Functional disorders in patients with chronic constipation: Review of the literature and personal experience

Abstract

Most patients with constipation do not require surgical treatment unless the cause of their symptoms is organic, such as entero-sigmoidocele or rectal intussusception. This review focuses on patients whose constipation is functional, such as slow-transit constipation or anismus. Selecting the appropriate treatment can be challenging in such cases, and surgery may worsen symptoms. This is because a relevant psychological component may be present, in which case psychiatric or psychological treatment may be more appropriate than surgery. The authors report their personal experience and review the literature with the aim of suggesting practical clinical guidelines. Obstructed defecation (OD) is examined in detail, considering both functional and organic etiologies. Apart from the frequent rectocele and rectal mucosal prolapse, which are usually easily diagnosed, OD often reflects additional functional disorders that are not easily detected. The most common are psychological distress, anismus, and rectal hyposensitivity. These conditions require accurate diagnosis and targeted treatment.

Key Words: Constipation; Obstructed defecation; Anismus; Slow-transit; Rectal hyposensation

Core Tip: Obstructed defecation is frequently driven by functional disorders that are often overlooked, leading to inappropriate surgical treatment and poor outcomes. Using the iceberg model, this article emphasizes that anxiety, depression, anismus, rectal hyposensitivity, slow transit constipation, and pudendal neuropathy account for most hidden causes of obstructed defecation. Careful functional evaluation and multidisciplinary management allow surgery to be avoided in the majority of patients and significantly reduce treatment failure and complications. Surgery should be reserved for selected organic conditions, while functional disorders require targeted, non-surgical therapies to achieve durable symptom improvement.

INTRODUCTION

Chronic constipation may present as four distinct clinical entities: Slow transit constipation, obstructed defecation (OD), irritable bowel syndrome, and Hirschsprung’s disease. Before considering functional mechanisms, organic causes of constipation, including colorectal cancer and complicated diverticular disease, must be excluded through appropriate clinical assessment and investigations, and reconsidered if symptoms change over time (Figure 1). Patients with OD often need to strain excessively to evacuate. They may use their fingers either to extract stool from the rectum or to stimulate the perineum to elicit a motor reflex aimed at emptying the rectal ampulla. In our experience, the signs and symptoms of OD can be conceptualized as an “iceberg” with two visible rocks rectocele and rectal internal mucosal prolapse and ten submerged “occult” rocks that, if not adequately recognized (diagnosed and treated), may lead to the sinking of the “surgical ship”. As shown in Figure 2, five occult lesions are functional (left) and five are organic (right).

Figure 1 Flow chart of clinical assessment and investigations in patients with obstructed defecation.

Figure 2 The iceberg diagram for obstructed defecation showing evident and occult diseases. IBS: Irritable bowel syndrome.

Twenty years ago, we conducted a prospective study of 100 patients with OD (most of whom were women) and reported the prevalence of the above-mentioned conditions[1]. Since then, this iceberg diagram has been useful for evaluating OD. The term “iceberg” reflects the fact that most OD disorders are not easily recognized, akin to submerged rocks that can sink the surgical ship. Using this framework, we identified the patients who required an operation (fewer than had previously been considered “surgical”). The subsequent step was to avoid surgery in patients whose predominant problem was functional rather than organic. This editorial focuses on the functional etiologies of OD.

ANXIETY-DEPRESSION

Among functional cases, the most frequent were those with anxiety and/or depression, accounting for nearly two-thirds of OD cases. By avoiding surgery in these difficult patients, we were often able to prevent treatment failure. Notably, we had both a psychologist and a psychiatrist available to support patients with psychological distress. For example, among patients who underwent a stapled transanal rectal resection (STARR) procedure for OD, those with significant psychiatric comorbidity had an almost predictable failure[2]. Our policy in OD is to minimize the number of patients exposed to potentially troublesome surgical treatment, similarly to the approach adopted by Madbouly et al[3] who had 60% of either persisting or recurrent constipation 4 years after surgery. With this approach, two-thirds of our surgical patients were cured or improved at 6-year follow-up[1]. Conversely, in series in which most OD patients underwent surgery (e.g., 500 cases in 9 years, all treated with STARR), nearly 20% experienced life-threatening complications[4].

ANISMUS

As shown in Figure 2, after psychiatric comorbidity, the most frequent problem in our patients with OD was anismus (i.e., a non-relaxing puborectalis muscle). In our series, it occurred in 44% of cases. This condition can be suspected on digital rectal examination by inserting a finger into the anal canal and asking the patient to strain after taking a deep breath and generating an abdominal push. The examiner may detect failure of puborectalis relaxation during straining. In cases of diagnostic uncertainty, functional imaging may be useful, such as endoanal ultrasound with a rotating probe or defecography. Conventional defecography remains a widely available and highly sensitive tool for assessing evacuation dynamics, while magnetic resonance defecography (MRD) offers superior soft-tissue contrast and multiplanar assessment without radiation exposure. MRD is particularly valuable in patients with suspected multicompartment pelvic floor dysfunction or when conventional studies provide equivocal findings, although its higher cost and limited availability preclude its routine use in all patients[5].

