The epidemiology of TOA is closely related to that of pelvic inflammatory disease which is estimated to one million people yearly.

Complications of TOA are related to the possible removal of one or both ovaries and fallopian tubes. Without these reproductive structures, fertility can be affected. Surgical complications can develop and include:

- Allergic shock due to anesthetics

- A paradoxical reaction to a drug

- Infection

The major cause for distal tubal occlusion is pelvic inflammatory disease (PID), usually as a consequence of an ascending infection by chlamydia or gonorrhea. However, not all pelvic infections will cause distal tubal occlusion. Tubal tuberculosis is an uncommon cause of hydrosalpinx formation.

While the ciliae of the inner lining (endosalpinx) of the fallopian tube beat towards the uterus, tubal fluid is normally discharged via the fimbriated end into the peritoneal cavity from where it is cleared. If the fimbriated end of the tube becomes agglutinated, the resulting obstruction does not allow the tubal fluid to pass; it accumulates and reverts its flow downstream, into the uterus, or production is curtailed by damage to the endosalpinx. This tube then is unable to participate in the reproductive process: sperm cannot pass, the egg is not picked up, and fertilization does not take place.

Other causes of distal tubal occlusion include adhesion formation from surgery, endometriosis, and cancer of the tube, ovary or other surrounding organs.

A hematosalpinx is most commonly associated with an ectopic pregnancy. A pyosalpinx is typically seen in a more acute stage of PID and may be part of a tuboovarian abscess (TOA).

Tubal phimosis refers to a situation where the tubal end is partially occluded, in this case fertility is impeded, and the risk of an ectopic pregnancy is increased.

As pelvic inflammatory disease is the major cause of hydrosalpinx formation, steps to reduce sexually transmitted disease will reduce incidence of hydrosalpinx. Also, as hydrosalpinx is a sequel to a pelvic infection, adequate and early antibiotic treatment of a pelvic infection is called for.