Table 2.

Characteristics of hospitalizations, for non-AKI hospitalizations, all AKI hospitalizations, and hospitalizations with AKI listed as the first discharge diagnosis^a

Total Cohort	Non-AKI Hospitalizations	AKI by ICD Code in
		Any Position (all AKI)	First Position (for AKI)
n	16,773	492	112
Percent of total hospitalizations	97.2%	2.8%	0.6%
Mean length of stay, days	5.5	14.6	9.7
Mean time since visit 4, days	1647.7	2047.1	2096.6
High-risk hospitalization (%)b	5.4	5.7	0.0
AKI first diagnosis code (%)	0.0	22.8	100.0
Received dialysis in hospital (%)	1.9	12.8	23.2
In-hospital death (%)	2.5	18.9	4.5

^aFor the comparison of non-AKI hospitalizations to AKI hospitalizations, all P values <0.001 with the exception of % high-risk hospitalization (P = 0.8). For the comparison of AKI hospitalizations defined by ICD code in the first position to those defined by an ICD in any other position (not shown), all P values <0.001 with the exception of mean length of stay (P = 0.04) and mean time since visit 4 (P = 0.8).

^bHigh-risk hospitalization defined as a hospitalization with an ICD-9 code for open heart surgery (including coronary bypass surgery) or percutaneous coronary intervention.