Kidney stones are a common medical condition that are associated with an increased risk for the development of chronic kidney disease. Whilst much is known about the epidemiology of the disease, less is known about health service utilisation, especially presentations to emergency departments and admissions to hospital. The aims of this study were to quantify the number of presentations to hospital for kidney stones over a 15-year period in one regional health district of New South Wales, Australia.
This retrospective cohort study analysed routine administrative data from two cohorts of patients: (i) patients presenting with kidney stones to any Emergency Department (ED) within the health district between 01 March 2009 to 30 June 2016 and (ii) patients admitted with kidney stones to any hospital in the health district between 1 July 2001 and 30 June 2016. The relevant SNOMED and ICD9 and ICD10 codes were used to identify patients.
There were 1168 emergency department presentations for kidney stones in the eight year study period. This included presentations from 660 unique individuals, the majority of whom were male (69%). Visits to ED due to kidney stones represented 5% of all ED presentations. The median age was 50 years (Interquartile range, IQR: 41-63 years) with males significantly older than females (male median age 53 years IQR: 43-64 years; females median age 45 years IQ: 36-58 years; p<0.0001). Most individuals had only one presentation to ED with kidney stones (60%, IQR: 1-2). However, 17.7% of individuals had three or more presentations in the eight-year period (range 3-11 presentations).
Regarding inpatient hospital admissions, there were 24 374 admissions from 3653 unique individuals with kidney stones over the 15 year study period. The majority of admissions with kidney stones were male (56%) with a median age of 67 years (IQR: 53-76). Females admitted with kidney stones were significantly younger than males (p<0.0001). The median number of admissions to hospital per individual with kidney stones was 7 (IQR: 4-14), with a median length of stay of 2 days (IQR: 0-7 days). The most common comorbidities associated with individuals who were admitted with kidney stones were smoking (11.1%), diabetes (9.4%) and urinary tract infections (3.8%).
Health service use by adults with kidney stones is not insignificant. Reasons for the differences in age between genders is unclear. Unlike previous studies, the sex ratio in this cohort is different and appears to be closer to 1:1, rather than 2:1. Reasons for this are unknown. The strength of this study was the use of routine administrative data capturing all presentations and admissions in the health district. Limitations include a lack of detail regarding kidney stone type and no information on interventions performed during the admission. Data from private hospital admissions were unavailable, and the non-identifiable nature of the data meant we were unable to link ED admissions and hospital presentations. Further exploration is warranted regarding the comorbidities associated with kidney stones such as smoking and diabetes. Analysis of longitudinal data is highly informative and provides insights into patient demographics and the burden of kidney stones on the health system. Work is required to identify risk factors in those with kidney stones who are high users of hospital services.