Abstract Background and Aims Point-of-Care Ultrasonography (POCUS) is a novel approach where the treating physician directly performs ultrasonography at the bedside, enabling rapid understanding of the patient's condition, diagnosis, and immediate connection to treatment. Venous Excess Ultrasound (VExUS), one method in POCUS, can swiftly identify structural or functional abnormalities in internal organs, allowing for more accurate assessment of congestion in organs. Here, we report a typical case which illustrates the usefulness of VExUS in correct diagnosis and appropriate management of congestive kidney failure. Method A case report. Results A 51-year-old woman with mitochondrial myopathy with chronic heart failure was admitted due to loss of appetite and failure to thrive. She presented with acute kidney injury (AKI) and severe acidemia. Given her medical history and physical examination, prerenal causes (hypovolemia/hypotension) of AKI were considered most likely. However, with a significantly elevated NT-proBNP level of 14700, congestive kidney was also considered. Bedside echocardiography showed no evidence of low output syndrome, whereas VExUS (Venous Excess Ultrasound) Score indicated assessed as Grade 2 (moderate congestion). In addition to administering fluids for the suspected prerenal causes (hypovolemia/hypotension), sodium bicarbonate was administered suspecting a negative impact of severe acidemia on cardiac function. With the improvement of acidemia and only a small volume of fluid therapy, there was a rapid improvement in AKI with normalization of VExUS score. This suggested that the main cause of AKI was congestive kidney. Conclusion This case demonstrated the significant contribution of VExUS in accurate diagnosis and treatment.