Perianal disease is the presenting symptom in 5% of patients with Crohn disease, but overall up to 80% of patients experience anal symptoms. An understanding of the pathophysiology of the anal disease is basic to appropriate management and successful control of symptoms. The purpose of this chapter is to present a rational approach to dealing with perianal disease in patients with Crohn disease.
The key to successful treatment of perianal Crohn disease is recognition of perianal Crohn disease, in which the anoderm and perineal skin are affected by Crohn disease at a microscopic level. The Crohn disease–related inflammation, including granulomas, is in the perianal and perineal tissues themselves. When this is the case, incisions do not heal and local surgery is doomed to fail. Perineal Crohn disease does respond well to anti–tumor necrosis factor (TNF)-α therapy, however. Perineal Crohn disease can be diagnosed clinically by the appearance of the tissues. Waxy perineal edema, spontaneous ulceration, painless fissures, large edematous tags, and a split in the skin of the natal cleft are characteristic findings. Figg and Church describe these appearances, some of which are shown in Figure 44-1 . Histologically, granulomas can be found in most patients. The proportion of patients with these extremely symptomatic findings is likely to vary between studies and centers, accounting for some of the variation in results achieved by surgery or anti-TNF-α treatment. The presence of perineal Crohn disease has the following implications:
Surgical incisions will not heal.
Symptoms will respond to biologic agents.
After a proctectomy, the perineal wound still may not heal and biologic agents might still be needed.
The alternative pathophysiology in patients with Crohn disease in whom perianal disease develops is cryptoglandular sepsis, chronic diarrhea-induced anal stenosis, hemorrhoidal disease, or the “common” fissure made more common and more severe by diarrhea related to Crohn disease. Here the perianal skin and anoderm look normal, and treatment for the manifestations can be the same as the standard treatment in patients without Crohn disease. Incisions will heal, but biologic therapy will be ineffective.
It is obvious that the success rate of biologic agents and surgery in the management of perianal disease in any series will depend on the proportion of patients with perineal Crohn disease in any treatment group. The combination of biologic agents first and then surgery is ideal for patients with perineal Crohn disease.
Other considerations in the management of perianal Crohn disease are the small bowel and colon, the rectum, and the anus itself.
If patients have had a functionally significant amount of bowel removed, the impact of stooling on the anus is magnified. In this case, “significant” means loss of enough bowel to cause chronically more frequent or more liquid stools.
If the rectum is affected by active Crohn disease, the symptoms of urgency and tenesmus may be added to stool frequency. In addition, ulcerations in the low rectum preclude any surgery.
The anus itself can be affected by Crohn disease or by treatments that others might have performed. Anal stenosis is a common finding in patients with chronic diarrhea because the constant liquid stools do not have the dilating effect of normal, formed stools. The anal stenosis makes access to the anal canal difficult for surgeons and endoscopists. At the other end of the spectrum, anal laxity—a consequence of ill-advised surgery, childbirth, or aging—produces incontinence or mucus seepage that aggravates any symptoms from the Crohn disease itself.
Perianal abscess and fistula are the most common manifestations of perianal disease in patients with Crohn disease. The abscess often follows an accelerated course, especially when perineal disease is present. Spontaneous or therapeutic drainage leads to a fistula. Crohn fistulas are atypical in that the internal opening(s) can be eccentric and multiple, and tracts can be complex. Patients with Crohn disease seem to have reduced resistance to spread of sepsis in the perineum, which makes early control of the sepsis important. Uncontrolled sepsis spreads across the perineum, creating new external openings and complex cavities.
Large “elephant ear” anal tags are diagnostic of Crohn disease and cause irritation for patients. Because of the possibility of perineal Crohn disease, they should not be excised. Hemorrhoidal tags also may be present but generally need no treatment.
Painful anal fissures are generally due to diarrhea and are indicative of underlying anal sphincter hypertonicity. They can be treated in the same way as most fissures: with nitric oxide donor ointments or a sphincterotomy. Painless fissures are a sign of perineal Crohn disease and should be left alone.
Anal stenosis in a patient with Crohn disease may be the effect of chronic diarrhea. In this case there is no point in dilation because the stenosis will always recur. It is usually not symptomatic because it is an adaptation to the diarrhea. However, the anus must be dilated to gain access for procedures involving the anoderm or anal canal.
Perianal Skin Irritation
Chronic wetness due to discharge or seepage damages the perianal skin and causes pruritus. Scratching then further damages the skin. The only way to correct this condition is to minimize physical trauma and keep the perineum dry.
Internal Hemorrhoidal Prolapse
Treatment of internal hemorrhoids in patients with Crohn disease can be tricky. Diagnosis of perineal Crohn disease is key because it mandates against any sort of surgery. In the absence of evidence of perineal or anal Crohn disease, hemorrhoidectomy could be performed. However, removal of the anal cushions can predispose to seepage. Elastic band treatment is also possible, although the chances of a normal bowel habit will determine its success.