Kidney Veno-Muscular Characteristics and Kidney Disease Progression: A Native Kidney-Biopsy Study

Rationale & Objective

Assessment of kidney biopsies provides crucial information for diagnosis and disease activity, as well as prognostic value. Kidney-biopsy specimens occasionally contain veno-muscular complex (VMC), which consists of muscle tissues around the kidney venous system in the corticomedullary region. However, the role of VMC and the clinical significance of VMC variants are poorly understood. In the present study, we investigated kidney prognostic values of VMC variants.

Study Design

Retrospective cohort study.

Setting & Participants

Among 808 patients who underwent a kidney biopsy from 2011 to 2019, 246 patients whose kidney biopsy specimens contained VMC were enrolled.

Predictors

VMC variants; inflammatory-VMC (an infiltration of ≥80 inflammatory cells/mm2-VMC area) and VMC hypertrophy (hyper-VMC, a VMC average width ≥850 μm), and the interstitial fibrosis/tubular atrophy (IFTA) score.

Outcomes

A decline in estimated glomerular filtration rate (eGFR) ≥40% from the baseline or commencement of kidney replacement therapy.

Analytical Approach

Cox proportional hazards model.

Results

Among 246 patients with data on VMC, mean baseline eGFR was 56.0±25.6 ml/min per 1.73 m2; 80 had high inflammatory-VMC, and 62 had VMC hypertrophy. There were 51 kidney events over median follow-up of 2.5 years. We analyzed 2 VMC variants. Multivariable logistic regression analysis revealed that eGFR negatively correlated with the presence of both inflammatory-VMC and hyper-VMC. A Cox proportional hazards analysis revealed that inflammatory-VMC (but not hyper-VMC) was independently associated with the primary outcome after adjustments for known risk factors of progression, including proteinuria, eGFR, and the interstitial fibrosis/tubular atrophy (IFTA) score (hazard ratio, 1.97; 95% confidence interval, 1.00-3.91).

Limitations

Single-center study and small sample size.

Conclusions

Assessment of inflammatory-VMC provides additional kidney prognostic information to known indicators of kidney disease progression in patients who undergo kidney biopsy.

Plain-Language Summary

Assessment of kidney biopsies provides crucial information for diagnosis, disease activity, and prognostic value. Kidney-biopsy specimens occasionally contain veno-muscular complex (VMC), which consists of muscle tissues around the kidney venous system. Currently, the role of VMC in kidney health and diseases and the clinical significance of VMC variants are poorly understood. In the present study, we have shown that an infiltration of ≥80 inflammatory cells/mm2-VMC area (inflammatory-VMC) is independently associated with kidney disease progression after adjustments for known risk factors of progression. Therefore, assessment of inflammatory-VMC provides additional kidney prognostic information to known indicators of kidney disease progression in patients who undergo kidney biopsy.

The association between hypothyroidism and proteinuria in patients with chronic kidney disease: a cross-sectional study

Hypothyroidism is known to be correlated with kidney function and nephrotic range proteinuria. However, it is uncertain whether non-nephrotic proteinuria is associated with hypothyroidism. This study aimed to evaluate the association of proteinuria and hypothyroidism in chronic kidney disease (CKD) patients. We conducted a cross-sectional study composed of 421 CKD patients in a single hospital with measurements of 24-h urine protein excretion (UP) and thyroid function tests. Spearman correlation analysis revealed that 24-h Cr clearance (24hrCcr) was positively (r = 0.273, p < 0.001) and UP was negatively (r = - 0.207, p < 0.001) correlated with free triiodothyronine. Frequency distribution analysis stratified by CKD stage and UP for hypothyroidism revealed that the prevalence of hypothyroidism was higher among participants with higher CKD stage and nephrotic range proteinuria. Multivariate logistic regression analysis revealed that 24hrCcr and UP were significantly correlated with hypothyroidism (24hrCcr/10 mL/min decrease: odds ratio [OR], 1.29; 95% confidence interval [CI], 1.18-1.41; UP/1 g increase: OR, 1.10; 95% CI, 1.03-1.17). In addition, nephrotic range proteinuria, but not moderate UP (UP: 1.5-3.49 g/day), was significantly correlated with hypothyroidism compared to UP < 0.5 g/day. In summary, decreased kidney function and nephrotic range proteinuria, not non-nephrotic proteinuria, are independently associated with the hypothyroidism.

Prevalence of Chronic Kidney Disease and Variation of Its Risk Factors by the Regions in Okayama Prefecture

Objective: The prevention of chronic kidney disease (CKD) progression is an important issue from health and financial perspectives. We conducted a single-year cross-sectional study to clarify the prevalence of CKD and its risk factors along with variations in these factors among five medical regions in Okayama Prefecture, Japan. Methods and Results: Data concerning the renal function and proteinuria as well as other CKD risk factors were obtained from the database of the Japanese National Health Insurance. The proportion of CKD patients at an increased risk of progression to end-stage renal disease (ESRD), classified as orange and red on the CKD heatmap, ranged from 6–9% and did not vary significantly by the regions. However, the causes of the increased severity differed between regions where renal dysfunction was predominant and regions where there were many patients with proteinuria. CKD risk factors, such as diabetes mellitus, hypertension, hyper low-density lipoprotein-cholesterolemia, obesity, smoking and lack of exercise, also differed among these regions, suggesting that different regions need tailored interventions that suit the characteristics of the region, such as an increased health checkup ratio, dietary guidance and promotion of exercise opportunities. Conclusions: Approximately 6–9% of people are at an increased risk of developing ESRD (orange or red on a CKD heatmap) among the population with National Health Insurance in Okayama Prefecture. The underlying health problems that cause CKD may differ among the regions. Thus, it is necessary to consider intervention methods for preventing CKD progression that are tailored to each region’s health problems.

