Testing for and the role of anal and rectal sensation

Faecal incontinence: Retentive, non-retentive and when to suspect organic pathology

BACKGROUND

Faecal incontinence is a highly prevalent and very distressing condition that occurs throughout the entire paediatric age.

AIM

To summarise advances in the understanding of the epidemiology, pathophysiology, evaluation and treatment of children with faecal incontinence due to either disorders of gut-brain interaction or organic diseases.

METHODS

Literature review on prevalence, impact, diagnosis and treatment options for children with faecal incontinence, interspersed with observations from the author's lifelong career focused on evaluation of children with motility disorders.

RESULTS

Faecal incontinence in children is most commonly due to unrecognised or insufficiently treated functional constipation with overflow incontinence. Non-retentive faecal incontinence (NRFI) is probably more common than previously thought and is particularly challenging to treat. Organic diseases such as anorectal malformations (ARMs), Hirschsprung disease and spinal defects are often associated with faecal incontinence; in these conditions, faecal incontinence has a profound impact on quality of life. Recognition of the different pathophysiologic mechanisms causing the incontinence is essential for a successful treatment plan. A thorough physical examination and history is all that is needed in the diagnosis of the causes of faecal incontinence related to disorders of gut-brain interaction. Colonic transit studies or x-rays may help to differentiate retentive from NRFI. Manometry tests are helpful in determining the mechanisms underlying the incontinence in children operated on for ARMs or Hirschsprung diseases. Multiple behavioural, medical and surgical interventions are available to lessen the severity of faecal incontinence and its impact on the daily life of affected individuals.

CONCLUSIONS

Recent advances offer hope for children with faecal incontinence.

Examining linaclotide for the treatment of chronic idiopathic constipation

INTRODUCTION

Chronic idiopathic constipation (CIC) is characterized by infrequent bowel movements and hard stools lasting for at least three months or longer. This disease affects 8-12% of the US population and 10-17% of the world population. Treatment and management involve identifying the primary cause, changing dietary habits, and adequate physical activity. Linaclotide is a guanylate cyclase-agonist acting locally in the luminal surface of the intestinal enterocyte leading to a signal transduction cascade, activation of the cystic fibrosis transmembrane conductance regulator (CFTR), thus increasing secretion of chloride and bicarbonate into the intestinal lumen with eventual increased intestinal fluid and faster transit time.

AREAS COVERED

We reviewed multiple studies and did a thorough literature review on CIC including its pathophysiology. Through this literature review, we were able to discuss and give the context and rationale for drug regimens indicated for CIC.

EXPERT OPINION

The era we live in right now is akin to nutrient-rich and fertilized soil as knowledge and resources are abundant. The opportunities and potential are endless. Constipation being more extensively studied, our understanding of medications and diseases broadens, leading to novel medications being discovered. Linaclotide is a pioneer in this aspect and can pave the way for future generations.

Anorectal Manometry in Patients With Fecal Incontinence After Ileal Pouch-Anal Anastomosis for Ulcerative Colitis: A Cohort Study

Background

Fecal incontinence commonly occurs in patients with ulcerative colitis and ileal pouch-anal anastomosis. There is a paucity of manometric data in pouch patients. We aimed to better define manometric parameters in pouch patients with fecal incontinence.

Methods

We compared clinical and manometric variables in ulcerative colitis patients with pouch and fecal incontinence to ulcerative colitis patients with pouch without fecal incontinence and to non-ulcerative colitis patients with fecal incontinence. Manometric data for the 3 cohorts were compared to established normative data. An independent-samples t-test was performed for continuous variables, and chi-square test was used for categorical variables. Logistic regression was performed to identify predictors of incontinence in pouch patients (P < .05).

