Physiology and pathophysiology of anal function

Ameliorating Effects of Transcutaneous Electrical Acustimulation at Neiguan (PC6) and Zusanli (ST36) Acupoints Combined with Adaptive Biofeedback Training on Functional Outlet Obstruction Constipation

BACKGROUND

Stimulant laxatives are still considered the most common treatment for functional outlet obstruction constipation (FOOC). However, the effectiveness of laxatives is unsatisfactory, and the long-term use of laxatives may cause certain adverse events. With this in mind, it is, however, paramount that novel complementary treatment(s) and/or other forms of alternative medicine are adequately investigated.

AIMS

The study aims to explore the effects and potential mechanism(s) of transcutaneous electrical acustimulation (TEA) combined with adaptive biofeedback training (ABT) on FOOC.

METHODS

A total of forty-five patients with FOOC were recruited and were randomly assigned to receive either Macrogol 4000 Powder (MAC, 10 g bid) (group A, n = 15) only, ABT + MAC + Sham-TEA (group B, n = 15), or TEA + ABT + MAC (group C, n = 15) in a six-week study. Individual patients' constipation-symptoms (PAC-SYM) and constipation-quality of life (PAC-QOL) were both assessed and scored. Serum acetylcholine (Ach) and nitric oxide (NO) were measured from drawn blood samples while individual patients' heart rate variability (HRV) was calculated at baseline and after each corresponding therapy. Anorectal manometry and balloon expulsion test were both performed before and after treatment.

RESULTS

Firstly, participants in group C had significantly lower scores of PAC-SYM, PAC-QOL, and a decreased anal defecating pressure (ADP) as compared to participants in group B (all p < 0.050). These results, however, suggest the TEAs effect. Secondly, the low-frequency band (LF)/(LF + HF) ratio in groups B and C were decreased as compared to group A (p=0.037, p=0.010, respectively) regarding HRV. On the other hand, the high-frequency band (HF)/(LF + HF) ratio in groups B and C showed an opposite outcome. Finally, the serum Ach in groups B and C was significantly higher as compared to group A (p=0.023, p=0.012, respectively). Of significant importance, the serum NO in groups B and C were notably low as compared to group A (p=0.001, p < 0.001, respectively).

CONCLUSIONS

TEA, combined with ABT, effectively improves constipation symptoms as well as QOL in FOOC patients. It is, however, achieved by decreasing ADP, which mechanisms are mediated via the autonomic and enteric mechanisms.

Anorectal incontinence: a challenge in diagnostic and therapeutic approach

Anorectal incontinence is a symptom of a complex multifactorial disorder involving the pelvic floor and anorectum, which is a severe disability and a major social problem. Various causes may affect the anatomical and functional integrity of the pelvic floor and anorectum, leading to the anorectal continence disorder and incontinence. The most common cause of anorectal incontinence is injury of the sphincter muscles following delivery or anorectal surgeries. Although the exact incidence of anorectal incontinence is unknown, various studies suggest that it affects ~2.2-8.3% of adults, with a significant prevalence in the elderly (>50%). The successful treatment of anorectal incontinence depends on the accurate diagnosis of its cause. This can be achieved by a thorough assessment of patients. The management of incontinent patients involves conservative therapeutic procedures, surgical techniques, and minimally invasive approaches.

Evaluation of anal sphincter resistance and distensibility in healthy controls using EndoFLIP ©

BACKGROUND

Ano-rectal disorders are common in the general population. Although they are not life threatening conditions, they do represent a social stigma and a reduced quality of life for the sufferer. The underlying physiology of muscle function contributing to ano-rectal competence is complex and there is room for a much better understanding so that treatments can improve.

METHODS

A cylindrically shaped, liquid filled bag (12 cm long), mounted on a catheter was inserted into the anus and positioned straddling the ano-rectal region in 20 healthy volunteers (10 females). Series of volume-controlled distensions (40 mL min(-1) to 40 mL) were carried out and data on 16 CSA at 5 mm apart and bag pressure were recorded. Provocative tests using squeeze and cough at bag volumes of 20, 30, and 40 mL were carried out.

