Pelvic Floor Disorders: Surgical Approach

11. Chronic Anorectal Pain: Pathophysiological Aspects, Diagnosis, and Treatment

Heman M. Joshi and Oliver M. Jones 

(1)

Oxford Pelvic Floor Centre, Department of Colorectal Surgery, Oxford University Hospitals NHS Trust, Oxford, UK

Oliver M. Jones

Email: oliver.jones@ouh.nhs.uk

Abstract

Chronic anorectal pain is a syndrome made up of a complex interaction between neurological, musculoskeletal, and endocrine systems that is further affected by behavioral and psychological factors [1]. The ambiguity of the pathophysiology related to this pain has created several synonyms, but chronic idiopathic perineal pain is an umbrella term used to describe the subgroups of patients who present with chronic anorectal pain [23].

11.1 Introduction

Chronic anorectal pain is a syndrome made up of a complex interaction between neurological, musculoskeletal, and endocrine systems that is further affected by behavioral and psychological factors [1]. The ambiguity of the pathophysiology related to this pain has created several synonyms, but chronic idiopathic perineal pain is an umbrella term used to describe the subgroups of patients who present with chronic anorectal pain [23].

Chronic proctalgia is a term traditionally used for the most common pain syndromes termed proctalgia fugax, levator ani syndrome, and coccygodynia, although the Rome III criteria use only levator ani syndrome and proctalgia fugax in its classification [3]. These syndromes will overlap and pose a diagnostic and therapeutic challenge as they tend to represent variations of the same disorder, and pelvic diagnostic investigations to detect such structural or anatomical pathology are nugatory [46].

Pudendal neuralgia is the term used to describe pain secondary to injury to the pudendal nerve, while pudendal pain syndrome refers to pain when there is no obvious injury to the nerve.

11.2 Anatomy

Without a thorough understanding of the anatomy and physiology of the pelvic floor it is impossible to understand the pathology of chronic anorectal pain. The pelvic floor is a biomechanical composite of muscles, ligaments, and fascia that creates an opening in the pelvis for the pelvic organs to pass into the perineum. The predominant muscle in the pelvic floor is the levator ani, which is composed of four parts: puborectalis, pubococcygeus, ileococcygeus, and coccygyeus. These muscles confer support to the pelvic organs and are essential to functions such as continence, defacation, micturition, delivery, and sexual function [7]. The levator ani and sphincteric muscles are situated in a state of continuous tonic activity, relaxed only during bowel and bladder motility.

The pudendal nerve arises from the S2, S3, and S4 nerve roots. It passes through the greater sciatic notch before wrapping round the ischial spine/sacrospinous ligament before re-entering the pelvis through the lesser sciatic notch below the levator ani. At this point, it lies within a fascial condensation on the medial aspect of obturator internus called Alcock’s canal. It passes below the pubic symphysis before dividing into three branches: the inferior anorectal nerve, the superficial perineal nerve, and the deep perineal nerve. This anatomy is covered in more detail in Chapter 3.

11.3 Proctalgia Fugax

Thaysen introduced the term proctalgia fugax in the 1950s. It is characterized by sudden, short (less than 30 min), intense pain that is anal in distribution (90%) [8]. In most patients, it occurs less than five times per year. It tends to occur at night (30%) and is self-limiting, affecting 8–18% [910] of the population aged 30-60 years and its prevalence shows similar sex predilection [11]. Unlike levator ani syndrome, patients are asymptomatic during examination and no characteristic clinical findings can be found to support the diagnosis.

11.4 Chronic Idiopathic Anal Pain or Levator Ani Syndrome

Smith used the term levator spasm syndrome associated with perineal pain, and Todd reported symptoms of a dull, pressure sensation or a foreign body feeling [12]. The pain is exacerbated by sitting and lasts for hours to days. The prevalence in the general population is 6–7% between the ages of 30 and 60 years with a female predilection [13]. There is an association with previous pelvic surgery/ injury and psychological stress/anxiety. Clinically there is tenderness on palpation of the levator ani muscles [14].

11.5 Coccygodynia

Simpson described the relation between coccyx injury and coccygodynia over 150 years ago. Thiele used the term coccygodynia to relate the levator spasm with anal pain [15]. It refers to severe rectal, perineal, and sacrococcygeal pain, mainly in women (5:1). The key to diagnosis is manipulation of the coccyx, which will trigger the pain and thus differentiate it from levator spasm syndrome.

11.6 Pudendal Neuralgia

Pudendal neuralgia is typically perceived in the perineum from anus to clitoris. Classically, it is a burning pain, worse with sitting, and many patients remain standing [16]. Those with unilateral pain often favor sitting on one buttock. On clinical examination, pain may be elicited by pressure over the path of the pudendal nerve either by rectal or by vaginal examination.

