This is a single-center, prospective, randomized, controlled trial comparing two established transurethral electrical resection methods of urinary bladder tumors regarding their risk of stimulating the obturator nerve.

One of the major safety issues with transurethral resection is bladder perforation as a consequence of obturator nerve stimulation followed by muscle contraction of. This is mostly a risk of resection of lateral bladder wall tumors near the course of the obturator nerve. It has been advocated that bipolar may be superior to monopolar resection, based on its different electrical properties. This is an important safety aspect for the patient.

Main study question: In patients with lateral wall urinary bladder tumors, is bipolar superior to monopolar transurethral electroresection regarding risk of stimulation of the obturator nerve without preoperative nerve block?

Inclusion Criteria:

• neoplasms of the lateral wall of the urinary bladder (laterally to the corresponding ostium)
• operability given based on general medical condition
• informed consent

Exclusion Criteria:

• antiplatelet drugs stopped <7days (except acetylsalicylate <= 100mg p.o. qd)
• prothrombine time <70%
• age <18 years
• patronized Patients
• pregnancy
• severe poor medical condition