Asymptomatic Rosai-Dorfman-Destombes disease presenting as isolated bilateral perinephric infiltration: a case report and review of the literature.

Background: Rosai-Dorfman-Destombes disease (RDD) is a rare histioproliferative disease with unknown etiology. It commonly occurs in lymph nodes and can affect extra-nodal tissues and organs. Renal RDD is extremely rare, only a few cases have been reported, and its clinical symptoms and imaging findings are non-specific. To date, no literature has summarized its imaging manifestations in a large number of cases. Due to the involvement of different tissues and organs, there is no standard treatment for RDD. It has been reported that RDD patients with kidney involvement have a poor prognosis. Thus, understanding of renal RDD need to be extended.

Case Description: We present a rare case of renal RDD in an asymptomatic 67-year-old male. The results of an ultrasound examination indicated that both kidneys were surrounded by hypoechoic soft tissue lesions, and there was a huge mass in the left kidney, which had a clear boundary with the renal capsule. The results of contrast-enhanced ultrasound (CEUS) showed hypo-enhancement in the bilateral perinephric lesions and mass. However, the computed tomography urography (CTU) findings revealed no obvious enhancement. The patient then underwent a series of laboratory tests, but no relevant information was found. To make a clear diagnosis, the urologist then removed the left perirenal mass and some perirenal tissues, and the patient was finally pathologically diagnosed with extra-nodal RDD. The patient remains asymptomatic, and no treatment has been administered to date.

Conclusions: This case may be the first reported case in which CEUS was performed and the second reported case of asymptomatic renal RDD. Based on the previous literature reports, we found that some specific characteristics of renal RDD include bilateral perirenal lesions with a "hairy kidney" appearance. CEUS and/or CTU can be used to help differentiate a solitary mass of RDD from common tumors, to avoid misdiagnosis leading to unnecessary nephrectomy.