Lassa fever, an acute viral hemorrhagic illness caused by the Lassa virus and transmitted by the rodent Mastomys natalensis, remains endemic in West Africa and poses significant public health challenges. This study aimed to sonographically evaluate renal changes in Lassa fever patients and correlate these findings with serum creatinine levels. A total of 80 participants, including 40 confirmed Lassa fever patients and 40 healthy controls, underwent grayscale renal ultrasonography using a 3.5 MHz probe. Renal parameters assessed included length, width, depth, volume, cortical thickness, and parenchymal echogenicity. Statistical analysis was performed using SPSS version 20.0, with significance set at p ≤ 0.05. Results demonstrated that Lassa fever patients exhibited significantly lower renal measurements compared to controls, particularly in kidney length, depth, and cortical thickness. Additionally, 92.5% of patients showed increased parenchymal echogenicity. A strong positive correlation was observed between serum creatinine levels and echogenicity (r = 0.731; p = 0.000), indicating that renal structural changes are closely associated with functional impairment in affected patients. These findings underscore the utility of renal ultrasonography as a non-invasive tool for assessing kidney involvement in Lassa fever and highlight the importance of integrating imaging with biochemical markers for early detection and management of renal complications.