Brief Answer:
It could be due to lesion in the bladder.

Detailed Answer:
Hello
Thanks for your query.Based on the facts that you have posted it appears that you have visible blood in the urine ( Hematuria)noticed since last 15 days.

I shall be happy if you can post me few more details to make comments on your problem.
1) Do you have any urinary complaints such as burning urination ,increased frequency of urination ,Urgency etc.?
2) Do you have pain while passing blood or it is a painless hematuria.?
3) Do you have pain in loin or back ache?
4) Do you have fever?
5) Are you taking any medications ?

Most of the time hematuria is either due to UTI especially Cystitis or due to stones in urinary system or any tumour in the urinary system and needs tio be investigated thoroughly to find out the source of blood.
Please consult qualified Urologist for evaluation and get following investigations done under his guidance.
1) Routine urine test and urine culture.
2) C.T scan of the urinary system
3) Blood coagulation profile
4) Endoscopic examination of bladder ( Cystoscopy)
5) I.V.P (intravenous pyelography.)
Further treatment will depend upon the findings of these tests and final diagnosis.

Hope I have answered your query. If you have any more questions please feel free to ask me I shall be happy to help you
Dr.Patil.

---

Brief Answer:
It could be due to bladder infecton.

Detailed Answer:
Hello
Thanks for feedback.

Since your C.T scan does not reveal ant mass lesion hematuria that you have could be due to Cystitis.However you need to get endoscopic examination of bladder( Cystoscopy) done to confirm the nature of infection.

In the mean while take broad spectrum antibiotics along with urinary antiseptics like Nitrofurantoin twice daily.

Ensure to rink more water to keep your urine dilute.

Thanks and Regards.
Dr.Patil.

---