Asymptomatic urate-crystals deposits in patients with stages 3-5 chronic kidney disease detected by ultrasound

 

Enrique Calvo-Aranda, Boris Anthony Blanco-Caceres, Laura Barrio Nogal, Marta Novella-Navarro, Diana Peiteado, Eugenio De Miguel, Alejandro Prada-Ojeda, Luis Sala-Icardo, Jaime Arroyo Palomo, Roberto Alcazar Arroyo, Juan Antonio Martin Navarro, Marco Antonio Vaca Gallardo, Milagros Fernandez Lucas, Martha Diaz Dominguez, Monica Vazquez Diaz, Maria Teresa Navio Marco

Hospital Universitario Infanta Leonor, Madrid

 

Background: one in ten patients with hyperuricemia may develop gout over time, with urate deposition sometimes asymptomatic. Recent reviews support ultrasound (US) to assess asymptomatic hyperuricemic (AH) patients to detect gout lesions, showing double contour (DC) and tophus the highest specificities and positive predictive values. Hyperuricemia and gout are common in chronic kidney disease (CKD), especially with glomerular filtration rate (GFR) <60, and are associated with worse prognosis. US gout lesions have been found more frequently in AH (up to 35%) than in normouricemic (NU) patients, but evidence is scarce in CKD.

Objectives: To assess the prevalence of urate deposit in stages 3-5 CKD detected by US, and to investigate if there are differences between AH and NU patients.

Methods: Case-control study, recruiting patients aged ≥18 years with AH and stages 3-5 CKD in 4 hospitals from january 2020 to december 2021. Controls were patients with stages 3-5 CKD and NU.

Exclusion criteria: Previous diagnosis of gout, tophi. Hyperuricemia was defined as serum uric acid (sua) >6.8 mg/dl, documented at least twice during the last 12 months. A standardized US exam of the knees and bilateral first metatarsophalangeal joints was performed to assess patients for DC/tophus as defined by omeract. Demographic, clinical and laboratory data were recorded. A descriptive analysis was performed using spss. Pre-clinical gout (pcg: DC and/or tophus) was considered as outcome variable. Chi-square and fisher's exact test were used for qualitative variables, and mann-whitney u test for quantitative variables; significant threshold p<0.05.

Results: Forty-four patients with stages 3-5 CKD (59.6% stage 3, 19.1% stage 4, 21.3% 5) were recruited, 35 AH and 9 NU. Hyperuricemia was associated with a higher prevalence of US findings, with significant differences between cases (AH) and controls (NU): pcg 19 vs 1 (p=0.023), DC 13 vs 1, and tophus 11 vs 0. No significant differences were found in demographic variables, comorbidities and treatments. Sua levels, were higher in patients with pcg (8.3±1.4 vs 7.6±2.2; p=0.36), and these patients also showed lower GFR (31.4±14.1 vs 33.7±16.9; p=0.62). Patients with pcg also showed a non-significant trend towards shorter duration of CKD [6.3±5.7 vs 8.3±4.9 years; p=0.1] and younger age (66.4±15.1 vs 70.0 ±11.0; p=0.30).

Conclusions: We found an outstanding prevalence of asymptomatic urate deposits in our cohort of patients with stages 3-5 CKD, that is higher in hyperuricemic than in normouricemic patients. The prevalence of DC and tophus in our cohort of AH patients with stages 3-5 CKD was higher than that reported in AH patients in studies conducted in general population (37% vs 16-31% and 31% vs 16%, respectively). Early diagnosis of pre-clinical gout by ultrasound might change therapeutic approach in CKD.

 

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