Splenic Sequestration

Splenic sequestration is seen in patients with sickle cell disease. It is due to trapping of red blood cells in the spleen's tortuous microcirculation. During sequestration the spleen is enlarged. On CECT studies (as above), peripheral low attenuation with high attenuation of the hilum is seen. MR imaging may demonstrate patchy areas of abnormal signal intensity on both T1 and T2 weighted images. On T1WI, a hyperintense region with peripheral low intensity will be seen in subacute hemorrhage.


REFERENCES
Lonergan GJ, Cline DB, and Abbondanzo SL. Sickle cell anemia. Radiographics 2001;21:971-94.
Rabushka LS, Kawashima A, and Fishman EK. Imaging of the spleen: CT with supplemental MR examination. Radiographics 1994;14:307-32.

The Hurricane Sign

SPECT studies are often used with myocardial perfusion studies for evaluation of ischemia. Long acquisition times for SPECT images increase susceptibility to artifacts, especially those caused by patient motion. The hurricane sign refers to an artifact caused by lateral patient motion during image acquisition. On the short axis views a circular object with spirals extending from the 12:00 and 6:00 positions causing discontinuity in the ventricular walls is seen. This pattern does not correspond with normal coronary artery anatomy.


REFERENCES
Burrell S and MacDonald A. Artifacts and pitfalls in myocardial perfusion imaging. J Nucl Med Technol 2006;34:193-211.
Sorrell V, Figueroa B, Hansen CL. The "hurricane sign": evidence of patient motion artifact on cardiac single photon emission computed tomographic imaging. J Nucl Cardiol 1996;3:86-8.

Emphysematous Pyelonephritis

Emphysematous pyelonephritis (EP) is a life threatening condition with a high overall mortality rate. About 90% of patients presenting with EP have uncontrolled diabetes mellitus. Urinary collecting system obstruction may also be present. E coli is the most common infecting organism. 

Typical US findings are shown above: the renal parenchyma appears echogenic with "dirty" shadowing. CT can confirm the presence of gas.

There is classification of EP into two types based on its CT appearance. Type 1 is characterized by diffuse replacement of the renal parenchyma with gas, without presence of discrete fluid collections. Type 2 EP demonstrates scattered foci of gas with associated regions of fluid attenuation. Type 1 EP carries a worse prognosis and is a surgical emergency.


REFERENCES
Craig WD, Wagner BJ, and Travis MD. Pyelonephritis: radiologic-pathologic review. Radiographics 2008;28:255-76.
Grayson DE, Abbott RM, Levy AD, et al. Emphysematous infections of the abdomen and pelvis: a pictorial review. Radiographics 2002;22:543-61.

Benign Neoplasms of the Spleen

1. Splenic cysts
• true cyst - has endothelial lining
• epidermoid
• parasitic
• pseudocyst - lacks endothelial  lining 
• post traumatic - most common
• both are well defined masses, attentuation similar to water on CT, do not enhance with contrast administration, high signal on T2WI
2. Hemangioma
• most common benign neoplasm
• US: small cystic masses, may show flow on color Doppler
• CT: hypodense on NCECT, post contrast images show early centripetal nodular enhancement with delayed uniform enhancement
• MR: hypointense on T1WI, hyperintense on T2WI
• diffuse hemangiomatosis
• Klippel-Trenaunay-Weber
• Kasabach-Merritt-like
• Beckwith-Weidemann
3. Hamartoma
• associated with tuberous sclerosis
• heterogeneously hyperintense relative to spleen on T2WI
• diffuse enhancement in early post contrast phase that becomes more uniform on delayed images
4. Lymphangioma
• US: well defined, hypoechoic mass, internal septations, may have echogenic debris
• CT: splenomegaly, single or multiple hypodense masses, may have peripheral calcifications, no enhancement post contrast
• MR: hypointense T1WI, hyperintense T2WI

REFERENCES

Elsayes KM, Narra VR, Mukundan G, et al. MR imaging of the spleen: spectrum of abnormalities. Radiographics 2005;25:967-82.

Urrutia M, Mergo PJ, Ros LH, et al. Cystic masses of the spleen: radiologic-pathologic correlation. Radiographics 1996;16:107-29.

Mesenteric Panniculitis

Mesenteric panniculitis is characterized by increased attenuation of an inflamed mesentery with a thin surrounding pseudocapsule. Note the "halo sign" representing spared fat around the mesenteric vessels.

Littoral Cell Angioma of the Spleen

• rare, primary splenic neoplasm
• littoral cells line the red pulp sinuses in the spleen
• CECT: 
• enlarged spleen with innumerable hypoattenuating masses
• no calcifications
• no lymphadenopathy
• no hepatomegaly
• US:
• diffuse, coarse, heterogenous echotexture of the spleen
• Differential diagnosis
• neoplasms
• hemangiomas - appear similar but rarely have diffuse involvement, may calcify
• hemangiomatosis - diffuse splenic hemangioma with same enhancement pattern as hepatic hemangioma
• lymphoma - look for extra-splenic lymphadenopathy
• metastatic disease - ovary, breast, endometrium, melanoma
• granulomatous disease
• sarcoidosis - increased echogenicity of spleen, + adenopathy
• TB - look for chest involvement
• infection
• disseminated fungal disease
• septic emboli
• Kaposi's sarcoma

REFERENCES
Kinoshita LL, Yee J, and Nash SR. Littoral cell angioma of the spleen: imaging features. AJR Am J Roentgenol 2000;174(2):467-9.
Levy AD, Abbott AM, and Abbondanzo SL. Littoral cell angioma of the spleen: CT features with clinicopathologic comparison. Radiology 2004;230:485-90.

Portal Vein Varix

Varix of the portal vein is a rare congenital anomaly of unknown origin and refers to focal dilatation of the portal vein. It is sometimes improperly referred to as an aneurysm of the portal vein. The varix is usually asymptomatic and tends to be an incidental finding.

The above images are from a patient who presented with right sided flank pain and was presumed to have renal colic. NCECT demonstrates a portal vein varix with luminal high density consistent with thrombosis.


REFERENCES
Lee WK, Chang SD, Duddalwar VA, et al. Imaging assessment of congenital and acquired abnormalities of the portal venous system. Radiographics 2011;31:905-26.