Wednesday, October 31, 2012

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.

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.

Tuesday, October 30, 2012

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.

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.

Monday, October 29, 2012

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.

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.

Friday, October 26, 2012

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

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.

Thursday, October 25, 2012

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.

Wednesday, October 24, 2012

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

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.

Tuesday, October 23, 2012

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.

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. 

Monday, October 22, 2012

Intramedullary Marrow Hyperplasia in Sickle Cell Anemia

Red marrow is present in the fetal skeleton and converts to yellow marrow after birth. In sickle cell anemia (SCA) destruction of RBCs causes anemia which prevents the conversion of red marrow to yellow marrow. The persistent red marrow is seen in all bones of patients with SCA and has pathologic and radiologic consequences. Red marrow stimulation leads to widening of the medullary spaces and cortical thinning which can cause pathologic fractures. Coarse trabeculation and osteopenia may also be seen. Persistent red marrow presents as low signal intensity in osseous structures on T1WI. On skull radiographs the widening of the diploic spaces is a manifestation of bone marrow expansion. The hair on end appearance of the skull is secondary to coarse trabeculation from new bone formation. In the spine, cortical thinning results in biconcave deformities of the vertebral bodies sometimes referred to as the fish-mouth appearance.

Ejindu VC, Hine AL, Mashayekhi M, et al. Musculoskeletal manifestations of sickle cell disease. Radiographics 2007;27:1005-21.

Friday, October 19, 2012

Secretory Calcifications

Calcifications frequently appear on mammograms and need to be classified as benign or malignant. One  benign pattern is that of secretory calcifications. These calcifications (red arrows above) are smooth, linear or rounded, and radiate towards the nipple (long axis pointed towards the nipple). A branching pattern may be seen. The calcifications may have a radiolucent center indicating the noncalcified ductal lumen. Secretory calcifications are often bilateral and symmetric in distribution. 

The blue arrows show a region of smaller, clustered calcifications which were found to be malignant.

Sickles EA. Breast calcifications: mammographic evaluation. Radiology 1986;160;289-93.

Thursday, October 18, 2012

Fibrosing Mediastinitis

Fibrosing mediastinitis (FM) is due to abnormal proliferation of collagen and fibrous tissue in the mediastinum. It can present either focally or diffusely with the latter type involving multiple mediastinal compartments. Causes are either idiopathic or secondary to granulomatous infection (Histoplasmosis in the United States). 

FM is the most common benign cause of SVC obstruction. Imaging findings include a hilar or mediastinal mass causing mediastinal widening. The right paratracheal region is the most common location for occurrence of a mass. Focal FM tends to have calcified masses whereas calcification is less common in diffuse FM. 

Differential considerations include:
  • lymphoma
  • bronchogenic carcinoma - usually older patient, doesn't calcify

Rossi SE, McAdams HP, Rosado-de-Christenson ML, et al. Fibrosing mediastinitis. Radiographics 2001;21:737-57.

Wednesday, October 17, 2012

Dyke Davidoff Masson Syndrome

Dyke Davidoff Masson Syndrome (DDMS) is a neurodegenerative disorder likely due to cerebral injury in utero or early in life. The main finding is cerebral hemiatrophy. Associated findings include ipsilateral compensatory calvarial thickening, enlarged frontal sinus, elevation of the petrous ridge and sphenoid wing.

The above images are from a young boy who presented with a history of seizures. There is asymmetric atrophy of the left cerebral hemisphere. Bone window examination demonstrates enlargement of the left frontal sinus.

