Many think of it as 'sticking.' implantation in humans always occurs when the embryo is between 6-7 days old. A very popular concept on the internet now in 2012, 'implantation bleeding, ' is speculative and mostly not useful.
Also, urinary stones can form in the bladder lining due to an accumulation of debris and chemicals. Broken blood vessels can cause blood in the urine, often because of torn or enlarged veins on the inner surface of the prostate. Blood in the urine also can be caused by the sudden stretching of the bladder wall.
Trauma or a medical procedure. Blood in the semen is common after medical procedures. For instance, as many as four out of five men may temporarily have blood in their semen following a prostate biopsy. Procedures done as treatment for urinary problems can also cause mild trauma that leads to temporary bleeding.