Anorectal Manometry in Premature Infants By K. L. Bowes and S. Kling Edmonton, Alberta, Canada 9 T w e n t y - e i g h t unselected p r e m a t u r e infants w e r e subjected to anorectal pressure studies, using an infusion m a n o m e t r i c technique, w i t h a v i e w to establishing normal p a r a m e t e r s in this age group. Satisfactory rectal and sphincter pressure readings w e r e obtained in all but one case. In all of t h e s e t h e r e w a s a normal anorectal reflex. L o w birth w e i g h t and p r e m a t u r i t y do not preclude a normal anorectal reflex as measured by this technique. INDEX WORDS: Anorectal manometry,
A N O M E T R I C T E S T I N G for Hirschsprung's disease (aganglionic megacolon) has been demonstrated by Howard and Nixon,' Schnaufer, 2 Tobson? and others to be a simple, noninvasive test of considerable diagnostic value. Almost a century ago, Gowers demonstrated that distending the rectum by an appropriate bolus induced relaxation of the anal canal. Within the past decade the above noted authors were able to show that this anorectal relaxation reflex requires a normally innervated internal anal sphincter. This reflex is absent in Hirschsprung's disease, presumably because of the absence of the intramural ganglion cells. Recent work in this area has been directed towards refinement of the technique of the test so as to permit quantitative evaluation of the sphincter pressure responses and assess the reliability of the test in premature infants.
M
MATERIALS AND METHODS The technique we have independently devised proves to be very similar to that of Boston and Scott. 4 Resting rectal and sphincter pressures are recorded by use of a special catheter. This catheter is composed of four fine, fused polyethylene tubes each with a side opening located 0.5 cm apart (Fig. 1C). Water is infused through these tubes by a Harvard pump at a constant rate of 0.4 ml/min. The tubes are connected via transducer to a Beckman No. R411 multichannel recorder with printout facility. The special catheter is inserted well into the rectal ampulla and after an equilibration period the catheter is gradually withdrawn down to and through the sphincter complex. Observations are recorded of the resting rectal and sphincter pressures and frequency of the contractions. A typical tracing is seen in Fig. 2. Another catheter is used for measurement of sphincter response to rectal distention. This catheter, (Fig. 1 B) like the previously described catheter, consists of four, fine-fused polyethylene tubes. Three of these are used for monitoring
Journal of Pediatric Surgery, Vol. 14, No. 5 (October), 1979
pressure and have side openings each 0.5 cm apart. The fourth tube connects with a balloon situated at the tip of the catheter and is used to inflate the balloon (Fig. IA). This catheter is introduced well into the rectal ampulla. After a period of equilibration the catheter is slowly withdrawn until the recorder indicates the monitoring tubes are at the level of the sphincter complex. Sphincter pressures and rhythm are recorded. The balloon is then distended by 1 ml increments to a m a x i m u m of 5 ml and relaxation response of the spincter complex observed. A characteristic tracing is shown in Fig. 3.
Subject Material These studies were conducted on patients in the Neonatal Intensive Care Unit (N.1.C.U.) of the University of Alberta Hospital. All the subjects were in the N.I.C.U. because of prematurity, respiratory problems or both. They were selected at random. Although several did have episodes of abdominal distension during their stay in the N.1.C.U., none were seriously considered to have Hirschsprung's disease on clinical criteria. In a limited follow-up none subsequently developed Hirschsprung's disease. All were sedated with sodium pentobarbital to facilitate the test and increase the accuracy of the readings, In all, 28 neonates were studied. This data is summarized in Table 1.
RESULTS
The following parameters were studied: (1) Resting rectal pressure, (2) resting sphincter pressure, (3) sphincter pressure during relaxation phase, (4) rectal/sphincter gradient during sphincter relaxation, and (5) contraction rate of sphincter complex. Resting rectal pressure ranged from 5-15 cm of water with a mean of 9.2 cm, Resting spincter pressure varied between 10-120 cm of water with a mean of 47.4 cm. Thus the average gradient between resting spincter and rectal pressure is 35 cm of water. During rectal distension the relaxed sphincter pressure drops to a From the Department of Surgery, University of Alberta Medical School and the University of Alberta Hospital. Presented at the lOth Annual Meeting of the Canadian Association of Pediatric Surgeons, Vancouver, January 25, 1978. Address reprint requests to S. Kling, Professor, Room 8-113, Clinical Sciences Building, University of Alberta, Edmonton, Alberta, Canada T6G 2G3. ce~1979 by Grune & Stratton, Inc. 0022-3468/79/1405-0007501.00/0 533
534
BOWES AND KLING
Fig. 1. The right-hand catheter (C) is used for recording pressures only. It consists of four separate but fused tubes each w i t h a side opening spaced at 0.5-cm levels. The center catheter (B) is of similar construction but has only t h r e e pressure recording openings. The fourth tube is used to inflate and deflate the balloon, The left-hand picture (A) illustrates the inflated balloon.
