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Internal Anal Sphincter Arch Dis Child: first published as 10.1136/adc.43.231.569 on 1 October 1968. Downloaded from Arch. Dis. Childh., 1968, 43, 569. Internal Anal Sphincter Observations on Development and Mechanism of Inhibitory Responses in Premature Infants and Children with Hirschsprung's Disease E. R. HOWARD and H. H. NIXON From The Hospitalfor Sick Children, Great Ormond Street, London W.C.1 The relative importance of the internal and obstruction to constipation alone. During this external sphincters to the maintenance of tone in study physiological abnormalities were observed in the anal canal has been shown in previous studies of the reflexes of premature infants, which showed anal physiology (Gaston, 1948; Schuster et al., 1965; similarities to those seen in patients with Hirsch- Duthie and Watts, 1965). sprung's disease. On repeated examinations over The external sphincter is a striated muscle, but several days, however, the physiological responses shows continuous activity on electromyography. were found to change until normal reflexes were Inhibition and stimulation is mediated by spinal eventually established. cord reflexes, through the pudendal nerves and In order to help determine the nervous pathway sacral segments of the spinal cord (Floyd and Walls, through which the reflexes of the internal sphincter copyright. 1953; Porter, 1961). Voluntary control is possible are mediated, we have examined normal bowel over this part ofthe anal sphincter. and aganglionic bowel from cases of Hirschsprung's The internal sphincter is made up of smooth disease by pharmacological and histochemical muscle fibres, continuous with the muscle layers of methods. the rectal wall, and under resting conditions pro- vides most of the tone of the anal canal (Duthie and Physiological Study Watts, 1965). Methods. Two methods were used to measure The internal sphincter is also under reflex pressures within the anal canal-an air-filled system http://adc.bmj.com/ control and a rise of tension in the rectal wall based on the principle of miniature balloons, and strain results in a decrease of tone-the relaxation reflex gauges mounted on thin strips ofberyllium copper. The of the internal sphincter (Gowers, 1878; Denny- extreme sensitivity of the latter method was especially Brown and Robertson, 1935). Recently, Lawson and useful in detecting any rhythmical activity in the sphinc- Nixon (1967) have emphasized that the internal ters with very low pressures found in some infants sphincter is characterized by rhythmical activity. during the neonatal period. Inhibition of this activity accompanies the decrease (a) Air-filled system. This method has recently been in tone seen during the recto-sphincteric relaxation described in detail (Lawson and Nixon, 1967). A on September 29, 2021 by guest. Protected reflex. cylindrical brass probe, 5mm. in diameter, contains 2 Reflex response of the internal sphincter is or 4 air-filled chambers each 0 8 cm. in length. The absent in Hirschsprung's disease, while the reflexes chambers are covered with thin Paul's tubing and of the external sphincter remain intact (Lawson and connected to pressure transducers (Solatron NT4-313 Nixon, 1967; Schnaufer et al., 1967). 10 p.s.i.) by thin nylon tubing. An inflatable rectal balloon is incorporated, and pressure changes recorded The possibility of using this abnormal response as on a modified Ofner 8 channel EEG recorder. A a routine diagnostic procedure for Hirschsprung's pressure change of 100 cm. H,O results in a potential disease was examined in the present study. The difference change of 3mV across each transducer. physiological responses of the internal sphincter This is amplified and fed into the pen recorder. were examined in 60 children who presented with evidence of bowel dysfunction. The symptoms (b) Strain gauge system. Two miniature silicon varied in severity from those of acute intestinal semiconductor strain gauges (Ether 2A-3A-120 P) were bonded to 0 * 008 cm. thick beryllium copper strips with Received April 30, 1968. a phenolic stoving cement (Bakelite cement J.11185). 569 Arch Dis Child: first published as 10.1136/adc.43.231.569 on 1 October 1968. Downloaded from 570 Howard and Nixon of lcm. lo I ., . _ a,I,- to$ _ - -- ----316cmiPhe . -0 II -I I -- 12.2r. 1 II A. ' 1+ ~~~~~~-3-6ctm. - 0-2 Co n. .-4c. b' *: II I I Co. II II _I ..._LjAajO----4__C= ;'!-- l-- -. - - r4-oi a Weryliu I I I I L~~~~ I Beryllium ... copper I c 1 1-3cm. Siliconrflgouge FIG. 1.