A review of renal disease in cystic fibrosis

Close monitoring and early intervention: management principles for cystic fibrosis in Denmark

Cystic fibrosis (CF) care in Denmark has been characterized by close monitoring and pre-emptive treatment of lung disease and other CF-related complications. Continuous evaluation through data collection and commitment to clinical research has incrementally improved outcomes. This approach has been in line with best practices set forth by European Standards of Care but has also gone beyond Society standards particularly pertaining to early treatment with high-dose combination antimicrobial therapy. Despite a high prevalence of severe CF variants, lung function has been among the best in Europe. In this review, the Danish approach to management of CF prior to the introduction of new CF modulator treatment is explained and benchmarked. Downsides to the Danish approach are discussed and include increased burden of treatment, risk of antimicrobial resistance, side-effects and costs.

Identification of prognostic biomarkers for antibiotic associated nephrotoxicity in cystic fibrosis

BACKGROUND

Our objective was to discover novel urinary biomarkers of antibiotic-associated nephrotoxicity using an ex-vivo human microphysiological system (MPS) and to translate these findings to a prospectively enrolled cystic fibrosis (CF) population receiving aminoglycosides and/or polymyxin E (colistin) for a pulmonary exacerbation.

METHODS

We populated the MPS with primary human kidney proximal tubule epithelial cells (PTECs) from three donors and modeled nephrotoxin injury through exposure to 50 µg/mL polymyxin E for 72 h. We analyzed gene transcriptional responses by RNAseq and tested MPS effluents. We translated candidate biomarkers to a CF cohort via analysis of urine collected prior to, during and two weeks after antibiotics and patients were followed for a median of 3 years after antibiotic use.

RESULTS

Polymyxin E treatment resulted in a statistically significant increase in the pro-apoptotic Fas gene relative to control in RNAseq of MPS: fold-change = 1.63, FDR q-value = 7.29 × 10-5. Effluent analysis demonstrated an acute rise of soluble Fas (sFas) concentrations that correlated with cellular injury. In 16 patients with CF, urinary sFas concentrations were significantly elevated during antibiotic treatment, regardless of development of AKI. Over a median of three years of follow up, we identified seven cases of incident chronic kidney disease (CKD). Urinary sFas concentrations during antibiotic treatment were significantly associated with subsequent development of incident CKD (unadjusted relative risk = 2.02 per doubling of urinary sFas, 95 % CI = 1.40, 2.90, p < 0.001).

CONCLUSIONS

Using an ex-vivo MPS, we identified a novel biomarker of proximal tubule epithelial cell injury, sFas, and translated these findings to a clinical cohort of patients with CF.

Peri-operative and long-term outcomes of kidney transplantation in patients with cystic fibrosis

INTRODUCTION

There is a lack of data regarding the peri-operative and long-term outcomes of kidney transplantation in cystic fibrosis (CF) patients. Herein, we report the peri-operative and long-term outcomes of kidney transplantation in CF patients.

MATERIALS AND METHODS

All CF patients who received a kidney transplant at the national kidney transplant center between 1993 and 2022 were identified. Recipients of the contralateral donor kidney were selected as a control group. Primary outcomes included 1-, 5-, and 10- year death-censored graft survival and overall survival. Secondary outcomes included peri-operative morbidity, acute graft rejection, delayed graft function (DGF), and length of stay (LOS).

RESULTS

Fourteen patients received a kidney transplant over the study period. Median age at transplantation was 35 (IQR 31, 40) years. The 1-, 5-, and 10-year death-censored graft survival was 92, 74, and 74% in the CF group compared to 100, 92, and 92% in the control group (p = .44). The 1-, 5-, and 10-year overall survival in the CF group was 85, 66, and 57% compared to 100, 92, and 82% in the control group (p = .036). There was no significant difference in peri-operative outcomes including LOS (10 vs. 11 days, p = .84), ICU admission (1 vs. 0 patients, p > .99), acute rejection episodes (2 vs. 1 patients, p > .99), and DGF (1 vs. 2 patients, p = .60).

CONCLUSION

CF patients have good long-term graft survival, however, overall survival was worse compared to a matched cohort. These data provide important information for transplant surgeons when considering suitable donor allografts in this unique patient population.

Mathematical models of cystic fibrosis as a systemic disease

Cystic fibrosis (CF) is widely known as a disease of the lung, even though it is in truth a systemic disease, whose symptoms typically manifest in gastrointestinal dysfunction first. CF ultimately impairs not only the pancreas and intestine but also the lungs, gonads, liver, kidneys, bones, and the cardiovascular system. It is caused by one of several mutations in the gene of the epithelial ion channel protein CFTR. Intense research and improved antimicrobial treatments during the past eight decades have steadily increased the predicted life expectancy of a person with CF (pwCF) from a few weeks to over 50 years. Moreover, several drugs ameliorating the sequelae of the disease have become available in recent years, and notable treatments of the root cause of the disease have recently generated substantial improvements in health for some but not all pwCF. Yet, numerous fundamental questions remain unanswered. Complicating CF, for instance in the lung, is the fact that the associated insufficient chloride secretion typically perturbs the electrochemical balance across epithelia and, in the airways, leads to the accumulation of thick, viscous mucus and mucus plaques that cannot be cleared effectively and provide a rich breeding ground for a spectrum of bacterial and fungal communities. The subsequent infections often become chronic and respond poorly to antibiotic treatments, with outcomes sometimes only weakly correlated with the drug susceptibility of the target pathogen. Furthermore, in contrast to rapidly resolved acute infections with a single target pathogen, chronic infections commonly involve multi-species bacterial communities, called "infection microbiomes," that develop their own ecological and evolutionary dynamics. It is presently impossible to devise mathematical models of CF in its entirety, but it is feasible to design models for many of the distinct drivers of the disease. Building upon these growing yet isolated modeling efforts, we discuss in the following the feasibility of a multi-scale modeling framework, known as template-and-anchor modeling, that allows the gradual integration of refined sub-models with different granularity. The article first reviews the most important biomedical aspects of CF and subsequently describes mathematical modeling approaches that already exist or have the potential to deepen our understanding of the multitude aspects of the disease and their interrelationships. The conceptual ideas behind the approaches proposed here do not only pertain to CF but are translatable to other systemic diseases. This article is categorized under: Congenital Diseases > Computational Models.

