1
Q
Splenule (Accessory Spleen)
What is it? Why do they form?
Do they have clinical significance?
How to Dx? If in doubt, how to confirm?
A
- Also called an accessory spleen, a splenule is a focus of normal splenic tissue separate from the main body of the spleen, due to the embryologic failure of fusion of the splenic anlage. The most common location is the splenic hilum.
- Although usually an incidental finding, the presence of a splenule does have significance in certain clinical settings. For instance, splenectomy for consumptive thrombocytopenia may not be curative if there is sufficient unresected accessory splenic tissue present. A splenule may be mistaken for a lymph node or mass when in an unusual location. As previously discussed, an intrapancreatic splenule may be mistaken for a hypervascular pancreatic mass.
- A splenule should follow splenic tissue on all MRI sequences. If in doubt, a Tc-99m sulfur colloid scan or a heat-damaged Tc-99m RBC scan can be confirmatory.
2
Q
Polysplenia Syndrome
What is it? Relative to stomach?
Association? Prognosis?
Venous association?
A
- Polysplenia syndrome is a spectrum of anatomic disorders characterized by some degree of visceral heterotaxia in addition to multiple discrete foci of splenic tissue. Multiple spleens may be on the right or left, but are always on the same side as the stomach.
- Polysplenia is usually associated with severe congenital cardiac anomalies. Most patients die in early childhood, but a few may have only minor cardiac defects and may be incidentally discovered as adults.
- Polysplenia is associated with venous anomalies including interruption of the IVC with azygos or hemiazygos continuation. A less common association is a preduodenal portal vein.
3
Q
Wandering Spleen
What is it?
Possible presentation?
A
- A wandering spleen is a normal spleen with abnormal laxity or absence of its fixed ligamentous attachments.
- Wandering spleen may present clinically as an abdominal mass or may cause acute abdominal pain secondary to torsion.
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Q
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5
Q
Splenic Hemangioma
What is it? Common distribution and size?
Associated with what two syndromes?
Imaging appearance?
Nuclear medicine techniques to visualize these lesions?
A
- Hemangioma is the most common benign splenic neoplasm. Hemangioma may be solitary or multiple, and lesions tend to be small.
- Splenic hemangiomas are associated with Kasabach-Merritt syndrome (anemia, thrombocytopenia, and consumptive coagulopathy) and Klippel-Trenaunay-Weber syndrome (cutaneous hemangiomas, varicose veins, and extremity hypertrophy). These visceral hemangiomatosis syndromes are usually associated with phleboliths.
- On CT, hemangiomas are typically iso- or hypoattenuating pre-contrast and hyperenhancing. On MR, hemangiomas are typically hyperintense on T2-weighted images and may enhance peripherally or homogeneously. However, the classic pattern of discontinuous nodular enhancement seen in hepatic hemangiomas is uncommon.
- Nuclear medicine scintigraphy with Tc-99m labeled red blood cells would show increased activity within the lesion on delayed images. In contrast, Tc-99m sulfur colloid scanning may show either increased or decreased activity.
6
Q
Kasabach-Merritt Syndrome
A
- AKA hemangioma thrombocytopenia syndrome
- Kasabach-Merritt syndrome, also known as haemangioma thrombocytopenia syndrome, is a rare life-threatening disease found in infants in which a rapidly growing vascular tumor is responsible for thrombocytopenia, microangiopathic hemolytic anemia, and consumptive coagulopathy.
- Associated with splenic hemangiomas
7
Q
Klippel-Trenaunay-Weber Syndrome
A
- Klippel-Trénaunay-Weber syndrome (KTWS) is a syndrome combination of capillary malformations, soft-tissue or bone hypertrophy, and varicose veins or venous malformations. It is considered an angio-osteo-hypertrophic syndrome.
- Associated with splenic hemangiomas
- KTS classically comprises a triad of:
- port wine nevi
- bony or soft tissue hypertrophy of an extremity (localised gigantism)
- varicose veins or venous malformations of unusual distribution
8
Q
Splenic Hamartoma
What is it? Possible association?
Imaging appearance?
A
- Splenic hamartoma is a rare, benign lesion composed of malformed red pulp elements. It may be associated with tuberous sclerosis.