-Diagram of strain gauge probe, with exploded view to show gauge connexions. Each strip measured 12 mm. x 2 mm. These were Electromyography. Surface electrodes and stain- mounted across 1 cm. gaps cut in an 8 cm. length of less steel clips were used to record action potentials ofthe brass tubing of 5 mm. diameter. One end of each extemal sphincter. These were amplified, shown on an strip was bonded to the brass with epoxy-resin (Araldite), oscilloscope screen, and written out by the Ofner pen and a potential difference of 4j volts was applied across recorder. each gauge (Fig. 1). The probe was covered with To obtain satisfactory tracings of intemal sphincter Paul's tubing and suspended in an air-tight chamber activity in infants and small children, it is essential to connected with a water manometer and sphygmomano- reduce stimulation to a minimum. We therefore copyright. meter hand pump. Calibration was performed at omitted the electromyograph electrodes during the different pressures by measuring resistance changes in first part of each recording. Restlessness obscures the each gauge through a Wheatsone bridge circuit and rhythmical activity and responses of the intemal voltmeter. sphincter. Sedation was not used. A pressure of 100 cm. H2O resulted in a potential difference change of approximately 60 mV across each Results. Recordings of 60 infants and children gauge. suspected of having Hirschsprung's disease were As in the air-filled system, a rectal balloon was made using either the balloon or strain gauge systems incorporated to lie approximately 5 cm. from the anal 2 http://adc.bmj.com/ verge. The output from the Wheatstone bridge (Fig. and Table I). At the beginning of the study circuit was amplified and fed into an Ofner EEG machine. both probes were used on several patients for com- Both types of probe were designed to measure rectal parison purposes. Pressure measurements were and anal canal pressures synchronously without moving found to be similar, but during the investigation of the probe. the very low pressures found at times in the smaller Organic 9 obstruction on September 29, 2021 by guest. Protected -Normal 28- Constipationonly 13 Obstruction 3 _ Neonatal 6 _ Ganglaonic colostomy Perforat ion 3 biopsy later Anal sphincter response to rectal distension - Hirschsprung 24 confirmed with histolojy in 60 patients { Premature 5 - Atypical 8- Meconium I - Full term 3 ileus (all 2 days Hirschsprung 2 of age) FIG. 2.-Results of studies of anal sphincter responses in patients with bowel dysfunction. Arch Dis Child: first published as 10.1136/adc.43.231.569 on 1 October 1968. Downloaded from Internal Anal Sphincter 571 TABLE I on the relative sizes of the probes to the diameters Ages of Patients in Anal Sphincter Studies of the anal canals at different ages may account for this difference in response. Normal responses 6 days to 14 years Of the younger children in this group, 9 presen- (28) ted with vomiting and constipation within the Hirschsprung responses .. 4 days to 9 years (24) first few weeks of life. Subsequent diagnoses of an Atypical responses (a) Premature, 2 days to 10 days organic cause for their symptoms were made at (8) (5) (b) Full term, 2 days barium examination or operation and included (3) meconium ileus, ileal atresia, ileo-caecal dupli- cation, and hiatus hernia (Table II). Examinations were made of 13 children because infants the greater amplification possible with the of constipation from early infancy. Internal sphinc- strain gauge method allowed easier recognition of ter responses were within normal limits, though any rhythmical activity that might be present. changes of rectal inertia were often present (Cal- Results fell into the following groups. laghan and Nixon, 1964). Six children had undergone laparotomy and Normal sphincter physiology. 28 patients showed colostomy during the neonatal period. All had a normal internal sphincter response to rectal presented with intestinal obstruction, and at distension. Their ages ranged from 6 days to 14 laparotomy cones typical of Hirschsprung's dis- years. All these recordings showed resting sphinc- ease had been found, but biopsies taken at sites ter pressures greater than 30 cm. H20 and rhyth- selected for colostomy were ganglionic. 4 of mical activity of 12-16 contractions per minute these children were admitted to hospital 1 year which could be inhibited by rectal distension. later for definitive surgical treatment, but physio- This inhibition of rhythmical activity was accom- logical examination revealed normal anal reflexes, panied by a fall in pressure for 10-15 seconds in the and subsequent rectal biopsies were ganglionic. 2 older child (Fig. 3), but in smaller infants the mean patients were examined a few days after enter- copyright. pressure of the sphincter did not show a change on ostomies had been fashioned. Normal physiology many occasions. Mechanical factors dependent was shown, and biopsies indicated normal myenteric http://adc.bmj.com/ on September 29, 2021 by guest. Protected 30ml. air (Rectal inflation) FIG. 3.-Normal anal sphincter response to rectal distension by air in a boy of 1O years. E.S. shows the external sphincter contraction corresponding to increased EMG activity. I.S. shows internal sphincter inhibition in the upper two-thirds of the anal canal. Units of pressure are cm. H20 in Fig. 3-5. Arch Dis Child: first published as 10.1136/adc.43.231.569 on 1 October 1968.
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