Department of Nephrology and the Nephrology Unit, both based at the Bielański Hospital in Warsaw and working jointly, form a tertiary level nephrological service for the 500.000 local population, both urban and suburban. The service was initiated early in 2005, and after the initial period of 2 years the full range of services has been permanently available. Dialysis services were outsourced before creating the nephrological service and ever since. The alarmingly high incidence of medical patients requiring acute dialysis for acute renal failure was noticed and has not been decreasing over time. The reasons for this high demand were not clear and we hypothesized the age of the population served could contribute to it.

Acute kidney injury (AKI) is defined as an increase in serum creatinine by a minimum of 0,3 mg/dl (24.3 mcmol/l) in 48 hours. It reflects a sudden onset of a prolonged reduction in glomerular filtration (GFR), which may be accompanied also by 6-12 hours oligo/ /anuria (1). AKI worsens the prognosis of inpatients (2), also during the post-discharge follow-up (3). The frequency of AKI in population is not well known, for hospital admissions due to the AKI represents only a minor fraction of all AKI cases, when the condition is serious enough to consider dialysis. The scarce data published so far indicate that the incidence of AKI approximates to 2100/mln, correlates with age, and is continuously growing (4), but dialysis is required in 200/mln (5). More data are available for AKI requiring hospitalization, but the admission rates vary significantly depending on the specialty of the reporting unit (6). The AKI acquired during hospitalisation (HARI – Hospital Acquired Acute Renal Injury), especially high in the ICU patients, is only a minor fraction of all AKI observed at hospitals. Since only 5% of all AKI needs dialysis (4), which remains stable over time, the aging populations would face increased demand for dialysis, and the incidence of AKI among patients admitted to the hospital renal units would increase over time. However, only limited data on AKI incidence in the elderly exists (7-10). Based on these data we hypothesised, that the number of AKI patients at our Department would grow.

Using a retrospective design of the study, we defined that it’s primary objective was to verify if the frequency of AKI diagnosis among nephrology service inpatients older than 65 years of age has been growing over time. The secondary objectives were to evaluate if the trend was similar among younger inpatient medical population, and what was the relative total impact of AKI among elderly on the demand for AKI services.

Retrospective search of the hospital database was performed to identify all medical records of patients admitted to the Department of Nephrology between January 1, 2007 and December 31, January 2011. All records with AKI as a primary or accompanying diagnosis were identified. The remaining records served as a control population. The yearly incidence of AKI was evaluated in patients 65 years old and older (65+), and below 65 years of age (< 65).