Clinical History
A 69-years-old female patient, with a long history of controlled high blood pressure (lasting at least 15 years), developed severe hypertension and renal failure
Imaging Findings
A 69-years-old female patient, with long history of controlled hypertension (lasting at least 15 years), developed severe hypertension, associated with stage III retinopathy, renal failure and
eccentric left ventricular hypertrophy. Patient underwent a Color-coded Duplex ultrasonographic study which detected severe bilateral renal artery stenosis. Magnetic resonance imaging (MRI) with
angiographic study (MRA) was performed to confirm the renal artery stenosis. On MRI, an expansive mass was found in the upper pole of the right kidney, characterized by smooth margins, low signal
intensity on T1-weighted FSPGR sequence (Fig. 1) and homogeneously moderate high signal intensity on T2-weighted SSFSE sequence (Fig. 2). On delayed FSPGR sequence with fat saturation, the mass
showed high and homogeneous enhancement (Fig. 3). A renal tumour, such as a lymphoma, was therefore suspected. MRA demonstrated severe left renal artery stenosis (Fig. 4). The right renal artery
showed an early dichotomy with a segmental artery for the upper pole: the main renal artery was occluded proximally whereas the segmental artery showed a moderate stenosis at the origin and entered
the renal mass. On MRA single partitions, the enhancement of the mass resembled that of the normal renal parenchyma with the typical cortico-medullary differentiation (Fig.5). Based on this finding,
a renal tumor appeared to be a less likely diagnosis and a pseudomass was finally suspected. An ultrasonography-guided biopsy of the renal mass was performed; the histological analysis revealed
regular renal tubuli and vessels. Therefore, the final diagnosis was a renal pseudotumour due to hypertrophic compensatory changes of the parenchyma.
Discussion
Renal pseudotumours represent an important topic in the differential diagnosis of renal masses. Congenital pseudotumours are normal variants (prominent renal columns of Bertin, renal dysmorphism, and
dromedary humps), while acquired pseudotumours consist of hypertrophic renal parenchyma with a tumourlike appearance. In the subset of patients with chronic ischemic renal disease, the common finding
is represented by renal atrophy with reduction of cortical thickness, renal size and perfusion. In some instances, chronic renal infarcts have been described resembling a pseudo-mass [1]. Little
attention has been focused on pseudo-masses caused by focal renal parenchymal sparing in atrophic ischemic kidneys [2]. In some patients, a peculiar anatomic situation of the renal vessels can lead
to the development of a pseudo mass. In particular, a bilateral severe stenosis or occlusion of the main renal artery associated with a patent branch or a patent accessory vessel could cause
hypertrophic compensatory changes of the spared parenchyma. A pseudo mass can therefore develop, that is usually easily differentiated from tumours [3]. In the case we presented, differential
diagnosis was difficult due to the size of the mass and its apparent expansive growth. Indeed, initially a renal lymphoma was hypothesized because of the signal homogeneity of the mass and the
absence of fat and necrosis on pre-contrast MRI images [4]; encasement of vessel with lumen sparing represented a further finding supporting this diagnosis. However, when evaluating the single MRA
partitions in the arterial phase, the characteristic cortico-medullary differentiation was appreciated within the mass, thus excluding the diagnosis of a renal tumour and allowing proper
identification of a pseudo mass [5]. In conclusion, according to our experience, the diagnosis of a pseudo-mass has to rely also upon the evaluation of all the phases of the contrast dynamic study,
in order to identify the normal cortico-medullary differentiation within the suspected mass.
Differential Diagnosis List
Renal pseudotumor due to compensatory segmental hypertrophy within atrophic kidney
Final Diagnosis
Renal pseudotumor due to compensatory segmental hypertrophy within atrophic kidney