Grossman RI, Yousem DM. Neuroradiology, the requisites. Mosby Inc. (2003)

Tuesday, October 16, 2012

Congenital Midline Nasofrontal Masses

Midline nasofrontal masses are due to faulty regression of the midface dural diverticulum during embryologic development. The differential diagnosis includes:

  • Epidermoid and dermoid cysts
    • dermoid  
      • ectoderm + skin appendages
      • usually midline and tend to occur at the glabella
    • epidermoid
      • ectoderm without skin appendages
      • usually paramidine
  • Nasal gliomas
    • not a neoplasm
    • cerebral heterotopia
    • can be intranasal (lateral nasal wall, middle turbinate, nasal septum) or extranasal (usually at glabella, +/- overlying skin telangectasia)
    • T1WI - isointense/hypointense to gray matter
    • T2WI - hyperintense to gray matter
  • Encephaloceles
    • herniation of intracranial content through a skull defect with a persistent connection to the subarachnoid space
    • high prevalence of associated intracranial abnormalities
      • intracranial cysts, callosal agenesis, interhemispheric lipomas, facial clefts, schizencephaly
    • usually isointense to gray matter on all MR sequences 
      • may be hyperintense on T2WI due to gliosis

Lowe LH, Booth TN, Joglar JM, et al. Midface anomalies in children. Radiographics 2000;20:907-22.

Monday, October 15, 2012

Gallstone Ileus

The above clip demonstrates multiple calculi and air within the gall bladder, dilatation of distal loops of small bowel with relative collapse of the large bowel, and a large gallstone in the distal ileum. Tracing the distal common bile duct reveals a biliary-enteric fistula.

Friday, October 12, 2012

Trapped Periosteum in Physeal Injuries

Physeal injuries are common in the pediatric population and are usually classified by the Salter Harris system. One of the complications of physeal fractures is trapped periosteum. This can render a fracture as irreducible which may result in premature physeal closure. Trapped periosteum is important to recognize on imaging because it requires open reduction to prevent growth disturbances. 

On radiographs and CT with mulitplanar reconstruction, peristent physeal widening > 3mm after closed reduction is suggestive of trapped periosteum. The MRI findings of trapped periosteum have not been adequately described in the literature. A few reports seem to concur that on proton density weighted fat-suppressed images trapped periosteum appears as a low signal band insinuating at the physis. 

Barmada A, Gaynor T, Mubarak SJ. Premature physeal closure following distal tibia physeal fractures: a new radiographic predictor. J Pediatr Orthop 2003;23:733-9.
Whan A, Breidahl W, Janes G. MRI of trapped periosteum in a proximal tibial physeal injury of a pediatric patient. AJR Am J Roentgenol 2003;181:1397-9.

Thursday, October 11, 2012

Subtalar Dislocation

The above images demonstrate a medial subtalar dislocation (the foot and calcaneus are medially displaced). The mechanism of this injury is usually due to a fall from a height or a severe twisting injury as in the basketball player above who landed on an inverted foot.

Prompt reduction of this injury is necessary because associated damage to the tibial nerve, and posterior tibial artery and veins may be present and long term sequelae of neurovascular injury should be avoided.

Lawrence SJ and Singhal M. Open hindfoot injuries. J Am Acad Orthop Surg 2007;15(6):367-76.

Wednesday, October 10, 2012

Sclerotherapy for Treatment of Anuerysmal Bone Cysts

Aneurysmal bone cysts (ABCs) are benign expansile lytic bone lesions of unknown origin that occur in the pediatric population. Characteristics of ABCs were previously discussed here.

Typically, the treatment of ABCs involves resection and curettage with or without bone grafting. However, there is a high recurrence rate reported with this treatment method with some studies reporting up to a recurrence rate of greater than 50%.

Surgical resection of ABCs is less favored as an extensive resection may be necessary and may immobilize the patient for a prolonged period. Furthermore, as ABCs are highly vascular lesions, surgical procedures carry the risk of significant blood loss.

Radiotherapy was previously used to treat ABCs but has since been abandoned due to studies demonstrating malignant transformation of the lesions and development of secondary tumors.

The traditional interventional radiology technique of embolization has been used effectively in the treatment of some ABCs. Preoperative selective embolization of the feeding vessel is used to reduce intraoperative blood loss as well as to treat lesions that are surgically inaccessible. Challenges of this therapy include risk of particle embolization to the vertebrobasilar and spinal arterial systems resulting in ischemia to vital structures. Additionally, not all ABCs have a feeding vessel that can be selectively embolized. 

