Faecal incontinence (FI) is a disease characterised by the lack of control over solid or liquid bowel contents. There is also a concept of anal incontinence, when there is additional loss of control over gases (1, 2). The incidence of faecal incontinence is estimated by various authors between 2.2 and 25% (2-4). The problem affects all age groups, but mainly the elderly, with higher prevalence among women (5). Incontinence significantly affects the daily functioning of patients and can severely deteriorate their quality of life, leading to social disability. Despite such significant consequences, patients are often too embarrassed to report continence problems to their GPs. Therefore, clinicians should take the initiative and ask direct questions about incontinence in the case of patients with risk factors for faecal incontinence (1).

The mechanism for efficient faecal continence depends on different factors, including anatomical factors (e.g. the presence of venous plexuses, the integrity of the anal sphincters and the puborectalis muscle, the anorectal angle, transverse rectal folds), as well as adequate anorectal sensation, and correct rectal compliance (6). The movement of faecal masses is conditioned by high-amplitude peristaltic contractions, most often occurring after waking up or a meal. The basic mechanism underlying bowel movement was first described already in 1935 by Denny-Brown and Robertson (7). Stretching of the rectum induces a reaction in the form of its subsequent contraction, combined with the relaxation of the anal sphincters. During this time, other pelvic floor muscles, the puborectalis muscle in particular, also relax. The increase in intra-abdominal pressure caused by squeezing plays a certain role in the defecation process. Normally, if the time for a bowel movement seems inappropriate, it can be postponed due to voluntary contractions of the external anal sphincter (EAS) and the puborectalis muscle (6). The ability to assess the nature of the contents accumulating in the rectum (solid/loose stool, gas) is also necessary for the proper functioning of this mechanism. Faecal continence and bowel movement are therefore complicated mechanisms that depend not only on the proper functioning of the anal sphincter and the pelvic floor, but also on the correct somatovisceral reflexes, largely dependent on the efficiency of the sensory receptors located in the rectal ampulla.

Proper diagnosis of the source of the problem is extremely important for the implementation of appropriate treatment. In terms of the aetiology of faecal incontinence, the clearest classification system is presented in the “Rome IV Guidelines” (tab. 1) (8).

The most common causes of faecal incontinence include obstetric injuries (mechanical trauma to the sphincter muscles or stretching of the pudendal nerve during vaginal delivery) and complications after anorectal procedures.

Factors increasing the risk of faecal incontinence symptoms include chronic diarrhoea, previous cholecystectomy, smoking, rectocele, sudden urges to pass a stool, high BMI, advanced age, comorbidities, sphincter muscle injury (e.g. obstetric trauma, surgery) and poor physical activity (2, 8). Chronic diseases particularly associated with an increased risk of faecal incontinence include diabetes mellitus, stroke, multiple sclerosis, Parkinson’s disease, systemic scleroderma, myotonic dystrophy, spinal cord injuries, faecal impaction, pelvic organ prolapse, diarrhoeas, inflammation of the colon and rectum, and radiation proctitis (9).

There is no uniform approach to the classification of faecal incontinence, therefore the aetiology of the disease, pathophysiology, type of incontinence and its intensity (severity of symptoms) should be assessed individually in each case (2).

The type of stool incontinence can be assessed with a 3-grade scale: grade I - leakage and difficulty controlling gas and liquid faeces, grade II - inability to control gas and liquid faeces, and limited or lost control over loose stool, grade III - inability to control a properly formed stool (10). We can also distinguish urge, passive, and mixed incontinence (1, 2). In the first case, the patient experiences a pressing urge that cannot be postponed, and is most often associated with weakened anal sphincter muscles. The second type involves involuntary stool loss (without urge), usually caused by nerve damage. Anorectal manometry is an excellent tool to help distinguish between the two types of faecal incontinence.

The severity of faecal incontinence can also be determined by considering the subjective symptoms of patients. The currently used scales include the Fecal Incontinence Severity Index (FISI) by Rockwood, Jorge-Wexner score, Vaizey score, Pescatori score, American Medical Systems Scale – Fecal Incontinence Scoring System or Holschneider score (which also takes into account manometric results) (5). In our centre, we use the Jorge-Wexner score (also known as the Cleveland score) (tab. 2) (11).

Due to the complex aetiology of the problem, all patients with faecal incontinence should undergo full, thorough diagnosis based on medical history and physical (proctological) examination. The perianal area should be inspected for scars, skin lesions/maceration, leakage of contents from the anus, perianal fistulas, enlarged haemorrhoidal plexuses, prolapsed anal mucosa, and thinning of the rectovaginal septum (which may indicate the presence of rectocele). The Valsalva maneuver may reveal rectal/uterine prolapse, or pelvic floor depression. Rectal examination allows for the preliminary exclusion of pathological resistance in the rectum and provides information on the length of the anal canal, the tension of the sphincter at rest and at squeezing, as well as an assessment of the thickness of the anal sphincter. Sensory disturbances may indicate neurological aetiology of impaired bowel movements (12). When planning treatment strategy, it is essential to verify whether fecal incontinence is caused by morphological damage to the sphincter muscles or a neurogenic disorder.

