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Background: Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ([ 18 F]FDG PET/CT) has been suggested as a useful imaging method for diagnosing cyst infections in patients with autosomal dominant polycystic kidney disease (ADPKD). The aim of this article is to provide evidence-based data in this setting., Methods: A systematic literature review (exploring several bibliographic databases) and a bivariate meta-analysis were carried out to calculate the pooled diagnostic performance of [ 18 F]FDG PET/CT in diagnosing probable cyst infection in ADPKD., Results: Ten studies (282 PET/CT scans and 249 patients) were included in the analysis. The pooled sensitivity and specificity of [ 18 F]FDG PET/CT in this setting were 84.6% (95% confidence interval: 75.4-90.7) and 94.9% (95% confidence interval: 72.6-99.2), respectively, without statistical heterogeneity or significant publication bias. [ 18 F]FDG PET/CT significantly changed patient management in more than half of ADPKD patients with suspected cyst infection., Conclusions: [ 18 F]FDG PET/CT has high performance in diagnosing probable cyst infections in ADPKD patients with an impact on management in the majority of patients. Although more studies are warranted, the provided evidence-based data are an important step towards the integration of [ 18 F]FDG PET/CT in clinical and diagnostic guidelines on probable cyst infection in ADPKD patients.

Background: To assess the impact of malignant cystic renal masses (CRM) rupture on oncologic outcomes., Methods: The study included 406 cases with partial nephrectomy (PN) and 17 cases with cyst decortication confirmed as malignant CRM by pathology. Recurrence-free survival (RFS), metastasis-free survival (MFS), cancer-specific survival (CSS), and overall survival (OS) were analyzed by the Kaplan-Meier method and log-rank test. Cox regression was used to identify risk factors associated with RFS, MFS, CSS, and OS. Logistic regression was performed to explore predictors of rupture., Results: Tumor rupture occurred in 32 of 406 cases (7.9%). With median follow-up of 43 months, 4 (12.5%) and 5 (1.3%) cases experienced recurrence in rupture and non-rupture group, respectively (P = 0.003). Estimated RFS, MFS, and CSS were shorter in cyst ruptured (CR) group than non-ruptured (nonCR) cases (P < 0.001; P = 0.001; P < 0.001). Cox regression analysis indicated that CR was an independent prognostic factor for RFS (HR = 7.354; 95% CI = 1.839-29.413; P = 0.005), MFS (HR = 8.069; 95% CI = 1.804-36.095; P = 0.006), and CSS (HR = 9.643; 95% CI = 2.183-42.599; P = 0.003). Multivariable logistic regression showed that Bosniak IV was a protective factor for CR (OR = 0.065; 95% CI = 0.018-0.239; P < 0.001). However, compared to Bosniak III and I-IIF, Bosniak IV CRMs showed higher rate of clear cell renal cell carcinoma (ccRCC) (76.8% vs 36.5% vs 81.4%) (P < 0.001) and lower rate of Fuhrman I staging (11.2% vs 66.7% vs 7.4%) (P < 0.001). Therefore, in ruptured cases, the recurrence rate was higher in CRM with Bosniak IV (50%, 2/4) than Bosniak I-III (4.4%, 2/45) (P = 0.029)., Conclusions: Intraoperative malignant CRM rupture had negative impacts on oncologic outcomes. Bosniak IV was more aggressive than Bosniak I-III and had a higher risk of recurrence after rupture. However, Bosniak IV had a lower risk of rupture, which could weaken even cover-up of the true effect of tumor rupture on oncologic outcomes., (© 2022. The Author(s).)

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary cystic kidney disease, with patients often having a positive family history that is characterized by a similar phenotype. However, in atypical cases, particularly those in which family history is unclear, a differential diagnosis between ADPKD and other cystic kidney diseases is important. When diagnosing ADPKD, cystic kidney diseases that can easily be excluded using clinical information include: multiple simple renal cysts, acquired cystic kidney disease (ACKD), multilocular renal cyst/multilocular cystic nephroma/polycystic nephroma, multicystic kidney/multicystic dysplastic kidney (MCDK), and unilateral renal cystic disease (URCD). However, there are other cystic kidney diseases that usually require genetic testing, or another means of supplementing clinical information to enable a differential diagnosis of ADPKD. These include autosomal recessive polycystic kidney disease (ARPKD), autosomal dominant tubulointerstitial kidney disease (ADTKD), nephronophthisis (NPH), oral-facial-digital (OFD) syndrome type 1, and neoplastic cystic kidney disease, such as tuberous sclerosis (TSC) and Von Hippel-Lindau (VHL) syndrome. To help physicians evaluate cystic kidney diseases, this article provides a review of cystic kidney diseases for which a differential diagnosis is required for ADPKD.

