Clear Cell Renal Carcinoma in an Ulcerative Colitis Patient Under Short-Term Immunosuppressive Therapy: A Case Report

<b>Background/Objectives:</b> Renal cell cancer is a rare occurrence in patients with ulcerative colitis (UC), with no clearly demonstrated association between UC and an increased risk of renal malignancies. In this article, a case report concerning this relationship is presented. <b>Methods:</b> Our research group presented a case of clear cell renal carcinoma in a 56-year-old male with UC who had previously undergone ileorectal anastomosis and subtotal colectomy. <b>Results:</b> The patient developed a complex renal cyst that progressed to malignancy within one year while on immunosuppressive therapy with infliximab and then filgotinib. Previous ultrasound examinations of the kidney highlighted only simple cysts in the contralateral kidney in previous years. The neoplasm was promptly examined using contrast-enhanced ultrasound, confirming the diagnosis of a Bosniak IV cyst, which was corroborated by a subsequent computed tomography study. <b>Conclusions:</b> The patient underwent a nephrectomy and is currently scheduled for therapy with vedolizumab. Given the increasing use of biologics and small molecules in UC management, periodic ultrasound screening may be a valuable tool for the long-term monitoring of these patients.