New research was presented at SCM 2021 Virtual, the Spring Clinical Meetings of the National Kidney Foundation, from April 6-10. The features below highlight some of the studies that emerged from the virtual conference.


Factors Associated With Volume Overload Identified in Patients With Pulmonary Arterial Hypertension

Although evidence indicates that volume overload in pulmonary arterial hypertension (PAH) is a frequent and early complication in the absence of overt kidney dysfunction that leads to right heart failure, data are lacking on the pathophysiology of volume overload and the role of the kidneys in sodium and water retention. To identify factors associated with volume overload in patients with PAH, investigators reviewed the charts of patients with PAH, with those on loop diuretics considered to be volume overloaded. With a median follow-up of 4 years, the 56% of patients on loop diuretics were significantly more edematous (1.24 vs 0.27 score), had higher BMIs (30.5 vs 25.1 kg/m2), and had shorter 6-minute walk test distances (360 vs 420 meters) than those not on diuretics. On right heart catheterization, those on diuretics had significantly higher right arterial pressure (7.9 vs 3.8 mmHg), with a trend toward higher mean pulmonary artery pressure (49 vs 42 mmHg) but no differences in cardiac index or pulmonary vascular resistance. The diuretic group also had higher serum alkaline phosphates (106.8 vs 76.2 U/L), but no differences in other blood work, including brain natriuretic peptide and glomerular filtration rate, when compared with the non-diuretic group.

Increased Calcium-Phosphate Nephrolithiasis Risk in CKD With NaHCO3?

Despite being commonly prescribed to patients with CKD, oral sodium bicarbonate (NaHCO3) has been postulated to increase calciumphosphate nephrolithiasis risk by increasing urinary pH. Researchers assessed the effects of NaHCO3 on urinary pH, calcium, phosphate, and citrate levels at baseline, week 12, and week 28 in adults with CKD to test this hypothesis. Participants were randomized to higher dose NaHCO3 (0.8 mEq/kg/d), lower dose NaHCO3 (0.5 mEq/kg/d), or placebo. Lower dose and higher dose NaHCO3 both increased mean urinary pH (+0.77, +0.97, respectively) and citrate (+108.3%, +145.7%) levels and decreased mean urinary phosphate (-145.9 mg/d, -87.6 mg/d) levels when compared with placebo. However, neither dose significantly affected mean urinary calcium levels (-9.2% for lower dose, 5.0% for higher dose) when compared with placebo. “Although NaHCO3 increases urinary pH, the increase in urinary citrate levels and decrease in urinary phosphate levels may mitigate the risk of developing calcium-phosphate nephrolithiasis in CKD patients,” conclude the study authors.

A Close Look at Hyperoxaluria Causes, Risk Factors & Change Over Time

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To determine the incidence of each category of hyperoxaluria (idiopathic, enteric, or primary) and analyze associated urine metabolic risk factors, rates of genetic testing, and change in hyperoxaluria over time, researchers completed a retrospective review of patients with at least one level of urinary oxalate excretion above 75 mg/day who were evaluated in a multidisciplinary stone clinic between 2006 and 2019. Among participants, 27% had an enteric cause, and 74% had idiopathic hyperoxaluria, with one individual undergoing genetic testing and found to have primary hyperoxaluria type 2. Patients had an average age of 62, 70% were male, and they had a median of three stone episodes. Primary stone type did not differ between those with enteric and idiopathic hyperoxaluria. Across all patients, the median urine oxalate level was 100.6 mg/day. Urine metabolic risk factors in the enteric group included low calcium, citrate, and urine pH; this group also had higher urinary oxalate and super saturation of uric acid. After a median follow-up of 46.6 months, the entire cohort experienced a significant drop in urinary oxalate of -33.8 mg/day, with the final oxalate remaining significantly higher in the enteric group, at 88.9 mg/day versus 60.1 mg/day in the idiopathic group.

Substantial Increase in Anemia of CKD Cases Predicted

With anemia occurring in approximately 15% of patients with CKD and associated with a high risk of complications and reduced quality of life, researchers used the Inside ANEMIA of CKD microsimulation model to project the burden of anemia of CKD in the United States until 2025. Using demographic and epidemiologic data drawn from the US Census Bureau, the CDC, and NHANES, the study team created a virtual cohort representing the US population. Age- and sex-stratified CKD status and anemia status were ascribed to all virtual individuals, key comorbidities were assigned to reflect countryspecific population statistics, and cardiovascular complication incidence rates were drawn from the literature. The microsimulation model projected the number of individuals with anemia of CKD in the US to increase by approximately 15% between 2020 and 2025, from 8.9 million to 10.7 million, according to preliminary results. Moderate-to-severe cases were projected to increase approximately 26%, with cardiovascular complication incidence rates also projected to increase in those with anemia of CKD by 2025.

Relatively High Prevalence of Pre-Dialysis Hyperkalemia

Research indicates that pre-dialysis hyperkalemia (HK) is the strongest single independent predictor of mortality for patients on hemodialysis (HD). To provide an updated estimate on the prevalence of pre-dialysis HK and an assessment of patient characteristics associated with higher prevalence of HK, investigators conducted a retrospective, observational analysis of patients with at least one potassium (K+ ) lab result within 1 year of enrollment among Dialysis Outcomes and Practice Patterns Study survey data from in-center, thrice-weekly HD patients in the United States from 2018-2020. Prevalence rates within 1 year of enrollment were 74% for any pre-dialysis HK (K+ >5.0 mEq/L), 43% for moderate-to-severe HK (K+ >5.5 mEq/L), and 17% for severe HK (K+ >6.0 mEq/L). Upon multivariate regression analysis, female sex, Hispanic ethnicity, and younger age were associated with higher HK prevalence rates, whereas recent (2018-2019) initiation of first dialysis at the facility, Black race, and cancer were associated with lower rates.