the vasculogenic theory of female sexual dysfunction

by Chris Steidle, MD

The second theory of the origin of female sexual dysfunction, that of decreased blood flow, is based on the concept that female sexual dysfunction is related to a loss of blood flow to the pelvic tissues and a decrease in muscle relaxation in the tissues that comprise the vaginal tube and clitoris. These changes result in a decrease in vaginal lubrication and changes in the shape and diameter of the vaginal tube. Basically, this means the vaginal tube fails to dilate adequately in preparation for penetration.

This theory is based on the idea that the female clitoris is very similar to the male penis and since erectile dysfunction in men is associated with a decreased blood flow, the problem must have a similar cause in women.

Furthermore, low testosterone in men is almost never a cause of male erectile dysfunction unless it is the rare individual who has a truly low testosterone level. When a woman experiences a decrease in blood flow to the vagina, it can be manifested by a decrease in engorgement of the vagina with blood and a decrease in vaginal lubrication, which results in painful intercourse, diminished vaginal sensation, and an inability to achieve an orgasm. An implication of this theory is that drugs like Viagra may have a potential role in the treatment of female sexual dysfunction.

Unfortunately, this is a very difficult theory to test in real life. In men it’s easy. When blood flow to the penis is restored, you need only to measure the erection, its rigidity, and the length of time it took to create the erection, to know if the medication worked. This is not as easy in women.

One could ask, “How much lubrication is there?” It is not well known that the lubrication in a woman’s vagina is a transudate from the blood stream. A transudate is made up of the fluid part of blood that leaks from the blood vessels. How can one know what is a normal amount? It is generally agreed that roughly a teaspoon or 5 cc is about the amount of fluid produced by a woman when she becomes aroused. Decreased fluid production is a direct response to decreased blood flow.

Very elegant research done by Dr. Irwin Goldstein, a noted Urologist, indicates that increasing blood flow in a rabbit vagina is a very effective model for us. His research found that by creating blockages in the arteries to the pelvis of a rabbit, the vaginal engorgement and clitoral erection are decreased.

The real difficulty lies in proving this theory. Apparently, there are several new techniques that are used to measure vaginal blood flow. One technique uses a Doppler ultrasound probe, basically a small camera, that measures the speed of blood flow in the tissues as a noninvasive way to detect changes in the vaginal and clitoral blood supplies. This is a technique that is also used in men to measure how fast the blood enters the penis, which provides very valuable information as to the cause of problems with erections.

Another useful tool is that of vaginal photoplethysmography. Basically, this is a tampon shaped device that can actually measure the amount of blood that flows through blood vessels in the vagina. By shining light on this area and recording the reflected light, one can measure the amount and changes in blood flow. Using this technique, we can actually measure increased blood flow in the vagina in response to medications.

Another useful technique is that of taking vaginal temperatures with a device that can measure minor differences in temperature, which can also be an indicator of blood flow. In addition to blockages as a result of heart disease, other causes of decreased blood flow include problems from pelvic fracture as a consequence of motor vehicle accidents. Additionally, Dr. Goldstein has postulated that chronic perineal pressure, which is pressure in the area between the vagina and the rectum, can actually cause decreased blood flow to the vagina and clitoris and can be the result of riding a bicycle. This syndrome is seen in men and has been documented to be a source of erectile dysfunction as well.

Another risk factor for vasculogenic female sexual dysfunction is elevated cholesterol. As in men, we know that when the good cholesterol (also known as the HDL or high density lipoproteins) is decreased, this is a sign that there is substantial vascular disease present that can lead to problems. Fortunately, women are relatively protected from heart disease by the effects of female hormones.

In women with primary female arousal disorders or primary orgasmia, this decreased blood flow is a very attractive hypothesis. Consequently, there have been many efforts to study newer drugs that promote the dilatation or relaxation of these blood vessel beds in the pelvic structures as a way to increase blood flow and thereby remedy the situation.

January 2000