According to the 2014 ACG (American College of Gastroenterology) guidelines, anorectal manometry, and balloon expulsion test (BET) should be performed first in patients in whom conservative treatment has failed. If sphincter complex dysfunction is found, the diagnosis should be extended to include imaging techniques (endoanal ultrasound [EAUS] or magnetic resonance imaging [MRI]) and electromyography (EMG) (1). These guidelines are in line with the recommendations of another American organisation, i.e. the American Society of Colon and Rectal Surgeons (13). These tests are necessary to plan a potential repair.

Many imaging and functional tests can be used in the diagnosis of faecal incontinence, such as: endoscopy of the lower GI tract, endosonography, MRI, defecography, manometry, electrography with the assessment of the asymmetry of sphincter innervation, barostat measurement, central and peripheral magnetic stimulation, evaluation of anorectal temperature sensation and electrical stimulation, as well as the assessment of functional morphology and the cells of Cajal. In this paper, we will focus on selected diagnostic methods that are most often used in everyday practice.

It is necessary to perform an endoscopic examination of the lower gastrointestinal tract (colonoscopy or sigmoidoscopy) before initiating the treatment of faecal incontinence to exclude potential organic aetiology (cancer, adenoma, inflammatory bowel diseases). It also allows for collecting mucosal biopsy to diagnose the cause of disturbed bowel movement rhythm (8).

Endosonography (transrectal ultrasound) is an essential diagnostic test for any symptoms of faecal incontinence. It enables an accurate assessment of the integrity of the sphincter muscles and visualisation of morphological changes ranging from minor atrophy to complete disruption of their continuity. It also allows for visualising the layered structure of the anal canal, as well as both anal sphincters and the puborectalis muscle. Its relatively low cost, short performance time and simplicity are undoubted advantages of the method. Subjectivity and low measurement repeatability, which is an important diagnostic element in patients with incontinence, especially when assessing the thickness of the sphincter muscle, are disadvantages of this technique (14). EAUS is the leading imaging method for the internal anal sphincter (IAS). However, it shows lower accuracy in assessing EAS damage than, for example, MRI, due to its poorer ability to visualise the muscle outlines against the background of the ischioanal fat tissue (the MRI signal from the striated muscles significantly differs from the one in fat tissue) (15). However, comparative studies of MRI and three-dimensional endosonography have shown high consistency of measurements in both methods despite the tendency of ultrasonography to overestimate EAS thickness and underestimate IAS thickness (16). The primary goal of the investigation is to determine whether the reported symptoms of incontinence are caused by morphological damage to the sphincters. The extent of the damage is measured by showing which of the muscles has been damaged, at what level and in which part of the circumference, what is the size of the defect (> or < 50% of the circumference), and what is the condition of the remaining sphincter mass. Exclusion of morphological abnormalities and a correct image of the sphincter muscles raise the suspicion of a neurogenic aetiology.

Sector, sector/linear and mechanical (rotating) transducers with high frequencies (7.0-16 MHz) are used for the imaging of the anal canal. No preparation is needed. Inserting the transducer several centimeters deep into the anal canal allows for the assessment of the anal canal on three levels: the upper (the loop of the puborectalis muscle, the upper part of the external sphincter), the middle (external and internal sphincter) and the lower level (distal part of the external anal sphincter). Additionally, the method allows for cross-sectional imaging of the layered structure of the anal canal wall (inner subepithelial layer, internal sphincter, intersphincteric zone, external anal sphincter along with the puborectalis muscle) (17). As the possibility of obtaining a three-dimensional image significantly improves endosonographic accuracy of the examination, the advantage of MRI becomes less important.

Magnetic resonance imaging plays an important role in the diagnosis of patients with suspected congenital anatomical malformations. It is also useful in cases of complex anal fistulas, which, as a focus of continuous infection, may cause persistent symptoms described as incontinence. It allows the visualisation of the anatomy of the sphincters and all pelvic floor structures without patient exposure to harmful radiation (18). MRI with torso pelvic or endorectal coil is considered the method of choice in the diagnosis of inflammatory diseases. The advantages of MRI include multidimensionality, tissue specificity and measurement repeatability (16). Good quality image of the anal sphincters is obtained both in MRI and endosonography, therefore the choice of the method depends largely on its availability and the experience in a given centre.

A test using X-rays to assess the behaviour of the anus and rectum at various stages of bowel movement is one of the basic diagnostic methods allowing for the assessment of bowel movement disorders. Approximately 300 mL of thick barium paste for rectal administration is used as a contrast agent. Defecography allows for the assessment of the length of the anal canal and the anorectal angle, pelvic floor mobility and the time of barium paste expulsion in real time (19). The method can be used to diagnose, among other things, anatomical and functional features that impair defecation, including rectocele, intussusception or rectal prolapse. MR defecography is a type of X-ray defecography (20).

Manometry