Archives of Disease in Childhood 1994; 71: 186-193

ORIGINAL ARTICLES

Is encopresis always the result of constipation?

M A Benninga, H A Buller, H S A Heymans, G N J Tytgat, J A J M Taminiau

AbstractEncopresis is often the result of chronicconstipation in the majority of paediatricpatients. In clinical practice, however,encopresis is also seen without consti-pation and it is unkown whether thesetwo clinical variants are based on similaror different pathophysiological mech-anisms, requiring different therapeuticapproaches. We analysed clinical symp-toms, colonic transit time (CTI), orocae-cal transit time (OCTT), anorectalmanometric profiles, and behaviouralscores. Patients were divided into twogroups, one consisted of 111 children withpaediatric constipation, and anothergroup of 50 children with encopresis and/orsoiling without constipation.

Significant clinical differences inchildren with encopresis/soiling existedcompared with children with paediatricconstipation regarding: bowel movementsper week, the number of daytime soilingepisodes, the presence of night timesoiling, the presence and number ofencopresis episodes, normal stools, painduring defecation, abdominal pain, andgood appetite.

Total and segmental CTT were signifi-candy prolonged in paediatric constipationcompared with encopresis/soiling, 62-4(3.6-384) and 40 2 (10*8-104-4) hours,respectively. No significant differenceswere found in OCTT. Among the twogroups, all manometric parameters werecomparable, except for a significantlyhigher threshold of sensation in childrenwith paediatric constipation. The defeca-tion dynamics were abnormal in 59o/oand 46% in paediatric constipation andencopresis/soiling, respectively, and weresignificantly different from controls.Using the child behaviour checklist nosignifcant differences were found whencomparing children with psediatric consti-pation and encoprsis/soiling, while bothpatient groups differed significanty fromcontrols.

In conclusion, our findings support theconcept of the existence of encopresis as adistinct entity in children with defecationdisorders. Identification ofsuch children isbased on clinical symptoms, that is,normal defecation frequency, absence ofabdominal or rectal palpable mass, incombination with normal marker studies

and normal anal manometric threshold ofsensation. Thus, encopresis is not alwaysthe result of constipation and can be theonly clinical presentation of a defecationdisorder.(Arch Dis Child 1994; 71: 186-193)

Children with faecal incontinence are notcapable of controlling their bowels. Manydoctors regard it as a trivial symptom whichwill eventually disappear. Apart from theshame and fear of discovery, however, it maylead to social withdrawal, low self esteem, anddepression.1-3 Despite these consequences inchildren, encopresis and soiling have receivedless attention than enuresis.The term encopresis was originally intro-

duced by Weissenberg in 1926 to characterisethe faecal equivalent of enuresis.4 Manyhave tried to define and classify encopresis,but no agreement has been reached. Someworkers divide encopresis into either faecalincontinence with evidence of constipation(psychogenic constipation, psychogenic mega-colon, paradox diarrhoea, or overflow inconti-nence),5-8 so called retentive encopresis, ornon-retentive encopresis. The latter is furthersubdivided into a primary (or continuous)form (faecal incontinence with no evidenceof constipation occunring in children whohave not been toilet trained successfully) andsecondary (or discontinuous) non-retentiveencopresis (occurring in children who werecompletely toilet trained and subsequentlyregressed to incontinence).9 11 In contrast,however, Levine stated that virtually allchildren with encopresis retain stools.' Hesuggested that a plain radiograph of theabdomen often exposed substantial faecalretention, despite a normal history andphysical examination. He therefore consideredthe term 'encopresis without constipation' tobe incorrect.The term faecal incontinence encompasses

encopresis and soiling. The important differ-ence is the amount of faeces lost. These twoterms are often used indistinguishably in pub-lished work. In this study we define encopresisas the voluntary or involuntary passage of anormal bowel movement in the underwear(or other unorthodox locations), after theage of 4 years, occurring on a regularbasis without any organic cause.5 12 13 Thusencopresis is defined on the basis of asign, rather than the presence or absence of

