A middle-aged gentleman was seen for elevated serum creatinine. He had a history of recurrent urinary tract infections, urinary urgency, and microscopic hematuria for about 2 years. Kidney ultrasound demonstrated bilateral moderate hydronephrosis. There was no obvious source of obstruction and the patient denied having any symptoms suggestive of renal colic. CT scan of the abdomen and pelvis found a small non-obstructing stone in the left kidney as well as reported ‘diffuse urothelial thickening’. No prostatomegaly or mass lesions were identified. Cystoscopy findings shown. What is the diagnosis?