More recently, studies have shown intralesional sclerotherapy to be an effective treatment for ABCs. Sclerosing agents act by damaging the endothelial lining which leads to activation of the coagulation cascade and thrombotic vascular occlusion. Agents that have been used for sclerotherapy include ethanol based solutions, methylprednisone, calcitonin, and doxycycline. Patients usually require several injections of the agent. Post procedure imaging typically shows sclerosis of the lesion with long term complete ossification. Patients have reported a relief of symptoms and low recurrence rates have been reported. This data suggests that image guided sclerotherapy of ABCs may be a safe, minimally invasive method of treating these lesions. 

Rai AT and Collins JJ. Percutaneous treatment of pediatric aneurysmal bone cyst at C1: a minimally invasive alternative: a case report. AJNR Am J Neuroradiol 2005;26:30-3.
Rastogi S, Varshney MK, Trikha V, et al. Treatment of aneurysmal bone cysts with percutaneous sclerotherapy using polidocanol. J Bone Joint Surg [Br] 2006;88-B:1212-6.

Tuesday, October 9, 2012

Epiploic Appendagitis

Epiploic appendages are peritoneal outpouchings attached to the serosal surface of the colon that contain fat and blood vessels. They occur anywhere from the cecum to the sigmoid, are largest in the sigmoid, and are generally only visible when they are inflamed (i.e. if surrounded by ascites). Torsion of an epiploic appendage or thrombosis of its central vein causes epiploic appendagitis. 

Patients typically present with acute abdominal pain, usually in the left lower quadrant which often leads to its being mistaken for acute diverticulitis (it may be mistaken for acute appendicitis if a cecal epiploic appendage is involved).

CECT will demonstrate an ovoid, fat containing mass adjacent to the anterior colonic wall. Surrounding inflammatory changes are typically seen. A hyperattenuating ring around the mass may be seen. The central dot sign - presence of central high attenuation representing the thrombosed vein - is seen in a minority of cases. Reactive thickening of the adjacent colon may be seen.

The above images are from a patient who presented to the emergency room and was worked up for acute diverticulitis. No colonic diverticula were seen. Instead, in the left lower quadrant there is an ovoid, fat containing mass with inflammatory changes and the central dot sign (arrow). The findings are compatible with epiploic appendagitis.

Rao PM and Novelline RA. Primary epiploic appendagitis. Radiology 1999;210:145-8.
Singh AK, Gervais DA, Hahn PF, et al. Acute epiploic eppendagitis. Radiographics 2005;25:1521-34.

Monday, October 8, 2012

Phantom Calyx

A phantom renal calyx refers to a calyx that does not opacify after administration of contrast due to obstruction or stricture at the infundibulum. The differential diagnosis for this finding includes:
  • neoplasm - most likely transitional cell carcinoma
  • infection - tuberculosis, acute pyelonephritis
  • stricture - due to trauma or passage of stone
  • renal contusion
  • ischemia/renal infarct
  • congenital anomaly

Dyer RB, Chen MY, Zagoria RJ. Classic signs in uroradiology. Radiographics 2004;24:S247-80.

Friday, October 5, 2012

Traumatic Aortic Transection

The above images are from a patient who suffered a motor vehicle accident. The axial image demonstrates a mediastinal hematoma and an intimal flap in both the ascending and descending aorta. The sagittal image better demonstrates the continuity of the intimal flap along with aortic contour abnormality. These findings are pathognomonic for acute traumatic aortic injury.

A finding that is not demonstrated on these images is active extravasation of intravenous contrast material. Its presence would be concerning for exsanguination. 

Kuhlman JE, Pozniak MA, Collins JC, et al. Radiographic and CT findings of blunt chest trauma: aortic injuries and looking beyond them. Radiographics 1998;18:1085-1106.
Steenburg SD, Ravenel JG, Ikonomidis JS, et al. Acute traumatic aortic injury: imaging evaluation and management. Radiology 2008;248:748-62.

