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.
High blood pressure in the portal vein (portal hypertension) can cause enlargement of the spleen and bleeding from veins in the esophagus. The eggs of Schistosoma hematobium typically lodge in the bladder, sometimes causing ulcers, bleeding into the urine, and scarring.