A kid in his early 20s is urinating blood doctors ruiled everything out what are some other possibilities that woyldnt show up on a blood test?

? Urethrorrhagia. Kid may have urethrorrhia which presents with a little bleeding at the end of urination, or a few drops of blood coming from the urinary opening. Usually associated with mild burning on urination. Is benign + self-limiting, though sometimes worrying, condition and all tests are negative. Can be due to a yreaplasma infection which would respond to eryhromycin. Cystoscopy reveals mild urethritis.
See a urologist. Initial testing for blood in the urine that is visible should include: -urine culture (infx) and cytology (cancer cells) -ct scan of the abdomen and pelvis with and without dye -cystoscopy (bladder scope) until this is done he hasn't been worked up. Blood testing isn't enough. If these tests are negative microscopic exam of the urine could show clues of inflammatory or autoimmune kidney disease.
Full work up needed. Urinating blood is an abnormal process and needs a full evaluation including urinalysis, cystoscopy (looking in bladder with a scope), ct scan to rule out upper tract (kidney etc) problems like stone, polyp, tumor and then there are a variety of kidney related ailments that may need to be evaluated. The most common reason for a young healthy male to bleed would be urinary tract infection , trauma o.