During the first 10 years in which we used the iceberg diagram, our first-line treatment for anismus was biofeedback, delivered by an experienced physiotherapist to train pelvic floor relaxation. Because many patients with anismus were anxious women, we developed a combined approach termed psycho-echo-biofeedback. The proctologist inserts an ultrasound probe into the patient’s vagina, while a psychologist facilitates relaxation. The session then includes “guided imagery” (a combination of relaxing music and hypnotic suggestions). After approximately one hour and four simulated defecation attempts (straining while viewing the puborectalis muscle on the ultrasound screen), many patients achieve at least partial pelvic floor relaxation. In our experience, anismus was cured or improved in approximately two-thirds of cases[6].

Another therapeutic option is injection of botulinum toxin A into the puborectalis muscle (up to 100 units). When combined with biofeedback, the success rate is approximately 70% at 8 months[7].

Finally, over the last 12 years, we have performed bilateral partial puborectalis myotomy in carefully selected patients who do not respond to physiokinesitherapy and who have an intact sphincter apparatus, with the aim of minimizing postoperative incontinence. We have published our technique and outcomes, with a success rate of approximately 70% at 1 year. A meta-analysis from Cleveland Clinic Florida, including approximately 200 patients, reported that most patients remained continent after myotomy[8]. With strict selection criteria, we operated on few patients and observed no cases of permanent anal incontinence. To reduce complications such as bleeding and sepsis, we use a minimally invasive approach[9]. Patients are discharged after the first bowel movement, usually on postoperative day 2.

However, anismus likely reflects more than a non-relaxing puborectalis muscle. It may represent a marker of multi-site functional disorders involving the pelvic floor and the urogynecological system, and possibly other organ systems[9].

RECTAL HYPOSENSITIVITY

Rectal hyposensitivity occurs in approximately one-third (33%) of patients with OD. In these patients, rectal sensation is impaired and stool may remain in the rectum for more than 24-36 hours. Water is reabsorbed, resulting in small, hard stools that fail to trigger an effective defecatory reflex. As a result, the rectum may be unable to expel stool, leading to OD. Not uncommonly, this disorder is misdiagnosed, and surgeons unfamiliar with pelvic floor physiology may incorrectly attempt to treat it by resecting a segment of the rectum (often via STARR, a procedure that has been aggressively marketed). A safer and less costly approach is to increase rectal sensation, either with balloon training under a physiotherapist’s supervision or with home-based rectal electrical stimulation using a small electrode. In addition, patients should be advised to drink adequate amounts of water and follow a high-residue diet (e.g., bran, leafy vegetables, and fruit with the skin), while recognizing that stool consistency and rectal sensitivity are also influenced by gut microbiota composition and its metabolic activity. Alterations in microbial fermentation and short-chain fatty acid production may contribute to impaired rectal sensation and colonic motility, and in selected patients dietary modulation or targeted supplementation may help restore a more physiological bowel function.

SLOW INTESTINAL TRANSIT/IRRITABLE BOWEL SYNDROME

Slow intestinal transit and irritable bowel syndrome are present in approximately 28% of patients with OD. In the past, slow transit constipation was sometimes treated with colectomy and ileorectal anastomosis, but outcomes were often disappointing. Some patients developed diarrhea and fecal incontinence, and adhesions with chronic abdominal pain were not uncommon[10]. Patients with constipation and irritable bowel syndrome often report pain in the left lower abdomen, where a tense, painful, muscle-like mass may be palpable; this may reflect sigmoid hypersegmentation. Many of these patients have a psychosomatic component.

PUDENDAL NEUROPATHY

Pudendal neuropathy is a troublesome condition affecting approximately 15% of patients with OD, mainly women who experience chronic perineal stretching due to multiple vaginal deliveries and repeated straining. This stretching may damage the anal sphincters and contribute to fecal incontinence. The diagnosis can be supported by measuring pudendal nerve terminal motor latency, although pudendal nerve testing does not generally contribute to surgical decision-making[11]. Perineal descent during straining can also be assessed; a descent greater than 2 cm is consistent with descending perineum syndrome with pudendal nerve stretching, which may be associated with both incontinence and perineal pain. A simple bedside assessment is to gently touch the perianal skin with a fine needle and observe the sphincter response (i.e., the anal reflex).

CONCLUSION

This paper focuses on patients with chronic constipation due to functional disorders (left column in Figure 2). The right column lists organic diseases causing OD. Surgery is more often indicated for organic disease; however, many “organic” cases do not require surgery and can be managed adequately with the help of other specialists, such as urologists and gynecologists (e.g., prostatism and mild hysterocele). The conditions that more often require surgery include enterosigmoidocele and recto-rectal intussusception. Surgical options include obliteration of the Douglas pouch with mesh and ventral rectopexy. Compared with laparoscopy, a robotic technique does not appear to provide additional benefit and is associated with longer operative time[12]. To properly treat patients with OD, the coloproctologist should work within a multidisciplinary team that includes, at minimum, a psychologist/psychiatrist and a physiokinesitherapist, and often a urogynecologist and a gastroenterologist. Surgery is rarely indicated (in fewer than 20% of patients). Patients with poor outcomes after surgery are frequently affected by psychological or more severe psychiatric comorbidities.

ACKNOWLEDGEMENTS

The authors wish to thank Mrs. Mugisha for English editing.