Leading articles Br. J. Surg. 1992, Vol. 79, October, 988-989
Tests of anorectal function The management of defaecatory disorders is often challenging, especially when the underlying abnormality is a disturbance of anorectal function. The symptoms produced by such disorders are usually unpleasant and at times cause great distress. The outcome of remedial surgery is often unpredictable and may be disappointing, so it is not surprising that the surgeon looks to specialist investigations for help in selecting the most appropriate treatment. In this context, an ideal test of anorectal function is one that can define underlying abnormalities with a high degree of sensitivity and specificity, predict their natural history, and indicate the likely outcome of surgery. In some circumstances these criteria can all be satisfied. A good example is the use of anorectal manometry in the investigation of adult constipation, where the absence of a rectoanal inhibitory reflex indicates myenteric aganglionosis and thus Hirschsprung’s disease’. Manometry will not only diagnose or exclude the disorder, but the anal pressure profile will also provide useful information on the selection of patients for surgery. Unfortunately, only a tiny minority of adult patients with constipation have Hirschsprung’s disease and many surgeons insist on taking a full-thickness rectal biopsy for histological examination to corroborate manometric findings. In practice, this approach diminishes the value of the investigation to that of a screening exercise. Other instances in which tests of anorectal function can make an important contribution to management are the use of concentric-needle electromyography in the diagnosis and localization of sphincter tears, and the use of nerve conduction studies in the assessment of incontinence (if this defines a treatable lesion such as cauda equina compression caused by intervertebral disc prolapse). In both instances, however, anorectal function tests may soon be superseded by new radiological techniques such as anal endosonography and magnetic resonance imaging. Most other disorders of anorectal function are less easy to define. The causes of idiopathic anorectal incontinence and obstructed defaecation are unknown and, at the time they present (perhaps many years after an initial insult), they are associated with physiological abnormalities that are complex, diffuse and poorly understood. Furthermore, current treatments have only limited success and the relationship between the abnormalities detected and the outcome of treatment is rarely obvious. In idiopathic anorectal incontinence the sphincter is short and weak, rectal compliance is reduced, sampling is abnormal and anorectal sensation is dimini~hed’,~. A ubiquitous feature is an electromyographic change consistent with denervation and subsequent reinnervation of the striated muscle of the external sphincter and pelvic floor. This observation is not diagnostic, however, since equivalent changes may be found in the same muscles of subjects who are normally continent3. The extent of the manometric and electromyographic abnormality demonstrated cannot be used reliably to forecast the outcome of surgery, even though predictive differences have been reported between some groups of patients4. Verification of these findings is required. The investigation of obstructed defaecation has also proved disappointing. Two phenomena are commonly demonstrated, both of which are thought to be responsible for the presenting symptoms. First, inappropriate contraction of the puborectalis occurs during defaecation (anismus), which is demonstrated by a recording of increased electromyographic activity in the puborectalis during attempted defaecation. Second, internal rectal intussusception occurs; this can be detected at sigmoidoscopy but is more commonly diagnosed by evacuation proctography. Whether or not these findings truly reflect abnormal anorectal behaviour is questionable, as both may be demonstrated in normal asymptomatic individual^^.^ and symptoms may persist in spite of apparently effective treatment’**. In addition to its role in the assessment of anorectal dysfunction, manometry is used widely in the assessment of patients about to undergo sphincter-preserving surgery for inflammatory bowel disease or carcinoma. However, the experienced surgeon can obtain just as much information from digital examinationg, and in reality few patients are refused surgery solely on the basis of an abnormal anal canal pressure profile. A pressure gradient between the rectum and anus is essential but it is not the only factor preserving continence. This issue highlights an important deficiency for, until recently, tests of anorectal function have focused on the measurement of
988
0007-1323/92/10098842
0 1992 Butterworth-Heinemann
Ltd
Leading articles
phenomena in isolation, often for relatively short periods of time and in the artificial environment of the anorectal physiology laboratory. To overcome this deficiency, ambulatory as well as integrated monitoring techniques have been introduced. Several measurements can now be made simultaneously and recorded for a number of hours as the patient undertakes normal activities. These provide a more natural and global picture of anorectal activity but are time consuming to obtain and, with increasing complexity, more difficult to interpret. They are also unlikely by themselves to reveal much about the mechanisms, neural and muscular, that subserve normal anorectal function. Insight into these more fundamental aspects of anorectal physiology will be gained only through basic scientific research. In summary, tests of anorectal function have made a major contribution to the understanding of normal and abnormal anal sphincter activity, but they have not so far lived up to expectation in clinical practice. While every self-respecting colorectal surgery department should have a physiology laboratory and patients should be studied, there is still no substitute for clinical acumen and a healthy realism in the selection of patients for surgery.