11.7 Etiology

Advanced or high-grade internal rectal prolapse appears to be very commonly associated with chronic idiopathic perineal pain, particularly when symptoms of obstructed defecation are present. Neil and Swash [17] commented on the high prevalence of pelvic floor laxity in patients suffering from chronic rectal pain and the real significance of internal prolapse only began to be addressed seriously much later in the 1990s and 2000s [18]. Chronic anorectal pain is a common symptom in patients with advanced posterior compartment prolapse presenting with defecatory dysfunction. About 50% of such patients will complain of pain at least some of the time. This pain often responds to antiprolapse surgery [1920].

Many patients with pudendal neuralgia will have a clear history of injury. This may be from previous surgery including a neuropraxia related to positioning during hip surgery, or from transvaginal or transobturator tapes and sacrocolpopexy. Other causes include obstetric trauma and rarer infiltrative causes including tumors. More chronic causes include chronic constipation and straining bringing about a stretch of the nerves, prolonged sitting and exercise (especially cycling).

11.8 Other Pathologies and Tests for their Exclusion

It is crucial to exclude the more simple causes of organic pain. These include the proctological conditions, most commonly anorectal sepsis, abscess, or thrombosed hemorrhoids. Intraluminal pathology (typically anal or rectal cancer) can be excluded by endoscopy, while extraluminal/presacral pathology may be delineated by magnetic resonance imaging scanning.

11.9 Investigations

Anorectal physiology and ultrasound (see Chapters 6 and 7) should be standard work-up investigations. Simple benign proctology can be excluded with ultrasound. A thick, hypertensive (more than 5 mm) internal anal sphincter on physiology and ultrasound is indicative of a rare inherited internal sphincter myopathy and should be confirmed by biopsy and demonstration of inclusion bodies on electron microscopy. A hypotensive, thickened (anterior, upper anal canal) internal sphincter suggests high-grade (anal) internal rectal prolapse (rectoanal intussusception). Why this causes pain is not fully understood, though it may be due to the stretching of the vault during intussusception or the response of the internal sphincter to repeated prolapse and localized ischemia [14]. Pudendal nerve latency may also be tested, but in many patients with pudendal neuralgia, this will be normal.

Defecating proctography (Chapter 5) is very helpful when an underlying diagnosis of prolapse is suspected. When chronic idiopathic perineal pain and obstructed defecation are present, the proctogram will demonstrate these findings in 75% of patients. When a patient presents with chronic idiopathic perineal pain alone, a posterior prolapse can be identifed in 50% of cases.

Proctography may underestimate the presence of posterior compartment prolapse. It is of paramount importance to pursue a potential prolapse disorder in patients with chronic idiopathic perineal pain where there is a high clinical suspicion and inconclusive proctography. This is especially important if an enterocele is seen on proctography. Enterocele causes a feeling of pelvic pressure and pain and is suggestive of a posterior compartment prolapse and general pelvic floor weakness [21]. Examination under anesthesia is an extremely useful diagnostic tool where proctography has failed, as the true grade of prolapse can be assessed with the patient pain free and relaxed. In our experience the preferred technique for assessment of prolapse would be to use the circular anal dilator device (Frankenman International Ltd, Hong Kong). The advantage over the use of the cumbersome Eisenhammer speculum is that the prolapse can fall circumferentially into the proctoscope without being trapped under the bivalvular long blades [20].

11.10 Multidisciplinary Approach

Patients with chronic idiopathic perineal pain should be assessed by a colorectal surgeon and a chronic pain specialist to assess for a pelvic floor disorder and possible pain syndrome. It is imperative to have established this clinical relationship prior to rushing into any surgical intervention [16].

A chronic pain care package can be formulated for the individual patient, and it may involve pharmacological, rehabilitational, and psychological approaches. This teamwork is vital.

Pharmacological treatment uses many of the treatments established for chronic pain in other parts of the body. One of the most common is the tricyclic antidepressant amitriptyline, with the antiepileptic drugs, most commonly gabapentin, also in common usage. Opioids may be useful though they may exacerbate constipation.

If there is a pudendal nerve entrapment, then an injection of steroid and local anesthetic under the guidance of a nerve stimulator to identify the nerve at the ischial spine may be useful while blocks of other nerves may also be undertaken and where necessary done under radiological guidance. There is increasing interest in nerve decompression, which is usually undertaken via the transgluteal or transperineal route [22].

Many patients with chronic idiopathic perineal pain will have evidence of posterior compartment prolapse [14]. Many, but not all, of these patients have symptoms of obstructed defecation. Published data are awaited, but there is some emerging evidence that with careful case selection, treatment of this prolapse may bring about relief of the pain.

11.11 Conclusions

The diagnosis of perineal pain syndromes is difficult because they constitute overlapping functional entities. Organic pathology should be excluded in the first instance. Specific nerve entrapment syndromes, while a relatively small part of the group as a whole, should also be sought, as their treatment is quite different and specific.

Historically, for the management of patients with chronic idiopathic perineal pain, there has been something of a “silo mentality”, whereby patients with similar presentations and signs receive very different treatments determined by little more than which specialty they happen to see. Working in groups and adopting a multidisciplinary approach will allow better regulation of treatment and opportunities for learning and research in this emerging field.

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