Fissure-in-ano - A painful embarrassment
In surgical practice, very often we're faced with a middle aged patient with a concerned look on their face and after the initial pleasantries, will tell you with a low, anxious voice that they've been experiencing bleeding while performing their elementary alimentary function.
"Bleeding per rectum" is probably one of the more common reasons for a surgical consult, both as an outpatient, and in patients admitted for something else under another specialty (second only to acute pain abdomen).
In this article, let's look at, and simplify one of the most frequent causes of bleeding per rectum - fissure-in-ano.
What is fissure-in-ano?
If you want to go by textbook definitions, "an anal fissure is described as a linear defect/ laceration in the anoderm, the part of the anal canal located between the dentate line and the anal verge".
Let's break that down a little, shall we?
A defect/laceration at the anoderm.
What exactly is the anoderm?
Anatomically speaking, the anal canal starts from the dentate line which is considered as the true junction between the embryonic endoderm (the gut tube and the ectoderm (the body wall). This distinction is important to understand, as proximal to the dentate line the nerve supply is from the body's autonomics, but distal to the dentate line, it’s supplied by somatic nerve fibres. Why this matters, we'll discuss a little later; just keep reading!
Surgically, the anal canal extends from the puborectalis sling (which is a part of the levator ani muscle complex) to the point where the anal canal becomes skin. So for all intents and purposes, there’s a small cuff of the surgical anal canal that's truly speaking part of the distal rectum - in other words, the anatomical anal canal is a part of the surgical anal canal, but the opposite is not true.
So where is the anoderm then?
The anal mucosa is columnar to begin with (the distal rectal mucosa, i.e the surgical anus); at around the dentate line it appears purplish - this is called the "anal transition zone (ATZ)", which is where the columnar mucosa transitions to squamous epithelium.
The anoderm begins distal to the dentate line and is lined by squamous epithelium devoid of hair, sweat and sebaceous glands.
Fig 1 - Anatomy of the Anal Canal
A breach in this part of the anal canal epithelium, is called Fissure-in-ano.
Why does this happen?
Passing hard stools is arguably the commonest cause of fissure-in-ano. Patients usually give a history of an episode of constipation forcing them to apply force to push the stools out.
Alternately, frequent passing of stools as in the case of diarrheal diseases, and some systemic diseases such as AIDS, Crohn's, lymphomas and infections like tuberculosis and syphilis are uncommon causes that need to be remembered, especially when dealing with "atypical" fissures or recurrent disease despite appropriate treatments.
So how do patients present?
The most striking part of the patient's presentation is painful defecation with streaks of blood on the stool itself, or if the patient is "wiper, not a washer" then, blood on the tissue paper after wiping. The pain is typically described as a burning discomfort following passing of hard stools, and lasts anywhere from a few minutes to hours after onset.
Examination must be careful, patient & gentle; the pain caused by aggressive examination will be memorable for all the wrong reasons. Inspection of the anal verge by spreading of the buttocks will display the fissure.
Fig 2 - Inspection showing a fissure-in-ano
In acute fissure-in-ano, there is only a breach in the mucosa at the posterior region of the anal verge. (6 o' clock) An acute fissure-in-ano will appear as a bright red streak against the pink mucosa.
Patients with chronic fissure-in-ano, will obviously present with a long standing, on & off history of constipation followed by painful defecation with bleeding. Both the pain and the bleeding are usually much milder compared to the acute variant, and they might have other symptoms like a perianal swelling (the sentinel tag), discharge and sometimes even perianal pruritis. Inspection will reveal a healing ulcer at the posterior position, often with a sentinel tag; the clinching point will be the appearance of reddish brown fibres of the internal sphincter running across the base of the ulcer.
Strictly speaking, clock face descriptions are to be avoided due to variability in examining position and it's recommended by colorectal surgeons to describe anatomical quadrants, such as left anterior, right posterior, posterior denoting 10-11 o' clock, 4-5 o'clock, 6 o' clock respectively, and so on.
Fig 3 - Difference in morphology of acute vs chronic fissure
Once a fissure is seen on inspection, all other parts of the anorectal examination must be deferred till the fissure heals completely, as any form of palpation, instrumentation or endoscopy will cause tremendous amount of pain for the patient.
Click here to read about the right way to perform a complete anorectal examination.
Now why would the fissure be painful? If you've been paying attention to the article, you'd understand the embryological basis for it. Distal to the dentate line the mucosa is supplied by somatic nerve efferents, and is thus pain sensitive. This is why internal hemorrohoids, or even surgical manipulation above the dentate line (this forms the basis of many oncological rectal resections - the surgical anus vs anatomical anus concept) is virtually painless.
Fig 4 - Frequency of fissure location
Now you might catch yourself wondering --
Why are posterior fissures the most common?
There have been countless theories, but the most compelling, and a pretty cool explanation to why fissure-in-ano occurs posteriorly is best described by the vascular anatomy of the internal sphincter complex.
Klosterhalfen et al., in 1989 did detailed anatomic dissections of the territory of supply of the inferior hemorrhoidal artery. In as high as 85% of the cadavers, they found that the posterior commissures did not have any direct blood supply -- instead, they were perfused by end arterioles, which had perpendicular branch off points from the feeder vessels.
