Hematuria ranges from microscopic to gross. Microscopic means blood that can only be seen with a microscope, and gross means visible to the naked eye. In trauma, we only care about gross hematuria, which ranges from the faintest of pink to the deepest red.
In trauma, gross hematuria is a result of an injury to kidney, ureter or bladder. Blunt injury to the ureter is so rare it’s reportable, so you can pretty much forget that one unless the mechanism is extreme. So you really just need to focus on kidney and bladder.
Any victim of blunt trauma that presents with visible hematuria needs to be evaluated by CT of the abdomen and pelvis with an added CT cystogram. Standard CT technique is done without a urinary catheter, or with the catheter clamped. Only 50% of bladder injuries show up with this technique.
CT cystogram is an add-on to the standard CT, and consists of the administration of contrast into the bladder which is then kept under pressure while the scan is done. Delayed slices through the pelvis after the bladder is depressurized and emptied is routine. Nearly 100% of bladder injuries are detected using this technique.
If the CT shows a renal laceration or hematoma, the patient should be admitted and managed according to your solid organ injury protocol. Kidney injuries fare better that livers and spleens, and only rarely require surgery. If no kidney or bladder injury is seen, the default diagnosis of a renal contusion is the culprit. No treatment is needed, and the patient can be discharged if no other injuries are present. The blood will clear over a few days, but may disappear and reappear a few times in the process. The patient can followup with their primary care physician in a week or two.