Results

Among 26 pouch patients with fecal incontinence (73% female), 26 pouch patients without fecal incontinence (35% female), and 84 patients with fecal incontinence without ulcerative colitis (68% female), there were no differences in anorectal pressures between patients with fecal incontinence. Lower pressures were observed in pouch patients with fecal incontinence compared to those without fecal incontinence. Resting pressure was similar between pouch patients with fecal incontinence and healthy controls (60.9 ± 36.1 mmHg vs. 66.9 ± 3.2 mmHg, P = .40). Female sex (P = .019) and defecatory disorders (P = .033) each independently predicted fecal incontinence in pouch patients.

Conclusions

Pouch patients with fecal incontinence have lower anorectal pressures compared to pouch patients without incontinence, though have similar pressures to non-ulcerative colitis patients with fecal incontinence. Pouch patients with fecal incontinence have similar resting pressures as healthy controls. Distinct manometric normative values for pouch patients are needed.

Pain Trajectory after Short-Stay Anorectal Surgery: A Prospective Observational Study

The evolution of pain after anorectal surgery has not been well characterized. The main objective of this study is to evaluate patterns in acute postoperative pain in patients undergoing short-stay anorectal surgery. A total of 217 patients were included in the study, which used group-based trajectory modeling to estimate postoperative pain and then examined the relationships between sociodemographic or surgical factors and pain trajectories. Three distinct postoperative pain trajectories were determined: hemorrhoidectomy (OR, 0.15), higher anxiety (OR, 3.26), and a higher preoperative pain behavior score (OR, 3.15). In multivariate analysis, they were associated with an increased likelihood of being on the high pain trajectory. The pain trajectory group was related to postoperative analgesic use (p < 0.001), with the high-low group needing more nonsteroidal analgesics. The study showed that there were three obvious pain trajectories after anorectal surgery, including an unreported low-moderate-low type. More than 60% of patients maintained moderate to severe pain within 7 days after the operation. These postoperative pain trajectories were predominantly defined by surgery factors and patient factors.

Novel insights into physiological mechanisms underlying fecal continence

The machinery maintaining fecal continence prevents involuntary loss of stool and is based on the synchronized interplay of multiple voluntary and involuntary mechanisms, dependent on cooperation between motor responses of the musculature of the colon, pelvic floor, and anorectum, and sensory and motor neural pathways. Knowledge of the physiology of fecal continence is key toward understanding the pathophysiology of fecal incontinence. The idea that involuntary contraction of the internal anal sphincter is the primary mechanism of continence and that the external anal sphincter supports continence only by voluntary contraction is outdated. Other mechanisms have come to the forefront, and they have significantly changed viewpoints on the mechanisms of continence and incontinence. For instance, involuntary contractions of the external anal sphincter, the puborectal muscle, and the sphincter of O'Beirne have been proven to play a role in fecal continence. Also, retrograde propagating cyclic motor patterns in the sigmoid and rectum promote retrograde transit to prevent the continuous flow of content into the anal canal. With this review, we aim to give an overview of primary and secondary mechanisms controlling fecal continence and evaluate the strength of evidence.

Electroacupuncture for postoperative pain in mixed hemorrhoids: A meta-analysis

BACKGROUND

To investigate the efficacy of electroacupuncture for postoperative pain in mixed hemorrhoids.

METHODS

Randomized controlled trials were searched in PubMed and Cochrane Library. The risk of bias assessment tool was used to assess methodological quality. Stata 14.0 software was used for meta-analysis. Weighted mean differences were calculated if all outcome variables were reported the same way, while standardized mean differences (SMD) were calculated if they were different.

RESULTS

From 27 identified studies, 5 Chinese studies (465 patients) were included in this meta-analysis. The electroacupuncture group had significantly lower postoperative pain scores compared with the control group at 6 hours postoperatively (SMD = -0.89, 95% CI: -1.091 to -0.692; P < .001), at 12 hours postoperatively (SMD = -1.089, 95% CI: -1.336 to -0.843; P < .001), at 24 hours postoperatively (SMD = -0.548, 95% CI: -0.721 to -0.374; P = .547), and 72 hours postoperatively (SMD = -1.089, 95% CI: -1.336 to -0.843; P < .001).