Background: Co-occurrence of polycystic kidney disease and hyperinsulinemic hypoglycemia has been reported in children in a few families associated with a variant in the promotor of the PMM2 gene, at position -167 upstream of the coding sequence. PMM2 encodes phosphomannomutase 2, a key enzyme in N-glycosylation. While biallelic coding PMM2 mutations are involved in congenital disorder of glycosylation CDG1A, that particular variant in the promoter of the gene, either in the homozygous state or associated with a mutation in the coding exons of the gene, is thought to restrict the N-glycosylation defect to the kidney and the pancreas., Methods: Targeted exome sequencing of a panel of genes involved in monogenic kidney diseases., Results: We identified a PMM2 variant at position -167 associated with a pathogenic PMM2 variant in the coding exons in 3 families, comprising 6 cases affected with a cystic kidney disease. The spectrum of phenotypes was very broad, from extremely enlarged fetal cystic kidneys in the context of a COACH-like syndrome, to isolated cystic kidney disease with small kidneys, slowly progressing toward kidney failure in adulthood. Hypoglycemia was reported only in one case., Conclusion: These data show that the PMM2 promotor variation, in trans of a PMM2 coding mutation, is associated with a wide spectrum of kidney phenotypes, and is not always associated with extra-renal symptoms. When present, extra-renal defects may include COACH-like syndrome. These data prompt screening of PMM2 in unresolved cases of fetal hyperechogenic/cystic kidneys as well as in cystic kidney disease in children and adults. Graphical Abstract.

Renal hypodysplasia and cystic kidney diseases, the common non-glomerular causes of pediatric chronic kidney disease (CKD), are usually diagnosed by their clinical and imaging characteristics. The high degree of phenotypic heterogeneity, in both conditions, makes the correct final diagnosis dependent on genetic testing. It is not clear, however, whether the frequencies of damaged alleles vary among different ethnicities in children with non-glomerular CKD, and this will influence the strategy used for genetic testing. In this study, 69 unrelated children (40 boys, 29 girls) of predominantly Han Chinese ethnicity with stage 2-5 non-glomerular CKD caused by suspected renal hypodysplasia or cystic kidney diseases were enrolled and assessed by molecular analysis using proband-only targeted exome sequencing and array-comparative genomic hybridization. Targeted exome sequencing discovered genetic etiologies in 33 patients (47.8%) covering 10 distinct genetic disorders. The clinical diagnoses in 13/48 patients (27.1%) with suspected renal hypodysplasia were confirmed, and two patients were reclassified carrying mutations in nephronophthisis ( NPHP ) genes. The clinical diagnoses in 16/20 patients (80%) with suspected cystic kidney diseases were confirmed, and one patient was reclassified as carrying a deletion in the hepatocyte nuclear factor-1-beta gene ( HNF1B ). The diagnosis of one patient with unknown non-glomerular disease was elucidated. No copy number variations were identified in the 20 patients with negative targeted exome sequencing results. NPHP genes were the most common disease-causing genes in the patients with disease onsets above 6 years of age (14/45, 31.1%). The children with stage 2 and 3 CKD at onset were found to carry causative mutations in paired box gene 2 ( PAX2 ) and HNF1B gene (11/24, 45.8%), whereas those with stage 4 and 5 CKD mostly carried causative mutations in NPHP genes (19/45, 42.2%). The causative genes were not suspected by the kidney imaging patterns at disease onset. Thus, our data show that in Chinese children with non-glomerular renal dysfunction caused by renal hypodysplasia and cystic kidney diseases, the common causative genes vary with age and CKD stage at disease onset. These findings have the potential to improve management and genetic counseling of these diseases in clinical practice., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Wang, Xiao, Yao, Xu, Liu, Su, Zhang, Guan, Zhong, Zhang, Ding and Wang.)