T. J. O’Kelly N. J. McC. Mortensen Department of Surgery and Gastroenterology John Radclife Hospital Heading ton Oxford OX3 9DU UK 1.
2.
3.
4.
5.
Meunier P, Marechal J-M, Mollard P. Accuracy of manometric diagnosis of Hirschsprung’s disease. J Pediarr Surg 1978; 13: 411-15. Miller R, Bartolo DCC, Locke-Edmunds JC, Mortensen NJMcC. Prospective study of conservative and operative treatment of faecal incontinence. Br J Surg 1988; 75: 101-5. Womack NR, Morrison JFB, Williams NS. The role of pelvic floor denervation in the aetiology of idiopathic faecal incontinence. Br J Surg 1986; 13: 404-7. Yoshioka K, Hyland G, Keighley MRB. Physiological changes after post-anal repair and parameters predicting outcome. Br J Surg 1988; 75: 1220-4. Jones PN, Lubowski DZ, Henry MM,
Br. J. Surg.. Vol. 79, No. 10, October 1992
6. 7.
8. 9.
Swash M. Is paradoxical contraction of puborectalis muscle of functional imporlance? Dis Colon Rectum 1987; 30:667-70. Stevenson GW, Shorvon PJ. Proctography (symposium). Int J Colorecral Dis 1988; 3 : 67-89. Kamm MA, Hawley PR, Lennard-Jones JE. Lateral division of the puborectalis muscle in the management of severe constipation. Br J Surg 1988; 75: 661-3. McCue JL, Thomson JPS. Rectopexy for internal intussusception. Br J Sury 1990; 77: 632-4. Hallan RI, Marzouk DEM, Waldron DJ, Womack NR. Williams NS. Comparison of digital and manometric assessment of anal sphincter function. Br J Surg 1989; 76: 973-5.
989
Tests of anorectal function The management of defaecatory disorders is often challenging, especially when the underlying abnormality is a disturbance of anorectal function. The symptoms produced by such disorders are usually unpleasant and at times cause great distress. The outcome of remedial surgery is often unpredictable and may be disappointing, so it is not surprising that the surgeon looks to specialist investigations for help in selecting the most appropriate treatment. In this context, an ideal test of anorectal function is one that can define underlying abnormalities with a high degree of sensitivity and specificity, predict their natural history, and indicate the likely outcome of surgery. In some circumstances these criteria can all be satisfied. A good example is the use of anorectal manometry in the investigation of adult constipation, where the absence of a rectoanal inhibitory reflex indicates myenteric aganglionosis and thus Hirschsprung’s disease’. Manometry will not only diagnose or exclude the disorder, but the anal pressure profile will also provide useful information on the selection of patients for surgery. Unfortunately, only a tiny minority of adult patients with constipation have Hirschsprung’s disease and many surgeons insist on taking a full-thickness rectal biopsy for histological examination to corroborate manometric findings. In practice, this approach diminishes the value of the investigation to that of a screening exercise. Other instances in which tests of anorectal function can make an important contribution to management are the use of concentric-needle electromyography in the diagnosis and localization of sphincter tears, and the use of nerve conduction studies in the assessment of incontinence (if this defines a treatable lesion such as cauda equina compression caused by intervertebral disc prolapse). In both instances, however, anorectal function tests may soon be superseded by new radiological techniques such as anal endosonography and magnetic resonance imaging. Most other disorders of anorectal function are less easy to define. The causes of idiopathic anorectal incontinence and obstructed defaecation are unknown and, at the time they present (perhaps many years after an initial insult), they are associated with physiological abnormalities that are complex, diffuse and poorly understood. Furthermore, current treatments have only limited success and the relationship between the abnormalities detected and the outcome of treatment is rarely obvious. In idiopathic anorectal incontinence the sphincter is short and weak, rectal compliance is reduced, sampling is abnormal and anorectal sensation is dimini~hed’,~. A ubiquitous feature is an electromyographic change consistent with denervation and subsequent reinnervation of the striated muscle of the external sphincter and pelvic floor. This observation is not diagnostic, however, since equivalent changes may be found in the same muscles of subjects who are normally continent3. The extent of