CONCLUSION

Electroacupuncture can improve pain after surgery for mixed hemorrhoids. It is an effective method to improve the pain after hemorrhoidectomy, which deserves further research and promotion.

Understanding the physiology of human defaecation and disorders of continence and evacuation

The act of defaecation, although a ubiquitous human experience, requires the coordinated actions of the anorectum and colon, pelvic floor musculature, and the enteric, peripheral and central nervous systems. Defaecation is best appreciated through the description of four phases, which are, temporally and physiologically, reasonably discrete. However, given the complexity of this process, it is unsurprising that disorders of defaecation are both common and problematic; almost everyone will experience constipation at some time in their life and many will develop faecal incontinence. A detailed understanding of the normal physiology of defaecation and continence is critical to inform management of disorders of defaecation. During the past decade, there have been major advances in the investigative tools used to assess colonic and anorectal function. This Review details the current understanding of defaecation and continence. This includes an overview of the relevant anatomy and physiology, a description of the four phases of defaecation, and factors influencing defaecation (demographics, stool frequency/consistency, psychobehavioural factors, posture, circadian rhythm, dietary intake and medications). A summary of the known pathophysiology of defaecation disorders including constipation, faecal incontinence and irritable bowel syndrome is also included, as well as considerations for further research in this field.

A new method for assessing anal distensibility with a barostat and magnetic resonance imaging in healthy and constipated women

OBJECTIVES

Defecation requires relaxation of the internal and external anal sphincters. High anal resting pressure is associated with painful constipation, defecatory disorders, and increased healthcare utilization in constipated patients; the mechanisms are unclear. Perhaps patients with a high anal resting pressure have a less distensible canal, which impedes defecation.

METHODS

In 50 of 64 participants (33 healthy and 17 constipated women), anal pressures and distensibility were measured, respectively, with manometry and balloon distention combined with magnetic resonance imaging; rectal balloon expulsion time (BET) was also studied.

RESULTS

The BET (P = .006) was longer, and the mean (SD) rectoanal pressure gradient (-58[40] vs -34[26] mm Hg, P = .03) was more negative in constipated than healthy women; anal resting pressure was not different. During anal distention, the balloon expanded rapidly at an opening pressure of 49 (18) mm Hg, which was lower (P < .0001) than resting pressure (90 [25] mm Hg). The resting pressure was correlated with the opening pressure (r = 0.57, P < .0001) and inversely (r = -0.38, P = .007) with maximum volume but not with anal distensibility (volume-pressure slope). In healthy women, the difference (opening-resting pressure) was correlated with anal relaxation during evacuation (r = 0.35, P = .04). Anal distensibility and sensory thresholds were not different between constipated and healthy women.

CONCLUSIONS

Among healthy and constipated women, a greater anal resting pressure is correlated with greater opening pressure and lower maximum volume during distention, and, hence, provides a surrogate marker of anal distensibility. The difference (opening-resting pressure), which reflects anal relaxation during distention, is correlated with anal relaxation during evacuation. Anal resting pressure and distensibility were comparable in healthy and constipated women.

Difference in Defecation Desire Between Patients With and Without Chronic Constipation: A Large-Scale Internet Survey

INTRODUCTION

Defecation desire (DD) is an important physiological component of normal defecation. However, knowledge of DD in the general population and in individuals with chronic constipation (CC) is lacking. We aimed to assess the prevalence of DD in the general population and individuals with CC and to understand the impact of treatment on DD among individuals with CC.

METHODS

We conducted an online questionnaire survey targeting the Japanese general population in 2019. DD was reported as never, rarely, usually, or always. Individuals who self-reported constipation and met the Rome IV criteria for functional constipation but did not for irritable bowel syndrome were included in the CC group, while the same number of age-/sex-matched controls who met neither functional constipation nor irritable bowel syndrome criteria was included in the non-CC group. Individuals who reported DD as rarely or never were defined as having loss of DD (LODD).

