Unilateral Renal Cystic Disease: A Rare and Benign Renal Pathology

URCD was first described in 1964 as unilateral polycystic kidney disease [10]. Subsequently, the topic was revised over and over until, in 1989, Levine et al. first named the condition unilateral renal cystic disease (URCD), as it has been famed for the time being [1]. Imaging with ultrasound (US) and contrast-enhanced computed tomography (CECT) plays a crucial role in diagnosing and evaluating URCD. They can effectively demonstrate the morphological changes in the affected kidney, including numerous cysts of different sizes and locations replacing the renal parenchyma focally or diffusely. The cysts are typically Bosniak type I and contain clear, low-attenuation fluid (less than 10 HU). However, they might have dense and even haemorrhagic contents with superimposed complications. In the long term, cysts might undergo calcification. The affected kidney maintains normal excretory function; thus, the residual renal tissue is compressed and displaced peripherally. The calyxes are stretched and moulded around the cysts, giving a characteristic spider-leg appearance. Often, no further cysts are seen within the confinement of other abdominal solid organs, particularly the liver and biliary system [5].

It is important to note that URCD can be diagnosed at any age, and although most reported cases are in the 3rd and 4th decades of life, URCD has been described in 72 elderly individuals. Paediatric URCD requires careful evaluation to differentiate it from ADPKD, as the latter can initially present as unilateral disease in children and progress to asymmetric bilateral disease over time [3]. Scarce cases of URCD are mentioned in the literature. Salupo et al. [8] reported the youngest typical case of URCD in a 22-year-old female. Serial US, MRI, and/or CT scans should be recommended, at an appropriate time interval, before a final diagnosis can be made. Alternatively, ADPKD can be excluded clinically with the aid of genetic screening, monitoring of renal function, and/or phenotype screening of family members using US [9].

In terms of treatment and therapeutic options for URCD, there are currently no specific robust, society-based guidelines mentioned in the literature for dealing with URCD. Since URCD is considered an originally nongenetic disorder with a satisfactory prognosis, unlike ADPKD, the management approach is typically conservative. Moreover, an ominous cystic renal neoplasm has been once reported with URCD, which might even be coincidental! [10]. Long-term surveillance is recommended to monitor for any potential malignant transformation of the cysts [8, 10]. Conclusively, URCD should be addressed as a unique disease. Familiarity with such a condition can aid in arriving at an accurate diagnosis and negate the need for undue testing. It also plays a role in reassuring the patient and family. Further research and guidelines are needed to establish standardized approaches for the surveillance and treatment of URCD patients.