Dear Katie: You are correct, fibroids can increase both uterine cramping and trigger a heavier flow. In addition to the painful cramps you also mentioned accompanying diarrhea. Both cramps and diarrhea can be linked to excessive production of prostaglandins.
Common menstrual cramps are caused by the release of prostaglandins from the lining of the uterus. Prostaglandins create both the cramps of labor and menstrual cramps by making the uterus contract. Common cramps may start prior to the onset of flow and usually last 72 hours. There are also receptor sites for prostaglandins in the bowel and central nervous system. Thus prostaglandins can produce not just cramps but also nausea/vomiting, diarrhea, headaches, and other "flu-like" symptoms.
Ways to block prostaglandins can include birth control pills (not an option for you), or anti-prostaglandin drugs (eg ibuprofen, naproxen sodium, ketoprofen, etc.). Some alternative healthcare providers such as naturopaths stress using of Omega 6 fatty acids in dietary choices, and cramp bark.
Katie, if the fibroids are the sole culprit here is the best summary citation on treatment found at the National Library of Medicine site:
Eur J Obstet Gynecol Reprod Biol. 2012 Dec;165(2):156-64. doi: 10.1016/j.ejogrb.2012.07.030. Epub 2012 Aug 29.
Therapeutic management of uterine fibroid tumors: updated French guidelines.
Marret H, Fritel X, Ouldamer L, Bendifallah S, Brun JL, De Jesus I, Derrien J, Giraudet G, Kahn V, Koskas M, Legendre G, Lucot JP, Niro J, Panel P, Pelage JP, Fernandez H.
Source
Service de gyn?cologie, Centre Hospitalier R?gional Universitaire de Tours, H?pital Bretonneau, 2 boulevard Tonnel?, 37044 Tours, France. Electronic address: marret@med.univ-tours.fr.
Abstract
The medical management of symptomatic non-submucosal uterine fibroid tumors (leiomyomas or myomas) is based on the treatment of abnormal uterine bleeding by any of the following: progestogens, a levonorgestrel-releasing intrauterine device, tranexamic acid, nonsteroidal anti-inflammatory drugs, or GnRH analogs. Selective progesterone receptor modulators are currently being evaluated and have recently been approved for fibroid treatment. Neither combined estrogen-progestogen contraception nor hormone treatment of the menopause is contraindicated in women with fibroids. When pregnancy is desired, whether or not infertility is being treated by assisted reproductive technology, hysteroscopic resection in one or two separate procedures of submucosal fibroids less than 4cm in length is recommended, regardless of whether they are symptomatic. Interstitial, also known as intramural, fibroids have a negative effect on fertility but treating them does not improve fertility. Myomectomy is therefore indicated only for symptomatic fibroids; depending on their size and number, and may be performed by laparoscopy or laparotomy. Physicians must explain to women the potential consequences of myomas and myomectomy on future pregnancy. .......
Yours,
Jane