The color of urine is an important indicator of your dog’s health status. Normal urine is typically transparent and yellow or amber in color. Any discoloration of urine is abnormal and should be considered an alarming sign in most cases.
When discoloration is caused by the presence of blood in the urine (a condition referred to as “hematuria” by physicians and veterinarians), the color of urine may be red, brown or even black depending on the possible alterations of the main pigment of the blood, that is hemoglobin. Sometimes, however, the presence blood in the urine of your dog is not macroscopically detectable upon visual inspection. In this case it can be ascertained only through microscopic examination of urine sediment, which reveals the presence of red blood cells in it.
When blood in urine is immediately visible to the naked eye (macroscopic hematuria), the color of urine varies depending on the amount of blood lost: a hemorrhage of 1 ml of blood (approximately one fifth of a teaspoon) is enough to make the phenomenon visually detectable. In this case urine usually assumes a red color with various gradations of tone. Sometimes, however, the traces of blood in the urine of your dog can impart to the urine itself a color different from red. For example, if urine is particularly acidic, the color is usually dark brown. Dark brown is also the color of urine with blood that has remained in the urinary tract for a prolonged period of time: this type of discoloration is caused by the oxidation of hemoglobin present in the traces of blood.
Causes for Blood a Dog's Urine
Before talking about the possible causes for the presence of blood in the urine of your dog, it must be outlined that the color of urine can be red or reddish brown in the absence of hematuria, too. For example, the red color of urine may rarely result from the consumption of certain drugs (e.g., neoprontosil, rifampim, phenotiazines) or foods (e.g., blackberries, beets), or can be the result of certain diseases characterized by red urine without blood, such as porphyrias (winy red color of urine from an excess of pigments called porphyrins) and myoglobinuria (reddish brown color of urine caused by the presence of muscle myoglobin resulting from a muscle damage). All this explains why, if you suspect that your dog has blood in its urine, your pet needs to get a urine examination done as early as possible, in order to confirm the actual presence of blood in its urine, as well as to rule out other possible causes of red urine.
The presence of blood in the urine of you dog is not a disease in itself, but can be a symptom of many different health conditions. So its treatment depends on the treatment of the underlying disease. A first differentiation must be made between hematuria of urinary tract origin (kidneys, ureters, bladder, urethra) and hematuria from genital tract contamination (prostate, prepuce, vagina).
As regards the first group, the most obvious cause for the presence of blood in the urine of your dog is trauma, which may result from blunt trauma (e.g. car accident) or sometimes from traumatic diagnostic procedures (urine collection through catheter or cystocentesis, renal biopsy). Other common causes of hematuria of urinary tract origin include urolithiasis (presence of stones in the urine) and neoplasia or infections of the kidneys, bladder and urinary passages. Sometimes your dog has blood in its urine because of a systemic alteration of the blood itself. This is especially exemplified by coagulopathies, that are diseases characterized by an altered ability of blood to form clots (e.g, warfarin intoxication, reduced number of platelets).
Hematuria from genital tract contamination is usually caused by inflammatory, neoplastic and traumatic lesions of the genital tract or it can be associated with estrus in bitches. Of course, in the latter case, it is not a sign of any particular disease. It is physiologic.
For the diagnosis of the underlying disease, other than laboratory and instrumental examinations, it is of paramount importance the evaluation of the other associated symptoms. In this process the cooperation of the pet owner may be crucial. For example, if the loss of blood in the urine is concomitant with signs of severe abdominal colic-type pain, it is likely due to the presence of kidney or urethral stones. Again, if your dog has blood in its urine and it shows extreme difficulty in urination, it is likely due to urethral obstruction from prostatic disease or urethral urolithiasis.
As already said, there is no universal treatment for hematuria, since therapy must be targeted to the underlying cause. In any case, however, whenever you notice the presence of blood in the urine of your dog, it is of paramount importance to immediately take the pet to the veterinarian, as early as possible. In fact, some of the underlying conditions mentioned (such as traumatic injury and rupture of the bladder, or urethral obstruction) can seriously put at risk your dog's life in the very short-term and must be promptly treated.