Pruritus Ani

Theodore Saclarides, MD
Professor of Surgery
Rush Medical College
Head, Section of colon and Rectal Surgery
Rush-Presbyterian-St. Luke's Medical Center
Chicago, IL

Pruritus ani is a frequent reason for patients to seek medical advice and, unfortunately, it is often incumbent upon the colorectal surgeon to diagnose and treat this malady. One should remember that pruritus may be a symptom of an underlying disorder that is potentially more serious than simple itching. One should therefore maintain a high index of suspicion as to these potential associated conditions. With respect to benign anorectal diseases that can cause pruritus ani, one must consider hemorrhoids, fecal incontinence of varying magnitude and severity, anal fistulae and condyloma. Pruritus may also be a manifestation of non-invasive perianal malignancies, such as Paget's disease and Bowen's disease. Non-primary anal diseases that can be associated with pruritus ani include contact dermatitis, fungal infections, diabetes, pinworm infections, psoriasis and seborrhea.

Anal manometry has been used to study patients with pruritus and it has been noted that patients so afflicted may demonstrate increased relaxation of the anal sphincter following rectal distension above and beyond what is considered normal. An abnormal anorectal inhibitory reflex has also been demonstrated.

The work-up of affected patients is not standardized, nor is it uniformly agreed upon. It stands to reason that if the patient is over the age of 50 and presents with symptoms referable to the lower GI tract that screening for colorectal cancer as per the American Cancer Society's recommendation should be followed. If the patient is less than 50 years of age, then at least a flexible sigmoidoscopy should be performed. One may also consider obtaining skin scrapings for culture to rule out a cutaneous yeast infection. Clearly, if there are visible abnormalities of the perianal skin, then one should consider performing a limited skin biopsy to rule out Paget's or Bowen's disease.

With respect to treatment, a variety of magic potions have been tried not surprisingly without success. Improvement in symptoms has been noted with the subcutaneous injection of 30cc of 0.5% of methylene Blue. Dietary modifications can be tried, such as the restriction of caffeinated or carbonated beverages, dairy products, alcohol, tomato-based food products, cheese and chocolate. With respect to hygiene, a lack of cleanliness is not the problem. In fact, the opposite is more likely to be noted in these patients. Patients complaining of pruritus ani must be convinced that the anus should not be scrubbed and attempts at sterilization are not appropriate. Liberal use of plain water rinses can be quite helpful and after bathing, soap must be rinsed off. Following defecation, water-moistened cloths or toilet paper is preferable to using dry tissue. In between defecation, cotton balls placed next to the anal orifice may help to absorb sweat which when mixed with fecal residue can cause skin irritation and breakdown. Moisture barriers, such as zinc oxide, may ameliorate symptoms. When all else fails, a short-term course of topical steroids may provide symptom relief, however, long-term use of these products should be avoided as they cause skin atrophy. The use of anesthetic ointments should also be avoided.

In summary, when pruritus ani is a frequent complaint, it will more often than not fall on the shoulders of the colorectal surgeons for diagnosis and treatment. First and foremost, one must understand that this may be a symptom of an underlying and potentially serious condition such as Paget's or Bowen's disease. If there are visible abnormalities of the perianal skin, then biopsy should be strongly considered. Long-term topical steroid therapy should be avoided.

Anal Fissure

An anal fissure is defined as a tear in the mucosa between the dentate line and the mucocutaneous border of the anal canal. Because of the fact that greater than 90% of fissures occur in the posterior midline and the remainder occur in the anterior midline, it has been postulated that fissures are due to the elliptical rather than the circular orientation of the sphincter muscle. This causes a lack of support to the anoderm at the apices of the ellipse, namely, the midline locations. If one encounters an anal fissure in another location, one must consider cancer, inflammatory bowel disease, syphilis, tuberculosis, or an HIV-related ulcer. Acute anal fissures appear as shallow ulcerations without the typical findings of chronicity, namely, a sentinel pile or hypertrophied anal papilla within the anal canal. The majority of acute anal fissures will heal with conservative therapy, however, once a fissure has become chronic, measures other than increasing dietary fiber intake are frequently required.

The diagnosis of an anal fissure may be made based on history alone. The typical presentation is pain with defecation. This pain may last for hours following the completion of the bowel movement and may be aggravated by sitting for long periods of time. On physical examination, a fissure may be seen after gentle spreading apart of the buttocks and inspection of the midline regions. Once should avoid overzealous attempts at a digital rectal examination. The combination of seeing a sentinel pile and intense sphincter spasm is generally considered enough to establish a diagnosis of an anal fissure. If one is uncertain about the diagnosis or if one is concerned about local anorectal sepsis or cancer, then an examination under anesthesia is warranted.

There is no completely satisfactory explanation as to why fissures occur. It is postulated that trauma, hypertonicity of the anal canal, local ischemia, and infection all play a role. Angiographic studies have shown a relative lack of arterioles and capillaries supplying the subcutaneous space and the internal anal sphincter in the posterior midline. This has been confirmed with Doppler laser flowmetry. This relative ischemia of the posterior midline may be exacerbated with spasm of the internal sphincter which reduces flow of blood even further. Using manometry, increased anal pressures have been noted in patients afflicted with anal fissures compared to control subjects. Lowering of the anal canal pressure in these patients correlates with symptom relief. Also noted manometrically is the overshoot phenomenon that occurs with rectal distension; namely, there is the return of anal canal pressure after initial sphincter relaxation. However, the pressure returns to a level above the baseline transiently to a higher level.

