shows absent IVC and azygous continuation.
image
Axial CECT shows PSP and congenital absence of all but the head of the pancreas image.
image
Axial CECT in a patient with PSP shows situs ambiguous, absent IVC, and azygous continuation.
image
Axial CECT in a patient with PSP shows retroaortic right renal vein leading to azygous continuation.
image
Axial CECT in a patient with PSP shows liver abnormalities and azygous continuation.
image
Axial CECT in patient with PSP shows prior resection of small intestine due to volvulus and infarction.
image
Axial CECT demonstrates truncation or hypoplasia of the pancreatic tail image, a commonly associated abnormality in PSP.
image
Axial CECT demonstrates 2 discrete spleens image in the left upper quadrant.
image
Axial CECT demonstrates a horseshoe kidney, a known associated embryologic abnormality in PSP syndrome.

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