The correlation of uterine and tubal changes in tubal gestation

Abstract The paper is based upon the study of twenty-one cases of tubal pregnancy in which, in addition to the tubal gestation sac, the uterine mucosa was available for study, thus affording an opportunity of correlating the uterine and tubal changes in this connection. In fifteen cases the uterine mucosa was available because a hysterectomy had been done, in three because a preliminary curettage had been performed, and in three because a more or less perfect uterine cast had been expelled by the patient. The decidual reaction occurring in the uterus with extrauterine pregnancy is found to be identical with that of normal gestation so long as the embryo is alive. With the death of the latter, however, the superficial compact portion, with at times a considerable part of the spongy glandular layer, is cast off. Its expulsion from the woman's vagina, however, may not take place for a considerable period, perhaps many days, after its separation from the deeper layers. The mechanism of the separation is strongly suggestive of that observed in connection with the throwing off of the corresponding portions of the endometrium in the nonpregnant woman at the time of menstruation. The same statement applies to the process of regeneration. In view of the degenerative and autolytic changes involving the sequestrated decidua, it is not infrequently thrown off in smaller particles rather than as a large cast of the uterine cavity. We have found no evidence, in our own series, that the decidua merely involutes or shrinks, without loss of tissue, as has been claimed by some. It is possible that the “physiological thrombosis” which apparently occurs in the venous channels of the endometrium may play an important part in the degeneration and separation of the decidual layer, perhaps by its effect upon the blood supply of the tissues. From what has been said, it follows that the decidual cast of extrauterine pregnancy is made up chiefly of a mass of decidual cells, representing the superficial or compact layer of the placenta. The surface epithelium is very flat, as is that lining the few slit-like gland spaces near the surface. Very often, however, a considerable portion of the spongiosa is attached to the compacta, being characterized especially by the presence of the typical pregnancy glands. Large venous thromboses are also commonly observed. The overwhelming majority of cases of tubal pregnancy come under observation only after the death of the embryo. In these cases the endometrium has retrogressed from its originally decidual character. The microscopic examination of uterine curettings in such cases is of very little diagnostic value. On the other hand, the histologic study of the uterine mucosa in those cases where the pregnancy is still developing actively shows a typical decidual reaction. When curetting, in a doubtful case, yields such a mucosa, without villi, the information gained is very valuable, though not conclusive. Unfortunately, however, cases of this type are curetted far less frequently than those of the other group, for they are characterized clinically by amenorrhea, with the possibility of intrauterine pregnancy. The external or vaginal bleeding of tubal pregnancy is characteristically of endometrial origin, having its source, as Sampson has shown, in the venous channels of the endometrium. It is initiated by the separation of the placenta, although other factors, probably of hormone nature, are undoubtedly concerned in its frequent continuance for many weeks. The source of this factor in keeping up the bleeding is probably in some unknown way associated with the persistence of trophoblastic elements in the tubal wall long after the actual death of the embryo. The analogy with both the normal and the abnormally prolonged menstrual bleeding may again be invoked. Decidual reaction in the tubal wall occurs in at least a fraction of the cases. It is never in any way comparable with that seen in the uterus, being usually patchy in its distribution. Mistakes in the diagnosis of decidual tissue in such cases are frequent, for a pseudodecidual picture is common in the connective tissue from simple hyperemia or edema. Moreover, great care is necessary to avoid mistaking for decidua the trophoblastic cells which invade the tubal wall so widely. In certain cases, however, the morphology of the cells is so typically that of decidual cells, their distinctness from the gestation site is so clearly discernible, and their derivation from the connective tissue so definitely suggested by the presence of transition stages, that the diagnosis permits of no doubt. Furthermore, the occurrence of certain cases in which the reaction is noted in the nonpregnant tube of the opposite side is even more convincing. Finally, attention has been called to the not infrequent finding of islands of “ectopic decidua” on the ovary, the posterior surface of the uterus, and many other locations in the pelvis, and the suggestion is offered, without as yet any definite proof, that there may be some connection between such decidual islands and the “endometrial implants” described by Sampson. The latter, it will be recalled, have pretty much the same distribution as that of ectopic decidua. In conclusion, we wish to express to Dr. Thomas S. Cullen our appreciation of his kindness in placing the clinical and pathologic resources of the department so completely at our disposal. Moreover, we must once more publicly acknowledge our heartfelt appreciation of the warm interest and cooperation of Dr. George L. Streeter, the director of the Carnegie Laboratory of Embryology, who opened up to us his rich storehouse of material and gave us every possible assistance.