Background <p>Oxidized regenerated cellulose (ORC) is widely used as a local hemostatic agent during thyroid surgery. Although manufacturers report complete absorption within 7–14 days, persistent ORC is frequently observed in postoperative follow-up, often mimicking residual or recurrent thyroid tissue. This misinterpretation can result in unnecessary investigations or biopsies. The present study aimed (1) to define the ultrasonographic features of persistent ORC to prevent misleading radiological interpretations and (2) to identify the risk factors associated with delayed ORC resorption.</p> Methods <p>A retrospective review was conducted on 145 consecutive patients who underwent thyroid surgery between May 2022 and April 2024. Ultrasonographic follow-up findings were analyzed to identify persistent ORC. Potential clinical and hematological predictors of delayed absorption were evaluated. Statistical analyses included chi-square tests, t-tests, and Cox regression models to determine independent risk factors influencing ORC persistence.</p> Results <p>Persistence of ORC was significantly associated with a history of reoperation (<i>p</i> = 0.002), presence of coronary artery disease (<i>p</i> = 0.006), low neutrophil count (&lt; 3.785 × 10⁹/L; <i>p</i> = 0.003), and the use of the Pahacel^® brand of ORC. In contrast, ORC from the Surgicel^® brand showed significantly faster absorption. These findings suggest that both patient-related and product-related factors contribute to the delayed resorption of ORC.</p> Conclusions <p>Persistent ORC may mimic recurrent thyroid tissue on postoperative imaging. Awareness of its ultrasonographic appearance and understanding of related risk factors are essential to avoid unnecessary diagnostic procedures. Surgeons, endocrinologists, and radiologists should exercise caution during postoperative assessment, especially in patients with risk factors for delayed absorption.</p> Trial registration <p>This study is a retrospective analysis and was not prospectively registered.</p>