mean of 10.5 cm of water for a pressure gradient of only 1.3 cm of water. This permits evacuation to occur, This data is summarized in Table 2. In addition, we studied the time lapse from the onset of rectal distension to the onset of spincter relaxation. We also studied the time lag from the release of rectal distention until the recovery of normal sphincter time. This data is summarized in Table 3. Most infants gave a normal response with rectal balloon volumes of 2-3 ml. Occasionally 5 m] was required. An inhibitory response of the anal sphincter complex was observed in all but one infant on the
Fig. 3. A typical normal anorectal reflex. The b o t t o m tracing shows the point at which the balloon was inflated w i t h 5 ml of water. The resultant fall in sphincter pressure is well-demonstrated.
Fig, 2. A typical "'pullthrough'" pressure tracing of the sphincter complex showing the characteristic contractions. The sphincter contracts at a mean rate of 9.1/rain.
rhythmic
ANORECTAL MANOMETRY
535
Table 1. Parameters on 28 Subjects Studied
Table 3. Lag Times
Range
Mean
Weight
1000-2700 g
1624,1 _+ 96
Gestational age
27-42 wk
3 4 , 5 § 0.6
Birth age
1 - 2 8 days
11.7 + 2.3
From onset of rectal distention to onset of
Table 2. Results Parameter
Mean
Resting rectal pressure
9.2 + 0.5 cm H2Q
Resting sphincter pressure
4 7 . 4 + 4 . 0 cm H20
Relaxation sphincter pressure
10.7 + 1 6 5 c m
H20
Relaxation rectal/sphincter gradient
1.5
Sphincter contraction rate
9.1 + 0.4/rain
initial test. This infant was 2 days old at the time of testing and had an extremely low sphincter pressure. A repeat test one week later gave an entirely normal response. DISCUSSION
In this study we have described a technique for accurately measuring rectal and sphincter pressures, rate of contraction of the sphincter complex, and response to rectal distention. Application of the test on 28 neonates of varying degrees of prematurity by weight and gestational age, produced a readily discernible relaxation
sphincter relaxation-- 1.8 _+ 0 . 1 5 sec From release of rectal distention to recovery sphincter t o n e - - 2 . O + 0.2 sec
reflex in all but one. In this patient, there was a borderline qualitative response but the resting sphincter complex pressure was too low to permit a reliable quantitative response. Our findings are at variance with those reported by lto, Donahoe, and Hendren 5 who concluded that a normal reflex does not occur in neonates "in whom maturational age (gestational age plus age after birth) has yet to reach 39 weeks and who average less than 6 lbs.'" Based on this study of 28 premature neonates, it would appear that a normal anorectal reflex should be found in at least 95% of cases. Low birth weight and prematurity do not appear to interfere with a normal anorectal relaxation reflex as measured by this technique. ACKNOWLEDGMENT The authors wish to acknowledge the invaluable assistance of Ken Cote and the cooperation of Dr. D. Schiff and the Staff of the Neonatal Intensive Care Unit of the University of Alberta Hospital.