Regarding the treatment of anal fissures, one should pursue conservative management for both acute and chronic cases by increasing the dietary fiber supplements, increasing water intake and maintaining anal hygiene without overzealous attempts at cleansing. One should refrain from prescribing topical agents administered either in suppository or enema form, as this can exacerbate the pain. Most acute anal fissures will heal with these maneuvers. However, chronic fissures will frequently require additional steps such as the application of nitroglycerine, Botox, Nifedipine, or diltiazem. Regarding nitroglycerine, studies have shown that nitric oxide mediates relaxation of the internal anal sphincter. Nitroglycerine is a nitric oxide donor. Studies have shown that 0.2% preparations of nitroglycerine produce an approximate 25% reduction in maximum anal resting pressures, as well as increasing anodermal blood flow. A minimum concentration of 0.2% is needed to lower the anal pressure by at least this 25%. The main side affect of nitroglycerine is headaches which occur in up to 90% of patients. Success rates in the literature have been quoted at 48-78%. The presence of a sentinel pile significantly correlates with treatment failures as well as recurrence of the anal fissure.

The use of Botox for anal fissures was first described in 1993. Botox inhibits the release of acetylcholine at the presynaptic membrane. Injection of 2.5 up to 10 units at 2-4 different sites within the anal canal is commonly practiced. Although improvement in pain may be noted within 24 hours, healing of the tissue may take significantly longer. Healing rates of 78-90% have been quoted in the literature, and a recurrence rate of 8% has been noted within 6 months. Since the toxin cannot be stored, there may be considerable loss of money, as unused portions must be discarded.

Calcium antagonists, such as Nifedipine and diltiazem prevent the flow of calcium into the sarcoplasm of smooth muscle, thereby decreasing the contractility of the internal anal sphincter when placed around the anal canal. These agents also cause vasodilatation of the anoderm. These agents are usually applied topically, although oral preparations have been tried albeit with a lower success rate. Healing has been noted in up to 95% of patients taking nifedipine and up to 67% in patients taking diltiazem.

When conservative measures fail, more aggressive forms of therapy should be considered; namely, anal dilatation and internal sphincterotomy. Anal dilatation using the Lord's technique has been criticized because of the unpredictable amount of sphincter injury sustained. This technique utilizes the stretch provided by one to up to three fingers of each hand inserted into the anal canal, pronated, and then distracted in opposite directions. This form of dilatation has been replaced by a more precise form of stretch with a 40 mm hydrostatic balloon or by a Park's retractor. The balloon dilator is 6 cm in length and is inserted until only 1 cm of the balloon protrudes from the anal canal. The balloon is then inflated up to 20 pounds per square inch for 6 minutes. Sohn has treated 495 patients with this technique and noted a healing rate of 80% within 3 months; 0.7% of patients experienced temporary incontinence of flatus and only 0.3% experienced permanent incontinence of flatus.

Regarding internal sphincterotomy, controversies include the location of the incision (midline vs. lateral), open vs. closed technique, and whether to perform concomitant procedures such as fissurectomy and hemorrhoidectomy. A posterior midline incision is associated with a keyhole deformity which can cause significant problems with anal wetness and soiling. Up to 40% of patients develop some degree of incontinence. A lateral incision is associated with a much lower incidence of soilage and incontinence and is generally the preferred approach. Whether an open or closed technique is chosen, the results and complication rates are similar. One should exercise extreme caution when performing concomitant procedures because of the increased risk of complications and the added time for healing. Many patients with hemorrhoids and sentinel piles will notice regression of these abnormalities once a sphincterotomy has been performed. When a sphincterotomy is carried out, one must divide all fibers of the internal sphincter distal to the dentate line, preserving all of the external anal sphincter and the proximal fibers of the internal anal sphincter. Complication rates vary in the literature but soilage has been noted in 0-40% of patients and incontinence in 0-34% of patients in the immediate to postoperative period. Less than 10% of patients experience any long-term problems. Women and the elderly are at increased risk of complications. Recurrence rates of less than 5% are noted and one can expect 98-99% to have healing of their fissures within two months of surgery. The primary cause of a recurrent or persistent anal fissure is an incomplete prior internal sphincterotomy. One must also consider Crohn's disease, sexually transmitted disease, infections and HIV-related problems. If the anus is hypertensive, a repeat internal sphincterotomy can be considered. If the anus is not hypertensive either clinically or manometrically, one should avoid performing a repeat internal sphincterotomy and, in these instances, anoplasty with tissue advancement flaps should be considered. It is worthwhile before instituting any form of surgical therapy for one to resume conservative treatment with increased fiber intake, increased dietary water intake, and the use of topical agents.

The decision to pursue topic treatment vs. surgery should be individualized, based on the degree of pain the patient is experiencing. Some patients are severely symptomatic and simply cannot invest the 1-3 months necessary for topical agents to provide relief and, in these instances, surgery may be preferable at the onset.