Approximately 95% of epistaxis is caused by bleeding originating from blood vessels in Little's area, located at the anterior inferior septum. This area contains a confluence of vessels from the various nasal sources called the Kiesselbach plexus.
[Figure caption and citation for the preceding image starts]: Nasal vasculature demonstrating the vessels that form the Kiesselbach plexusFrom the collection of David A. Randall, Springfield Ear Nose Throat and Facial Plastic Surgery, MO [Citation ends].
Posterior epistaxis originates from the posterior nasal cavity or nasopharynx.[3]Santos P, Lepore M. Epistaxis. In: Bailey B, Healy G, Johnson J, et al., eds. Head & neck surgery-otolaryngology. Philadelphia: Lippincott, Williams & Wilkins; 2001:415-428.[4]Massick D, Tobin E. Epistaxis. In: Cummings C, Flint P, Harker L, et al., eds. Otolaryngology-head and neck surgery. Philadelphia: Elsevier Mosby; 2005:942-961.
Vessels may bleed due to:
Neoplasm represents an atypical and, if located in a paranasal sinus, particularly difficult cause to identify. Neoplasms associated with nosebleed include:
Sinus tumours: associated with exposure to wood dust and certain chemicals
Juvenile nasal angiofibroma: a rare nasopharyngeal tumour of young men that can produce significant posterior haemorrhage, and may be associated with nasal obstruction.[8]Davis KR. Embolization of epistaxis and juvenile nasopharyngeal angiofibromas. AJR Am J Roentgenol. 1987 Jan;148(1):209-18.
http://www.ajronline.org/doi/pdf/10.2214/ajr.148.1.209
http://www.ncbi.nlm.nih.gov/pubmed/3024474?tool=bestpractice.com
[9]Pryor SG, Moore EJ, Kasperbauer JL. Endoscopic versus traditional approaches for excision of juvenile nasopharyngeal angiofibroma. Laryngoscope. 2005 Jul;115(7):1201-7.
http://www.ncbi.nlm.nih.gov/pubmed/15995507?tool=bestpractice.com
[10]Tunkel DE, Anne S, Payne SC, et al. Clinical practice guideline: nosebleed (epistaxis). Otolaryngol Head Neck Surg. 2020 Jan;162(suppl 1):S1-38.
https://aao-hnsfjournals.onlinelibrary.wiley.com/doi/10.1177/0194599819890327
http://www.ncbi.nlm.nih.gov/pubmed/31910111?tool=bestpractice.com
Adults with nosebleed often have elevated blood pressure (BP), although there is uncertainty about whether hypertension is a causative factor or the elevated BP is secondary to anxiety.[10]Tunkel DE, Anne S, Payne SC, et al. Clinical practice guideline: nosebleed (epistaxis). Otolaryngol Head Neck Surg. 2020 Jan;162(suppl 1):S1-38.
https://aao-hnsfjournals.onlinelibrary.wiley.com/doi/10.1177/0194599819890327
http://www.ncbi.nlm.nih.gov/pubmed/31910111?tool=bestpractice.com
[11]Viducich R, Blanda MP, Gerson LW. Posterior epistaxis: clinical features and acute complications. Ann Emerg Med. 1995 May;25(5):592-6.
http://www.ncbi.nlm.nih.gov/pubmed/7741333?tool=bestpractice.com
[12]Charles R, Corrigan E. Epistaxis and hypertension. Postgrad Med J. 1977 May;53(619):260-1.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=876933
http://www.ncbi.nlm.nih.gov/pubmed/876933?tool=bestpractice.com
[13]Ibrashi F, Sabri N, Eldawi M, et al. Effect of atherosclerosis and hypertension on arterial epistaxis. J Laryngol Otol. 1978 Oct;92(10):877-81.
http://www.ncbi.nlm.nih.gov/pubmed/712220?tool=bestpractice.com
[14]Lubianca-Neto JF, Bredemeier M, Carvalhal EF, et al. A study of the association between epistaxis and the severity of hypertension. Am J Rhinol. 1998 Jul-Aug;12(4):269-72.
http://www.ncbi.nlm.nih.gov/pubmed/9740920?tool=bestpractice.com
[15]Herkner H, Havel C, Müllner M, et al. Active epistaxis at ED presentation is associated with arterial hypertension. Am J Emerg Med. 2002 Mar;20(2):92-5.
http://www.ncbi.nlm.nih.gov/pubmed/11880870?tool=bestpractice.com
Whether atherosclerotic change, secondary to hypertension, increases vessel fragility is also debated, but is plausible in that elevated BP impairs intraoperative surgical haemostasis.[11]Viducich R, Blanda MP, Gerson LW. Posterior epistaxis: clinical features and acute complications. Ann Emerg Med. 1995 May;25(5):592-6.
http://www.ncbi.nlm.nih.gov/pubmed/7741333?tool=bestpractice.com
[12]Charles R, Corrigan E. Epistaxis and hypertension. Postgrad Med J. 1977 May;53(619):260-1.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=876933
http://www.ncbi.nlm.nih.gov/pubmed/876933?tool=bestpractice.com
[13]Ibrashi F, Sabri N, Eldawi M, et al. Effect of atherosclerosis and hypertension on arterial epistaxis. J Laryngol Otol. 1978 Oct;92(10):877-81.
http://www.ncbi.nlm.nih.gov/pubmed/712220?tool=bestpractice.com
[14]Lubianca-Neto JF, Bredemeier M, Carvalhal EF, et al. A study of the association between epistaxis and the severity of hypertension. Am J Rhinol. 1998 Jul-Aug;12(4):269-72.
http://www.ncbi.nlm.nih.gov/pubmed/9740920?tool=bestpractice.com
[15]Herkner H, Havel C, Müllner M, et al. Active epistaxis at ED presentation is associated with arterial hypertension. Am J Emerg Med. 2002 Mar;20(2):92-5.
http://www.ncbi.nlm.nih.gov/pubmed/11880870?tool=bestpractice.com
Recent or regular high alcohol intake is associated with an increased risk of epistaxis, probably due to the effect of alcohol on bleeding time.[16]Beck R, Sorge M, Schneider A, et al. Current approaches to epistaxis treatment in primary and secondary care. Dtsch Arztebl Int. 2018 Jan 8;115(1-02):12-22.
https://www.doi.org/10.3238/arztebl.2018.0012
http://www.ncbi.nlm.nih.gov/pubmed/29345234?tool=bestpractice.com