Prevalence, risk factors and outcomes of cardiac disease in cystic fibrosis: a multinational retrospective cohort study

BACKGROUND

Although people living with cystic fibrosis (PwCF) often have some risk factors for cardiovascular disease, including diabetes and chronic inflammation, little is known about the long-term cardiac risk in this condition. We aimed to determine the characteristics, rates and outcomes for cardiac disease in CF.

METHODS

We looked at rates and outcomes for cardiac disease in 5649 adult PwCF in the UK CF Registry and 6265 adult PwCF in TriNetX (a global federated database of electronic healthcare record data). We used propensity matching to compare risk of major adverse cardiac events (MACE) (myocardial infarction, left-sided heart failure and atrial fibrillation) in PwCF against matched non-CF comparators in the general population and other inflammatory diseases.

RESULTS

PwCF had a high prevalence of diabetes but low rates of hypertension and obesity. Some cardiac risk factors (age, diabetes and hypertension) were associated with MACE, but relationships between disease-specific risk factors (lung function and intravenous antibiotic days) were also observed. In propensity score-matched analyses, PwCF had higher risk of MACE than matched general population comparators (hazard ratio (HR) 1.65, 95% CI 1.40-1.95; p<0.001) and an equivalent or higher relative risk compared with other inflammatory conditions considered "high risk" for cardiovascular disease, including systemic lupus erythematosus (HR 0.95, 95% CI 0.82-1.09; p=0.44), rheumatoid arthritis (HR 1.21, 95% CI 1.00-1.48; p<0.001) and HIV (HR 0.93, 95% CI 0.82-1.06; p=0.29).

CONCLUSIONS

PwCF are at increased risk of adverse cardiac disease events. Future work should focus on defining determinants of cardiovascular risk such that appropriate risk stratification can be employed.

CFTR and PC2, partners in the primary cilia in autosomal dominant polycystic kidney disease

Defects in the primary cilium are associated with autosomal dominant polycystic kidney disease (ADPKD). We used a combination of animal models, Western blotting, and confocal microscopy and discovered that CFTR and polycystin 2 (PC2) are both colocalized to the cilium in normal kidneys, with the levels of both being decreased in cystic epithelia. Cilia were longer in CFTR-null mice and in cystic cells in our ADPKD animal models. We examined septin 2, known to play a role in cilia length, to act as a diffusion barrier and to serve as an enhancer of proliferation. We found that septin 2 protein levels were upregulated and colocalized strongly with CFTR in cystic cells. Application of VX-809, the CFTR corrector, restored CFTR and PC2 toward normal in the cilia, decreased the protein levels of septin 2, and drastically reduced septin 2 colocalization with CFTR. Our data suggest that CFTR is present in the cilia and plays a role there, perhaps through its conductance of Cl-. We also postulate that septin 2 is important for localizing CFTR to the apical membrane in cystic epithelia.NEW & NOTEWORTHY CFTR is present in the primary cilia together with polycystin 2 (PC2). Ablation of CFTR makes cilia longer suggesting that CFTR plays a role there, perhaps through its conductance of Cl.

Beyond the Lungs-Emerging Challenges in Adult Cystic Fibrosis Care

Cystic fibrosis (CF) is a multisystem disease. This article provides an up-to-date review of many of the nonrespiratory complications of CF, including mental health issues, nutritional and gastrointestinal problems, fertility issues, diabetes mellitus, bone health and musculoskeletal problems, liver disease, renal problems, and risk of malignancy. It highlights the recent impact of new therapies, including CF transmembrane conductance regulator modulators, on the nonrespiratory complications of CF and provides insights into the potential challenges faced by an aging population of adults with CF and their caregivers, including the potential future risk for cardiovascular disease.

Evaluation of the safety of piperacillin-tazobactam extended infusion in pediatric cystic fibrosis patients

BACKGROUND

Patients with cystic fibrosis (CF) may be treated with piperacillin-tazobactam (PZT) for acute pulmonary exacerbations. Extending the infusion of PZT is one strategy to increase efficacy. Direct comparison, with respect to the incidence of acute kidney injury (AKI), between these two strategies has not been evaluated in pediatric patients with CF. The primary objective of this study was to compare the incidence of AKI in pediatric CF patients receiving extended infusion (EI) PZT versus traditional infusion (TI).

METHODS

This IRB-approved, retrospective analysis included patients ages 30 days to 18 years that received PZT for at least 48 h between January 1, 2008, and January 1, 2020. PZT was infused over 30 min (TI group) or 4 h (EI group).

RESULTS

Two hundred and four patients were included (TI: 109, EI: 95). Median age was 8 years (4-13) and 7 years (3-12) in the TI and EI groups (p = 0.15). The groups did not differ significantly in their baseline characteristics. There were 12 (11%) AKIs in the TI group and 8 (8.4%) in the EI group (p = 0.53). There was one occurrence of serum sickness in the TI group and none in the EI group. The incidence of thrombocytopenia was similar between the two groups. Median treatment duration was 8 days (5-11) and 9 days (5-13) for the TI and EI groups, respectively (p = 0.24).

CONCLUSIONS

There was no significant increase in AKI in pediatric patients with CF receiving PZT by EI compared with TI. EI may be utilized to optimize the pharmacokinetics of PZT in pediatric CF patients.

