Internal Sphincter Activity Research Articles

Anorectal function after low anterior resection of the rectum.

Impaired neorectal function or sphincter incompetence have been respectively implicated as causative factors of increased frequency of defaecation or incontinence after low anterior resection of the rectum (LARR) for rectal carcinoma, although individual mechanisms of anorectal function have not been fully studied. Functional and laboratory results were evaluated in 19 subjects, who had a LARR for rectal carcinoma before and after the procedure, and were compared to those of normal subjects. LARR worsened anorectal function, mostly by significantly increasing the daily number of defaecations (p < 0.001), while major incontinence was reported in three cases. Patients with rectal carcinoma have a decreased resting anal pressure on manometry, as compared to controls (p < 0.001). LARR further reduces anal resting pressure (p < 0.001) as well as all parameters that express internal sphincter activity, such as presence and amplitude of either slow (p < 0.05 and p < 0.01) or ultraslow waves. LARR also impaired external anal sphincter activity, as expressed by the reduction in anal squeeze pressure (p < 0.001). Anorectal sampling was found reduced in incidence and frequency in LARR patients as compared to controls (p < 0.01 and p < 0.001), and was impaired even further postoperatively (p < 0.001). Rectoanal inhibitory reflex was present in all but three patients postoperative, but significantly impaired as compared to controls. Rectal volumes to elicit transient or permanent desire to defecate, maximal tolerable rectal volume and rectal compliance were also significantly reduced after LARR (p < 0.001, p < 0.001, p < 0.01 and p < 0.001 respectively). Large bowel transit was significantly enhanced after LARR (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Sustained internal sphincter hypertonia in patients with chronic anal fissure

This study was designed to determine whether functional variations of internal sphincter activity occur in order to differentiate between patients with anal fissures from those with hemorrhoids. Thirty patients with chronic anal fissure (median age, 28 years; 12 females), 22 patients with hemorrhoids (median age, 37 years; 7 females), and 33 control volunteers (median age, 48.5 years; 21 females) underwent ambulatory anal sphincter fine-needle electromyography and anorectal manometry. The median internal sphincter electromyography frequency was similar: fissure group, 0.49 Hz; hemorrhoid group, 0.46 Hz (P > 0.05), and control group, 0.44 Hz (P > 0.05). Median anal resting pressures were similar in the fissure group (132 cm. H2O) and the hemorrhoids group (116 cm of H2O) (P > 0.05), but significantly greater than those in the control group (94 cm. H2O) (P < 0.05). The median number of transient relaxations of the internal and sphincter with an associated rise in rectal pressure and fall in anal pressure was 1 (range, 0-4) per hour in the fissure group, 6 (range, 4-7) per hour in the hemorrhoid group, and 4 range, 3-6) per hour in the control group. Six patients with fissures were reassessed following lateral internal sphincterotomy. Median and pressure was 102 cm of H2O (P > 0.1 vs. controls) and the number of internal sphincter relaxations increased to 4 per hour (P < 0.01 vs. preoperative number). Internal anal sphincter relaxation occurs on fewer occasions in patients with chronic anal fissures that have failed to heal in comparison to patients with hemorrhoids and normal controls. This evidence further supports the hypothesis that internal sphincter hypertonia may be relevant to the pathogenesis of this disorder.

Internal anal sphincter activity after restorative proctocolectomy for ulcerative colitis:

The aim of this study was to further investigate continuous ambulatory anal manometry which has recently been introduced as a method for studying anorectal activity in ambulant patients, thereby avoiding many of the potential drawbacks of static techniques. In this study continuous ambulatory manometry was used to assess the activity of the internal anal sphincter in patients who had undergone restorative proctocolectomy, and, in particular, to compare patients who had undergone conventional mucosal proctectomy with sutured endoanal, ileoanal anastomosis with patients who had undergone restorative proctocolectomy with preservation of the entire anal canal by means of stapled, end-to-end, ileoanal anastomosis without mucosectomy. Evidence of basal internal sphincter activity was found in only 38 percent of patients after mucosal proctectomy with sutured endoanal anastomosis, whereas all patients after restorative proctocolectomy with stapled end-to-end anastomosis and all control individuals showed such activity of the internal sphincter. Similarly, the number of sampling episodes seen in patients after mucosal proctectomy with endoanal anastomosis was significantly less (median, 0.0/hours (0-30/hours)) than the number of sampling episodes observed in patients after end-to-end anastomosis (median, 4.5/hours (1-48/hours)) or in control individuals (median, 5.6/hours (0-31/hours)) (P < 0.001). These results suggest that the internal anal sphincter is damaged in the course of mucosal proctectomy and endoanal anastomosis. In contrast, after restorative proctocolectomy with stapled, end-to-end anastomosis normal function of the internal sphincter is preserved.

Anal manometry in patients with fissure-in-ano before and after internal sphincterotomy.

