Abstract Background In patients admitted for acute decompensated heart failure (ADHF), residual congestion at discharge is associated with adverse clinical outcomes. Traditionally, the extent of congestion has been inferred from central venous pressure, but it has also been highlighted that this is insufficient for a comprehensive evaluation of residual congestion. On the other hand, renal congestion is an important finding of organ congestion, and Superb Microvascular Imaging (SMI), a technique that reveals minute flow details, is promising for assessing renal circulation. We hypothesized that in patients with ADHF, assessment of renal circulation using SMI may be superior to conventional methods in assessing residual congestion. Methods In this prospective study, we enrolled 45 consecutive patients admitted with ADHF. We performed comprehensive evaluations including blood tests, echocardiography, and renal ultrasonography using SMI. The vascular index (VI), as measured by SMI, was calculated as the percentage of blood flow signal area in the region of interest. Subsequently, we calculated the intra-renal perfusion index (IRPI), representing cyclic variation in VI, as (maximum VI - minimum VI) within one cardiac cycle, divided by the maximum VI (Figure). Brain Natriuretic Peptide (BNP) levels were utilized to evaluate the state of decongestion. Results At discharge, the mean IRPI was 0.61±0.04, while the median BNP levels were 204.9 pg/ml (interquartile range: 102.7, 428.2). Patients exhibiting elevated log BNP levels at discharge (>2.31, based on median value) displayed significantly higher IRPI values [0.61(0.49, 0.86) vs 0.53(0.35, 0.59), p=0.02] and were older (80.8±8.5 vs 70.3±14.9 years, p=0.010). However, no significant differences were observed regarding laboratory parameters including hematocrit and creatinine levels, as well as echocardiographic parameters such as ejection fraction, E/e' ratio, and estimated right atrial pressure (RAP). Moreover, at discharge, creatinine levels (p=0.56) and estimated RAP (p=0.06) exhibited no significant correlation with IRPI. Conclusion Renal circulation evaluated by SMI may serve as a useful indicator of the extent of residual congestion at discharge compared to blood tests and echocardiographic estimates of right atrial pressure in patients admitted for ADHF.