Kidney and combined kidney and pancreas transplantation may be under-utilized in cystic fibrosis

Cystic fibrosis (CF) is a multisystem disorder and represents the most common inherited condition leading to death in Western countries. Previous reports of chronic kidney disease (CKD) in CF focus on cases post lung, or other solid organ, transplantation but CKD in CF patients pre transplantation is increasingly recognized as a challenging complication of CF. CKD can evolve as a sequel to acute kidney injury for example after prolonged treatment with aminoglycoside antibiotics during episodes of infection. Nephrolithiasis, diabetic nephropathy and a variety of glomerular lesions, such as amyloidosis and Immunoglobulin A nephropathy are also seen. Muscle depletion is common in CF, hence creatinine-based estimates of kidney function may underestimate the degree of renal impairment and lead to delayed diagnosis and management. Improved treatment options for CF patients have resulted in a sustained increase in life expectancy with increasing numbers of CF patients with CKD approaching end-stage renal failure prior to consideration of lung transplantation. We believe that kidney or combined kidney-pancreas transplantation are under-utilized in this population. We provide a brief primer on the landscape of CF and CKD and discuss transplant options. Suitable patients with CF and advanced CKD should be formally assessed for kidney or kidney-pancreas transplantation.

Longitudinal assessment of renal function after lung transplantation for cystic fibrosis: transition from post-operative acute kidney injury to acute kidney disease and chronic kidney failure

INTRODUCTION

The clinical trajectory of post-operative acute kidney injury (AKI) following lung transplantation for cystic fibrosis is unknown.

METHODS

Incidence and risk factors for post-operative AKI, acute kidney disease (AKD) and chronic kidney disease (CKD) were retrospectively analyzed in cystic fibrosis patients undergoing lung transplantation. Logistic regressions, Chi-square, Cuzick rank tests, and Cox-proportional hazard models were used.

RESULTS

Eighty-three patients were included. Creatinine peaked 3[2-4] days after transplantation, with 15(18%), 15(18%), and 20(24%) patients having post-operative AKI stages 1, 2, and 3, while 15(18%), 19(23%) and 10(12%) developed AKD stage 1, stage 2 and 3, respectively. Higher AKI stage was associated with worsening AKD (p = 0.009) and CKD (p = 0.015) stages. Of the 50 patients with AKI, 32(66%) transitioned to AKD stage > 0, and then 27 (56%) to CKD stage > 1. Female sex, extracorporeal membrane oxygenation support as a bridge to lung transplant and at the end of the surgery, the use of intraoperative blood components, and cold-ischemia time were associated with increased risk of post-operative AKI and AKD. Higher AKI stage prolonged invasive mechanical ventilation (p = 0.0001), ICU stay (p = 0.0001), and hospital stay (p = 0.0001), and increased the incidence of primary graft dysfunction (p = 0.035). Both AKI and AKD stages > 2 worsened long-term survival with risk ratios of 3.71 (1.34-10.2), p = 0.0131 and 2.65(1.02-6.87), p = 0.0443, respectively.

DISCUSSION

AKI is frequent in cystic fibrosis patients undergoing lung transplantation, it often evolves to AKD and to chronic kidney disease, thereby worsening short- and long-term outcomes.

Renal Function in Patients with Cystic Fibrosis: A Single-Center Study

Cystic fibrosis (CF) is the most common incurable autosomal recessive disease affecting the Caucasian population. As the prognosis for life extension of CF patients improves, co-morbidities, including kidney disease, become more common. Identifying those at the highest risk of kidney injury is therefore extremely important. The aim of this study was to evaluate the biomarkers of renal function in 50 CF patients using the estimated glomerular filtration rate (eGFR) based on creatinine and cystatin C equation as well as serum creatinine (sCr), serum cystatin C (CysC), serum urea and urinary neutrophil gelatinase-associated lipocalin (uNGAL) concentrations. sCr, CysC, urea and uNGAL were estimated. eGFR was calculated according to the CKD-EPI formula. CysC was significantly increased, while eGFR was significantly lower in the CF group than in the controls (p < 0.001 and p < 0.01, respectively). There was no significant difference in the sCr, urea and uNGAL concentrations between patients with CF and healthy subjects. For the purpose of our analysis, in order to assess renal function in patients with CF in clinical practice, the concentration of serum CysC and eGFRCKD-EPI should be determined. Patients with CF presented with renal function impairment pictured by increased serum CysC and decreased eGFR values compared to controls. Unchanged uNGAL concentrations suggested preserved tubular function despite aminoglycoside treatment. Further prospective studies are needed to clarify whether kidney impairment observed in the course of CF progresses.

Yield of chest computed tomography angiogram in cystic fibrosis patients with suspected pulmonary embolism

Introduction

Individuals with cystic fibrosis (CF) may be at increased risk of pulmonary embolism (PE). Symptoms of PE overlap substantially with those of CF respiratory exacerbations. CF patients commonly undergo chest computed tomography (CT) angiograms (CTPA) to evaluate for PE, but little is known about the clinical presentation and diagnosis of PE in this population.

Objectives

The objectives of this study are to determine the diagnostic yield of CTPA for PE in adult patients with CF and assess the utility of the Revised Geneva Score (RGS) in this population.

Methods

Retrospective review of all CTPA results was performed on CF patients with suspected PE at a large CF center from 1 January 2011 through 31 March 2017. Patient demographics, medical history, and presenting signs and symptoms were abstracted by chart review.

Results

A total of 103 unique CTPA studies were performed in 68 patients. Most were hospitalized at the time of CTPA, predominantly for respiratory manifestations of CF. CTPA identified four patients with PE. The small number of positive studies precluded analysis of predictors of PE. Fewer PE were diagnosed than predicted by the Revised Geneva Score, which was intermediate probability in 77/103 (75%) patients.

Conclusion

The prevalence of PE in CF patients undergoing CTPA for suspected PE was 4%, which is lower than predicted by the Revised Geneva Score. This may be due to a large overlap in the signs and symptoms of PE and exacerbations of CF lung disease.