Thursday, October 4, 2012

Cervical Spine Change in Rheumatoid Arthritis

60-80% of patients with rheumatoid arthritis have cervical spine involvement. Manifestations include:
  • atlantoaxial subluxation - do flexion/extension films, increased atlantodens interval
    • multilevel, "stepladder" subluxations may be seen
  • erosion of the dens
    • calcified pannus around the dens is NOT rheumatoid arthritis - usually CPPD
  • cranial settling - decreased distance from occiput to C2
    • due to facet joint erosions
  • spinous process erosions
  • erosions at the foramen of Luschka

Sommer OJ, Kladosek A, Weiler V, et al. Rheumatoid arthritis: a practical guide to state-of-the-art imaging, image interpretation, and clinical implications. Radiographics 2005;25:381-98.

Wednesday, October 3, 2012

Dural Sinus Thrombosis

Dural sinus thrombosis (DST) is a venous occlusion likely secondary to increased intracerebral venous pressure. The classic sign on NCECT is hyperdense thrombus in the occluded sinus. CECT may demonstrate the empty delta sign: a filling defect that represents the thrombus surrounding by dural enhancement and collateral venous circulation. The MRI findings in DST are discussed here.

The first two images above demonstrate hyperdensity in superior sagittal sinus and torcular herophili. A left temporal lobe intraparenchymal hemorrhage is also noted. CT venogram (third image) demonstrates abrupt cut off at the level of the mid sagittal sinus that continues posteriorly. 

Leach JL, Fortuna RB, Jones BV, et al. Imaging of cerebral venous thrombosis: current techniques, spectrum of findings, and diagnostic pitfalls. Radiographics 2006;26:S19-41.

Tuesday, October 2, 2012

Sequelae of Tuberculous Pleural Disease

Tuberculosis can have varied presentations in the chest including pleural effusions. Tuberculous pleuritis has a high incidence in immunosuppressed patients, especially those with HIV. Complications of tuberculous pleural disease include:
  • pleural thickening
  • fibrothorax - calcified and thickened pleura, loss of lung volume, adjacent rib hypertrophy, epipleural fat pads, often unilateral
  • chronic persistent pleural effusion - content of the effusion are near soft tissue density
  • empyema necessitans - decompression of an empyema through the chest wall, fistulous tract between a pleural collection and an extrathoracic fluid collection may be seen, other sites of extension include breast, esophagus, pericardium, vertebral column, retroperitoneum, flank, groin
  • bronchopleural fistula - air/fluid collections in the pleural space, pleural thickening, atelectasis and bronchiectasis in ipsilateral lung, fistulous connection may be seen

Heffner JE, Klein JS, Hampson C. Diagnostic utility and clinical application of imaging for pleural space infections. Chest 2010;137(2):467-79.
Jung-Ah C, Hong KT, Oh YW, et al. CT manifestations of late sequelae in patients with tuberculous pleuritis. AJR Am J Roentgenol 2001;176(2)441-5.

Monday, October 1, 2012

Colovesicular Fistula

A middle aged male presented to the emergency room with acute abdominal pain. CECT revealed sigmoid diverticulitis. A focus of air was also seen within the bladder. 3D reformatted images demonstrated a fistulous connection between the sigmoid colon and bladder (best seen on the second and third images above). The diagnosis of colovesicular fistula was made.

Colovesical fistulas arise most often in the setting of diverticular disease. Findings that suggest fistula formation on CT include intravesical air, bladder wall thickening and perivesicular inflammatory changes. The precise fistulous connection is not always visualized.

In addition to diverticulitis, colovesicular fistulas can occur in the setting of inflammatory bowel disease, gastrointestinal or genitourinary neoplasms, radiation therapy, pelvic surgery, and foreign body impaction.

Yu NC, Raman SS, Patel M, et al. Fistulas of the genitourinary tract: a radiologic review. Radiographics 2004;24:1331-52.