RESULTS

Of the 20,986 participants, 2,587 were included in the CC group (12.3%). LODD was significantly higher in the CC individuals than in the non-CC controls (57.4% vs 8.3%, respectively, P < 0.001, odds ratio 14.84 [95% confidence interval 12.65-17.42]). Satisfaction with treatment for constipation was lower in individuals with persistent LODD (25.9%) compared with those with improved LODD (56.5%) on treatment (P < 0.001, odds ratio 2.48 [1.39-4.43]).

DISCUSSION

LODD is common in CC and is associated with decreased satisfaction to treatment. Greater attention should be paid to DD when treating patients with CC.

Pulse article: How do you do the international standards for neurological classification of SCI anorectal exam?

STUDY DESIGN

Online survey of spinal cord injury (SCI) practitioners.

OBJECTIVES

Determine provider understanding and routine performance of International Standards for Neurologic Classification of Spinal Cord Injury (ISNCSCI) anorectal examination.

SETTING

International online questionnaire.

METHODS

A descriptive survey was developed to assess current performance of the ISNCSCI anorectal exam. Information about this survey was disseminated through social email and international societies between the months of March and April 2017.

RESULTS

Two hundred and fifteen SCI practitioners completed the survey. Of these, 157 (73%) were specialists in physical medicine and rehabilitation, 32 (15%) were physical therapists, 6 were neurologists, 6 were orthopedists, and 3 were neurosurgeons. Of responders, 90% routinely personally performed the anal exam of the ISNCSCI, of whom, 42 placed firm pressure against the anal sphincter, 58 placed firm pressure against the rectal wall, and 87 placed firm pressure against the anal sphincter and rectal wall as part of the exam. On a routine basis, 74% tested sensation at the junction of the anal sphincter and skin, 82% had the patient attempt to squeeze their finger, and 50% performed the bulbocavernosus reflex.

CONCLUSIONS

Marked inconsistency exists in the performance of the ISNCSCI anal examination. Researchers and clinicians need more education about the performance of the examination. Consideration should be given for the components of deep rectal sensation and anal pressure to be separately documented in the neurologic exam and for researchers to focus separately on recovery of sacral function vs. ambulatory function in clinical trials.

Electrophysiological characterization of human rectal afferents

It is presumed that extrinsic afferent nerves link the rectum to the central nervous system. However, the anatomical/functional existence of such nerves has never previously been demonstrated in humans. Therefore, we aimed to identify and make electrophysiological recordings in vitro from extrinsic afferents, comparing human rectum to colon. Sections of normal rectum and colon were procured from anterior resection and right hemicolectomy specimens, respectively. Sections were pinned and extrinsic nerves dissected. Extracellular visceral afferent nerve activity was recorded. Neuronal responses to chemical [capsaicin and "inflammatory soup" (IS)] and mechanical (Von Frey probing) stimuli were recorded and quantified as peak firing rate (range) in 1-s intervals. Twenty-eight separate nerve trunks from eight rectums were studied. Of these, spontaneous multiunit afferent activity was recorded in 24 nerves. Peak firing rates increased significantly following capsaicin [median 6 (range 3-25) spikes/s vs. 2 (1-4), P < 0.001] and IS [median 5 (range 2-18) spikes/s vs. 2 (1-4), P < 0.001]. Mechanosensitive "hot spots" were identified in 16 nerves [median threshold 2.0 g (range 1.4-6.0 g)]. In eight of these, the threshold decreased after IS [1.0 g (0.4-1.4 g)]. By comparison, spontaneous activity was recorded in only 3/30 nerves studied from 10 colons, and only one hot spot (threshold 60 g) was identified. This study confirms the anatomical/functional existence of extrinsic rectal afferent nerves and characterizes their chemo- and mechanosensitivity for the first time in humans. They have different electrophysiological properties to colonic afferents and warrant further investigation in disease states.

Anorectal toxicity of external beam radiotherapy in the treatment of prostate cancer

Introduction:

Maximising radiotherapy dosage is associated with better tumour response in prostate cancer. High dose three-dimensional conformal radiotherapy (3D CRT) has allowed dose escalation to be safely achieved and the current standard dose in the UK with this technique is 74 Grays (Gy). Documenting normal tissue tolerance is critical and forms the basis of this prospective study of anorectal toxicity.