Role of urinary NAG enzyme in early detection of renal impairment in cystic fibrosis patients

Background

Cystic fibrosis (CF) is the most common life-limiting autosomal recessive disease among people in the USA and Europe with increased prevalence in Egypt. Affected children are in danger of acute kidney injury and the development of chronic renal disease through exposure to multiple nephrotoxic agents. N-acetyl beta-D-glucosaminidase (NAG) is a lysosomal enzyme present in high concentrations in the proximal tubular cells, thus raising urinary NAG levels to reflect tubular dysfunction. The aim of our study is to detect the role of the urinary NAG enzyme in the early detection of renal impairment in CF patients. This cross-sectional study enrolled 40 CF patients diagnosed in the CF Clinic in Children’s Hospital of Cairo University. They were age- and sex-matched to 40 healthy controls. All patients had glomerular filtration rate (GFR), serum creatinine, blood urea nitrogen (BUN), albumin/creatinine (A/C) ratio measured, urine analysis, urinary NAG enzyme using enzyme-linked immunosorbent assay (ELISA), and renal ultrasound (U/S) were done.

Results

Our study showed high levels of urinary NAG in cases with a significant difference between cases and controls (P value < 0.001). There was a significant correlation between urinary NAG enzyme elevation and A/C ratio in urine, nephrotoxic drugs administration, and duration of disease (P value = 0.002, 0.005, 0.019), respectively.

Conclusion

Our study suggested that the NAG enzyme is a good early detector of renal impairment in CF patients before the conventional laboratory assays become deranged.

Systematic Review of the Prevalence of Kidney Stones in Cystic Fibrosis

Purpose: To investigate the prevalence of urolithiasis in cystic fibrosis (CF) and to summarize the available clinical features within this unique population. Methods: Studies reporting the prevalence of urolithiasis in CF patients were identified by a systematic search of the literature from inception to July 31, 2020 on three databases: Ovid Medline, Ovid Embase, and Web of Science. Data were extracted on a predetermined standardized form by two independent authors. Results: A total of 596 publications were retrieved and screened, 15 of which met the eligibility criteria. The publications were published between 1993 and 2019 and were all observational in design. There was a total of 2982 patients with CF included in this review. The overall prevalence of stone formation in the CF population was 4.6% (137/2982). The mean age of diagnosis was 25.1 ± 9.6 and ranged from 0.25 to 47. Ultrasound was the most common imaging modality for kidney stone diagnosis. There was no apparent sex difference, with a female to male ratio of 1:1. Surgical intervention was required in 37.8% (34/90) of cases. Stone recurrence was reported in 42.9% (33/77) of stone formers. Conclusions: This review provides the most recent update for the prevalence of urolithiasis in CF patients and summarizes the available clinical data. Our findings suggest that patients with CF could be at risk for developing stones at a younger age and require interventional management strategies at higher rates compared with the general population. Given the heterogeneity of the literature for urolithiasis in CF, larger population-based studies reporting the epidemiology, clinical features, and management strategies are required to further our understanding of urolithiasis in CF.

Cystic fibrosis in the kidney: new lessons from impaired renal HCO3- excretion

PURPOSE OF REVIEW

A key role of cystic fibrosis transmembrane conductance regulator (CFTR) in the kidney has recently been uncovered. This needs to be integrated into the understanding of the developed phenotypes in cystic fibrosis (CF) patients.

RECENT FINDINGS

In the beta-intercalated cells of the collecting duct , CFTR functions in very similar terms as established in the exocrine pancreatic duct and both CFTR and SLC26A4 (pendrin) orchestrate regulated HCO3- secretion. Like in the pancreas, the hormone secretin is a key agonist to activate renal HCO3- secretion. In mice lacking CFTR or pendrin, acute and chronic base challenges trigger marked metabolic alkalosis because collecting duct base secretion is defective. Also in CF patients, the ability to acutely increase renal HCO3- excretion is markedly reduced.

SUMMARY

The now much enlarged understanding of CFTR in the kidney may permit the measurement of challenged urine HCO3- excretion as a new biomarker for CF. We suggest a new explanation for the electrolyte disorder in CF termed Pseudo-Bartter Syndrome. The hallmark electrolyte disturbance features of this can be well explained by a reduced function of collecting duct Cl-/HCO3- exchange. Eventually, we suggest the diagnostic term distal renal tubular alkalosis to cover those disturbances that causes metabolic alkalosis by a reduced collecting duct base secretion.

Unknown Renal Impairment: A Rare Case of Inhaled Tobramycin Induced Acute Kidney Injury in a Cystic Fibrosis Patient

Acute kidney injury is a reversible medical condition commonly caused by nephrotoxic agents. The infrequency that a nebulized medication elicits a renal insult presents a rare diagnostic challenge. Within this case, we report a 57-year-old cystic fibrosis patient with chronic kidney disease (CKD) Stage G3b (baseline 1.5–1.6 mg/dL) who developed an acute kidney injury (AKI) with a serum creatinine elevation to 4.08 mg/dL and associated worsening vestibular dysfunction related to twice-daily nebulized tobramycin inhalation solution (TIS). The patient was found to have a tobramycin serum level of 4.2 μg/mL 2.5 h after TIS dosing, with elevation remaining present at 1.1 μg/mL 24 h after discontinuation of therapy. Laboratory values at one month continued to show elevated creatinine levels at 2.1 mg/dL, suggesting progression of his baseline CKD. This case supports the benefit of obtaining tobramycin serum levels and vestibular/audiology function testing when evaluating patients on chronic nebulized TIS who present with acute or chronic renal dysfunction. From these serum levels, adjustments to daily dosing, regular monitoring of tobramycin serum levels, or discontinuation of treatment should be made to prevent permanent renal damage in patients with CKD. Calculated Naranjo ADR Probability Scale: 9; Definite.

Pulmonary Manifestations of Renal Disorders in Children

The causes of kidney disease in pediatric patients are evenly divided between congenital abnormalities of the kidney and urinary tract and acquired disorders. Nearly 10% to 15% of adults in the United States have chronic kidney disease (CKD); there are no comparable data in children. Regardless of patient age, CKD is a systemic problem that affects every organ system, including the lung. We review the tests used to diagnose and evaluate kidney disease and the main clinical syndromes that are likely to be encountered to aid the pulmonology consultant who is asked to evaluate patients with kidney disease.