KEY RESULTS

Ramp distension of the anal canal showed that the opening pressure for females (mean, 11 mmHg) was higher than for males (mean, 5 mmHg) (P < 0.001). Geometric profile of the anal canal at low distension volumes showed narrow bands at proximal and distal ends of the anal profile and shortening of a middle narrow zone at higher volumes. Inter-individual differences were observed in the behavior of the proximal end and the distal end of the anal profile during squeeze.

CONCLUSIONS & INFERENCES

This distensibility technique provides an important new way of studying the anal canal and hence may have a role in testing sphincter competence in patients with disorders.

Constipation of anorectal outlet obstruction: pathophysiology, evaluation and management

Constipation is a subjective symptom of various pathological conditions. Incidence of constipation fluctuates from 2 to 30% in the general population. Approximately 50% of constipated patients referred to tertiary care centers have obstructed defecation constipation. Constipation of obstructed defecation may be due to mechanical causes or functional disorders of the anorectal region. Mechanical causes are related to morphological abnormalities of the anorectum (megarectum, rectal prolapse, rectocele, enterocele, neoplasms, stenosis). Functional disorders are associated with neurological disorders and dysfunction of the pelvic floor muscles or anorectal muscles (anismus, descending perineum syndrome, Hirschsprung's disease). However, this type of constipation should be differentiated by colonic slow transit constipation which, if coexists, should be managed to a second time. Assessment of patients with severe constipation includes a good history, physical examination and specialized investigations (colonic transit time, anorectal manometry, rectal balloon expulsion test, defecography, electromyography), which contribute to the diagnosis and the differential diagnosis of the cause of the obstructed defecation. Thereby, constipated patients can be given appropriate treatment for their problem, which may be conservative (bulk agents, high-fiber diet or laxatives), biofeedback training or surgery.

Chronic idiopathic anal pain: analysis of ultrasonography, pathology, and treatment

PURPOSE

This study was undertaken to analyze whether intra-anal ultrasound examination, anorectal physiologic evaluation, and histopathologic examination in patients with chronic idiopathic anal pain presented any common features and whether the results of different treatment modalities correlated with these findings.

METHODS

Eighteen patients who met the criteria for chronic idiopathic anal pain were studied. All had an intra-anal ultrasound examination and a complete anorectal physiologic evaluation. In a selected group of patients, ultrasound-guided biopsy samples were taken from pathological areas in the internal and external sphincter. Treatment consisted of analgesics only in four patients, 0.2 percent nitroglycerin ointment in four, and ultrasound injection of botulin (botulinum toxin, Botox) into the intersphincteric space in nine. Two patients, including one who was previously treated with botulin, ultimately had a colostomy.

RESULTS

Four patients were managed satisfactorily on analgesic treatment under the guidance of the hospital's pain clinic. Nitroglycerin ointment resulted in temporary pain relief in one of four patients. Injection of botulin resulted in a permanent improvement in four patients, a temporary improvement in one patient, and no effect in four patients. Two patients had a colostomy, resulting in complete pain relief. The effect or lack of effect of nitroglycerin ointment and botulin was not related to changes in anal pressure.

CONCLUSION

Chronic idiopathic anal pain is a condition of unknown origin for which no proven therapy exists. As in other syndromes based on muscular dystonia, some patients may benefit from injection of botulin.

Pudendal nerve function in idiopathic fecal incontinence

PURPOSE

The study was undertaken to determine whether idiopathic fecal incontinence in middle-aged and elderly females is likely to be a result of pudendal nerve damage (neurogenic incontinence) or merely a consequence of aging.

METHODS

One hundred seventy-eight females over the age of 50 years with fecal incontinence were studied. The incontinence was classified as idiopathic because none of the patients related the incontinence to trauma (including obstetric trauma) or other events or diseases. All had an anal physiology examination, including determination of nerve conduction velocity of both pudendal nerves (pudendal nerve terminal motor latency).