- Splenic hamartoma is typically a well-circumscribed, iso- or hypoattenuating mass on unenhanced CT that enhances heterogeneously after contrast administration. On MR, a hamartoma is iso- to slightly hyperintense on T2-weighted images, featuring heterogeneous early enhancement and relatively homogeneous delayed enhancement.
9
Q
Congenital True (Epithelial) Splenic Cyst
What is it? Interesting lab findings?
Compare to pseudocyst
A
- A congenital true cyst is defined as having an epithelial lining. Interestingly, a splenic epithelial cyst may cause elevation of tumor markers including CA19-9, CA125, and CEA, despite its completely benign nature.
- Unlike a post-traumatic pseudocyst, a true cyst may have septations, but mural calcification is uncommon.
10
Q
Post-Traumatic Pseudocyst
What is it?
Compare to true (epithelial) splenic cyst
Imaging?
A
- A post-traumatic pseudocyst is the end result of the evolution of a splenic hematoma.
- Unlike a true epithelial splenic cyst, the periphery of a pseudocyst is not cellular but made of fibrotic tissue.
- On imaging, a post-traumatic pseudocyst appears as a well-circumscribed, fluid density lesion, with no peripheral enhancement.
- In contrast to a true cyst, septations are uncommon but there may be mural calcification.
11
Q
Intrasplenic Pancreatic Pseudocyst
When do you see this?
More similar to a true epithelial splenic cyst or post-traumatic pseudocyst?
Rare reported complication?
A
- A post-pancreatitis pseudocyst involving the tail of the pancreas may extend into the spleen. There is almost always a history of pancreatitis.
- Unlike a true congenital cyst, an epithelial lining is lacking and histology more closely resembles a post-traumatic pseudocyst.
- Splenic rupture has been reported in some cases of intrasplenic post-pancreatitis pseudocysts.
12
Q
Splenic Lymphangioma
What is it?
Classic appearance?
A
- Splenic lymphangioma is a rare, benign neoplasm usually diagnosed in childhood, which may be solitary or multiple.
- Lymphangioma features a classic imaging appearance of a multilocular cystic structure with thin septations. Post-contrast images may show septal enhancement.
13
Q
Sarcoidosis involving the spleen
Most common presentation and often association?
Other possible (less common) appearance?
This appearance is generally indistinguishable from what other entity?
A
- Sarcoidosis is a systemic disease of unknown etiology characterized histologically by multiple nodules composed of noncaseating granulomas.
- When sarcoidosis involves the spleen, splenomegaly is the most common presentation, often associated with hepatomegaly and lymphadenopathy.
- Less commonly, sarcoidosis may involve the spleen in a multinodular pattern with numerous hypoattenuating 1-3 cm lesions demonstrating essentially no enhancement.
- These nodules are formed by coalescent sarcoid granulomas and have low signal on all MRI sequences.
- Sarcoid nodules are most conspicuous on T2-weighted images and early-phase post-contrast T1-weighted images. On the post-contrast images, the non-enhancing nodules will stand out against the avidly enhancing splenic parenchyma.
- Imaging appearance is generally indistinguishable from splenic lymphoma.
14
Q
Splenic Inflammatory Pseudotumor
What is it?
Presentation?
Typical imaging appearance?
A
- Splenic inflammatory pseudotumor is a rare focal collection of immune cells and associated inflammatory exudate, of unclear etiology.
- Patients often have constitutional symptoms including fever and malaise.
- Inflammatory pseudotumor has a variable and nonspecific imaging appearance, but a typical presentation is of a well-circumscribed, heterogeneously enhancing mass.
15
Q
Splenic Pyogenic Abscess
Most commonly seen in what population?
A solitary abscess is more likely caused by what vs multifocal abscesses?
Characteristic US finding?
Treatment?
A
- Splenic bacterial abscesses are uncommon and usually seen in immunocompromised patients. A solitary abscess is much more likely to be bacterial. In contrast, multifocal small abscesses are more likely to be fungal.
- On CT, a bacterial abscess usually has an irregular, enhancing wall. Gas is not usually seen, but is highly specific for a bacterial abscess when present.