Cystic Fibrosis Related Diabetes - An Update

Cystic fibrosis (CF) is the most common life-threatening inherited condition in the Caucasian population, where mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene result in a multifactorial syndrome, with pulmonary disease representing the largest contributor to morbidity and mortality. Life expectancy has improved and the recent development of disease-modifying CFTR modulator therapies is likely to further improve survival. However, increasing life expectancy brings new challenges related to the complications of a chronic disease including an increasing prevalence of cystic fibrosis related diabetes (CFRD), itself associated with increased morbidity and early mortality. This review provides an update as regards the underlying mechanisms, investigation and management of CFRD.

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.

Advances in our understanding of genetic kidney disease using kidney organoids

A significant proportion of kidney disease presenting in childhood is likely genetic in origin with a growing number of genes implicated in its development. However, many children may have changes in previously undescribed or unrecognised genes. The recent development of methods for generating human kidney organoids from human pluripotent stem cells has the potential to substantially change the rate of diagnosis and the development of new treatments for some forms of genetic kidney disease. In this review, we discuss how accurately a kidney organoid models the human kidney, identifying the strengths and weaknesses of these potentially patient-derived models of renal disease.

Circulating biomarkers of antioxidant status and oxidative stress in people with cystic fibrosis: A systematic review and meta-analysis

Introduction

Oxidative stress may play an important role in the pathophysiology of cystic fibrosis (CF). This review aimed to quantify CF-related redox imbalances.

Methods

Systematic searches of the Medline, CINAHL, CENTRAL and PsycINFO databases were conducted. Mean content of blood biomarkers from people with clinically-stable CF and non-CF controls were used to calculate the standardized mean difference (SMD) and 95% confidence intervals (95% CI).

Results

Forty-nine studies were eligible for this review including a total of 1792 people with CF and 1675 controls. Meta-analysis revealed that protein carbonyls (SMD: 1.13, 95% CI: 0.48 to 1.77), total F₂-isoprostane 8-iso-prostaglandin F_2α (SMD: 0.64, 95% CI: 0.23 to 1.05) and malondialdehyde (SMD: 1.34, 95% CI: 0.30 to 2.39) were significantly higher, and vitamins A (SMD: −0.66, 95% CI -1.14 to −0.17) and E (SMD: −0.74, 95% CI: −1.28 to −0.20), β-carotene (SMD: −1.80, 95% CI: −2.92 to −0.67), lutein (SMD: −1.52, 95% CI: −1.83 to −1.20) and albumin (SMD: −0.98, 95% CI: −1.68 to −0.27) were significantly lower in the plasma or serum of people with CF versus controls.

Conclusions

This systematic review and meta-analysis found good evidence for reduced antioxidant capacity and elevated oxidative stress in people with clinically-stable CF.

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Blood biomarkers of oxidative stress were elevated in stable CF vs non-CF controls.

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Lipid peroxidation was positively correlated with age and immune cell count in CF.

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Antioxidants vitamins A & E, β-carotene, lutein and albumin were lower in stable CF.

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Antioxidants were positively correlated with body mass index and lung function in CF.

Retinopathy and microalbuminuria are common microvascular complications in cystic fibrosis-related diabetes

AIMS

To study the prevalence of microvascular complications and renal changes associated with cystic fibrosis-related diabetes (CFRD).

METHODS

This retrospective cohort study was conducted at the West Midlands Adult Cystic Fibrosis centre, United Kingdom. Data regarding age, sex, microalbuminuria, retinopathy neuropathy, and biochemical results were collected for all people with CFRD who had an annual review from 1 January 2018 to 31 December 2018 at the centre. Descriptive statistics were analysed using STATAv15.1.

RESULTS

A total of 189 patients were included, of which 56.6% were male and median age (interquartile range) was 33 (27-39) years; 79.4% (150/189) had their annual review in 2018. Those with a biochemically impaired renal function numbered 7.2% (13/180) and 22.7% (32/141) had microalbuminuria; 17.2% (10/58) had diabetes related retinopathy. No one in our cohort had diabetic ulcers; however, 10.3% (13/126) had absent foot pulses.

CONCLUSION

We found a higher prevalence of microalbuminuria compared with retinopathy in a large cohort of cystic fibrosis adults. This study demonstrates the need for regular specialist follow-up to facilitate early identification of such complications and a long-term prospective cohort to understand underlying mechanisms.

Renal involvement and metabolic alterations in adults patients affected by cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is one of the most frequent genetic diseases and the median survival of these patients has improved in the last few decades, therefore it becomes necessary to evaluate the long-term complications as renal and cardiovascular risk factors.

AIM OF THE STUDY

To evaluate the incidence, the manifestations of renal disease and the possible association with metabolic and endothelial dysfunction markers in the CF population.

MATERIALS AND METHODS

We performed a cross-sectional, observational study on 226 CF patients. Clinical and laboratory instrumental parameters (metabolic, inflammatory and endothelial dysfunction markers) were evaluated.

RESULTS

We showed 65 patients with chronic kidney disease (CKD) and 158 patients with a reduced value of forced expiratory volume in 1 s (FEV1), of which 58 patients with a severe reduction of FEV1. Moreover 28 patients had undergone lung transplantation and them had a significant lower estimated Glomerular Filtration Rate (eGFR) with respect to the non-transplanted patients (p < 0.001). We reported also a significant association between lower eGFR value and serum triglycerides, total cholesterol and low-density lipoproteins (LDL) (p = 0.005, p < 0.001, p = 0.040; respectively), with a significant negative correlation between eGFR and serum triglycerides (r = - 0.28; p < 0.01). Moreover we found a significant association between lower eGFR value and serum uric acid (SUA) (p = 0.005), while we did not found an association with 25-hydroxy-vitamin-D value, serum glucose and hemoglobin A1c levels.

CONCLUSIONS

Our study showed a high prevalence of CKD in CF patients. Moreover we showed an increase of endothelial dysfunction and metabolic indexes in patients with reduced renal function, as SUA, serum triglycerides and LDL, suggesting the need for an early and complete screening of the main metabolic indexes to reduce cardiovascular risk and progression of renal damage, in particular in patients with lung transplant.

