Case Author(s): Scott Winner, M.D. and Farrokh Dehdashti, M.D. , 9/27/96 . Rating: #D3, #Q3

Diagnosis: Small systemic right to left shunt

Brief history:

46-year old woman with Weber-Christian disease.

Images:

Anterior and posterior whole body images

View main image(pe) in a separate image viewer

View second image(pe). Anterior and posterior perfusion images

Full history/Diagnosis is available below

Diagnosis: Small systemic right to left shunt

Full history:

46-year old woman with chronic pulmonary disease, a history of pulmonary embolism (April, 1996) and Weber- Christian disease.

Radiopharmaceutical:

11.0 mCi Xe-133 gas by inhalation and 4.3 mCi Tc-99m MAA i.v.

Findings:

The comparison chest radiograph demonstrates a pacemaker projecting over the right hemithorax with elevation of the right hemidiaphragm. Xe-133 ventilation images demonstrate normal ventilation with the exception of a defect in the left lung base on the first breath image. On the washout images, there is retention of Xe-133 in this area. The perfusion images are normal; however, a defect related to the pacemaker is seen projecting on the anterior right lung. In addition to standard ventilation-perfusion images, whole-body anterior and posterior views were obtained, which showed extrapulmonary activity due to the patient1s known right-to-left shunt. Quantitative analysis revealed an approximately 9% systemic right-to-left shunt.

Discussion:

Weber-Christian disease is a chronic disorder characterized by relapsing febrile episodes and systemic nodular panniculitis (nodular relapsing fat necrosis). Recurrent crops of tender erythematous nodules may be accompanied by abdominal pain and fat necrosis in bone marrow, lungs, and other organs. A variety of distinctive disease entities, such as systemic lupus erythematosus (SLE), pancreatic disease, alpha-1-antitrypsin disease, lymphoproliferative neoplasia, infections, or trauma are associated with chronic panniculitis. The cause of this disease is due to the effect of pancreatic enzymes released into the circulation on fatty tissues. The accurate diagnosis of panniculitis requires an adequate deep skin biopsy showing inflammation of the subcutaneous layers. The febrile episodes and skin lesions responded dramatically with the use of oral corticosteroids.

There are two approaches for the quantfication of right-to-left shunt. One is the angiographic technique using Technetium-99m (Tc-99m) as pertechnetate or other forms. However, this technique is too cumbersome. Second is the technique using Tc-99m macroaggregated albumin (MAA). Whole body images will be performed and the activity in the whole body will be measured and compared with that in the lungs. In this patient with a known right to left shunt, scintigraphy with Tc-99m MAA was used to quantify the shunt. Normally, pulmonary capillaries should trap nearly all of the Tc-99m MAA on the first pass through the lungs. However, there is normally a small amount (approximately 4%) of intravenously injected particles that can cross over to the systemic circulation (physiologic shunting) but is not visible on routine images. Note that if the radiopharmaceutical is not freshly prepared, or if there is a delay after injection prior to imaging, the fraction of extrapulmonary activitiy in normal patients can be higher due to breakdown of the Tc-99m MAA. In this patient with Weber-Christian disease, the calculated value of 9% likely represents a small right to left shunt. The percent shunt is calculated as follows:

(Total body counts - pulmonary counts)/Total body counts x100

ACR Codes and Keywords:

References and General Discussion of Perfusion (only) Scintigraphy (Anatomic field:Heart and Great Vessels, Category:Normal, Technique, Congenital Anomaly)

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Case number: pe004

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