Association between urinary uric acid excretion and kidney outcome in patients with CKD.

Inhibiting tubular urate reabsorption may protect the kidney from urate-induced tubular injury. However, this approach may promote intratubular uric acid crystallization, especially in acidified urine, which could be toxic to the kidney. To assess how tubular urate handling affects kidney outcomes, we conducted a retrospective cohort study including 1042 patients with estimated glomerular filtration rates (eGFR) of 15-60 mL/min/1.73 m2. The exposures were fractional excretion of uric acid (FEUA) and urinary uric acid-to-creatinine ratio (UUCR). The kidney outcome was defined as a halving of eGFR from baseline or initiating kidney replacement therapy. The median FEUA and UUCR were 7.2% and 0.33 g/gCre, respectively. During a median follow-up of 1.9 years, 314 kidney outcomes occurred. In a multivariate Cox model, the lowest FEUA quartile exhibited a 1.68-fold higher rate of kidney outcome than the highest FEUA quartile (95% confidence interval, 1.13-2.50; P = 0.01). Similarly, lower UUCR was associated with a higher rate of kidney outcome. Notably, patients in the highest quartile of FEUA and UUCR were at the lowest risk of kidney outcome even among those with aciduria. In conclusion, lower FEUA and UUCR were associated with a higher risk of kidney failure, suggesting that increased urate reabsorption is harmful to the kidney.

Interstitial Eosinophilic Aggregates and Kidney Outcome in Patients with CKD.

BACKGROUND: Interstitial eosinophilic aggregates are observed in various kidney diseases, but their clinical implications remain unknown. We assessed the association between interstitial eosinophilic aggregates and kidney outcomes and further analyzed the association between blood eosinophil count, as a surrogate for interstitial eosinophilic aggregates, and the risk of kidney failure in patients with advanced CKD. METHODS: We analyzed datasets from two retrospective cohort studies: ( 1 ) the kidney biopsy cohort including 563 patients who underwent native kidney biopsy at Osaka University Hospital between 2009 and 2021 and ( 2 ) the retrospective CKD cohort including 2877 patients with an eGFR of 10-60 ml/min per 1.73 m 2 referred to the nephrology outpatient center at Osaka University Hospital between 2005 and 2018. Interstitial eosinophilic aggregates were defined as ≥5 interstitial eosinophils in the high-power field on hematoxylin and eosin staining. This study outcome was initiation of KRT or ≥40% decline in eGFR. RESULTS: In the kidney biopsy cohort, interstitial eosinophilic aggregates were found in 17% of patients, most frequently in those with diabetic nephropathy (50%). Interstitial eosinophilic aggregates were associated with a higher rate of the composite kidney outcome after adjustment for clinical and histological variables (hazard ratio, 3.61; 95% confidence interval, 2.47 to 5.29; P < 0.001). LASSO revealed that blood eosinophil count was the strongest predictor of interstitial eosinophilic aggregates. In the retrospective CKD cohort, higher baseline and time-updated blood eosinophil counts were significantly associated with a higher rate of KRT initiation in Cox proportional hazards models and marginal structural models. CONCLUSIONS: Interstitial eosinophilic aggregates were associated with a higher risk of a composite of KRT initiation or ≥40% decline in eGFR. PODCAST: This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2023_12_08_CJN0000000000000277.mp3.

Metabolic alkalosis due to short bowel syndrome in a hemodialysis patient.

A 53-year-old man on hemodialysis suffered from short bowel syndrome after subtotal colectomy and partial resection of the small intestine. Laboratory tests showed multiple electrolyte disorders and enlarged sodium and chloride ion (Cl-) gaps despite treatment with large volume of sodium chloride replacement via central venous infusion. Blood gas analysis showed slightly high bicarbonate ion levels and metabolic alkalosis was suspected, which is uncommon in end stage kidney disease. The measurement of electrolytes in feces from ileostomy showed relatively high Cl- excretion. The loss of Cl- to feces may have caused the metabolic alkalosis; thus, additional Cl- replacement may have been necessary.