Objective:To investigate the effect of usage of transthoracic echocardiography(TTE) on the prognosis of patients after acute kidney injury (AKI) in intensive care unit (ICU).Methods:The clinical data of patients with AKI in the Medical Information Mart for Intensive Care (MIMIC-Ⅲ v1.4) database was collected retrospectively, and the patients were divided into TTE group (with TTE within 24 hours of AKI diagnosis) and No-TTE group (without TTE examination or first TTE examination was more than 24 hours after AKI diagnosis). Propensity score matching (PSM) was utilized to balance the baseline variables between the two groups and Cox regression analysis was used to evaluate the independent risk factors for 28-day all-cause mortality (the primary outcome). Moreover, after PSM, the effects of TTE usage on the second outcomes (including the volumes of intravenous fluid and urine output in the first, second and third 24-hour after the diagnosis of AKI; the total number of mechanical ventilation-free days, renal replacement therapy-free days and vasopressor-free days within 28 days after ICU admission; use of diuretics after the diagnosis of AKI; reduction in serum creatinine within 48 hours after the diagnosis of AKI; and the length of ICU stay and hospital stay) were also evaluated.Results:Among 23 945 eligible AKI patients, 3 365 patients (14.1%) patients received TTE within 24 hours after the diagnosis of AKI and finally there were 3 361 patients in TTE group and No-TTE group included in this study after PSM based on the ratio of 1∶1. After PSM, all variables in the two groups were well balanced (standardized mean difference<0.1, respectively). Before and after PSM, patients in TTE group had lower 28-day all-cause mortality compared with patients in No-TTE group (10.76% vs 13.04%, χ2=13.535, P<0.001; 10.65% vs 18.80%, χ2=88.932, P<0.001), and Kaplan-Meier survival curves also revealed that patients in the TTE group had higher cumulative survival rate compared with patients in No-TTE group (Log-rank χ2=15.438, P<0.001; Log-rank χ2=75.360, P<0.001, respectively). Multivariate Cox regression analysis showed that TTE was an independent influencing factor for 28-day all-cause mortality before and after PSM ( HR=0.80, 95% CI 0.73-0.89, P<0.001; HR=0.58, 95% CI 0.51-0.65, P<0.001). And all subgroup analyses showed the similar results. Compared with patients in the No-TTE group, patients in the TTE group had higher volume of intravenous fluid on the first day and the second day after the diagnosis of AKI (both P<0.01). Patients in the TTE group had higher volume of urine output on the first day and the third day after the diagnosis of AKI (both P<0.01). The patients in the TTE group had a significantly lower duration of vasopressor-free and mechanical ventilation-free (both P<0.01). The usage of diuretic was significantly higher in the TTE group compared with that in the No-TTE group (54.1% vs 44.2%, χ2=65.609, P<0.001). With respect to serum creatinine, the reduction in serum creatinine within 48 hours after the diagnosis of AKI was higher in the TTE group than that in the No-TTE group [36.6(23.0, 97.2) μmol/L vs 30.1(14.2, 61.9) μmol/L, Z=-9.549, P<0.001]. Moreover, TTE group had shorter ICU stay than that in the No-TTE group [5.03(3.40, 8.90) d vs 5.37(3.77, 10.00) d, Z=-6.589, P<0.001]. There were no significant difference between the two groups in other secondary outcomes (all P>0.05). Conclusions:Timely TTE utilization after AKI incident is associated with better clinical outcomes for ICU patients.