The motility pattern of the internal anal sphincter was estimated manometrically in 42 patients with fissure-in-ano before and after left lateral internal sphincterotomy (LAS). Resting anal pressure and anal pressure during straining were significantly higher in patients than in controls (132 +/- 21 SD cmH2O vs 81 +/- 14 SD cmH2O P < 0.0002 and 46 +/- 16 SD cmH2O vs 13 +/- 4 SD cmH2O P < 0.0005), but were normal after LAS. Slow waves were more common in fissure patients (86 +/- 6 SD% of total recording time vs 68 +/- 11 SD% of total recording time, P < 0.0002), but also became normal after successful treatment. The presence of ultra slow waves was also more common in fissure patients (P < 0.0001), and although it was significantly reduced postoperatively (P < 0.0001), it did not return to normal. Sampling was less frequent in fissure patients (P < 0.0001) and improved significantly after successful treatment (P < 0.0002). Rectal distension produced significantly less reduction in anal pressure in fissure patients as compared to controls (P < 0.01), but successful treatment returned the response to normal. There were 2 patients with anal fissure who did not heal after left LAS. Those patients and a further 5 patients with non healed fissures after left LAS showed the same pathological manometric features as before surgery. Their fissures were successfully treated by additional right lateral internal sphincterotomy. In conclusion, increased internal sphincter activity is probably an aetiological factor in fissure-in-ano, while successful LAS improves anal sphincter function.(ABSTRACT TRUNCATED AT 250 WORDS)

Anatomy and Physiology of Urinary Continence

Each of the three components of the continence mechanism, that is, proximal urethral support, internal sphincter activity, and external sphincter function, contributes to continence. Any one alone may not be able to keep a patient dry. The pressures generated during a cough may easily overcome the internal and external sphincters closing powers, and the normal supportive mechanism works in such a way as to increase closure during increases in abdominal pressure. Normal support, conversely, is not sufficient in and of itself to maintain continence, and must have sufficient resting sphincteric activity to be effective. When one element is abnormal, the other mechanisms may be able to compensate and maintain continence. It is because there are these several interdependent parts of the continence mechanism that no single urodynamic parameter is predictive of stress continence. Each different etiologic type of stress incontinence reflects the malfunction of an anatomic component of the sphincteric mechanism. Therefore, a knowledge of this mechanism's structure is fundamental to an understanding of this common clinical problem. Technologic advances in assessment of the lower urinary tract have made the separation of different types of stress incontinence possible. The further realization that each type requires different treatment has made the distinctions between these clinically important entities.

The composition of anal basal pressure. An in vivo and in vitro study in man.

The maximal anal basal pressure (MABP) was measured with probes of 0.3, 1, 2 and 3 cm diameter in 21 subjects, 60 years old, without anal pathology. The components of MABP were analyzed by inducing a maximal internal sphincter (IS) relaxation, taking pressure measurements in the conscious state and during narcosis with curarization. In seven cases pressure measurements were done on isolated anorectum after abdominoperineal rectum amputation. MABP increases with probe diameter before as well as during anaesthesia with curarization. The contribution of the striated sphincter tonic activity is constant within the range of probe diameters used. At rest, i.e. when the 0.3 cm diameter pressure recording probe is used, 30% of MABP is made up by striated sphincter tonic activity, 45% of it is due to nerve induced IS activity, 10% to purely myogenic IS activity and 15% can be attributed to the expansion of the haemorrhoidal plexuses. Although MABP is mainly based on active forces generated by the smooth and striated sphincter apparatus, the presence of the anal cushions is essential for perfect anal continence, as they have to fill the gap within the IS ring to hermetically close the anal canal. The global IS activity, contributing 50-60% of MABP at rest, can completely be inhibited by a maximal rectoanal inhibitory reflex. Stretching of passive elements starts at 1 cm anal distension, but steeply increases thereafter, accounting for 65% of the MABP at 3 cm anal distension. It is deduced that optimal stool diameter is about 2 cm.

Internal anal sphincter response after electrical stimulation of the rectal myenteric nerve plexus in the rabbit.

The internal anal sphincter response to electrical stimulation of the rectal mucosa was studied in six rabbits. The anal canal was dissected free and then opened with an anterior, longitudinal incision to yield a flat sphincter preparation. After the external sphincter had been paralysed, isometric recordings of internal sphincter activity were performed. Electrical stimulation applied to the rectal mucosa elicited sphincter relaxations in all rabbits. Division of the gut beneath the point of stimulation blocked the response, as did local submucous anaesthesia. The results show (1) that electrical stimulation of the rectum can elicit internal sphincter relaxation, and (2) that the response is mediated via the myenteric and submucosal nerve plexuses.

Ano-rectal manometry in the diagnosis of Hirschsprung's disease in infants.

Manometric recordings of internal sphincter activity were performed during distension of the rectum in 10 healthy control infants and in 9 infants with clinical signs of Hirschsprung's disease. In 8 of the healthy infants relaxations of the internal sphincter were obtained, which were maximal 4 to 7 secs after rectal distension. This was also the case in 5 of the patients who were later proven not to have Hirschsprung's disease. In 3 patients no relaxations of the internal sphincter could be recorded. Subsequent rectal biopsy revealed absence of ganglion cells, confirming the diagnosis Hirschsprung's disease. The remaining 3 infants (2 controls and 1 patient) could not be calmed during the examination and the results were inconclusive. It is concluded that ano-rectal manometry is a valuable method of examination in the diagnosis of Hirschsprung's disease in infants. No false results were obtained in this study. Furthermore, it is an easy procedure without risk or discomfort for the patient.