Approach to simple kidney cysts in children

The finding of a simple kidney cyst in a child can pose a diagnostic and management challenge for pediatric nephrologists, urologists, and primary care providers. The reported prevalence varies from 0.22 to 1% in large ultrasonography-based series of more than 10,000 children each. The true prevalence, however, may be higher or lower, as factors such as variations in referral patterns, indications for ultrasonography, or technical considerations could impact prevalence rates. For many patients, simple kidney cysts may be found incidentally when imaging is performed for another indication. Although simple cysts can occur in children, they may also represent the first sign of autosomal dominant polycystic kidney disease (ADPKD) or other less common cystic kidney diseases. Definitive guidelines regarding the evaluation and monitoring of children with simple kidney cysts have not been established. The desire on the part of the practitioner and/or parents to establish a definitive diagnosis should be balanced with the cost and inconvenience of repeated imaging and visits with specialists. The goals of this review are to (1) outline the definition, epidemiology, clinical presentation, and natural history of simple kidney cysts in childhood; (2) describe clinical features that could suggest a diagnosis other than a simple kidney cyst; and (3) present a suggested framework for evaluating and monitoring of children with one or more simple kidney cysts.

Cystic kidney diseases in children

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.

Left supernumerary kidney: A rare case presentation

The supernumerary kidney is an extremely rare, congenital renal anomaly and there are less than 100 cases reported in the current literature. This renal anomaly has its own collecting system, blood supply and well-defined encapsulated tissue. We report a case of left supernumerary kidney and solitary cyst of left native kidney in a 51-year-old man.

Cystic dysplasia of the kidneys in extremely preterm infants following acute kidney injury

BACKGROUND

Various perinatal morbidities may adversely affect postnatal nephrogenesis in preterm infants. Kidney ultrasonographic findings following acute kidney injury (AKI) have not been well described in preterm infants. Herein, we describe three cases of extremely preterm infants who showed abnormal kidney ultrasonographic findings resembling dysplasia of the kidneys following AKI.

CASE-DIAGNOSIS/TREATMENT

Their median gestational age and birth weight were 25⁺⁶ (range 23⁺³-26⁺⁶) weeks and 620 (480-840) g, respectively. All infants suffered severe AKI during their third to seventh week of life. Their kidney function recovered with conventional management. Kidney ultrasonographies performed after AKI revealed increased kidney echogenicity, loss of corticomedullary differentiation, and multiple cortical cysts, which were similar to cystic dysplasia of the kidneys and were absent in previous kidney imaging. Three infants eventually developed at least one of the long-term kidney sequelae following AKI, including proteinuria, hypertension, and elevated levels of serum creatinine or cystatin C as determined during the last follow-up at the corrected age of 9-18 months.

CONCLUSIONS

Based on these cases, we can infer that AKI occurring during the early postnatal period may result in dysplasia of the kidneys with cortical cysts in extremely preterm infants, which may lead to chronic kidney disease in their later life. It is useful to follow up not only laboratory parameters but also kidney ultrasonographic findings in extremely preterm infants who suffered AKI during their early postnatal periods.

Targeting chloride transport in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent inherited kidney disease. Transepithelial fluid secretion is one of the key factors of cystogenesis in ADPKD. Multiple studies have suggested that fluid secretion across ADPKD cyst-lining cells is driven by the secretion of chloride, essentially mediated by the CFTR channel and stimulated by increased intracellular levels of 3',5'-cyclic adenosine monophosphate. This review focuses on the pathophysiology of fluid secretion in ADPKD based on the pioneering studies of Jared Grantham and colleagues, and on the follow-up investigations from the molecular level to the potential applications in ADPKD patients. Altogether, the studies of fluid and chloride transport in ADPKD paved the way for innovative therapeutic targets to prevent cyst volume expansion and thus, kidney disease progression.

Rapid identification of kidney cyst mutations by whole exome sequencing in zebrafish

Forward genetic approaches in zebrafish have provided invaluable information about developmental processes. However, the relative difficulty of mapping and isolating mutations has limited the number of new genetic screens. Recent improvements in the annotation of the zebrafish genome coupled to a reduction in sequencing costs prompted the development of whole genome and RNA sequencing approaches for gene discovery. Here we describe a whole exome sequencing (WES) approach that allows rapid and cost-effective identification of mutations. We used our WES methodology to isolate four mutations that cause kidney cysts; we identified novel alleles in two ciliary genes as well as two novel mutants. The WES approach described here does not require specialized infrastructure or training and is therefore widely accessible. This methodology should thus help facilitate genetic screens and expedite the identification of mutants that can inform basic biological processes and the causality of genetic disorders in humans.

Intraperitoneal rupture of renal cyst in autosomal dominant polycystic kidney disease

CONTEXT

To report a rare case of spontaneous rupture of an infected renal cyst into the peritoneal cavity.

CASE REPORT

We report a case of 66-year old man with autosomal dominant polycystic kidney disease and kidney dialysis who had suffered from intestinal obstruction and peritoneal syndrome for 2 days associated with purulent urine. An exploratory laparotomy found multiple hepatic cysts and bilaterally enlarged polycystic kidneys. We noted left renal cyst infected and ruptured into the peritoneal cavity causing general peritonitis. The patient died from septic shock and hemodynamic failure.

CONCLUSION

The peritoneal rupture of infected renal cyst is an exceptional and serious complication of polycystic kidney disease. Medical and surgical treatments are urgent to prevent lethal complications.

Cyst ablation using a mixture of N-butyl cyanoacrylate and iodized oil in patients with autosomal dominant polycystic kidney disease: the long-term results

Objective

We wanted to assess the long-term results of cyst ablation with using N-butyl cyanoacrylate (NBCA) and iodized oil in patients with autosomal dominant polycystic kidney disease (ADPKD) and symptomatic cysts.

Materials and Methods

Cyst ablation using a mixture of NBCA and iodized oil was performed in 99 cysts from 21 patients who had such symptoms as abdominal distension and pain. The collapse or reaccumulation of the ablated cysts after the procedure was assessed during the follow-up period of 36 to 90 months. The treatment effects, including symptom relief, and the clinical data such as the blood pressure and serum creatinine levels were also assessed, together with the complications.

Results

The procedure was technically successful in all 99 cysts from the 21 patients. Any procedure-related significant complications were not detected. Seventy-seven of 99 cysts (78%) were successfully collapsed on the follow-up CT. Twenty-two cysts showed reaccumulation during long-term follow-up period. The clinical symptoms were relieved in 17 of the 21 patients (76%). Four of 12 patients (33%) with hypertension and two of six patients (33%) with azotemia were improved. End stage renal disease (ESRD) occurred in six of the 21 patients (28%) during the follow-up period. The mean age of ESRD in our patients was 57 years. The mean time interval for the development of ESRD was 19 months.

Conclusion

Ablation using a mixture of NBCA and iodized oil may be an effective, safe method for obtaining symptom relief in patients with ADPKD.