Anal fissure (AF) is a common problem in clinical practice found in every age group (1). This disease involves the presence of a tear in the anal mucosa (anoderm) below the pectinate line (2). Ulceration of this site may also occur (3). Linear anoderm tear may be diagnosed in the lower half of the anal canal. In approximately 90% of cases in men and women posterior AF occur, which are located on the posterior wall of the anal canal along the midline of the body. Anterior AF occur in approximately 10% of patients and are more prevalent in women. In fewer than 1% of patients AF occurs in different sites than the midline of the body or multiple fissures occur, which may be associated with Crohn’s disease, anal cancer, tuberculosis or sexually transmitted infections (HIV, herpes virus, syphilis) (4). The first anatomical description of AF was compiled by Louis Lemmonier in 1869. The first description of a sphincterotomy procedure was published in “Traitè des maladies chirurgicales et des opèrations qui leur conviennent” by Alexis Boyer between 1818 and 1826 (5). The prevalence of AF depends on the age and sex of the patients. In the United States of America 342,000 new cases of AF are diagnosed every year, which is comparable to the number of appendectomy procedures performed in this country every year. The prevalence of AF in the U.S. is 1.1 per 100,000 persons per year. The mean risk of AF is 7.8% (6). The prevalence of AF is higher in women (1.14 per 100,000 persons per year) than in men (1.04 per 100,000 persons per year) (6). The peak incidence of the condition among women is during puberty and early adulthood. Men usually suffer from AF at middle age. It is suspected that the prevalence of AF depending on sex and age is associated with the different prevalence of constipation in given groups (7) and with other risk factors. The first observations concerning the association between constipation and AF were made by the aforementioned Boyer (5). Despite numerous studies the aetiology of AF remains unclear. The oldest theory is inflammation (cryptogenic) theory assuming that the cause of the disease is infection of the anal glands (8). Three other factors are also put forward as the causes of AF: mechanical trauma, ischaemia and increased pressure in the anal canal (9). Perfusion in the anal canal mucosa along the posterior midline of the body is 50% smaller than in other sites of the anal canal, which contributes to a decreased therapeutic effect (10). In addition, it was demonstrated that blood flow on the AF side is smaller than on the side of the anterior midline of the anal canal in a group of patients in comparison with a control group (11). Keck et al. find that as a result of AF elevated pressure is usually observed in the anal canal, which is probably due to the increased resting tension of the internal anal sphincter muscle (m. sphincter ani internus), as well as contraction of muscle tissue below the anoderm tear (12). The risk factors for AF may be pregnancy and postpartum period – the prevalence of the condition after the first delivery is 9% (8), the use of opioid analgesics, frequent constipation, large and hard stool masses, old age, comorbidities (especially the large intestine being affected with Crohn’s disease, which is manifested with AF in 50-80% of cases). Anal fissures may be divided into acute ones which heal after topical treatment within a few weeks and chronic ones which are present for 6 or more weeks and require intensified treatment (13). Acute AF are manifested by a sharp pain and strong contraction of the anal area. Patients describe this sharp pain occurring during defecation as “masses passing through broken glass” or “passing of sharp instruments”. Anal pain may be sharp and burning and occur for a few hours (from 1 to 2 hours) after defecation (4, 14). A typical symptom is bleeding during defecation or shortly after. The bleeding is usually very small, however, stool with a trace of blood may also appear. Diagnosis of AF involves taking the patient’s medical history (obtaining detailed information on the presence of risk factors), clinical physical examination consisting of inspection of the anal area, rectal examination and, additionally, anoscopy. The treatment of acute AF should be conservative in nature and involve increasing the amount of dietary fibre and fluids, taking warm sitz and regular baths and using topical analgesic ointments or ointments with calcium channel blockers or nitroglycerin. If symptomatic treatment fails, botulinum toxin injections into the internal anal sphincter muscle may be applied. These treatment methods are characterised by minimal side effects and a good prognosis (15). Warm bath treatment and increased dietary fibre intake leads to recovery in nearly half of acute AF cases (16). Warm sitz baths combined with regular baths cause the rectoanal reflex to occur, which leads to relaxation of the internal anal sphincter (17). Ointments containing nitrates cause the internal anal sphincter to relax by releasing nitrogen oxide (NO), which acts as an inhibitory neurotransmitter in this muscle (18). Efficacy of such treatment has been demonstrated (19). Ointments containing calcium channel blockers cause the internal anal sphincter to relax by blocking the influx of calcium ions to smooth muscle cells (20). Botulinum toxin is produced by Clostridium botulinum and acts as a neurotransmitter that inhibits the release of acetylcholine from the presynaptic terminals. Studies have demonstrated that it causes relaxation of both the internal and external anal sphincter muscles for up to 3 months (20, 21). According to various authors the treatment of AF in patients with Crohn’s disease may be successfully pursued using ointments with metronidazol, prednisone or sulfasalazine (15).