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.


REFERENCES
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.

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

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

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. 


REFERENCES
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.

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

REFERENCES 
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.

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. 

REFERENCES

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.

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

REFERENCES

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.

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.


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