OP0186 Nephrolithiasis as a complication of gout: a cross-sectional study with helical computed tomography
Authors: F.P. Ramos, A.T. Barbosa, R.B. Souza, F. Seragioli, R.D.N. Giorgi, R.F. Rosa
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Gout is the most prevalent inflammatory arthritis, secondary to persistent hyperuricemia. It has been associated with development and progression of cardiometabolic diseases and chronic kidney disease. Several studies have shown a relationship between hyperuricemia and history of nephrolithiasis, although cut-off levels for uric acid and other related risk factors are still not well established. <h3>Objectives</h3> To determine the frequency of nephrolithiasis (NL) detected by helical computed tomography (h-CT) and its associated risk factors in patients with gout in a tertiary hospital of São Paulo, Brazil. <h3>Methods</h3> This cross-sectional study, conducted from 2016 to 2017, included 80 patients with a diagnosis of gout, according to the criteria of the ACR/EULAR-2015. They were questioned about the previous history of NL and submitted to h-CT for NL. Two groups were established: with and without NL; and later, unilateral and bilateral lithiasis. Anthropometric data, disease duration, serum uric acid (UA), creatinine, urinary pH(pH) and urinary UA of groups were compared. Statistical analysis included: mean, standard deviation, relative percentages, t-student test, chi-square test and ROC curve. Comparison of time to event-rate was performed by Kaplan-Meier method with log rank test. p<i>&lt;0.05</i> was considered statistically significant. <h3>Results</h3> NL was confirmed by h-CT in 30% of patients. However, only 16% reported previous history of NL. Groups with NL and without NL were similar in mean age (65,96±5,54 and 68,89±9,58 years, p<i>=0.147</i>), disease duration (16,63±11,49 and 11,77±9,74 years, p<i>=0.056</i>) and BMI (29.72±5.09 and 28.82±5,08, p<i>=0.470</i>). The NL group had higher pre-treatment UA compared with patients without NL (9,36±1,09 and 8,80±1,08 mg/dL, p<i>&lt;0.05)</i> and the most acidic pH (5,26±0,42 and 5.74±0.62, p<i>&lt;0.05</i>). In addition, patients with bilateral NL presented higher BMI than unilateral patients (p<i>=0.036</i>). According to ROC curve analysis, the best cutoff value for pre-treatment UA was 8.5 mg/dL, yielding sensitivity and specificity of 75% and 50%, respectively, for predicting NL events in this study. Kaplan-Meyer analysis showed that after 20 years of disease, 55% of patients with pre-treatment AU ≥8.5 mg/dL had NL, while only 18% of patients with pre-treatment AU &lt;8.5 mg/dL. <h3>Conclusions</h3> Since prevalence of NL in gout patients cannot be determined reliably from the clinical history, an active screening test for NL should be performed in these patients. Our study suggests that urine acidification and UA ≥8.5 mg/dL are associated with an increased risk of NL during follow-up of gout patients and should be corrected in their treatment. <h3>References</h3> [1] Shimizu T, et al. The prevalence of nephrolithiasis in patients with primary gout: a cross-sectional study using helical computed tomography. J Rheumatol2009Sep;36(9):1958–62. doi:10.3899/jrheum.081128 (Epub: 2009 Jul 15). [2] Wan KS, et al. Nephrolithiasis among male patients with newly diagnosed gout. Hong Kong Med J2016Dec;22(6):534–7. (Epub: 2016 Sep 9). [3] Shimizu T, et al. Novel evaluation of nephrolithiasis as a complication of gout: a cross-sectional study using helical computerized tomography. J Urol2013May;189(5):1747–52. doi:10.1016/j.juro.2012.11.076 (Epub: 2012 Nov 15). [4] Kramer HJ, et al. The association between gout and nephrolithiasis in men: The health professionals follow-up study. Kidney Int2003Sep;64(3):1022–6. <h3>Disclosure of Interest</h3> None declared