Academic MedicalCentre, Amsterdam,The NetherlandsMA BenIingaH A BillerH S A HeymansJ A J M Taminiau

Department ofGastroenterologyGN J Tytgat

Correspondence to:Dr M A Benninga,Department of Paediatrics,Academical Medical Centre,Meibergdreef 9, 1105 AZAmsterdam, TheNetherlands.Accepted 24 May 1994

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constipation, and reflects defecation in theunderwear. Faecal soiling is defined as theinvoluntary seepage of faeces which is oftenassociated with faecal impaction, and reflectsstaining of the underwear.6 7 12

Encopresis is reported to be responsible for3% of referrals to teaching hospitals and hasbeen noted in 1-3% of those over 4 and in1-2% of 7 year olds.5 13 14-16 The prevalenceamong children of 10-12 years was 1-3% forboys and 0-3% for girls.5

Although faecal incontinence is a commonproblem in paediatric practice, the patho-physiological mechanisms are largelyunknown. Marker studies have shown thatthe total colonic transit time (CTI) in consti-pated children is significantly prolongedcompared with healthy controls.17-'9 Anorectalmanometry in children with constipation andencopresis showed an increased threshold toperceive rectal distention and an inabilityto relax the external anal sphincter duringdefecation.2023To find out whether faecal incontinence

exists in the absence of constipation and tounravel possible different pathophysiologicalmechanisms, we analysed children with consti-pation with or without encopresis/soiling andchildren with encopresis/soiling only.Differences among these patients regardingtheir clinical symptoms, CTT, orocaecaltransit time (OCTT), anorectal manometricprofiles, and scores on the child behaviourchecklist (CBCL) were evaluated.

MethodsSUBJECTSIn this study, 161 otherwise healthy patientswith defecation disorders, aged 5-17 years,were referred between 1991 and 1993 to ourpaediatric intestinal motility unit of a tertiaryacademic teaching hospital. Patients werereferred by general practitioners, school doc-tors, paediatricians, or child psychiatrists.Patients had to fulfil at least two of our fourcriteria of paediatric constipation to participatein the study: (a) stool frequency less than threeeach week; (b) two or more soiling/encopresisepisodes each week; (c) periodic passage oflarge amounts of stool at least once every sevento 30 days; and (d) a palpable abdominal orrectal mass. In addition, all patients wereenrolled with two or more episodes each weekof encopresis or soiling alone without any ofthe other criteria for paediatric constipation.A palpable rectal mass was defined as thepresence of a faecal lump in the rectal ampulla.Known causes of constipation, such asHirschsprung's disease, spina bifida occulta,hypothyroidism or other metabolic orrenal abnormalities, mental retardation, andchildren receiving drugs other than laxativeswere excluded.Each child underwent a complete work up

that encompassed a detailed medical historyand a thorough physical and digital rectalexamination. Specific attention was paid todefecation frequency on the toilet, questionsabout the amount of stools lost in the

underwear (encopresis, soiling), and time ofoccurrence. In addition, transit time studiesand anorectal manometry were performed andthe CBCL was completed. The study wasapproved by the hospital's medical ethicscommittee. Written informed consent wasobtained from patients or their parents, orboth.

Healthy controls for the OCTT test and forthe anorectal manometry were 39 and 15healthy children, respectively. Informedconsent was obtained from the subjects andtheir parents.

ASSESSMENT OF OCT1 AND CTTBecause of poor compliance in childrenregarding the intake of alimentary fibre, nostandardisation was attempted and measure-ment of OCTT and CTT were performed inpatients taking their own customary diet.Treatment with laxatives (pills or enemas) wasalways interrupted at least four days before thestudy. No subject had received antibiotics forat least three months before the test.24

COLONIC TRANSIT TIMETotal and segmental analysis of CCTs werecarried out as reported previously.25 Patientsingested a capsule with 20 radio-opaquemarkers on three consecutive days at 9.00 am.Abdominal radiographs were obtained on thesame time in the morning on day 1 and fourdays after ingestion of the last capsule.Additional abdominal radiographs were takenseven, 10, and 13 days after ingestion of thelast capsule if more than 20% of markers werestill present. Abdominal radiographs wereobtained using a high kilovoltage fast filmtechnique to reduce radiation exposure(estimated surface exposure 0-08 mrad perfilm).