REFERENCES
1. Howard ER, Nixon HH: Internal anal sphincter-observation on development and m e c h a n i s m of inhibitory responses in premature infants and children with Hirschsprung's disease. Arch Dis Child 43:569-578, 1968 2. Schnaufer L, Talbert Jk, Hailer JA, et al: Differential sphincteric studies in the diagnosis of anorectal disorders of childhood. J Pediatr Surg 2:538-543, 1967 3. Tobson F, Reid N C R W , Talbert JL, el al: Nonsurgical
test for the diagnosis of Hirschsprung's disease. N Engl J Med278:188 194,1968 4. Boston VE, Scott JES: Anorectal manometry as a diagnostic method in the neonatal period. J Pediatr Surg 11:9-16, 1976 5. lto Y, Donahoe PK, Hendren WH: Maturation of the rectoanal response in premature and perinatal infants. J Pediatr Surg 12:477 482, 1977
A N O M E T R I C T E S T I N G for Hirschsprung's disease (aganglionic megacolon) has been demonstrated by Howard and Nixon,' Schnaufer, 2 Tobson? and others to be a simple, noninvasive test of considerable diagnostic value. Almost a century ago, Gowers demonstrated that distending the rectum by an appropriate bolus induced relaxation of the anal canal. Within the past decade the above noted authors were able to show that this anorectal relaxation reflex requires a normally innervated internal anal sphincter. This reflex is absent in Hirschsprung's disease, presumably because of the absence of the intramural ganglion cells. Recent work in this area has been directed towards refinement of the technique of the test so as to permit quantitative evaluation of the sphincter pressure responses and assess the reliability of the test in premature infants.
M
MATERIALS AND METHODS The technique we have independently devised proves to be very similar to that of Boston and Scott. 4 Resting rectal and sphincter pressures are recorded by use of a special catheter. This catheter is composed of four fine, fused polyethylene tubes each with a side opening located 0.5 cm apart (Fig. 1C). Water is infused through these tubes by a Harvard pump at a constant rate of 0.4 ml/min. The tubes are connected via transducer to a Beckman No. R411 multichannel recorder with printout facility. The special catheter is inserted well into the rectal ampulla and after an equilibration period the catheter is gradually withdrawn down to and through the sphincter complex. Observations are recorded of the resting rectal and sphincter pressures and frequency of the contractions. A typical tracing is seen in Fig. 2. Another catheter is used for measurement of sphincter response to rectal distention. This catheter, (Fig. 1 B) like the previously described catheter, consists of four, fine-fused polyethylene tubes. Three of these are used for monitoring
Journal of Pediatric Surgery, Vol. 14, No. 5 (October), 1979
pressure and have side openings each 0.5 cm apart. The fourth tube connects with a balloon situated at the tip of the catheter and is used to inflate the balloon (Fig. IA). This catheter is introduced well into the rectal ampulla. After a period of equilibration the catheter is slowly withdrawn until the recorder indicates the monitoring tubes are at the level of the sphincter complex. Sphincter pressures and rhythm are recorded. The balloon is then distended by 1 ml increments to a m a x i m u m of 5 ml and relaxation response of the spincter complex observed. A characteristic tracing is shown in Fig. 3.
Subject Material These studies were conducted on patients in the Neonatal Intensive Care Unit (N.1.C.U.) of the University of Alberta Hospital. All the subjects were in the N.I.C.U. because of prematurity, respiratory problems or both. They were selected at random. Although several did have episodes of abdominal distension during their stay in the N.1.C.U., none were seriously considered to have Hirschsprung's disease on clinical criteria. In a limited follow-up none subsequently developed Hirschsprung's disease. All were sedated with sodium pentobarbital to facilitate the test and increase the accuracy of the readings, In all, 28 neonates were studied. This data is summarized in Table 1.
RESULTS
The following parameters were studied: (1) Resting rectal pressure, (2) resting sphincter pressure, (3) sphincter pressure during relaxation phase, (4) rectal/sphincter gradient during sphincter relaxation, and (5) contraction rate of sphincter complex. Resting rectal pressure ranged from 5-15 cm of water with a mean of 9.2 cm, Resting spincter pressure varied between 10-120 cm of water with a mean of 47.4 cm. Thus the average gradient between resting spincter and rectal pressure is 35 cm of water. During rectal distension the relaxed sphincter pressure drops to a From the Department of Surgery, University of Alberta Medical School and the University of Alberta Hospital. Presented at the lOth Annual Meeting of the Canadian Association of Pediatric Surgeons, Vancouver, January 25, 1978. Address reprint requests to S. Kling, Professor, Room 8-113, Clinical Sciences Building, University of Alberta, Edmonton, Alberta, Canada T6G 2G3. ce~1979 by Grune & Stratton, Inc. 0022-3468/79/1405-0007501.00/0 533
534
BOWES AND KLING
Fig. 1. The right-hand catheter (C) is used for recording pressures only. It consists of four separate but fused tubes each w i t h a side opening spaced at 0.5-cm levels. The center catheter (B) is of similar construction but has only t h r e e pressure recording openings. The fourth tube is used to inflate and deflate the balloon, The left-hand picture (A) illustrates the inflated balloon.
