AJR 2005; 185:697-699
© American Roentgen Ray Society
Pseudotumoral Renal Sarcoid: MRI, PET, and MDCT Appearance with Pathologic Correlation
Maureen Heldmann1,
William Behm1,
Madhusudhan P. Reddy1,
Caleb Bozeman2,
Greg Welman3,
Fleurette Abreo3 and
Alireza Minagar4
1 Department of Radiology, Louisiana State University Health Sciences Center,
1501 Kings Hwy., Shreveport, LA 71130.
2 Department of Urology, Louisiana State University Health Sciences Center,
Shreveport, LA 71130.
3 Department of Pathology, Louisiana State University Health Sciences Center,
Shreveport, LA 71130.
4 Department of Neurology, Louisiana State University Health Sciences Center,
Shreveport, LA 71130.
Received June 10, 2004;
accepted after revision September 30, 2004.
Address correspondence to M. Heldmann.
Introduction
Sarcoidosis is a systemic disease of unknown cause that rarely
involves the urinary system in macroscopic form. Granulomatous renal masses
(so-called pseudotumoral or psuedotumorous renal sarcoidosis) have been
described on sonography and CT, but the MRI and PET appearances of this
unusual event have not previously been reported, to our knowledge. We present
a man with renal sarcoidosis in the context of multisystem involvement and
describe the lesion characteristics on multiple imaging techniques.
Case Report
A 37-year-old black man was admitted with complaints of progressive lower
extremity weakness and gait ataxia of 2 years' duration, and more recent
episodes of bowel and bladder incontinence. There was no history of primary
malignancy, recent travel, or sickle cell trait, and no clinical evidence of
infection. MRI of the brain and lumbar spine revealed only L4-L5 disk
herniation, but no brain or cord lesion. Further imaging with CT revealed
mediastinal, pulmonary hilar, and periaortic lymph node enlargement in
addition to splenic and left renal lesions. Serum calcium and
angiotensin-converting enzyme levels were normal. Tests for HIV and purified
protein derivative were negative, and rapid plasmin reagin and the Venereal
Disease Research Laboratory test for syphilis were nonreactive. The
possibility of sarcoidosis was considered, and the patient underwent
bronchoscopy and transbronchial biopsy with no definitive diagnosis. The left
renal mass was subsequently biopsied under sonographic guidance, and
histopathologic examination revealed granulomatous inflammation with no
necrosis (Fig. 1A), and
negative stains for fungus and acid-fast bacilli. Renal MRI and whole body PET
(Fig. 1B) were performed.
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Fig. 1A —37-year-old black man with pseudotumoral renal sarcoid.
Specimen from core biopsy of renal mass shows noncaseating granulomata
characterized by aggregates of epithelioid macrophages. (H and E, original
magnification x100)
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The clinical context of a black man with progressive neurologic symptoms,
lymphadenopathy in mediastinal and hilar positions, and noncaseating
granulomas on renal biopsy with no detectable causative organism led to a
working diagnosis of sarcoidosis. The patient was treated with IV
methylprednisolone, 1 g daily for 5 days, with rapid improvement of his
neurologic and general health.
Abdominal CT with oral and IV contrast material
(Fig. 1C) showed a solid, 4
x 6 cm left posterior interpolar renal mass that was isodense to renal
tissue on unenhanced images (not shown), with little enhancement after the
injection of contrast material. No areas of calcification were identified in
the mass. Enlarged periaortic lymph nodes were present, as was mediastinal and
hilar lymphadenopathy. Sonography of the affected organ revealed mild
expansion of the left upper and mid pole parenchyma by a mildly heterogeneous,
minimally hypoechoic mass (not shown).
MR images (Figs. 1D, and
1E) showed an ovoid, poorly
circumscribed infiltrative mass in the left dorsal interpolar location with
extension to the left upper pole, that was slightly hypointense to surrounding
renal cortex, isointense to spleen, and hyperintense to renal medulla on
unenhanced T1-weighted imaging (not shown). T2-weighted images
(Fig. 1E) showed a subtle,
minimally heterogeneous area of abnormality that was predominantly isointense
to renal cortex. After injection of gadolinium, irregular enhancement was seen
to a lesser degree than in normal kidney that was most apparent centrally
(Fig. 1D). The zone of
transition between the mass and normal renal parenchyma was ill defined,
consistent with interstitial infiltration.
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Fig. 1D —37-year-old black man with pseudotumoral renal sarcoid. Fast
spoiled gradient echo T1-weighted MR image (TR/TE, 150/1.3; slice thickness, 7
mm) (D) and fast spin-echo T2-weighted image (2,500/96; 7-mm slice
thickness) (E) 90 sec after administration of contrast material show
pseudotumoral infiltration of left kidney as heterogeneity and regional
expansion that are best perceived after administration of gadolinium.
