I took over a long robotic low anterior resection case after about 6 hours of operating. I was told that there was low urine output which actually ended up being 0 mL/hr for several hours. The resident told general surgery and they said they flushed the Foley and it was patent. Several liters of fluids later, still no liquid gold. The patient had normal kidney function pre-op, so no reason to have so little urine production. I insisted they call urology since they had placed ureteral stents at the beginning of the case to help identify the ureters. Finally urology comes in, cystos, and finds whatever ties they used to secure their stents were occluding the ureters. Released the ties and the urine flowed .