RESULTS

With a cutoff value of 2.4 msec, 79 percent (95 percent confidence limit, 73-85) had normal pudendal nerve terminal motor latency on both sides, 13 bilaterally prolonged latency (7 percent; 4-11), and 25 unilaterally prolonged latency (14 percent; 9-19). With a cutoff value of 2.2 msec, 66 percent (59-73) had normal latency on both sides, 15 percent (9-20) bilaterally prolonged pudendal nerve terminal motor latency, and 20 percent (14-26) unilateral prolongation. No relationship between the groups with normal, bilateral, or unilateral prolongation of pudendal nerve terminal motor latency and anal resting and squeeze pressure was found. Anal resting pressure decreased with increasing age (P < 0.05).

CONCLUSION

Our data support the view that idiopathic fecal incontinence in the majority of females is likely to be a result of the aging process and that only a limited number may suffer from anal incontinence of neurogenic origin. Furthermore, unilateral prolongation of pudendal nerve terminal motor latency probably is without clinical significance.

Gastrointestinal motor and myoelectric correlates of motion sickness

The objectives of this study were to characterize the digestive tract motor and myoelectric responses associated with motion sickness. Twenty-two cats (1.5-3.0 kg) were chronically implanted with force transducers and electrodes on the stomach and small intestine. Motion sickness was activated by vertical oscillation (VO) at +/-0.5 g and identified as salivation, licking, or vomiting. Vomiting was initiated chemically by UK-14304 (2.5-15 microg/kg iv) or CuSO4 (10-50 mg ig). We found that VO caused vomiting (45% of trials), a decrease in gastrointestinal (GI) motility (69% of trials), salivation or licking (59% of trials), bradygastria (39% of trials), retrograde giant contraction (RGC, 43% of trials), giant migrating contraction (GMC, 5% of trials), and defecation (18% of trials). The decrease in GI motility occurred with (62% of trials) or without (69% of trials) vomiting. Motion sickness was accompanied by bradygastria (52% of trials) and decreased GI motility (70% of trials). Similar events occurred after CuSO4 and UK-14304, but the incidences of responses after CuSO4 were less frequent, except for vomiting, RGC, and GMC. UK-14304 never caused GMCs or defecation. The magnitude and velocity of the RGC were the same during all emetic stimuli, and RGCs never occurred without subsequent vomiting. Supradiaphragmatic vagotomy (n = 1) or atropine (n = 2, 10 or 50 microg/kg iv) blocked the RGC, but not vomiting, due to VO. We concluded that 1) oculovestibular stimulation causes digestive tract responses similar to other types of emetic stimuli, 2) decreased GI motility and bradygastria may be physiological correlates of the motion sickness, and 3) motion sickness may not be dependent on any specific GI motor or myoelectric response.

Normal pelvic floor physiology

This article outlines the normal physiology of the female pelvic floor, including normal urinary storage and voiding, normal colorectal storage, and defecation. Physiologic changes during a woman's lifetime that may affect bladder and bowel function are also considered. An important framework for understanding the normal physiology of the female pelvic floor is provided, so the reader may gain a more thoughtful approach to the recognition and treatment of pelvic floor pathophysiology.

Dynamic graciloplasty for severe anal incontinence

BACKGROUND

The surgical options for the treatment of anal incontinence where standard procedures have failed include transposition of striated muscles, primarily gracilis and gluteus maximus, and implantation of artificial sphincters. Due to a high proportion of fatigue-prone fibres in striated muscles, the results of transposition without stimulation have been disappointing. This study presents the results of stimulated graciloplasty in 13 patients with severe anal incontinence in whom other surgical procedures had failed.

METHODS

The gracilis muscle was transposed around the anal canal according to a previously described technique. Eight weeks later the intramuscular electrodes were implanted into the gracilis at the site of the nerve entry and a neurostimulator was placed in a subcutaneous pocket in the abdominal wall. The patients were followed from 7 to 27 months.

RESULTS

Six patients obtained satisfactory continence and five showed marked improvement. Two patients were considered failures. Rectal evacuation problems occurred in three patients, in one so severe that the patient, in spite of satisfactory continence, considered the treatment a failure.

CONCLUSION

Dynamic graciloplasty is a viable option in carefully selected patients with severe anal incontinence where other methods have failed.