Blockage of the outer, or fimbrial end of the fallopian tube, usually as a result of chronic salpingitis (but also sometimes from peritubal adhesions, from a salpingotomy or partial salpingectomy for a tubal pregnancy, or from fimbriectomy), resulting in its distension by watery contents. An untreated hydrosalpinx (even if only one tube is affected and the other tube is normal) can cause infertility and failure to conceive even with in vitro fertilisation.

An operation to remove the colon, performed in children for Hirschsprung's disease and in young women chiefly for ulcerative colitis and Crohn's disease, and notorious for leaving the fallopian tubes caught up in "repaired" serosa of the pelvic peritoneal cavity, producing a hydrosalpinx on the left side, with resultant sterility, even though the tube on the right side might be normal.

Also "fimbriated end": the open, outside end of the fallopian tube in contact with the surface of the ovary, from which it "picks up" the ovulated egg from the ruptured follicle. It's composed of delicate fimbriae -- finger-like projections of the tube lined by cells with tiny hairs (cilia), which beat towards the inside of the tube, carrying the sticky cumulus mass containing the egg into the ampulla before fertilisation. Easily damaged by infection (salpingitis) or careless surgery, after which it may be blocked, resulting in a hydrosalpinx, or have its correct movement inhibited by adhesions.

An operation for sterilisation or "tubal ligation" in which the fimbrial end of each fallopian tube is removed. It has a higher failure rate than most other sterilisation operations on the tubes and it also is more difficult to reverse if the woman intends to regain fertility. It can result in a hydrosalpinx, which can jeopardise success with in vitro fertilisation, and the microsurgery operation to reverse it, salpingostomy, is much less often followed by pregnancy than tubal anastomosis operations are.