Localisation of markers on abdominal filmsrelied on the identification of bony landmarksas described by Arhan et al.26 Markers werecounted in the right, left, and rectosigmoidregions, and mean segmental transit timeswere calculated as described.25 26 The normalrange for segmental transit times were takenfrom the limits (mean (2 SD)) from a study ofArhan et al in healthy children.26

OROCAECAL TRANSIT TIMEThe method used to study OCTT was asdescribed by van der Kley-van Moorsel et al.27Studies were performed after an overnight fast.End expiratory breath samples were takenbefore the ingestion of 10 g lactulose (20 ml of50% solution) and at 15 minute intervalsthereafter up to a maximum of 240 minutes.28At all time points, measurements consisted oftwo samples taken one minute apart. Thebreath was collected in a 60 ml plastic syringewith a side hole and a mouthpiece at the tipopening.27 The hydrogen content of theexpelled air was measured by the HoekloosLactoscreen27 and expressed in parts permillion (ppm). The OCTT7 was defined as the

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Table 1 Clinicalfeatures ofgroups defined by symptoms. The enties are number (%/o) ormedian (range)

Paediatric constipation Encopresis/soiling(n= I11) (n=50) p Value

Boys 75 (68) 43 (86) 0-02Age 8-0 (5-14) 9-0 (5-17) 0-01Age of onset of symptoms (months)<12 28 (25)12-48 52 (47)

Toilet trained 61 (56) 34 (69) 0-12Age at which toilet training started (years) 1-5 (0 8-4) 2-0 (1-4) 0-02Primary encopresis 27 (25) 23 (47) 0-02Family history of constipation 42 (38) 15 (30) 0-38Bowel movements/week 2-0 (0-10) 7-0 (3-17) <0-01Large amount of stools (7-30 days) 68 (61) 0 (0) <0-01Daytime soiling 86 (77) 34 (68) 0-33

Episodes/week 7-0 (0-56) 3-5 (0-28) 0-03Night time soiling 33 (30) 6 (12) 0-02

Episodes/week 0 (0-7) 0 (0-10) 0-02Encopresis 36 (32) 33 (66) <0-01

Episodes/week 0 (0-35) 3 0 (0-28) <0-01Normal stools (consistency) 60 (54) 41 (82) 0-03Pain during defecation 55 (50) 15 (30) 0-03No rectal sensation 20 (18) 3 (6) 0-05Abdominal pain 46 (41) 11 (22) 0-02Good appetite 64 (58) 39 (78) 0-01Daytime urinary incontinence 12 (11) 7 (14) 0-37Night time urinary incontinence 29 (26) 10 (20) 0-43Palpable abdominal mass 39 (35) 0 (0) <0-01Palpable rectal mass 31 (28) 0 (0) <0-01

period between lactulose intake by mouth andan increase in hydrogen excretion of 10 ppmabove basal values. The test was terminatedwhen this increase in hydrogen excretionsustained two subsequent time intervals. Non-hydrogen producers were defined as childrenwith a peak excess breath hydrogen concentra-tion <10 ppm after lactulose ingestion.

ANORECTAL MANOMETRYA five lumen manometric anal probe of 4-8mm outer and 0 8 mm inner diameter was

used as described earlier.29 Two side holes at a

spacing of 3 cm were perfused with sterilewater at a rate of 0 5 ml/min by a hydraulicinfusion system (Arndorfer).30 A rectaldistending balloon with a high compliance was

tied to the tip of the probe, 3 cm above thefirst side hole. Pressures were measured bytransducers in each perfusion line andconnected to PC Polygraf HR preamplifiers(Synectics Medical). The analogue signalsfrom the preamplifier were digitally convertedand transmitted via a fibre optic cable to a

