Background <p>Preserving kidney function is a pivotal aspect of the follow-up in patients with multicystic dysplastic kidney (MCDK). Kidney parenchymal abnormalities found in the contralateral kidney are commonly recognized as a poor prognosis for kidney injury. However, the clinical significance of these parenchymal features remains inadequately assessed. In this study, our team attempted to analyze the correlation between kidney parenchymal features and kidney function in patients with MCDK.</p> Methods <p>Our study is a retrospective, case–control study of 402 patients diagnosed with MCDK between January 2003 to December 2020. Clinical and ultrasonographic findings were retrieved. Patients were defined in the decreased kidney function group by decline in estimated glomerular filtration rate (eGFR), proteinuria, and presence of hypertension. Comparative analysis and logistic regression were used to evaluate risk factors of kidney injury.</p> Results <p>Kidney parenchymal features found in postnatal ultrasound including kidney cortical cysts (OR: 3.12, CI: 1.15–8.43) and increased kidney echogenicity (OR: 2.52, CI:1.18–5.36) were associated with a greater risk of kidney injury in patients with MCDK. Patients with longitudinal kidney length below the 25th percentile were also at greater risk of kidney injury (OR:3.20, CI:1.10–9.25). The presence of kidney cortical cysts was also associated with failure to reach compensatory hypertrophy (OR:0.22, CI:0.08–0.63).</p> Conclusions <p>This study is the first to isolate and evaluate parenchymal abnormalities in relation to kidney function in patients with&#xa0;MCDK. Our results warrant attention and closer follow-up for patients with MCDK who have abnormal parenchymal findings in their functioning solitary kidney.</p> Graphical abstract <p></p>