Hospitalization Burden of Patients with Kidney Stones and Metabolic Comorbidities in Spain during the Period 2017-2020.

Nephrolithiasis has become an increasing worldwide problem during the last decades. Metabolic syndrome, its components, and related dietary factors have been pointed out as responsible for the increasing incidence. The objective of this study was to evaluate the trends in the hospitalization rates of patients with nephrolithiasis, hospitalization features, costs, and how metabolic syndrome traits influence both the prevalence and complications of lithiasic patients. An observational retrospective study was conducted by analyzing hospitalization records from the minimum basic data set, including all patient hospitalizations in Spain in which nephrolithiasis has been coded as a main diagnosis or as a comorbidity during the period 2017-2020. A total of 106,407 patients were hospitalized and coded for kidney or ureteral lithiasis in this period. The mean age of the patients was 58.28 years (CI95%: 58.18-58.38); 56.8% were male, and the median length of stay was 5.23 days (CI95%: 5.06-5.39). In 56,884 (53.5%) patients, kidney or ureteral lithiasis were coded as the main diagnosis; the rest of the patients were coded mostly as direct complications of kidney or ureteral stones, such as "non-pecified renal colic", "acute pyelonephritis", or "tract urinary infection". The hospitalization rate was 56.7 (CI95%: 56.3-57.01) patients per 100,000 inhabitants, showing neither a significant increasing nor decreasing trend, although it was influenced by the COVID-19 pandemic. The mortality rate was 1.6% (CI95%: 1.5-1.7), which was higher, if lithiasis was coded as a comorbidity (3.4% CI95%: 3.2-3.6). Metabolic syndrome diagnosis component codes increased the association with kidney lithiasis when age was higher, reaching the highest in the eighth decade of life. Age, diabetes, and hypertension or lithiasis coded as a comorbidity were the most common causes associated with the mortality of lithiasic patients. In Spain, the hospitalization rate of kidney lithiasis has remained stable during the period of study. The mortality rate in lithiasic patients is higher in elderly patients, being associated with urinary tract infections. Comorbidity conditions such as diabetes mellitus and hypertension are mortality predictors.