Anorectal Diseases
Symptoms related to anorectal diseases are common among patients presenting to gastroenterologists and are sometimes challenging to diagnose and manage. During daily endoscopy practice, anorectal lesions are poorly recognized probably due to a lack of und
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Anorectal Diseases Sung Noh Hong
Contents
24.1 Anorectal Anatomy
24.1 Anorectal Anatomy
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24.2 A nal Cancers 24.2.1 A natomic Subsites of Malignant Anorectal Diseases 24.2.2 Anal Canal Cancers 24.2.3 Anal Margin Cancers 24.2.4 Anal Melanoma 24.2.5 Anal Intraepithelial Neoplasia (AIN)
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24.3 Condylomata Acuminata (Anal Warts)
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The anal canal is the most distal part of the gastrointestinal tract, which is located between the anal verge (anus, anal margin, anal orifice) in the perineum below and the rectum above (Table 24.1). The length of the anal canal is measured as about 4 cm (range, 3–5 cm). Despite its short length, the anal canal produces a variety of diseases reflecting its complex anatomic and histological structure (Fig. 24.1).
24.4 H emorrhoids 24.4.1 I nternal Hemorrhoid 24.4.2 E xternal Hemorrhoid
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Table 24.1 Anatomy of the anal canal and rectum (Fig. 24.1)
24.5 Anal Fissure
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24.6 H ypertrophied Anal Papillae and Fibroepithelial Polyp
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24.7 P erianal Abscess and Anal Fistula (Fistula-in-Ano)
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24.8 24.8.1 24.8.2 24.8.3
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Proctitis Infectious Proctitis Chronic Radiation Proctitis Solitary Rectal Ulcer Syndrome
References
S. N. Hong, M.D., Ph.D. Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea
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Structure Rectum (Fig. 24.5)
Boundary Rectosigmoid junction ~ anorectal ring – Usually have three Houston’s valves (transverse folds of rectum) (Surgical) Anal canal Anorectal ring ~ anal verge – Average 4 cm in length – Surrounded by the anal sphincter mechanism * Anatomic anal canal : Dentate line ~ anal verge, average 2 cm in length : Covered with modified squamous epithelium (anoderm) Upper border of the internal anal sphincter Anorectal ring (anorectal junction, and the puborectalis muscle – Anorectal ring cannot be seen under anorectal flexure, endoscopy but can be palpable at Fig. 24.4) approximately 1–2 cm proximal to the dentate line on digital rectal examination Mucocutaneous junction between columnar Dentate line epithelium and squamous epithelium (pectinate line, – Dentate line can be delineated under Fig. 24.2a) endoscopy but cannot be felt in digital rectal examination – Nerve innervation, blood supply, and lymphatic drainage are different above and below dentate line Junction between the anoderm and perianal Anal verge (anus, skin anal orifice, anal margin, Fig. 24.3b)
© Springer Nature Singapore Pte Ltd. 2018 H. J. Chun et al. (eds.), Clinical Gastrointestinal Endoscopy, https://doi.org/10.1007/978-981-10-4995-8_24
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The most important endoscopic landmark of anal canal is the dentate line (pectinate line), which is the mucocutaneous junction of columnar epithelium, originated from endoderm, and squamous epithelium, originated from ectoderm [1]. Two-thirds of anal canal lie above the dentate line and one- third below the dentate l
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