Sintilimab‑related cystitis/ureteritis in high‑grade endometrial stromal sarcoma: A case report and structured literature review.

Immune checkpoint inhibitors (ICIs) are cutting‑edge therapies in cancer treatment; however, they may trigger unique immune‑related adverse events (irAEs). Although irAEs can affect various organs, ICI‑induced cystitis/ureteritis has rarely been reported. We present a 44‑year‑old female patient with high‑grade endometrial stromal sarcoma who developed severe urinary frequency, urgency, and dysuria after three cycles of sintilimab combined with nab‑paclitaxel and carboplatin. Empirical antibiotic therapy failed to relieve her symptoms. Imaging revealed diffuse thickening of the bladder and ureteral walls with marked peri‑vesical and peri‑ureteral exudation. After treatment with methylprednisolone, the patient's symptoms improved dramatically. A subsequent urine culture grew Enterococcus faecalis, and the addition of piperacillin-tazobactam resulted in further symptom resolution. Following symptom resolution, she was rechallenged with sintilimab and developed only mild urinary tract symptoms. Subsequently, due to disease progression, treatment was switched to tislelizumab, and the urinary symptoms did not recur. The patient's urinary symptoms were sintilimab‑related cystitis/ureteritis with possible concomitant or partially suppressed bacterial infection. This case, together with a structured literature review of other immunotherapy‑related cystitis/ureteritis cases and subsequent ICI use, provides a practical reference for the diagnosis and management of ICI‑related urological irAEs and for subsequent anti‑tumor treatment.