The association of acute kidney injury with the concomitant use of vancomycin and piperacillin/tazobactam in children: A systematic review and meta-analysis

Concomitant use of vancomycin plus piperacillin/tazobactam (TZP) has been associated with increased risk of acute kidney injury (AKI) in hospitalized adults. In this systematic review and meta-analysis, we searched PubMed and EMBASE for pediatric studies examining this hypothesis, with reference to vancomycin monotherapy or in combination with another beta-lactam antibiotic. Out of 1381 non-duplicate studies, 10 met our inclusion criteria. We performed a random effects meta-analysis, based on crude odds ratios, and we accounted for both quality of included studies and publication bias. In primary analysis, concomitant vancomycin and TZP use yielded a statistically significant association with the development of AKI. More specifically, children with AKI had higher odds to have been exposed to vancomycin plus TZP, in comparison with vancomycin monotherapy (OR 8.15; 95% CI: 3.49-18.99), or vancomycin plus any other beta-lactam antibiotic (OR 3.48; 95% CI: 2.71-4.46). Based on the results of the Newcastle Ottawa Scale quality assessment, a secondary analysis including only higher quality studies (6 out of 10 studies) yielded again higher odds of exposure to vancomycin plus TZP, compared to vancomycin plus another beta-lactam antibiotic (OR 3.76; 95% CI: 2.56-5.51). Notably, even after controlling for possible publication bias our results remained statistically significant (OR 3.09; 95% CI: 2.30-4.14). In conclusion, the concomitant use of vancomycin and TZP could be associated with AKI development and the clinical significance of this potential association needs to be studied further in the pediatric population.

Meropenem potentiation of aminoglycoside activity against Pseudomonas aeruginosa: involvement of the MexXY-OprM multidrug efflux system

Objectives

To assess the ability of meropenem to potentiate aminoglycoside (AG) activity against laboratory and AG-resistant cystic fibrosis (CF) isolates of Pseudomonas aeruginosa and to elucidate its mechanism of action.

Methods

AG resistance gene deletions were engineered into P. aeruginosa laboratory and CF isolates using standard gene replacement technology. Susceptibility to AGs ± meropenem (at ½ MIC) was assessed using a serial 2-fold dilution assay. mexXY expression and MexXY-OprM efflux activity were quantified using quantitative PCR and an ethidium bromide accumulation assay, respectively.

Results

A screen for agents that rendered WT P. aeruginosa susceptible to a sub-MIC concentration of the AG paromomycin identified the carbapenem meropenem, which potentiated several additional AGs. Meropenem potentiation of AG activity was largely lost in a mutant lacking the MexXY-OprM multidrug efflux system, an indication that it was targeting this efflux system in enhancing P. aeruginosa susceptibility to AGs. Meropenem failed to block AG induction of mexXY expression or MexXY-OprM efflux activity, suggesting that it may be interfering with some MexXY-dependent process linked to AG susceptibility. Meropenem potentiated AG activity versus AG-resistant CF isolates, enhancing susceptibility to at least one AG in all isolates and susceptibility to all tested AGs in 50% of the isolates. Notably, meropenem potentiation of AG activity was linked to MexXY in some but not all CF isolates in which this was examined.

Conclusions

Meropenem potentiates AG activity against laboratory and CF strains of P. aeruginosa, both dependent on and independent of MexXY, highlighting the complexity of AG resistance in this organism.

Cystic Fibrosis: Advancing Along the Continuum

Cystic fibrosis (CF) is an autosomal recessive genetic disorder resulting from a mutation in the gene which encodes a cellular transmembrane protein channel known as the CF transmembrane conductance regulator. Located systemically on the surface of numerous cells, these altered channels yield multisystem dysfunction. Typical manifestations seen are chronic, progressive, obstructive lung disease, pancreatic insufficiency, CF-related diabetes mellitus, malabsorption and malnutrition, liver disease, and infertility.Once considered a pediatric disorder, through developments in innovative care and therapeutic modalities, CF now spans the life continuum and has established itself as an ageless disease. Facing management of maturing-life issues, advanced practice nurses (APNs) in pediatrics now find themselves needing to collaborate with or facilitate transition of care to other APNs, such as nurse midwives and adult APNs, as well as their counterpart specialists in medicine, all while maintaining open communication with the patient, family and managing CF center.

The renoprotective effect of concomitant fosfomycin in the treatment of pulmonary exacerbations in cystic fibrosis

Background

Fosfomycin, effective in Cystic Fibrosis (CF), competes with aminoglycosides at renal binding sites and may therefore afford a renoprotective effect when used in combination therapy. We explored this by using markers of acute renal tubular damage [N-acetyl-β-d-glucose-aminidase (NAG), alanine amino-peptidase (AAP) and β₂-microglobulin].

Methods

Using a prospective randomized crossover trial design, at an acute pulmonary exacerbation, 18 adult CF patients received either 14 days of intravenous (IV) tobramycin or IV tobramycin and IV fosfomycin, both in combination with a second IV antibiotic (colomycin).

Results

Urinary NAG (P = 0.003) and AAP (P = 0.03) following treatment with concomitant fosfomycin were lower than those after treatment with tobramycin and colomycin alone. Fosfomycin attenuated the total 24-h urinary protein leak (P = 0.0001). The 14-day improvements in all surrogate markers of exacerbation resolution (FEV₁% predicted, FVC, white cell count and C-reactive protein) were similar for both treatment regimens.

Conclusion

The addition of fosfomycin reduces acute renal injury caused by IV aminoglycoside therapy in CF pulmonary exacerbations.

Nephrotoxicity With Vancomycin in the Pediatric Population: A Systematic Review and Meta-Analysis

BACKGROUND

Vancomycin is frequently used to treat methicillin-resistant Staphylococcus aureus infections in pediatric patients. Vancomycin exposure may lead to an increase in frequency of nephrotoxicity. Our aim was to conduct a systematic review to describe predictors of nephrotoxicity associated with vancomycin, including documented trough concentrations ≥15 mg/L. We also aimed to use a meta-analysis to assess the impact of a vancomycin trough ≥15 mg/L on nephrotoxicity.