- A characteristic ultrasound finding is the wheel within a wheel or bull’s-eye appearance, which describes concentric hyperechoic and hypoechoic rings surrounding the abscess.
- Treatment is CT- or ultrasound-guided percutaneous drainage in addition to antibiotics.
16
Q
Splenic Fungal Abscess
Typical size and distribution?
Seen almost exclusively in what population?
Most common causes?
P. jiroveci in spleen has what classic appearance?
A
- Splenic fungal abscesses are typically multiple and small, usually 1 cm in size. Almost all patients with splenic fungal abscesses are immunocompromised.
- The most common causative agents include Candida, Aspergillus, and Cryptococcus, which all appear as multiple tiny hypoattenuating foci on CT.
- Splenic Pneumocystis jiroveci (formerly known as pneumocystis carinii) infection is rare, almost always seen in advanced AIDS, and has a classic appearance of multiple calcified splenic lesions.
17
Q
Splenic Echinococcal Cyst
How often do you get these?
Characteristic imaging finding?
A
- Splenic involvement of Echinococcus granulosus infection is unusual, seen in only 1 to 3% of echinococcal infections, and is almost always associated with infection of other organs as well.
- An echinococcal cyst is a true cyst with a cellular lining. As with echinococcal abscess elsewhere, characteristic imaging findings are a cystic lesion with internal undulating membrane and daughter cysts.
18
Q
Splenic Lymphoma
What is it?
Prevalence vs other lymphomas?
Contrast to splenic hamartoma or metastatic dz
What are the imaging presenations?
Most sensitive imaging modality?
A
- Splenic lymphoma is the most common splenic malignancy.
- Primary splenic lymphoma is rare, accounting for less than 1% of all cases of lymphoma, and usually presents as a solitary hypovascular mass. In contrast to splenic hamartoma or metastatic disease, primary splenic lymphoma may extend beyond the splenic capsule and involve adjacent organs.
- Secondary splenic involvement of systemic lymphoma is much more common. Four imaging presentations have been described, depending on the size of the lymphomatous masses:
- Miliary masses, in which discrete tiny masses may be difficult to see.
- Multiple small to moderate sized masses.
- One large mass.
- Splenomegaly without discrete mass.
- Conspicuity is highest on post-contrast T1-weighted images, where the involved portion of the spleen tends to be hypoenhancing.
- On ultrasound, lymphoma may appear cystic but color Doppler shows internal flow.
19
Q
Splenic Metastasis
Morphology and distribution?
Prevalence in cancer patients?
Theories for the rate of splenic mets?
Most common primary tumors to met to spleen are? Which ones typically cause cystic mets?
Calcifications are rare unless the primary is?
A
- Splenic metastases may be solitary or multiple, cystic or solid. However, metastases to the spleen are rare, occurring in 2-9% of cancer patients. Most patients with splenic metastases already have known widespread disease.
- Isolated splenic metastases are seen in only 5% of patients with metastatic involvement of the spleen.
- Several theories for the low rate of splenic metastases have been proposed, which is thought to be due to the antineoplastic properties of lymphoid-rich splenic tissue and lack of afferent lymphatics to bring tumor cells into the spleen.
- The most common primary tumors known to metastasize to the spleen include breast, lung, ovarian, and melanoma. Ovarian cancer and melanoma typically cause cystic metastasis.
- Calcification is rare unless the primary is a mucinous adenocarcinoma.
20
Q
Splenic Angiosarcoma
What is it?
Associations?
Presentation?
Imaging?
A
- Angiosarcoma is a rare, extremely aggressive malignancy, with 20% 6-month survival.
- Unlike hepatic angiosarcoma, the association with Thorotrast, vinyl chloride, and arsenic has not been well established.
- Angiosarcoma usually presents as enlarged, heterogeneous mass that may completely replace the normal spleen. Enhancement is variable and heterogeneous.
21
Q
Splenic Infarcts
Cause in older patients vs younger patients?
Classical manifestation?
MR appearance?
Lack of enhancement of entire spleen should raise concern for what?
A
- Splenic infarcts are most commonly due to emboli (in older patients) and thrombosis (in younger patients with hematologic disease).