personal computer.Maximum anal resting tone and maximum

squeeze pressure were measured by stationarypull through at a rate of 1 cm/min. Sensorythreshold was defined by the smallest repro-

ducible volume of rectal distension sensed.Critical volume, the minimum amount of airrequired to produce the sensation of a persis-tent urge to defecate (for at least one minute),was determined by filling the rectal balloonstepwise in increments of 30 ml at intervals of30 seconds. Intra-abdominal pressure was

defined as the increase of pressure above thesteady state level during a defecation attempt.The defecation dynamics, the manometricprofile obtained by expelling the rectal balloon,was assessed during at least five simulateddefecation trials. The rectoanal inhibitoryreflex was measured in response to balloondistension to exclude (short segment)Hirschsprung's disease. No sedation was used.

ELECTROMYOGRAPHYElectrical activity of the external anal sphincterwas recorded by one reference and two differ-ential electrodes connected to a bioamplifier IIand the PC Polygraf HR. Electrocardiogrampregelled disposable neonatal electrodesoverlaying the subcutaneous part of theexternal anal sphincter were used. The refer-ence electrode was located on a thigh.Defecation dynamics were defined as normal ifthe integrated electromyogram of the externalanal sphincter showed a decrease or no changeduring expulsion of the balloon in at leasttwo of five defecation attempts. Defecationdynamics were defined as abnormal if amanometric and myoelectrical increaseoccurred during bearing down in at least fourof the five defecation attempts.22 31 32

CHILD BEHAVIOUR CHECKLISTThe CBCL is a questionnaire developed byAchenbach and is designed to report in astandardised way the behaviour of childrenaged 4 to 16 years as assessed by their parentsor parent proxy.33 The CBCL was completedwithin 14 days after the initial visit.Normalised T scores for the social competencescale, the internalisation score, the externalisa-tion score, and the total behavioural scoreare standardised for age and gender.34 Thebehavioural ratings were compared with thebehavioural ratings of the CBCL normativesample of non-referred Dutch children(n=2076), all ofwhom are profiled by age andgender.34

STATISTICAL METHODSData were collected using an integrated patientdatabase. Results will be expressed using themedian and the range for continuous variablesand percentages for discrete variables. Groupswere compared using the Wilcoxon pairedsigned rank test for continuous variables andthe x2 test for discrete variables, calculatingexact p values for the latter. For all tests a levelof 0.05 was used for significance.

ResultsPATIENTSThis study encompasses 161 patients evalu-ated for constipation or encopresis/soiling, orboth. Based on our definition of paediatricconstipation, patients were divided into twogroups. The first group consisted of 111patients who fulfilled the criteria for paediatricconstipation as described earlier. The secondgroup consisted of 50 patients with encopresisor soiling alone, or both, without other criteriaof paediatric constipation.

In 39 healthy children (5-14 years,average 9-9 years; 18 boys and 21 girls) breathhydrogen samples were taken to obtain normalOCTs. Controls for the manometric valuesconsisted of 15 healthy children (7-15 years,average 1 1 years; 10 boys and five girls).

Apart from a significant preponderance ofboys in the encopresis/soiling group, children

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Table 2 C1T in hours (mean and range)

Paediatnc constipation Encopresis/soiling Arhan*(n= 111) (n=50) (n=23)

Right colon 13-8 (0-60) (p<0-01) 8-1 (0-26-4) 7-7 (18)Left colon 16-1 (0-110-4) (p<0-01) 7-0 (0-19-2) 8-7 (20)Rectosigmoid 51-0 (0-226-8) (p<0-01) 26-7 (4 8-93 6) 12-4 (34)Total colon 81-0 (3-6-380.4) (p<0-01) 41-7 (10-8-104-4) 29-0 (62)

*The last column represents the mean values; the values in brackets are upper limits of normalrange (mean (2 SD)) measured by Arhan et al.26

with encopresis/soiling were significantly olderthan the patients with paediatric constipation(table 1). The age at which parents firstremembered a bowel problem in the paediatricconstipation group was, in most children,between 12 and 48 months. In the 27 childrenwith secondary encopresis, bowel problemsstarted at a median age of 6 years (2-1 0years). The remaining 23 children of theencopresis/soiling group were never continentfor faeces (primary encopresis). The medianduration of constipation was 60 months in thepaediatric constipation group (2-171 months).In the encopresis/soiling group the medianperiod of the disorder was 10 years (5-14) and50 months (3-137) for primary and secondaryencopresis/soiling respectively.