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Fig. 1E —37-year-old black man with pseudotumoral renal sarcoid. Fast
spoiled gradient echo T1-weighted MR image (TR/TE, 150/1.3; slice thickness, 7
mm) (D) and fast spin-echo T2-weighted image (2,500/96; 7-mm slice
thickness) (E) 90 sec after administration of contrast material show
pseudotumoral infiltration of left kidney as heterogeneity and regional
expansion that are best perceived after administration of gadolinium.
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Attenuation-corrected whole-body PET was performed using 15.6 mCi (577.2
MBq) of 18F-FDG (Fig.
1B). Intense radiotracer uptake (standardized uptake value, 9.3)
was present in the superomedial and posterior aspects of the left kidney. Mild
bilateral hilar, mediastinal, right lower paratracheal, and bilateral inguinal
lymph node activity was seen. Increased radiotracer uptake in the muscles of
the upper extremities was thought to be the result of the use of crutches.
Two months after therapy, the patient was walking without assistance, and
bowel and bladder dysfunction had improved. Repeat CT
(Fig. 1F) confirmed regression,
with a parenchymal scar and a small residual hypoattenuating lesion.
Discussion
Boeck's sarcoid, or sarcoidosis, is a noncaseating granulomatous disease of
unknown cause that is more common in temperate climates and in the black
population. The pathogenesis of sarcoidosis remains unclear; both
environmental and genetic factors are probable
[1]. Clinical manifestations of
the disease are broad, from asymptomatic single-organ involvement to
multisystem disease refractory to immunosuppression. Gallium-67 imaging and
elevated levels of angiotensin-converting enzyme are of little diagnostic
value because of the lack of specificity; and there are no definitive blood,
tissue, or skin tests for sarcoidosis. Noncaseating granulomas, albeit the
sine qua non of sarcoidosis, are also seen with infectious agents such as
mycobacteria, parasites, and fungi; in neoplasia and autoimmune diseases; and
after occupational or environmental exposure to organic and inorganic agents
[1]. The diagnosis is one of
exclusion and is based on combined clinical, radiologic, and histologic
features [1].
The respiratory system is the most commonly affected site, with lung and
nodal involvement, but the disease may be asymptomatic and may regress
spontaneously. Extrapulmonary involvement is not unusual and most often occurs
in the skin and eye. The heart and musculoskeletal system are the next most
afflicted; clinically evident involvement by sarcoidosis of the
gastrointestinal tract, pancreas, and kidney is uncommon. Neurologic and other
extrapulmonary involvement is in general aggressively treated, with therapy
centering on glucocorticoids
[1].
Musculoskeletal involvement varies, with cystic lesions described in bone
and granulomatous inflammation within muscle. Renal sarcoidosis is most
commonly microscopic and may manifest as nephrolithiasis, glomerulonephritis,
a tubular concentrating defect, or acute renal failure. Abnormal calcium
metabolism may produce hypercalciuria, with or without hypercalcemia, which is
thought to be caused by an altered vitamin D metabolism
[1]. Macroscopic renal masses,
the so-called pseudotumoral sarcoid granulomatosis, are rare events described
in scattered reports in the worldwide literature
[2-5].
The appearance of lesions on imaging is nonspecific, with both hyper- and
hypoechoic masses reported, enhancing and non-enhancing lesions described, and
exophytic and nondeforming masses recorded on sonography and CT, respectively.
Our imaging findings were those of an infiltrative renal mass, slightly
hypoechoic on sonography, poorly enhancing on CT, and heterogenous but only
minimally hyperintense on T2-weighted MR images.
Jung et al. [6] recently
reported the MRI appearance of unusually large, confluent hepatic lesions in
sarcoidosis as homogeneous and slightly hyperintense to liver on T2-weighted
images, with undisturbed vascular architecture a noteworthy feature. In that
example, at least some of the coalescent lesions were demarcated, and it may
be that the tubular structure of the kidney and the highly cellular nature of
the noncaseating granulomas account for the poor visibility of the mass on
T2-weighted imaging. Conspicuity may be best with CT; and disruption of normal
renal parenchymal enhancement, rather than echogenicity or signal abnormality,
may offer the best sensitivity for anatomic imaging.
A high standardized uptake value on PET could be misconstrued as indicative
of malignancy, but increased FDG uptake has been described in sarcoidosis; and
clinical factors, patterns of FDG uptake, and newer PET radiotracers such as
fluoro-
-methyltyrosine, may aid in distinguishing this benign disease
from malignant tumor [7].
The differential diagnosis of infiltrative renal masses in the adult is
broad, including collecting duct carcinoma, medullary carcinoma, local
invasion of urothelial carcinoma, metastasis, lymphoproliferative disease, and
inflammatory processes. Sarcoidosis should be considered in the differential
diagnosis of infiltrative renal masses, and the imaging sensitivity for
pseudotumoral renal involvement by sarcoidosis may be best with CT and PET.
Specific tissue diagnosis is often not possible with imaging alone, and biopsy
may be necessary, as in our patient. PET may offer greater specificity in the
future.
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Introduction
Case Report