Patients and methods:

Seventeen consecutive men (median age 72 (range 50–79) years) with localised or locally advanced prostate cancer treated with 74 Gy of 3D CRT were studied. Wexner incontinence scores, comprehensive anorectal physiology and endoanal ultrasound were measured before and four months after completing treatment.

Results:

Wexner incontinence scores increased from a median of 0 to 1 (range 0–6) with treatment ( p=0.001). Patients developed faecal urgency (7/17), passive faecal loss (5/17) or a combination of both (3/17) as new anorectal symptoms. No patients reported episodes of frank faecal incontinence. A significant decline in rectal mucosal electrosensitivity (mean (standard deviation (SD)) thresholds increasing from 24.7 (10.7) to 34.3 (9.3) mA after treatment, p=0.003) and an increase in rectal elastance (mean (SD) of 0.056 (0.03) mm Hg/ml to 0.078 (0.036) mm Hg/ml pre- and post-treatment respectively, p=0.0181) was seen. No changes in anal canal manometry, rectal distension volumes and endoanal ultrasound were noted.

Conclusions:

Early anorectal symptoms are common after 3D CRT for prostate cancer. Rectal injury is evident with an increase in wall stiffness and a decrease in mucosal sensitivity. Longer term studies monitoring anorectal toxicity are warranted.

Rectoanal reflexes and sensorimotor response in rectal hyposensitivity

PURPOSE

Rectal hyposensitivity commonly causes anorectal disorders, but its underlying mechanism is unknown. We hypothesized that subjects with rectal hyposensitivity have altered rectoanal reflexes and/or sensorimotor response.

METHODS

We performed stepwise graded balloon distensions of the rectum in 30 subjects with constipation and rectal hyposensitivity and in 23 healthy controls. Thresholds for first sensation, desire, and urgency to defecate were assessed. The lowest balloon volume that evoked rectoanal inhibitory reflex, rectoanal contractile reflex, and sensorimotor response and manometric characteristics and rectal compliance were examined.

RESULTS

Reflex responses were present in all subjects. The balloon volumes were higher in subjects with rectal hyposensitivity for inducing rectoanal inhibitory reflex (P = .008) and contractile reflex (P = .001) compared with controls. All controls showed a sensorimotor response, but in 13 hyposensitive subjects (43%) the onset of sensorimotor response was associated with absent sensation and in 17 (57%), with a transient rectal sensation. Thresholds for eliciting sensorimotor response were similar between patients and controls, but the amplitude, duration, and magnitude of response were higher (P < .05) in patients. Rectal compliance was similar between controls and hyposensitive subjects with transient sensation but higher (P = .001) in subjects with absent sensation.

CONCLUSIONS

Constipated subjects with rectal hyposensitivity demonstrate higher thresholds for inducing rectoanal reflexes and abnormal characteristics of sensorimotor response. These findings suggest either disruption of afferent gut-brain pathways or rectal wall dysfunction. These altered features may play a role in the pathogenesis of bowel dysfunction in rectal hyposensitivity.

Neurophysiological testing in anorectal disorders

Neurophysiological tests of anorectal function can provide useful information regarding the integrity of neuronal innervation, as well as neuromuscular function. This information can give insights regarding the pathophysiological mechanisms that lead to several disorders of anorectal function, particularly fecal incontinence, pelvic floor disorders and dyssynergic defecation. Currently, several tests are available for the neurophysiological evaluation of anorectal function. These tests are mostly performed on patients referred to tertiary care centers, either following negative evaluations or when there is lack of response to conventional therapy. Judicious use of these tests can reveal significant and new understanding of the underlying mechanism(s) that could pave the way for better management of these disorders. In addition, these techniques are complementary to other modalities of investigation, such as pelvic floor imaging. The most commonly performed neurophysiological tests, along with their indications and clinical utility are discussed. Several novel techniques are evolving that may reveal new information on brain-gut interactions.

