Is Nephrolithiasis an Unrecognized Extra-Articular Manifestation in Ankylosing Spondylitis? A Prospective Population-Based Swedish National Cohort Study with Matched General Population Comparator Subjects

Abstract

BackgroundAnkylosing spondylitis (AS) is associated with several extra-articular manifestations. Nephrolithiasis (NL) has not been recognized as one of those, however, several factors known to increase the risk of NL are at play in AS patients. The objective was to estimate rates and predictors of NL in Swedish patients with AS compared to the general population.Methods and FindingsWe performed a prospective population-based nationwide cohort study based on linkage of data from Swedish registries. 8,572 AS patients were followed for 49,258 person-years (py) and 39,639 matched general population comparators were followed for 223,985 py. Patients were followed prospectively together with comparator subjects from January 2001 through December 2009. The first occurrence of NL during follow-up was the primary outcome. Hazard Ratios (HR) were used to compare these rates adjusting for comorbidities and treatment, and to assess predictors for NL. Mean age at study entry was 46 years (inter quartile range 36–56 years), 65% were males. Based on 250 vs. 466 NL events, the adjusted HR of NL in AS patients was 2.1 (95%CI 1.8 to 2.4). Predictors of NL within the AS group included prior diagnosis of inflammatory bowel disease (IBD) (HR 2.3; 95%CI 1.7 to 3.3), prior diagnosis of NL (HR 16.4; 95%CI 11.5 to 23.4), and patients receiving anti-TNF treatment (HR 1.6; 95%CI 1.2 to 2.1). Male sex was a risk factor for NL both in AS patients and in the general population.LimitationsThe risk for residual confounding and inability to study the chemical nature of NL were considered the main limitations of the study.ConclusionsPatients with AS are at increased risk of NL, which may be considered a novel extra-articular manifestation. Previous history of NL, IBD, AS disease severity and male sex were identified as predictors of NL in AS.

Nephrolithiasis in Ankylosing Spondylitis and its Relation with Disease Assessment Scales

“…An extra-articular involvement is common in inflammatory diseases. Although renal involvement has been shown in many studies on AS, the number of studies investigating the coexistence of renal calculi in AS is very limited [7][8][9][10][11][12][13].…”

“…Several studies showing an increased incidence of renal calculi in patients with AS have been published [7][8][9][10][11][12][13]. Jacobsen et al found the risk of nephrolithiasis in patients with AS to be more than twofold compared to the general population.…”

“…Jacobsen et al found the risk of nephrolithiasis in patients with AS to be more than twofold compared to the general population. The authors described nephrolithiasis as an extra-articular manifestation in AS and factors such as the male gender, history of inflammatory bowel disease, and previous history of kidney stones were significant and clinical important predictors of nephrolithiasis in patients with AS [12]. Furthermore, a recently published study from Taiwan with a large patient number assessed the risk of nephrolithiasis among patients with AS compared to matched general population.…”

The Risk of Nephrolithiasis Among Patients With Ankylosing Spondylitis: a Population-Based Cohort Study

“…Also, the result of another population-based study (sample of 8,572 AS patients) in Sweden indicated that 4.0% of the AS patients and 1.8% of the general population comparators had received a diagnosis of nephrolithiasis at the end of the study period. 16 Additionally, Liu et al 17 claimed that AS patients with DM or Crohn's disease were observed to have a higher risk of nephrolithiasis.…”

Urolithiasis as an extraarticular manifestation of ankylosing spondylitis

“…More recently, several studies have shown that urolithiasis is indeed frequently observed among patients with AS [5][6][7]. Since urolithiasis may have a relapsing nature and may necessitate surgical intervention [8], it may cause significant morbidity beyond the morbidity caused by AS alone.…”