METHODS

A literature search was performed using PubMed, Cochrane Library, Embase and Web of Sciences database. We included randomized clinical trials and observational studies evaluating the relationship between vancomycin troughs and nephrotoxicity in pediatric-age patients. Studies not measuring troughs or defining a different cut-off point than 15 mg/L were excluded. Data on age, exclusion criteria, nephrotoxicity definition, risk factors for nephrotoxicity and vancomycin trough levels were extracted from selected papers.

RESULTS

Ten studies were identified for meta-analysis. All subjects had comparatively normal baseline serum creatinine values. Common risk factors identified included elevated (≥15 mg/L) trough levels, renal impairment, hypovolemia and concurrent use of nephrotoxic medications. Troughs ≥15 mg/L increased nephrotoxicity by 2.7-fold (odds ratio (OR), 2.71; 95% confidence interval: 1.82-4.05; I(2) = 40%; Q = 0.09). These odds were further increased among patients in the pediatric intensive care unit (OR, 3.61; 95% confidence interval: 1.21-10.74; I(2) = 45%; Q = 0.18).

CONCLUSIONS

Though the rate of vancomycin-induced nephrotoxicity is increased in pediatric patients with higher vancomycin troughs, other factors such as intensive care unit admission, hypovolemia and concurrent nephrotoxic drug use appear to contribute to the development of nephrotoxicity.

Antimicrobial molecules in the lung: formulation challenges and future directions for innovation

Inhaled antimicrobials have been extremely beneficial in treating respiratory infections, particularly chronic infections in a lung with cystic fibrosis. The pulmonary delivery of antibiotics has been demonstrated to improve treatment efficacy, reduce systemic side effects and, critically, reduce drug exposure to commensal bacteria compared with systemic administration, reducing selective pressure for antimicrobial resistance. This review will explore the specific challenges of pulmonary delivery of a number of differing antimicrobial molecules, and the formulation and technological approaches that have been used to overcome these difficulties. It will also explore the future challenges being faced in the development of inhaled products and respiratory infection treatment, and identify future directions of innovation, with a particular focus on respiratory infections caused by multiple drug-resistant pathogens.

Cystic Fibrosis-Related Diabetes

Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian populations. Individuals with CF have seen significant increases in life expectancy in the last 60 years. As a result, previously rare complications are now coming to light. The most common of these is cystic fibrosis-related diabetes (CFRD), which affects 40-50% of CF adults. CFRD significantly impacts the pulmonary function and longevity of CF patients, yet a lack of consensus on the best methods to diagnose and treat CFRD remains. We begin by reviewing our understanding of the pathogenesis of CFRD, as emerging evidence shows the cystic fibrosis transmembrane conductance regulator (CFTR) also has important roles in the release of insulin and glucagon and in the protection of β cells from oxidative stress. We then discuss how current recommended methods of CFRD diagnosis are not appropriate, as continuous glucose monitoring becomes more effective, practical, and cost-effective. Finally, we evaluate emerging treatments which have narrowed the mortality gap within the CF patient group. In the future, pharmacological potentiators and correctors directly targeting CFTR show huge promise for both CFRD and the wider CF patient groups.

Prevalence and characteristics of chronic kidney disease among Danish adults with cystic fibrosis

BACKGROUND

With improved prognosis of CF, comorbidities including chronic kidney disease (CKD) are becoming increasingly important. Identification of those at highest CKD risk is hence a priority.

METHODS

In this cross-sectional study, adults with CF attending the Copenhagen CF Centre at Rigshospitalet with ≥2 measurements of serum creatinine from 2013 to 2015 were included. Data was obtained from an electronic CF database, which contains anonymised clinical and laboratory data on all individuals attending the clinic. CKD was defined as a confirmed (≥3months apart) estimated glomerular filtration rate≤60mL/min/1.73m².

RESULTS

Of 181 individuals, the CKD prevalence was 2.7% and increased to 11% after inclusion of lung transplanted patients. Individuals with CKD were generally older (median 39 (IQR, 36-45) vs. 31 (IQR, 24-39) years; p<0.001), diabetic (86% vs. 41%, p<0.001), with longer median duration of chronic pulmonary infection (28.3 (20.0-35.8) vs. 20.0 (9.9-34.7) years; p=0.008) and with longer intravenous aminoglycosides use (606 (IQR, 455-917) vs. 273 (IQR, 91-826) days, p=0.005).

CONCLUSIONS

The CKD prevalence is high and related to age, diabetes, chronic infection, transplantation and aminoglycosides use. These observations call for longitudinal studies investigating CKD predictors in adults with CF.

Bicarbonate in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF, mucoviscidosis) is caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), which is a chloride and bicarbonate channel necessary for fluid secretion and extracellular alkalization. For a long time, research concentrated on abnormal Cl^- and Na⁺ transport, but neglected bicarbonate as a crucial factor in CF.

METHODS

The present short review reports early findings as well as recent insights into the role of CFTR for bicarbonate transport and its defects in CF.

RESULTS

The available data indicate impaired bicarbonate transport not only in pancreas, intestine, airways, and reproductive organs, but also in salivary glands, sweat duct and renal tubular epithelial cells. Defective bicarbonate transport is closely related to the impaired mucus properties and mucus blocking in secretory organs of CF patients, causing the life threatening lung disease.

CONCLUSIONS

Apart from the devastating lung disease, abrogated bicarbonate transport also leads to many other organ dysfunctions, which are outlined in the present review.

