Why do fibroids in the uterus cause severe bleeding?

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Dr. Manu Lakshmi

19 May 2022

The most common condition underlying severe bleeding are uterine fibroids. Heavy bleeding can be defined as “excessive menstrual blood loss which interferes with a woman’s physical, social, emotional and/or material quality of life”. Severe bleeding during menstruation is typically defined as a period that lasts more than 8 days and requires frequent changing of sanitary products. Longer, more frequent periods with heavy flow or bleeding between periods can prevent a woman from participating in daily activities, being productive at work and from socialising. Women with fibroids often consider best uterus removal surgery in Chennai to prevent excess bleeding that can lead to complications like anaemia and infertility in women with fibroids. 

Different theories explain why fibroids cause severe bleeding

Severe bleeding is a common symptom of uterine fibroids. Heavy bleeding due to uterine fibroids has been shown to correlate with the position and number of fibroids. Though there are no one reason uterine fibroids cause heavy, prolonged periods, there are a few theories typically based on the location and type of the fibroids, contractility of the uterus, the presence of ancillary prostaglandins and any distortion to the lining of the uterus that explain why fibroids in uterus cause severe bleeding. 

  • Type and location of fibroid can cause severe bleeding – Uterine fibroids are classified according to their location relative to the uterine anatomy in the FIGO system. Submucosal fibroids studied through hysteroscopy are known to cause heavy menstrual bleeding leading to anaemia. Location of submucosal fibroids within the uterine cavity enlarge the surface area of the uterine lining or endometrium which may be a cause of heavy menstrual bleeding. Uterine submucosal fibroids, or leiomyomata known to be benign tumours of the myometrium arise within the uterus. Submucosal fibroids largely comprise of dense tissue characterized by excessive deposition of extracellular matrix substances, mainly collagen, within the tumour. An enlarged and deformed uterus formed from the bulk growth of this extremely dense tissue leads to key symptoms associated with fibroids such as heavy bleeding, abdominal pressure, abdominal pain and infertility. Whereas, intramural fibroids are known to cause heavy bleeding through a highly vascularised pseudo capsule. Intermenstrual bleeding as a symptom of uterine fibroids has been shown to correlate with the position and number of fibroids.
  • Physical mechanism can make fibroids cause severe bleeding – Fibroids may cause heavy bleeding through an increase in endometrial surface due to underlying fibroid growth. These fibroids may put pressure against the larger surface area of the uterine lining, which can cause more bleeding than usual. Proportion of fibroid that interrupts the uterine cavity is related to greater haemoglobin loss and more anaemia. Other physical ways that the fibroid may cause severe bleeding and require treatment at the best uterus removal surgery clinic in Chennai are through an influence on normal myometrial contractility patterns, through an ulcerated or degenerating fibroid or through uterine venous dilatation due to compression from the fibroids.
  • Angiogenesis in fibroids can cause severe bleeding – There is no other tissue in the human body that undergoes angiogenesis to the degree and frequency as the endometrium. A vast degree of angiogenic factors have been identified to be involved in the vascularization and growth of uterine fibroids. Angiogenesis is vital in various stages of the menstrual cycle that include growth of the endometrium in the proliferative phase, the build-up and elongation of spiral arteries in the secretory phase and the repairs during and after menstruation. Angiogenesis in the adjacent layer of the uterus, called the myometrium has been shown to be influenced by the presence of uterine fibroids through an increased proliferative response to hormones, oestrogen and progesterone in smooth muscle cells as compared to normal myometrium without fibroids.
  • Pseudocapsule in fibroids could explain severe bleeding – The fibroid mass is poorly vascularised but it can be surrounded by a pseudocapsule which is a highly vascularised tissue that develops only in intramural fibroids. A pseudocapsule is a specialized layer of tissue between the fibroid and the surrounding myometrium that develops with blood vessels in response to fibroid growth and is needed to sustain the fibroid. The cell type of pseudocapsule shows the same biologic structure as the neighbouring myometrium, but the vasculature of the pseudocapsule might have structural defects that are susceptible to breaking, leading to heavy bleeding during menstruation. Thus, heavy menstrual bleeding in women with uterine fibroids can be due to bursting of the vessels contained within the pseudocapsule. Hence, the symptom correlates only with the position of intramural fibroids.
  • Venous lakes in fibroids can be responsible for increased bleeding – Severe bleeding connected to uterine fibroids suggests physiological formation of venous lakes which are large sinusoidal structures within the uterine vasculature from arteriovenous anastomoses. The blood flow into the venous lakes was understood to cause low pressure in the capillary system and since the venous lakes do not have a closing mechanism, bleeding would continue until completely sloughed off. Dilated and enlarged venous lakes by virtue of increased interstitial pressure from the growing fibroids lead to increased menstrual bleeding. The loss of endometrium from menstruation would only stop on reaching the basal layer, supported by capillaries but without any arteriovenous anastomoses. This far it was believed that menstrual blood loss was largely venous in origin. However, advanced studies in molecular biology of angiogenic factors revealed that growth factors were largely responsible for the enlargement of veins and venous lakes and failure of the fibrin/platelet plugs needed to successfully close these blood vessels of increased diameter were the reasons for heavy bleeding in women with fibroids.
  • Aberrant architecture of fibroid can cause severe bleeding – The vasculature developing around uterine fibroids could show structural defects that could be highly irregular, with high tortuosity, shunting of vessels and non-patent ends. This renders fibroid vasculature leaky and prone to breaking.

Many women with fibroids require definitive surgical management after exhausting their medical management options directed towards controlling heavy bleeding. Apart from best hysterectomy surgery in Chennai, currently available treatment options that address this problem satisfactorily are to be analysed for an informed decision.

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