ONSET OF CONSTIPATIONAs mentioned by the parents, no definableevents were present at the onset of constipationin most paediatric constipation and enco-presis/soiling children (68% and 78%respectively). Definable events such as dietchanges (human to cows' milk), anal fissures,failed toileting, birth of a sibling, familyproblems, moving to a new home, changingschool, intercurrent illness, or sexual abusewere present at onset in a minority of cases(maximum 8%).

BOWEL FUNCTIONAs shown in table 1, the median number ofbowel movements in the paediatric constipa-tion group was two times each week, whereasthe encopresis/soiling patients defecated onthe toilet daily. As reported by the enco-presis/soiling patients or their parents, or both,the stools were of normal size, without aperiodic passage of a large amount of stools.The number of day or night time, or both,

soiling episodes was significantly higher in thepaediatric constipation group compared withthe encopresis/soiling group. The presenceand number of episodes of encopresis was

Table 3 Results of anorectal manometry (median and range)

Paediatricconstipation Encopresis/soiling Healthy controls(n= l l l) (n=50) (n= l5)

Maximum anal resting tone (mm Hg) 56-0 (27-93) 63-5 (18-95)* 46-0 (33-90)Maximum squeeze pressure (mm Hg) 138-0 (65-288) 140-5 (62-264) 167-0 (81-276)Abdominal resting pressure (mm Hg) 10-0 (1-35) 8-5 (1-34) 10-0 (4-18)Intra-abdominal pressure (mm Hg) 67-0 (16-151) 64-0 (0-180) 65-0 (32-131)Threshold of sensation (ml) 25-0 (5-360)*t 15-0 (10-90) 20-0 (5-50)Threshold of reflex (ml) 27-5 (5-60)* 25-0 (10-60)* 17-5 (5-40)Critical volume (ml) 150-0 (60-360) 120-0 (60-330) 120-0 (60-180)Defecation dynamics (normal) 41%* 54%/0* 93%

*Statistically significant from controls. tStatistically significant from encopresis/soiling group.

significantly more common in the encopresis/soiling group. In the paediatric constipationgroup 13% of the children, six boys (8%)and seven girls (19%), did not have faecalincontinence.

ASSOCIATED SYMPTOMSA large number of children with paediatricconstipation experienced abdominal pain,although this was only found in a minority ofencopresis/soiling children. A significantlyhigher proportion of encopresis/soiling patientshad a good appetite compared with the paedi-atric constipation patients. There was no signifi-cant difference in frequency between the twogroups regarding day or night, or both, urinaryincontinence. The existence of urinary tractinfection was not evaluated in this study.

ANORECTAL SYMPTOMS AND PHYSICALEXAMINATIONBy definition no faecal masses were palpable inthe encopresis/soiling group. In the paediatricconstipation groups, however, approximately athird revealed palpable abnormalities. Onrectal examination the tone of the internal analsphincter and voluntary contraction of theexternal anal sphincter was normal in thetwo groups. Anal fissures (only one in thepaediatric constipation group) and haemor-rhoids in the paediatric constipation (three)and encopresis/soiling (two) groups were rarelyseen.