- Splenic infarct classically manifests as a wedge-shaped peripheral region of nonenhancement, but a more heterogeneous, mass-like appearance can also be seen.
- On MR, the affected regions may be T1 hyperintense if acute and hemorrhagic, while chronic infarcts are T1 hypointense and T2 hyperintense.
- Lack of enhancement of the entire spleen should raise the concern for complete infarction, possibly due to a wandering spleen with torsion.
22
Q
Gamna-Gandy Bodies
What are they?
What other signs would be present?
Imaging appearance?
A
- Gamna-gandy bodies are multiple tiny foci of hemosiderin deposition resulting from portal hypertension
- Usually, other signs of portal hypertension and cirrhosis are apparent on imaging, such as splenomegaly, varices, recanalized umbilical vein, ascites, and nodular liver contour.
- The hemosiderin deposits demonstrate low signal on all sequences. On in- and out of- phase gradient-echo sequences, the longer TE of the in-phase images demonstrate blooming (relatively decreased signal on in-phase images), due to longer dephasing time and exaggeration of T2* effect.
23
Q
Gaucher Disease
What is it? What does it lead to?
Splenic manifestations?
Associated findings?
A
- Gaucher disease is an autosomal recessive deficiency of glucocerebrosidase, leading to accumulation of glucocerebrosides in the reticuloendothelial system.
- Splenic manifestations of Gaucher disease include splenomegaly (almost always) and multiple splenic nodules seen in one-third of Gaucher patients).
- Associated bony findings seen in Gaucher disease include the characteristic Erlenmeyer flask deformity of the distal femurs, femoral head avascular necrosis, and H-shaped vertebral bodies from endplate avascular necrosis.
24
Q
Overview of Splenic Trauma
Should we do a splenectomy?
What imaging phase needs to be used?
What is a splenic hematoma and where is it most commonly?
Splenic lacs can only be seen on what kind of study? what does it look like/
Active extravasation due to vessel injury appears as what?
Contrast this to pseudoaneurysm and an AVF.
A
- The spleen is the most commonly injured abdominal organ from blunt trauma.
- Splenectomy dramatically increases the risk of subsequent sepsis, which has driven the trend towards splenic preservation and conservative management of splenic trauma.
- The spleen must be evaluated for injury in the portal venous phase, as the physiologic heterogeneous enhancement in the arterial phase can both mask and mimic injury.
- A splenic hematoma is a focal collection of blood (hypoattenuating relative to enhanced spleen and hyperattenuating relative to unenhanced spleen), most commonly subcapsular. Less commonly, a hematoma may be intraparenchymal, where it may assume an irregular shape.
- A splenic laceration can only be well seen on a contrast-enhanced study, where it appears as a linear or branching area of decreased attenuation.
- Active contrast extravasation due to vessel injury appears as an area of increased attenuation (initially iso-enhancing to the arterial blood pool), which further increases in size on delayed scanning due to ongoing bleeding.
- In contrast to active extravasation, pseudoaneurysm and arteriovenous fistula are contained vascular injuries that also initially appear as a well-circumscribed area of increased attenuation but do not increase on delayed scanning.
25
What is a pseudoaneurysm?
What is a traumatic AVF?
How do you differentiate the two?
* A pseudoaneurysm is caused by injury to the intima and media of the arterial wall and is essentially a rupture contained only by the adventitia. There is a high chance of rupture without treatment.
* A traumatic arteriovenous fistula is indistinguishable from pseudoaneurysm by CT and is due to injury of an artery and the adjacent vein. **Splenic arteriography** is the only way to differentiate pseudoaneurysm from arteriovenous fistula.
26
Splenic Trauma Grading
What are the grading systems?
Which one is used?
* American Association for the Surgery of Trauma (AAST) grading scale
* The American Association for the Surgery of Trauma AAST splenic injury grading scale is based on the extent of injury seen at laparotomy and is therefore limited in practicality as many splenic injuries are now managed conservatively.
* An additional limitation of the AAST grading scale is the exclusion of vascular injury.
* MDCT-based splenic injury grading system.
* The most widely used CT grading system is the MDCT-based splenic injury grading system, which is similar to the AAST grading scale but incorporates vascular injury.
