Anal Fissure
(1).introduction
1. Benign anorectal diseases, including fissures, abscesses, fistulas, and hemorrhoids, are common.
2. Anal fissures occur at all ages but are more common in the 30~50 y/o.
3. It is associated with constipation, diarrhea, infectious etiologies, perianal trauma, and Crohn's disease.
4. An anal fissure is a tear in the lining of the anal canal distal to the dentate line, which most commonly occurs in the posterior midline. (posterior: anterior= 90%: 10%)
(2).cause
Primary: local trauma to the anal canal, such as after passage of hard stool.
Secondary: 肛門手術(痔瘡切除術或廔管切開術)後傷口癒合不良形成的。
身體的修補機能嘗試修補此裂口，因此肛裂周圍便有結疤組織，而增生修補機能於是向外推擠，形成增生性乳凸及肛門臨近外痔(其實都是發炎及結締組織)。
病理致病因素: internal sphincter muscle spasm
肛裂患者之肛門基礎壓力(basal anal tone)比正常人高，因為basal anal tone主要係由internal sphincter muscle來，因此有所謂內括約肌痙攣的說法。因肛門壓力高會造成肛門內襯面組織缺血，致使傷口癒合能力變差，同時也有缺血性疼痛(這可以解釋肛裂為何會出奇的痛)。另有人利用血管攝影，病理切片等方式證實在肛後中線部位之血液循環比其它部位還差，在肛內壓高時血液循環之影響更明顯，因此有裂口時不易癒合，肛裂於是形成。
(3).clinical
1. Triad:臨近的外痔(sentinel pile)，增生性乳凸(hypertrophic papilla)及肛裂中清晰可見的內括約肌，肛裂周圍的結疤。
2.少數病人肛裂會發炎，造成low short intersphincteric fistula。此外internal sphincter muscle會痙攣， 肛門內壓會昇高
3.severe pain: 尤其是在排便及便後之疼痛是病人主要症狀。通常是如刀切、撕裂般的疼痛。
4. bright rectal bleeding: 通常是鮮紅，量不多，出現在排便或便後。
5.discharge, itching: 因臨近外痔(Sentinel pile)在肛門口之刺激，致肛門有分泌物及騷癢。
6.其他少見的症狀如疼痛引起小便不順，頻尿等亦有。
(4).Diagnosis: history+ PE
Constipation or excessive diarrhea+ severe anal pain
Digital: 肛門很緊，會引起病人極度不適、疼痛，甚至無法讓醫師檢查。
肛門鏡檢Triad: sentinel pile， hypertrophic papilla及anal Fissure中清晰可見的內括約肌，肛裂周圍的結疤。
D/Dx with cancer, IBD
(5).Treatment
1.Acute: fresh laceration, usually< 6 wks, triad 尚未出現
Medical therapy — Medical therapy has traditionally consisted of three components: relaxation of the internal sphincter, institution and maintenance of atraumatic passage of stool, and pain relief.
These goals can be accomplished with fiber therapy to keep the stools soft and formed, and warm sitz baths following bowel movements to relax the sphincter.
60–90% will heal, but recurrence rates from medical therapy are higher.
Symptoms from an acute fissure usually resolve over 10-14 days with conservative treatment, however it may take 6-8 weeks for a fissure to actually heal.
2.Chronic: usually> 6 wks, triad出現
Medical therapy — aimed at decreasing the anal canal resting pressure including nifedipine or nitroglycerin ointment applied three times a day, and botulinum toxin type A, up to 20 units, injected into the internal sphincter on each side of the fissure. Surgical therapy — Surgery should be reserved for patients in whom anal fissures fail to heal despite adequate medical therapy. The goal of surgical therapy is to relax the internal anal sphincter(減低肛壓), which is most often accomplished by a lateral internal sphincterotomy.
(a)開放式側面肛內括約肌切開術:在肛門之左側或右側面做一切口，此切口必須從肛門口到齒狀線。將齒狀線以外的內括約肌切開，可用刀切或用電燒切開，將出血點止血，再將切口之肛門皮層(Anoderm)縫合。此法的好處為內括約肌切開術均在肉眼視察下為之，較安全，確實。缺點為多一傷口，延長癒合時間。至於切開術為何在側面，是因為如果切開術選在中線易造成日後的「鎖孔缺陷」(Keyhole deformity)，影響肛門的控制力，會有氣體及稀大便的滲漏11.12。
(b)封閉式側面肛內括約肌切開術:於左側或右側面，利用尖刀從內外括約肌間之凹處插入，將刀面轉向內括約肌，把下段內括約肌切開。此法之好處為沒有多的傷口，缺點為要有較純熟的技巧，否則可能變成開放式的或切的範圍不如預測的。
(c)肛門擴張法:在適當麻醉下，利用手指插入肛門，直到六至八根指頭插入肛門。此法好處為沒有新傷口，而缺點為內括約肌受傷的程度難以事前評估，術後可能有肛門失禁發生，目前此法已少人使用。
肛裂切除:將臨近外痔，肛裂及其結疤組織及增生性乳凸一併切除。通常做一扇形切口，將上述三組織切除，將切口黏膜邊緣用吸收線縫住以止血。切除後會留下一大面積傷口，可能需二至三週才會癒合，因此有人主張用V-Y肛門成形術:以肛裂為V型切開口之尖端，將皮膚切開，其挾角為90度，將此皮瓣做分離；次將肛裂切除，切口向直腸方向延長，把外面的皮瓣蓋住挖開的切口，並縫合。此法的好處除了可以去掉肛裂外，亦可加寬肛門，且無開放性傷口，癒合也較快。
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