TREATMENTIn the paediatric constipation and enco-presis/soiling group 59 and 28% of the patientsrespectively used laxative for long periods oftime without success. The duration of thelaxative treatment, including lactulose, mineraloil, and stimulant laxatives given by mouth or byenema, was 49 months (3-135 months) inchildren with constipation and 46 months (6-93months) in the other group. In the paediatricconstipation and encopresis/soiling group addi-tional psychiatric treatment was given to 26%and 18% respectively. In the encopresis/soilinggroup most (62%) had never received anyearlier treatment. In children with paediatricconstipation this was only 39%. These non-treated children initially visited a doctor at asignificantly older age, median 9 years (6-15years) in the encopresis/soiling group, comparedwith 8 years (5-14 years) in the paediatric con-stipation group. Separation within the paediatricconstipation and encopresis/soiling group intothose receiving laxative treatment and those whowere not treated before did not show any signifi-cant difference in the clinical features, except fora significantly higher frequency in large amountof stools (7-30 days) in the untreated paediatricconstipation patients.

COLONIC TRANSIT TIMETable 2 shows the different segmental andtotal CTT values. Total CTT was significantly

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higher in the paediatric constipation groupcompared with the encopresis/soiling group.

In 56 of 111 paediatric constipation patientsthe total CTT' was within the normal limits.26 In22 patients with paediatric constipation withtotal CTT >62 hours a significant delay intransit occurred in the rectosigmoid only,whereas significantly increased transit times inall segments were observed in 14 paediatric con-stipation patients. In the encopresis/soilinggroup 44 patients had a total CTT within thenormal range. In five encopresis/soiling patientswith a total CTT >62 hours, the accumulationof markers occurred in the rectosigmoid.

OROCAECAL TRANSIT TIMEThe OCTT (median and range) in paediatricconstipation, encopresis/soiling, and controlswas 60 (30-180), 60 (30-105), and 60(30-120) minutes respectively. In thepaediatric constipation group eight children(7%) were classified as non-hydrogenproducers, whereas in the encopresis/soilinggroup only two children (40/o) had breathhydrogen peaks <10 ppm above baselinevalues throughout the three hour test period.All healthy controls were hydrogen producerswith breath hydrogen peaks of > 10 ppm abovebaseline values.

ANORECTAL MANOMETRYIn 31 paediatric constipation children withextreme faecal retention, disimpaction withenemas was performed daily during the weekbefore manometry to guarantee an emptyrectal ampulla and to standardise the anorectalmeasurements for all patients. No enemaswere given on the day of manometric measure-ments. The remaining patients required noenemas before manometry. Table 3 shows thatall manometric parameters were comparablebetween the two patient groups, apart froma significantly higher threshold of sensation(p=0008) in children with paediatric con-stipation. Maximum anal resting tone wassignificantly higher in the encopresis/soilinggroup (p=0 04) than controls. Only the paedi-atric constipation group required significantlylarger balloon volumes to provoke a rectal sen-sation (p=0 02) compared with healthy con-trols. In encopresis/soiling patients thisthreshold was even lower than in controls.Significant higher balloon volumes wereneeded in the two patient groups comparedwith control children (p=0-02 and p=0-02respectively) in eliciting the rectoanalinhibitory response. The defecation dynamicswere abnormal in 59% and 46% in the paedi-atric constipation and encopresis/soilinggroups respectively and were significantly dif-ferent from controls (p<0-001). All childrenexhibited a rectoanal inhibitory reflex onballoon distension.

SUBDIVISION OF PATIENTSSubdivision of the constipated group ofchildren (paediatric constipation) into those

with and without faecal incontinence andsubsequent comparison with the encopresis/soiling group yielded no differences in theabove mentioned clinical features, transittimes, and manometric results, as presented intables 1-3. Similarly, no significant differencewas found between those children with paedi-atric constipation with faecal incontinenceand those without faecal incontinence. Thesefindings allow the separation into only twogroups.

CHILD BEHAVIOUR CHECKIUSTOn the CBCL, children with paediatricconstipation and encopresis/soiling showedhigh percentages (38-5% and 44.2% respec-tively) in the clinical range of behaviouralproblems, but no significant difference wasfound between the two groups. In the twogroups these scores for behavioural problemsdiffered significantly (p<001) compared withthe 10% abnormal clinical range found incontrol children.

