What causes blood in the urine no pain?

Painless hematuria.: A number of kidney problems can cause blood in urine without pain: glomerulonephritis, nephrotic syndrome, kidney tumors, vascular malformations and occusionally a large non-obstructing kidney stone. Benign and malignant tumors rare vascular malformations of bladder can cause painless hematuria. Bleeding disorders (ie hemophilia, von willebrands)plus anticoagulant medications & drug side effects.

Painful hematuria: Obstructing kidney or ureteral stones, pyelonephritis, mechanical blockage, trauma & tumors kidney. Bladder infections, interstitial cystitis, prostatitis & occasional drug side effects.