Defective CFTR leads to aberrant β-catenin activation and kidney fibrosis

Cystic fibrosis transmembrane conductance regulator (CFTR), known as a cAMP-activated Cl⁻ channel, is widely expressed at the apical membrane of epithelial cells in a wide variety of tissues. Of note, despite the abundant expression of CFTR in mammalian kidney, the role of CFTR in kidney disease development is unclear. Here, we report that CFTR expression is downregulated in the UUO (unilateral ureteral obstruction)-induced kidney fibrosis mouse model and human fibrotic kidneys. Dysfunction or downregulation of CFTR in renal epithelial cells leads to alteration of genes involved in Epithelial-Mesenchymal Transition (EMT) and kidney fibrosis. In addition, dysregulation of CFTR activates canonical Wnt/β-catenin signaling pathways, whereas the β-catenin inhibitor reverses the effects of CFTR downregulation on EMT marker. More interestingly, CFTR interacts with Dishevelled 2 (Dvl2), a key component of Wnt signaling, thereby suppressing the activation of β-catenin. Compared to wild type, deltaF508 mice with UUO treatment exhibit significantly higher β-catenin activity with aggregated kidney fibrogenesis, which is reduced by forced overexpression of CFTR. Taken together, our study reveals a novel mechanism by which CFTR regulates Wnt/β-catenin signaling pertinent to progression of kidney fibrosis and indicates a potential treatment target.

Glomerular and Tubular Renal Function after Repeated Once-Daily Tobramycin Courses in Cystic Fibrosis Patients

Introduction. Antibiotic treatment regimens against Pseudomonas aeruginosa lung infection in cystic fibrosis (CF) patients often include aminoglycoside antibiotics that may cause chronic renal failure after repeated courses. Aminoaciduria is an early marker of acute aminoglycoside-induced renal tubular dysfunction. We hypothesized that urinary amino acid reabsorption is decreased after repeated once-daily tobramycin therapies. Methods. In this prospective cross-sectional study creatinine clearance was estimated by the Schwartz and the Cockcroft-Gault formula. Tubular amino acid reabsorption was determined by ion exchange chromatography in 46 patients with CF who received multiple tobramycin courses (6.3 ± 10.1 (1–57)) in a once-daily dosing regimen and 10 who did not. Results. Estimated creatinine clearance employing the Cockcroft-Gault was mildly reduced in 17/46 (37%) of the patients who received tobramycin and 5/10 (50%) of the patients who did not but in none using the Schwartz formula. No association with lifetime tobramycin courses was found. Tubular amino acid reabsorption was not influenced by the amount of once-daily tobramycin courses. Conclusion. Clinically not significant reduction of eCCL occurred in a minority of CF patients. However, chronic tubular dysfunction was not present in patients with CF repeatedly treated with tobramycin in the once-daily dosing scheme.

Imaging the Abdominal Manifestations of Cystic Fibrosis

Cystic fibrosis (CF) is a multisystem disease with a range of abdominal manifestations including those involving the liver, pancreas, and kidneys. Recent advances in management of the respiratory complications of the disease has led to a greater life expectancy in patients with CF. Subsequently, there is increasing focus on the impact of abdominal disease on quality of life and survival. Liver cirrhosis is the most important extrapulmonary cause of death in CF, yet significant challenges remain in the diagnosis of CF related liver disease. The capacity to predict those patients at risk of developing cirrhosis remains a significant challenge. We review representative abdominal imaging findings in patients with CF selected from the records of two academic health centres, with a view to increasing familiarity with the abdominal manifestations of the disease. We review their presentation and expected imaging findings, with a focus on the challenges facing diagnosis of the hepatic manifestations of the disease. An increased familiarity with these abdominal manifestations will facilitate timely diagnosis and management, which is paramount to further improving outcomes for patients with cystic fibrosis.

Current and Emerging Therapies for the Treatment of Cystic Fibrosis or Mitigation of Its Symptoms

Clinical presentation of the chronic, heritable condition cystic fibrosis (CF) is complex, with a diverse range of symptoms often affecting multiple organs with varying severity. The primary source of morbidity and mortality is due to progressive destruction of the airways attributable to chronic inflammation arising from microbial colonisation. Antimicrobial therapy combined with practises to remove obstructive mucopurulent deposits form the cornerstone of current therapy. However, new treatment options are emerging which offer, for the first time, the opportunity to effect remission from the underlying cause of CF. Here, we discuss these therapies, their mechanisms of action, and their successes and failures in order to illustrate the shift in the nature of how CF will likely be managed into the future.

Cystic Fibrosis below the Diaphragm: Abdominal Findings in Adult Patients

Cystic fibrosis (CF) is the most common lethal autosomal recessive disease in the white population. Mutation of the CF transmembrane conductance regulator gene on chromosome 7 results in production of abnormally viscous mucus and secretions in the lungs of patients with CF. A similar pathologic process occurs in the gastrointestinal tract, pancreas, and hepatobiliary system. Inspissated mucus causes luminal obstruction and resultant clinical and radiologic complications associated with the disease process. Pancreatic involvement can result in exocrine and endocrine insufficiency, pancreatic atrophy, fatty replacement, or lipomatous pseudohypertrophy. Acute and chronic pancreatitis, pancreatic calcification, cysts, and cystosis also occur. Hepatic manifestations include hepatic steatosis, focal biliary and multilobular cirrhosis, and portal hypertension. Biliary complications include cholelithiasis, microgallbladder, and sclerosing cholangitis. The entire digestive tract can be involved. Distal ileal obstruction syndrome, intussusception, appendicitis, chronic constipation, colonic wall thickening, fibrosing colonopathy, pneumatosis intestinalis, gastroesophageal reflux, and peptic ulcer disease have been described. Renal manifestations include nephrolithiasis and secondary amyloidosis. The educational objectives of this review are to reveal the abdominal manifestations of CF to facilitate focused analysis of cross-sectional imaging in adult patients. Life expectancy in patients with CF continues to improve because of a combination of aggressive antibiotic treatment, improved emphasis on nutrition and physiotherapy, and development of promising new CF transmembrane conductance regulator modulators. As lung function and survival improve, extrapulmonary conditions, including hepatic and gastrointestinal malignancy, will be an increasing cause of morbidity and mortality. Awareness of the expected abdominal manifestations of CF may assist radiologists in identifying acute inflammatory or neoplastic conditions. (©)RSNA, 2015.