DiscussionIt is generally believed that encopresis issecondary to constipation; Levine, in partic-ular, suggested this association.' A pilot study,however, implied the existence of a group ofchildren with encopresis without evidence ofconstipation.29 In this study we show that suchchildren form a distinct group among patientswith defecation disorders, with discrete clinicaland manometric features and normal CTT. Inthese children solitary encopresis is the mostimportant clinical sign.Most parents of these children, especially in

those with primary encopresis, postponed aninitial visit to a doctor for many years, despitethe humiliation. Many parents were unawareof the existence of encopresis as a commonchildhood problem and ascribed it to laziness,inattention, poor hygiene, or stress; shame andcultural taboos were other common reasons forthis delay. In contrast, infrequent defecationappeared to be a more threatening and morerecognisable disorder and therefore parents ofchildren with paediatric constipation consulteda doctor earlier.

Levine has provided an age dependent list ofpotential risk factors for encopresis, based onconstitutional predispositions, circumstances,of environment, and critical life events.'Nevertheless, only in a minority of patients inthis study could these factors be identified. Inmost children the cause of constipation orencopresis, or both, was unknown. Moreimportantly, and in contrast with generalopinion, encopresis or soiling alone was notoften associated with too coercive and too earlybowel training as these children were lessand later toilet trained than the paediatricconstipation group. It is possible that changedcultural opinions and behaviour about boweltraining explains the differences between ourfindings and the previous studies.

In children with constipation, the retentionof stools often leads to a vicious circle

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in which the rectum is increasingly distendedby abnormally firm faecal contents.' Theinfrequent passage of these hard andlarge amounts of stools induces pain duringdefecation, inhibition of voluntary efforts,and results in abnormal sphincter contractionduring defecation. Finally, chronic rectaldistension causes soiling, sometimes enco-presis, loss of rectal sensitivity, and hencea normal urge to defecate.20 35 36 Levine statedthat in most children with faecal incontinencea plain radiograph of the abdomen wouldunmask extensive faecal retention.' This studyshows that a third of the children referred forfaecal incontinence show*ed no signs of consti-pation. Almost all encop*sis/soiling childrendefecated daily, resulting in significantly fewerconstipation associated complaints - forexample, abdominal pain and poor appetite.Importantly, and in contrast with children withpaediatric constipation, encopresis/soilingpatients exhibited no abnormalities onabdominal and rectal examination. Further-more, no aberrations were found on radio-graphic examination in most encopresis/soiling patients using Barr scores, suggestingthat children with encopresis/soiling form adistinct group of patients.37The existence of night time soiling, the loss

of loose stools in pyjamas, was significantlyhigher in the paediatric constipation groupthan in children with encopresis/soiling. Innearly all instances this was correlated withsevere faecal impaction and extreme prolongedtotal CT (>100 hours).38 In encopresis/soiling children this correlation was notobserved.

Preliminary treatment analysis showed thatchildren with paediatric constipation wereoften helped by laxative treatment, whereas,in contrast, children with encopresis/soilingwere seldom helped, and even becameworse. Review of published work showed thatvarious approaches have been recommendedfor the management of children with enco-presis. Among these have been individual andfamily psychotherapy, behaviour modificationprograms and bowel retaining regimens.39-42Most published studies were either singlecase reports or consist of small groups ofchildren with encopresis/soiling.43 Nolan et alshowed in children with encopresis andevidence of accumulated stool on plainabdominal radiograph, an obvious additionaladvantage of laxative drugs and behaviourmodification to behavioural modificationalone.44 Previously, we showed in a non-randomised study that children with enco-presis and soiling alone were significantlyimproved after biofeedback training.29The use of radio-opaque markers is

important to objectify reports of constipationand or faecal incontinence, which does notdepend on possible inaccurate recall.4547 Usingthe Metcalfmethod an important difference wasfound between the two groups.25 Total as wellas segmental CTT was significantly prolongedin children with paediatric constipation com-pared with those with encopresis/soiling. Thisconfirms that children with encopresis/soiling

have normal bowel movements daily. It isunclear whether children with rapid colonictransit and solitary encopresis without othersymptoms of constipation may be helpedby suppression of intestinal motility ratherthan laxative treatment. Interestingly, colonicinertia, slowing of markers through allcolonic segments, was only found in paediatricconstipation children.48 49No significant differences were found in