The Association of Postprandial Triglyceride Variability with Renal Dysfunction and Microalbuminuria in Patients with Type 2 Diabetic Mellitus: A Retrospective and Observational Study

OBJECTIVE

We examined whether or not day-to-day variations in lipid profiles, especially triglyceride (TG) variability, were associated with the exacerbation of diabetic kidney disease.

METHODS

We conducted a retrospective and observational study. First, 527 patients with type 2 diabetes mellitus (DM) who had had their estimated glomerular filtration rate (eGFR) checked every 6 months since 2012 for over 5 years were registered. Variability in postprandial TG was determined using the standard deviation (SD), SD adjusted (Adj-SD) for the number of measurements, and maximum minus minimum difference (MMD) during the first three years of follow-up. The endpoint was a ≥40% decline from baseline in the eGFR, initiation of dialysis or death. Next, 181 patients who had no micro- or macroalbuminuria in February 2013 were selected from among the 527 patients for an analysis. The endpoint was the incidence of microalbuminuria, initiation of dialysis, or death.

RESULTS

Among the 527 participants, 110 reached a ≥40% decline from baseline in the eGFR or death. The renal survival was lower in the higher-SD, higher-Adj-SD, and higher-MMD groups than in the lower-SD, lower-Adj-SD, and lower-MMD groups, respectively (log-rank test p = 0.0073, 0.0059, and 0.0195, respectively). A lower SD, lower Adj-SD, and lower MMD were significantly associated with the renal survival in the adjusted model (hazard ratio, 1.62, 1.66, 1.59; 95% confidence intervals, 1.05-2.53, 1.08-2.58, 1.04-2.47, respectively). Next, among 181 participants, 108 developed microalbuminuria or death. The nonincidence of microalbuminuria was lower in the higher-SD, higher-Adj-SD, and higher-MMD groups than in the lower-SD, lower-Adj-SD, and lower-MMD groups, respectively (log-rank test p = 0.0241, 0.0352, and 0.0474, respectively).

CONCLUSIONS

Postprandial TG variability is a novel risk factor for eGFR decline and the incidence of microalbuminuria in patients with type 2 DM.

Management of corticosteroid-dependent eosinophilic interstitial nephritis: A case report

INTRODUCTION

Drug-induced acute interstitial nephritis (DI-AIN) is an important cause of acute kidney injury. In renal biopsy specimens, tubulitis with eosinophilic infiltration is suggestive of DI-AIN. Although corticosteroid therapy and discontinuation of the offending drug can improve renal dysfunction in most cases of DI-AIN, some patients experience AIN recurrence, leading to corticosteroid dependency. Corticosteroid-dependent eosinophilic interstitial nephritis presents a difficult dilemma in diagnosis and information regarding optimum management is limited.

PATIENT CONCERNS

A 25-year-old man, who received treatment with carbamazepine, zonisamide, valproate, and lacosamide for temporal lobe epilepsy, showed an increase in serum creatinine level from 0.98 to 1.29 mg/dL over a period of 6 months. Although he exhibited no symptoms, his serum creatinine level continued to increase to 1.74 mg/dL.

DIAGNOSIS

Renal biopsy revealed tubulitis and interstitial inflammatory infiltrates with eosinophils. Immunological and ophthalmological examinations showed no abnormal findings, and thus, his renal dysfunction was presumed to be caused by DI-AIN. Although oral prednisolone (PSL) administration (40 mg/d) and discontinuation of zonisamide immediately improved his renal function, AIN recurred 10 months later. The increase in PSL dose along with discontinuation of valproate and lacosamide improved renal function. However, 10 months later, recurrent AIN with eosinophilic infiltration was confirmed by further biopsy. The patient was therefore diagnosed with corticosteroid-dependent eosinophilic interstitial nephritis.

INTERVENTIONS

To prevent life-threatening epilepsy, carbamazepine could not be discontinued; hence, he was treated with an increased dose of PSL (60 mg/d) and 1500 mg/d of mycophenolate mofetil (MMF).

OUTCOMES

MMF was well tolerated and PSL was successfully tapered to 5 mg/d; renal function stabilized over a 20-month period.

LESSONS

The presence of underdetermined autoimmune processes and difficulties in discontinuing the putative offending drug discontinuation are contributing factors to corticosteroid dependency in patients with eosinophilic interstitial nephritis. MMF may be beneficial in the management of corticosteroid-dependent eosinophilic interstitial nephritis by reducing the adverse effects related to high-dose and long-term corticosteroid use.