Rectoanal sensorimotor response in humans during rectal distension

PURPOSE

Rectal perception facilitates maintenance of continence and defecation. Whether perception is associated with motor changes in anorectum is unclear. We examined sensory and motor responses of the anorectum during rectal distention.

METHODS

Stepwise graded rectal balloon distensions were performed in 23 healthy subjects by placing a six-sensor probe in the anorectum. Manometric changes, rectoanal reflexes, and sensory thresholds were assessed. Studies were repeated in six subjects.

RESULTS

All subjects showed rectoanal inhibitory and contractile reflexes, but rectal perception was associated with an anal contractile response (sensorimotor response). In 4 subjects (17 percent) the sensorimotor response first occurred synchronously with a sensation of fullness (Group 1) and in 19 (83 percent) with a desire to defecate (Group 2). Mean balloon volume for inducing the sensorimotor response in Groups 1 and 2 were 80 +/- 14 ml and 96 +/- 26 ml (P > 0.05). The onset, amplitude, duration, and area under curve of the response were similar in both groups. At higher volumes of balloon distention, all subjects (n = 23) reported a desire and an urge to defecate. The sensorimotor response associated with an urge to defecate had higher amplitude (P = 0.01) and higher area under curve (P = 0.001) compared with that associated with a desire to defecate. Repeat studies showed good reproducibility (intraclass correlation coefficient = 0.9; P < 0.05).

CONCLUSIONS

A desire to defecate is associated with a unique, consistent, and reproducible anal contractile response: the sensorimotor response. This response could play an integral role in regulating anorectal sensation and function.

Sexual reward via vulvar, perineal, and anal stimulation: a proximate mechanism for female homosexual mounting in Japanese macaques

Female Japanese macaques (Macaca fuscata), in certain captive and free-ranging populations, frequently engage in same-sex mounting. Traditionally, same-sex mounting interactions in animals have been characterized as "sociosexual," that is, sexual in terms of their superficial form, but enacted to facilitate adaptive social goals. Sexual motivation is rarely ascribed to sociosexual interactions because their adaptive functions are often seen as their primary purpose, thus diminishing, or even negating, any sexual component that such activity might have. A substantial number of studies indicate that female-female mounting in Japanese macaques is not a sociosexual behavior. In contrast, several lines of circumstantial evidence suggest that these interactions are, indeed, sexual. In this study, we documented patterns of vulvar, perineal, and anal (VPA) stimulation during same-sex mounting in female Japanese macaques. During the majority of female-female mounts analyzed, female mounters engaged in repetitive VPA stimulation. Two forms of VPA manipulation by female mounters were observed. First, while sitting in a jockey-style position on the mountee, a female mounter would rub her VPA region against the mountee's back. Males never executed this type of mount posture or pelvic movement. Second, female mounters rubbed their VPA regions with their tails during same-sex mounts. Females mounters moved their tails in a voluntary, sex-specific manner and were never observed to do so in non-sexual contexts. Given the primary role of the VPA regions in mediating sexual response in primates, the results of this research provide direct evidence bearing on the sexual nature of female-female mounting in Japanese macaques and give further support for the conclusion that the term "homosexual behavior" is an appropriate label for these interactions.

Neurophysiological testing in anorectal disorders

The neurophysiological techniques currently available to evaluate anorectal disorders include concentric needle electromyography (EMG) of the external anal sphincter, anal nerve terminal motor latency (TML) measurement in response to transrectal electrical stimulation or sacral magnetic stimulation, motor evoked potentials (MEPs) of the anal sphincter to transcranial magnetic cortical stimulation, cortical recording of somatosensory evoked potentials (SEPs) to anal nerve stimulation, quantification of electrical or thermal sensory thresholds (QSTs) within the anal canal, sacral anal reflex (SAR) latency measurement in response to pudendal nerve or perianal stimulation, and perianal recording of sympathetic skin responses (SSRs). In most cases, a comprehensive approach using several tests is helpful for diagnosis: needle EMG signs of sphincter denervation or prolonged TML give evidence for anal motor nerve lesion; SEP/QST or SSR abnormalities can suggest sensory or autonomic neuropathy; and in the absence of peripheral nerve disorder, MEPs, SEPs, SSRs, and SARs can assist in demonstrating and localizing spinal or supraspinal disease. Such techniques are complementary to other methods of investigation, such as pelvic floor imaging and anorectal manometry, to establish the diagnosis and guide therapeutic management of neurogenic anorectal disorders.

