Adenomyosis, also known as internal endometriosis, is a uterine condition in which there is tissue from the inner layer of the uterus (endometrium) in the muscular layer of the uterus (myometrium). The causes of this condition are not clearly known, although it is known to be estrogen-dependent and, among the factors that predispose it to develop, we find having had at least one pregnancy and previous uterine surgeries (cesarean sections, curettage, hysteroscopies, etc.).
It is also very much related to age, especially after 40 years of age. That is why in some cases it is colloquially called uterine aging.
Certain adenomioses are only detected by special techniques such as a 4D ultrasound or a magnetic resonance imaging. For mild cases, there are very few treatments with apparent effectiveness and it is not fully demonstrated that they have a negative effect on patients' pregnancy rates. However, severe cases such as T-uteruses require corrective surgery through hysteroscopy.