To answer your questions:
1) Typically, hematuria is defined as more than 2 RBC's per high-power field. With this is mind, there is no "safe" lower limit where significant disease can be excluded.
2) Other potential causes can include a kidney stone, infection, bladder mass or intrinsic kidney disease.
3) It is possible that the irritation can cause the accompanying symptoms of bloating, nausea. Flank and abdominal pain may point towards a kidney stone being a cause. I would consider a helical CT scan to rule this out.
A urology referral would be the appropriate next step to evaluate this.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
Medical Weblog:
kevinmd_b