Renal cystic diseases (RCDs) can arise from utero to early adulthood and present with a variety of symptoms including renal, hepatic, and cardiovascular manifestations. It is well known that common RCDs such as autosomal polycystic kidney disease and autosomal recessive kidney disease are linked to genes such as PKD1 and PKHD1, respectively. However, it is important to investigate the genetic pathophysiology of how these gene mutations lead to clinical symptoms and include some of the less-studied RCDs, such as autosomal dominant tubulointerstitial kidney disease, multicystic dysplastic kidney, Zellweger syndrome, calyceal diverticula, and more. We plan to take a thorough look into the genetic involvement and clinical sequalae of a number of RCDs with the goal of helping to guide diagnosis, counseling, and treatment.

Cystic kidney disease comprises a broad group of heterogeneous diseases, which differ greatly in age at onset, disease manifestation, systemic involvement, disease progression, and long-term prognosis. As our understanding of these diseases continues to evolve and new treatment strategies continue to emerge, correctly differentiating and diagnosing these diseases becomes increasingly important. In this review, we aim to highlight the key features of the most relevant cystic kidney diseases, underscore important diagnostic characteristics of each disease, and present specific management options if applicable.

Cystic dysplasia of the rete testis (CDRT) is a rare cause of testicular masses in children. The pathogenesis of this malformation remains unclear. It is often associated with other genitourinary anomalies, commonly presenting as agenesis or dysplasia of the ipsilateral kidney. A case involving a 9-year-old boy with a testicular lesion and ipsilateral renal agenesis, who was diagnosed with CDRT after histological examination, is reported. In addition, a systematic review of the literature was performed to better understand this pathology to design the most appropriate treatment and follow-up strategy for patients with CDRT.

Renal cystic disease encompasses a large variety of illnesses with various phenotypic expressions that can manifest in utero, in infancy, and in childhood. These diseases may be unilateral or bilateral and present with single or multiple cysts. Various cystic diseases may also progress to chronic kidney disease (CKD), including kidney failure, and hepatic disease, thus potentially being life threatening. The prevalence and serious complications of CKD in the pediatric population make it vital that health care providers detect these conditions early and provide effective management. This installment of AJKD\'s Core Curriculum in Nephrology discusses various genetic and sporadic kidney cystic diseases, including multicystic dysplastic kidney, nephronophthisis, cystic dysplasia, hepatocyte nuclear factor 1-β (HNF1-β) nephropathy, Bardet-Biedl syndrome, Meckel-Gruber syndrome, Zellweger syndrome, calyceal diverticulum, autosomal recessive polycystic kidney disease (ARPKD), and autosomal dominant polycystic kidney disease (ADPKD). This article discusses the epidemiology, genetics and pathophysiology, diagnosis, presentation, and management for each of these renal cystic diseases, with particular attention to prenatal care and pregnancy counseling.

Cystic dysplasia of the rete testis (CDT) is a rare cause of scrotal swelling in children. It is a congenital disorder and it can be associated with other genitourinary abnormalities. At present, there is no clear consensus on treatment. Surgical approach has traditionally been the treatment of choice, while, more recently, conservative approach has been applied, justified by the benign nature of the lesion and after few cases of spontaneous regression have been documented. Ultrasonography, supported by negative tumor markers, plays a key role in the diagnostic work up and during observational follow-up. We report a further case of spontaneous regression of suspected CDT in an 18-month-old boy, who has been followed with clinic and ultrasonographic checks.

Cystic dysplasia of the testis is a rare, benign pathologic finding. We present two recent cases of cystic dysplasia of the testis to our practice. The first case involves an 11 month old male presenting with a non-palpable, intra-abdominal left testis. The second case involves a 7 year old male with left scrotal swelling and a history of left renal agenesis. After review of the literature, the first case represents the first report of cystic dysplasia of the testis in an undescended, intra-abdominal testicle.