Who was Sampson?
A bachelor gynecologist from Albany, New York.

What is Sampson's Theory?
The most popular and widely believed theory of origin of endometriosis, developed in the 1920's.

What does it say?
During menstruation each month, instead of all the menstrual blood flowing into the vagina, some of it goes in reverse and flows out the ends of the fallopian tubes. This menstrual blood carries with it some living cells from the lining of the uterus. These cells come to lie on the surfaces of the pelvis where they attach, implant, grow, and develop into endometriosis. An earlier version of the theory also postulated that endometriosis could occur by implantation resulting from rupture and spread of endometrioma cysts of the ovary.

Is there undeniable scientific proof supporting this theory?
No, and by now there should have been.

What does it predict?
Sampson's theory predicts that endometriosis will progressively spread throughout the pelvis with the passage of time, like dandelions seeding a field. More and more of the pelvic surfaces will be involved by the disease, and the recurrence rate after surgical removal will be 100%.

Is there undeniable scientific proof supporting this theory?
No, and by now there should have been. The literature on Sampson's theory details a variety of circumstantial evidence seeming to support almost every step in Sampson's theory. Bloody peritoneal dialysate has been found during the menstrual flow in women undergoing peritoneal dialysis for kidney disease (although that study did not look for actual endometrial cells).

At laparoscopy performed during menstruation, bloody fluid has been seen coming from the end of the fallopian tubes (although when we insert a rigid rod inside the uterus to manipulate it, this can also induce some bleeding which can be forced out the fallopian tubes). Endometrial cells have been found in the fallopian tubes, peritoneal fluid and also in menstrual blood.

The endometrial cells which are found in menstrual blood are viable and can be cultured in the lab (although they grew in the subcutaneous tissue of autologous donors only 11% of the time). Sampson showed that if a hysterectomy was done during the menstrual flow, that if the surgeon chopped off the fallopian tube next to the uterus and squeezed the body of the uterus between his fingers, he could make blood come out the end of the severed tube. The distribution of endometriosis in the pelvis has been offered as further evidence of Sampson's theory.

It was argued that the ovaries were the most commonly involved pelvic area since they were closest to the ends of the fallopian tubes, so attachment and implantation of regurgitated endometrial cells should occur most commonly here first (although Sampson eventually figured out that the ovaries are not the most commonly involved area - the bottom of the pelvis is).

It was later postulated that the bottom of the pelvis is the most commonly involved area due to the effects of gravity pulling viable endometrial cells down to the cul-de-sac (so Sampson's theory can mutate to accommodate the available information).

It has been suggested that endometriosis is a progressively spreading disease due to this continued seeding (although pelvic mapping studies have not found a greater distribution of disease in older age groups of untreated patients). It has been argued that the 100% recurrence rate after surgery is simply due to the fact that the pelvis gets re-seeded monthly after surgery (although the published recurrence rates after excision are much lower than this) and the high 'recurrence ' rate may simply be persistence of disease which was not destroyed by superficial laser vaporization or electrocoagulation or by medical therapy.

Joseph Meigs, a prominent gynecologist of the mid-century, wrote in 1953 that endometriosis could be cured by conservative surgery (that's right, he used the 'c' word).

If you don't look too deeply or too critically at Sampson's theory and ignore the words in the parentheses above, it looks pretty perfect. If only the reality that women with endometriosis experience would match the theory, life would be perfect. It doesn't. Life is imperfect because the theory is wrong, and there is undeniable scientific proof that it is wrong.

To understand the flaw of Sampson's theory, all you have to do is visualize a pine forest. When you walk across the forest floor, what is that crunching sound under your feet? It is the sound of pine cones under your shoes. As you look at the forest floor, you can see the pine cones attached by gravity to the surface of the ground. You may also see some pine seedlings and younger trees among the mature trees.

Now let's look at the pelvic floor. Sampson's theory predicts that individual endometrial cells should be attached to the surfaces of the pelvic floor in fairly large numbers. These cells are not small and should easily be seen with a light microscope. It should be absolutely easy to find these attached cells; one could almost take random biopsies blindfolded and expect to find them under the microscope. By now, textbooks should be filled with photomicrographs of dozens or hundreds of examples of these attached cells.

Furthermore, there should be similar abundant evidence of the progressive invasion of these attached cells into the pelvic surfaces, followed by the evolution of these cells into endometriosis. This continuum of the earliest attachment of endometrial cells changing into endometriosis should be easy information to come by and to be proved by photography. This pictorial evidence should introduce every discussion of Sampson's theory in every textbook, yet it doesn't because there is no such abundant evidence available.