Comparison of different local anesthesia techniques during TRUS-guided biopsies: a prospective pilot study

OBJECTIVES

To introduce two forms of anesthesia and compare them with standard local anesthesia techniques.

METHODS

A total of 114 consecutive patients underwent prostate needle biopsy. The patients were sequentially randomized to receive different kinds of anesthesia: 2% rectal lidocaine gel, 40% dimethyl sulfoxide (DMSO) with lidocaine, perianal injection of 1% lidocaine, or periprostatic nerve block. Pain perception was separately assessed for probe insertion and biopsies using a visual pain analog score. One-way analysis of variance was used to compare the data scale among the four groups. A linear regression model was used to define the independent variables that predicted the level of pain.

RESULTS

The groups were similar in terms of age, prostate-specific antigen levels, digital rectal examination findings, prostate volume, pain tolerance, biopsy time, and number of cores taken. The lowest pain scores for probe insertion were for the perianal injection and DMSO/lidocaine groups (0.89 and 1.38, respectively). The difference between these scores and those for the other two groups was statistically significant (P <0.001). Pain perception during biopsy did not differ significantly among the DMSO/lidocaine, perianal, or periprostatic groups and was greatest in the lidocaine gel group (4.147; P <0.001). We did not observe any statistically significant correlation between the pain level during probe insertion and biopsy and pain tolerance (P = 0.514 and P = 0.788, respectively). The anesthesia type was the strongest single predictor of the pain level during biopsy (P <0.001).

CONCLUSIONS

The use of 40% DMSO with lidocaine instilled into the rectal vault for 10 minutes avoids any need for injection and is capable of decreasing the discomfort or pain experienced during probe insertion and prostate biopsy comparable to the perianal and periprostatic protocols.

Functional brain imaging in irritable bowel syndrome with rectal balloon-distention by using fMRI

AIM: Irritable bowel syndrome (IBS) is characterized by abdominal pain and changes in stool habits. Visceral hypersensitivity is a key factor in the pathophysiology of IBS. The aim of this study was to examine the effect of rectal balloon-distention stimulus by blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) in visceral pain center and to compare the distribution, extent, and intensity of activated areas between IBS patients and normal controls.

METHODS: Twenty-six patients with IBS and eleven normal controls were tested for rectal sensation, and the subjective pain intensity at 90 mL and 120 mL rectal balloon-distention was reported by using Visual Analogue Scale. Then, BOLD-fMRI was performed at 30 mL, 60 mL, 90 mL, and 120 mL rectal balloon-distention in all subjects.

RESULTS: Rectal distention stimulation increased the activity of anterior cingulate cortex (35/37), insular cortex (37/37), prefrontal cortex (37/37), and thalamus (35/37) in most cases. At 120 mL of rectal balloon-distention, the activation area and percentage change in MR signal intensity of the regions of interest (ROI) at IC, PFC, and THAL were significantly greater in patients with IBS than that in controls. Score of pain sensation at 90 mL and 120 mL rectal balloon-distention was significantly higher in patients with IBS than that in controls.

CONCLUSION: Using fMRI, some patients with IBS can be detected having visceral hypersensitivity in response to painful rectal balloon-distention. fMRI is an objective brain imaging technique to measure the change in regional cerebral activation more precisely. In this study, IC and PFC of the IBS patients were the major loci of the CNS processing of visceral perception.

AGA technical review on anorectal testing techniques

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice and Practice Economics Committee. Following external review, the paper was approved by the committee on May 17, 1998.