A renal pelvis tumor is a rare growth in the kidney’s collecting funnel. Because it sits right where urine pools, the first warnings usually show up in the pee. Painless blood is the hallmark. Urine turns pink, rust, or contains small clots, and the color often comes and goes, so many blame infection at first. Flank ache creeps in. A dull, steady throb below the ribs can spread to the groin as the tumor blocks urine flow or clots pass. Urgency and frequency climb. You dash every hour, yet only a small amount comes out each time. Stream changes show... Learn more