Objectives: To develop and prospectively validate a novel weighted quantitative scoring system based on CT findings, namely, the renal cyst index (RCI), aimed at preoperatively predicting the pathological features of cystic renal masses (CRMs)., Methods: The RCI was based on four critical features of CRMs: the cyst wall, septal, nodule, and cyst contents. These parameters were scored with 1, 2, or 3 points. Weight coefficients for these parameters were determined by the multivariable logistic regression. The odds ratio (OR) and 95% confidence interval (95% CI) were used to summarise the results. The RCI was defined as the sum of these four weight coefficients. Malignancy risk prediction models were built based on the retrospective evaluation of 441 patients. We also compared the prediction ability of the RCI with the Bosniak classification in the 441 patients and applied these novel models to 152 masses resected in our institution to prospectively validate the efficiency of the RCI., Results: The wall point (OR = 5.71 [95% CI = 1.734-18.808, p = 0.004, point = 2], OR = 12.665 [95% CI = 3.750-42.770, p < 0.001, point = 3]), septal point (OR = 3.325 [95% CI = 1.272-8.692, p = 0.014, point = 3]), nodule point (OR = 4.588 [95% CI = 1.429-14.729, p < 0.001, point = 2], OR = 17.032 [95% CI = 5.017-57.820, p = 0.010, point = 3]), content point (OR = 22.822 [95% CI = 1.041-495.995, p = 0.047, point = 2], OR = 2.723 [95% CI = 1.296-10.696, p = 0.015, point = 3]), and RCI (OR = 1.247 [95% CI = 1.197-1.299, p < 0.001]) were significantly associated with malignancy. Masses with an RCI < 6 were regarded as benign masses; masses with an RCI ≥ 10 were regarded as malignant masses. The malignancy risk of masses with an RCI > 6 but < 10 were determined by a nomogram. The prediction ability of the RCI was significantly superior to the Bosniak classification for Bosniak IIF and III masses (AUC: 0.912 vs. 0.753, p = 0.001). The RCI also accurately predicted the pathological features of 152 masses., Conclusion: The RCI is a reliable quantitative scoring system in predicting the malignancy risk of CRMs, and it outperformed the Bosniak classification system in some ways., Key Points: • The renal cyst index (RCI) is a useful weighted quantitative classification system based on CT findings for diagnosing cystic renal masses. • The RCI outperforms the Bosniak classification system in some ways, especially for Bosniak IIF and III masses. • Masses with an RCI < 6 can be regarded as a simple cyst, while those with an RCI > 10 can be regarded as malignant masses.

Purpose: To carry out long-term follow-up of patients diagnosed with asymptomatic simple renal cysts (SRCs)., Materials and Methods: One hundred fifty-eight adult patients in whom SRCs were incidentally diagnosed by abdominal ultrasonography or abdominopelvic computed tomography between August 1994 and June 2004 were followed up for over 10 years. The retrospective analysis investigated sequential changes in the size, shape, and Bosniak classification of the renal cyst and analyzed risk factors for increased size and growth rate of the cysts., Results: The median follow-up period was 13.9 years (range, 10.0-19.8 years). Median patient age was 54.1 years (range, 22-86 years). Mean maximal cyst size was 33 mm (range, 2-90 mm). Among all patients, 120 (76%) showed a mean increase in maximum renal cyst diameter of 1.4 mm (6.4%) per year. Age at initial diagnosis was a risk factor for increased renal cyst maximum diameter. The probability of an increase in maximum diameter of an SRC was 7.1 times greater in patients aged 50 years or older at diagnosis than in those aged less than 50 years. However, among patients with an increased maximum diameter, the mean growth rate was lower in patients aged ≥50 years than in those aged <50 years., Conclusions: About three-quarters of adult patients with accidentally diagnosed SRCs presented with an increased maximum diameter. The only risk factor for an increase in maximum diameter was age. In patients with an increase in the maximum diameter, the growth rate of the maximum diameter was 6.4% per year during 10 years and decreased with age.