the manometric and electromyographic abnormality demonstrated cannot be used reliably to forecast the outcome of surgery, even though predictive differences have been reported between some groups of patients4. Verification of these findings is required. The investigation of obstructed defaecation has also proved disappointing. Two phenomena are commonly demonstrated, both of which are thought to be responsible for the presenting symptoms. First, inappropriate contraction of the puborectalis occurs during defaecation (anismus), which is demonstrated by a recording of increased electromyographic activity in the puborectalis during attempted defaecation. Second, internal rectal intussusception occurs; this can be detected at sigmoidoscopy but is more commonly diagnosed by evacuation proctography. Whether or not these findings truly reflect abnormal anorectal behaviour is questionable, as both may be demonstrated in normal asymptomatic individual^^.^ and symptoms may persist in spite of apparently effective treatment’**. In addition to its role in the assessment of anorectal dysfunction, manometry is used widely in the assessment of patients about to undergo sphincter-preserving surgery for inflammatory bowel disease or carcinoma. However, the experienced surgeon can obtain just as much information from digital examinationg, and in reality few patients are refused surgery solely on the basis of an abnormal anal canal pressure profile. A pressure gradient between the rectum and anus is essential but it is not the only factor preserving continence. This issue highlights an important deficiency for, until recently, tests of anorectal function have focused on the measurement of
988
0007-1323/92/10098842
0 1992 Butterworth-Heinemann
Ltd
Leading articles
phenomena in isolation, often for relatively short periods of time and in the artificial environment of the anorectal physiology laboratory. To overcome this deficiency, ambulatory as well as integrated monitoring techniques have been introduced. Several measurements can now be made simultaneously and recorded for a number of hours as the patient undertakes normal activities. These provide a more natural and global picture of anorectal activity but are time consuming to obtain and, with increasing complexity, more difficult to interpret. They are also unlikely by themselves to reveal much about the mechanisms, neural and muscular, that subserve normal anorectal function. Insight into these more fundamental aspects of anorectal physiology will be gained only through basic scientific research. In summary, tests of anorectal function have made a major contribution to the understanding of normal and abnormal anal sphincter activity, but they have not so far lived up to expectation in clinical practice. While every self-respecting colorectal surgery department should have a physiology laboratory and patients should be studied, there is still no substitute for clinical acumen and a healthy realism in the selection of patients for surgery.
T. J. O’Kelly N. J. McC. Mortensen Department of Surgery and Gastroenterology John Radclife Hospital Heading ton Oxford OX3 9DU UK 1.
2.
3.
4.
5.
Meunier P, Marechal J-M, Mollard P. Accuracy of manometric diagnosis of Hirschsprung’s disease. J Pediarr Surg 1978; 13: 411-15. Miller R, Bartolo DCC, Locke-Edmunds JC, Mortensen NJMcC. Prospective study of conservative and operative treatment of faecal incontinence. Br J Surg 1988; 75: 101-5. Womack NR, Morrison JFB, Williams NS. The role of pelvic floor denervation in the aetiology of idiopathic faecal incontinence. Br J Surg 1986; 13: 404-7. Yoshioka K, Hyland G, Keighley MRB. Physiological changes after post-anal repair and parameters predicting outcome. Br J Surg 1988; 75: 1220-4. Jones PN, Lubowski DZ, Henry MM,
Br. J. Surg.. Vol. 79, No. 10, October 1992
6. 7.
8. 9.
Swash M. Is paradoxical contraction of puborectalis muscle of functional imporlance? Dis Colon Rectum 1987; 30:667-70. Stevenson GW, Shorvon PJ. Proctography (symposium). Int J Colorecral Dis 1988; 3 : 67-89. Kamm MA, Hawley PR, Lennard-Jones JE. Lateral division of the puborectalis muscle in the management of severe constipation. Br J Surg 1988; 75: 661-3. McCue JL, Thomson JPS. Rectopexy for internal intussusception. Br J Sury 1990; 77: 632-4. Hallan RI, Marzouk DEM, Waldron DJ, Womack NR. Williams NS. Comparison of digital and manometric assessment of anal sphincter function. Br J Surg 1989; 76: 973-5.
989