This anatomical configuration predisposed the posterior mucosa for ischemia; adding fuel to the fire was the high resting pressures of the anal sphincter complex which worsens the ischemia.
Laser Doppler flowmetry studies have also confirmed that increased anal pressures correlated with reduced mucosal blood flow. The normal sphincter pressure ranges anywhere from 60-100 cm H2O in females, (slightly higher in men) and manometry studies show a saw-tooth pattern in patients with anal fissures. This vascular-anal hypertonia hypothesis is widely accepted and forms the basis of modern scientific management of fissure-in-ano.
The Vicious Cycle
As noted before, the sentinel event for the formation of a fissure-in-ano is almost always an episode of constipation followed by straining while defecation. Passage of this hard stool invariably injures the anoderm which is exquisitely painful, and will have an episode of minor bleeding, with prolonged pain. This pain produces reflex sphincter spasm and thereby raises the resting anal sphincter tone, and this high anal tone will predispose to more constipation, repeated injury to the anoderm, and thus propagating this vicious cycle.
Remember -- Although fissure-in-ano is pretty common, it makes sense to think of some other causes of perineal/perianal pain - proctalgia fugax (deeper pain and usually no bleeding), thrombosed hemorrhoids, and external plexus hematomas. Presence of atypical ulcers must also prompt a look into a systemic cause such as Crohn's, tuberculosis, or lymphomas.
Diagnosis
Fissure-in-ano is a clinical diagnosis. In fact, most diagnostic tests will not be tolerated in the clinic. An examination under anesthesia should be performed if the diagnosis is suspect, and you want to do a thorough anorectal examination. This anesthesia will be much appreciated by patients as it would render them pain-free, and it will give you an opportunity to perform diagnostic (biopsies, endoscopic examination) or even therapeutic (sphincterotomy/ botox injections) interventions.
Pro-tip: Almost all patients who present with bleeding per rectum need a colonoscopic evaluation of the entire colon and distal ileum; however, in patients with fissure-in-ano, treatment directed at healing the fissure comes first. The decision to perform colonoscopy will be dictated by the patient's clinical profile, and presenting symptoms.
Management
Congrats! You've now made a diagnosis of acute fissure-in-ano without causing any more pain than what the patient presented to you in the first place. This is a win, and the number of people who diagnose a fissure with the patient wincing in pain will surprise you. Given that you've made a diagnosis correctly, and given that the patient is in the surgical clinic, the management should obviously be surgical, right?
There's a popular saying amongst surgeon, and I'm guilty of overusing it myself -
"A good surgeon knows how to operate
A better surgeon knows when to operate
The best surgeon knows when NOT to operate"
Burn this into your cortex - the initial therapy for acute fissure-in-ano is conservative. Clinical Practice Guideline Committee of the American Society of Colon and Rectal Surgeons, 2010)
1. The initial steps include warm-water sitz baths and stool bulking agents (with or without topical applications). Warm-water sitz bath provides dramatic relief of pain and produces sphincter relaxation, and stool bulking agents (high fibre diet, psyllium & bran hdraw water into the stool and prevent formation of hard stool that causes trauma to the anoderm.
Conservative measures, along with lifestyle modifications (intake of dietary fibres, increasing water/fluid intake, and avoidance of straining at stools) cure 90% of acute fissure-in-ano, but only 40% of chronic fissure-in-ano. Most treatments are directed towards interrupting that vicious cycle of fissure-in-ano. Stool bulking agents reduce the incidence of constipation.
2. The next problem to be tackled is that of the high sphincter tone and the reduced blood supply. Local application of 200-500mg 0.2% nitroglycerin paste does both - produces vasodilation and relaxes the sphincter, but headache due to systemic absorption is dose limiting effect of any nitrate drug. But studies have found them to be only marginally superior to placebo.
3. In order to provide sustained relief of pain and to promote healing of the anoderm, chemical sphincterotomy using topical calcium channel blockers (produce smooth muscle relaxation) with nifedipine, and diltiazem or even botulinium toxin A, commonly called Botox injections to paralyse the skeletal muscle (external sphincter) can be done. They provide excellent pain relief while tackling the problem of high sphincter tone -- this leads to better perfusion of the anal mucosa and thus causes healing.
4. Surgical treatment (with or without chemical sphincterotomy) is recommended in chronic fissures that are refractory to adequate conservative treatment. Lateral internal sphnicterotomy (closed/open) is the surgery of choice for patients with fissure-in-ano. Details of the surgery itself, and the options for surgical management of the sentinel tag, are beyond the purview of this article and will be discussed in future articles.
Procedures such as fissurectomy and anal dilatation under anesthesia are surgeries of historical importance, and are included in this article just as a passing mention.
Finally, we finish the article with a flow chart summarising the treatment protocol for a patient presenting to you with fissure-in-ano.
Author: Anirudh Murali
Sources and citations
- Chapter 159: Fissure-in-ano, Shackleford’s Surgery of the Alimentary Canal, 8th Edition, pp. 1864-70
- Chapter 1: Anatomy and Embryology of the Colon, Rectum and Anus, The ASCRS Textbook of Colon and Rectal Surgery, 3rd Edition, pp. 3-26.