Which of the following is a common complication associated with superficial bladder cancer treatments?

Hematuria, or blood in the urine, is a common complication associated with treatments for superficial bladder cancer, such as transurethral resection of the bladder tumor (TURBT) or intravesical immunotherapy. These procedures often cause irritation to the bladder's lining, leading to bleeding. Patients frequently report hematuria as a result of the manipulation and trauma to the bladder tissue during these treatments.

While infection, urinary incontinence, and kidney stones can occur in patients with bladder cancer or as complications of various treatments, they are not as directly associated with the specific interventions for superficial bladder cancer as hematuria is. Hematuria is a more immediate and prevalent concern post-treatment, making it the most common complication in this context.