mean of 10.5 cm of water for a pressure gradient of only 1.3 cm of water. This permits evacuation to occur, This data is summarized in Table 2. In addition, we studied the time lapse from the onset of rectal distension to the onset of spincter relaxation. We also studied the time lag from the release of rectal distention until the recovery of normal sphincter time. This data is summarized in Table 3. Most infants gave a normal response with rectal balloon volumes of 2-3 ml. Occasionally 5 m] was required. An inhibitory response of the anal sphincter complex was observed in all but one infant on the
Fig. 3. A typical normal anorectal reflex. The b o t t o m tracing shows the point at which the balloon was inflated w i t h 5 ml of water. The resultant fall in sphincter pressure is well-demonstrated.
Fig, 2. A typical "'pullthrough'" pressure tracing of the sphincter complex showing the characteristic contractions. The sphincter contracts at a mean rate of 9.1/rain.
rhythmic
ANORECTAL MANOMETRY
535
Table 1. Parameters on 28 Subjects Studied
Table 3. Lag Times
Range
Mean
Weight
1000-2700 g
1624,1 _+ 96
Gestational age
27-42 wk
3 4 , 5 § 0.6
Birth age
1 - 2 8 days
11.7 + 2.3
From onset of rectal distention to onset of
Table 2. Results Parameter
Mean
Resting rectal pressure
9.2 + 0.5 cm H2Q
Resting sphincter pressure
4 7 . 4 + 4 . 0 cm H20
Relaxation sphincter pressure
10.7 + 1 6 5 c m
H20
Relaxation rectal/sphincter gradient
1.5
Sphincter contraction rate
9.1 + 0.4/rain
initial test. This infant was 2 days old at the time of testing and had an extremely low sphincter pressure. A repeat test one week later gave an entirely normal response. DISCUSSION
In this study we have described a technique for accurately measuring rectal and sphincter pressures, rate of contraction of the sphincter complex, and response to rectal distention. Application of the test on 28 neonates of varying degrees of prematurity by weight and gestational age, produced a readily discernible relaxation
sphincter relaxation-- 1.8 _+ 0 . 1 5 sec From release of rectal distention to recovery sphincter t o n e - - 2 . O + 0.2 sec
reflex in all but one. In this patient, there was a borderline qualitative response but the resting sphincter complex pressure was too low to permit a reliable quantitative response. Our findings are at variance with those reported by lto, Donahoe, and Hendren 5 who concluded that a normal reflex does not occur in neonates "in whom maturational age (gestational age plus age after birth) has yet to reach 39 weeks and who average less than 6 lbs.'" Based on this study of 28 premature neonates, it would appear that a normal anorectal reflex should be found in at least 95% of cases. Low birth weight and prematurity do not appear to interfere with a normal anorectal relaxation reflex as measured by this technique. ACKNOWLEDGMENT The authors wish to acknowledge the invaluable assistance of Ken Cote and the cooperation of Dr. D. Schiff and the Staff of the Neonatal Intensive Care Unit of the University of Alberta Hospital.
REFERENCES
1. Howard ER, Nixon HH: Internal anal sphincter-observation on development and m e c h a n i s m of inhibitory responses in premature infants and children with Hirschsprung's disease. Arch Dis Child 43:569-578, 1968 2. Schnaufer L, Talbert Jk, Hailer JA, et al: Differential sphincteric studies in the diagnosis of anorectal disorders of childhood. J Pediatr Surg 2:538-543, 1967 3. Tobson F, Reid N C R W , Talbert JL, el al: Nonsurgical
test for the diagnosis of Hirschsprung's disease. N Engl J Med278:188 194,1968 4. Boston VE, Scott JES: Anorectal manometry as a diagnostic method in the neonatal period. J Pediatr Surg 11:9-16, 1976 5. lto Y, Donahoe PK, Hendren WH: Maturation of the rectoanal response in premature and perinatal infants. J Pediatr Surg 12:477 482, 1977
