I'm surprised the Doctor dismissed this so easily. I had microscopic blood ( not visible to the eye) in my urine and was sent to a specialist. My kidneys and whole urinary tract was checked out including a cystoscopy (bladder scope). I was told all the tests were to exclude anything serious rather than finding the cause which is often not found but is unimportant. I was told the most common causes are not found about 92%, kidney stones, bladder stones and cysts about 5% and malignancies about 3%. I am female so that may make a difference. My G.P. repeated the urine tests for a couple of weeks first before sending me, as it can be caused by infection (which was ruled out first), exercise or a blow to that region. I wouldn't leave anything to chance if I were you. I'd get the Doc to repeat the urine tests for a couple of weeks and then I'd be off to a urologist. I wouldn't panic though ( I did) as a malignancy is the least likely cause. All the best to you and your husband.