OCT in all children studied, suggesting noaetiological role of the small bowel in constipa-tion or encopresis, or both, as describedpreviously.50

Studies of anal sphincter pressures inconstipated children with or without faecalincontinence have been contradictory; maxi-mum anal resting tone has found to beincreased, decreased, or not different fromcontrols.2' 22 51-53 The hypertonicity of theanal canal, as found in the encopresis/soilinggroup only, is uxiexplained. Arhan et alsuggested that hypertonicity of the anal canalcould lead to outlet obstruction.'7 In theencopresis/soiling group, however, no suchcorrelation could be found when rectosigmoidtransit time and maximum anal resting tonewere analysed. Similarly, no such correlationcould be found in patients with paediatricconstipation, despite a significant slowing ofmarkers in the rectosigmoid in this group.Therefore it seems unlikely that anal restingtone is an important factor in the pathophysio-logy of outlet obstruction in children withconstipation or faecal incontinence, or both.The threshold of sensation in children with

paediatric constipation was significantly higherthan in controls and, as stated before, mostlikely the result of faecal impaction.'9-2' 54Surprisingly, the balloon volume needed toprovoke rectal sensation in children withencopresis/soiling was even lower than incontrols, suggesting that patients with enco-presis/soiling are able to perceive normalrectoanal stimuli. Furthermore, none ofthese children had faecal impaction on rectalexamination and most showed normal totalCTT on marker studies. In most of those withencopresis/soiling 'accidents' happened after3.00 pm, whereas in paediatric constipationchildren lost faeces any time during the day.Children with encopresis/soiling commonlytrace the failure to 'no time to go to the toilet'or, 'I could not leave my computer game', or 'Idid sense the urge, but I was just too late', sug-gesting that these children deny or neglecttheir normal and appropriate physiologicalstimuli. Interestingly, many children withencopresis/soiling initially stated an absence ofany sense or urge to defecate.

In the two groups a high percentage ofchildren showed a paradoxal anal response tostraining - that is, contraction rather thanrelaxation of the anal sphincters on defecationattempts. This phenomenon was earlierreported to occur in up to 55% of children andadults with defecation disorders.22 23 55 Thecause of this pelvic floor dyssynergia isunknown. In children with paediatric consti-pation it is suggested that the pain related to

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Benninga, Buller, Hevmans, Tytgat, Tamniniau

the defecation of large, firm stools may resultin unconscious contraction of sphincters toavert or stop pain during defecation.22 56Encopresis/soiling patients had, however,except for two children, no history of constipa-tion and none reported the periodic passage oflarge amounts of stools. They had significantlyless pain during defecation and significantlymore normal stools than children withpaediatric constipation, suggesting that analpain is not the only reason for abnormalexpulsion patterns. In addition, within theencopresis/soiling group, rectosigmoid transittime did not differ among the children withnormal or abnormal defecation dynamics,whereas in children with paediatric constipa-tion, abnormal defecation dynamics were

significantly associated with slowing of markersin the rectosigmoid (p=0 03) compared withthose children with paediatric constipationwho had normal dynamics (data not shown).Loening Baucke showed a decrease inrectosigmoid motility in chronically consti-pated children.57 Thus, in patients withpaediatric constipation abnormal defecationdynamics are related to the slowing of rectosig-moid transit time and decreased rectosigmoidmotility. In contrast, abnormal defecationdynamics in children with encopresis/soilingdid not result in prolonged rectosigmoid or

total CTT, nor did it lead to abnormal defeca-tion frequencies. This suggests that thesechildren, despite a pathological defecationtechnique, are able to produce complete or

nearly complete bowels. As mentioned above,children with encopresis/soiling often be-grudge the time necessary to visit the toilet andconsequently lose some of their bowel contentsduring play. We suggest that after they sense

the urge to defecate they let go

their first stools and subsequently contracttheir voluntary sphincter muscles firmly. Bydoing this daily, they unconsciously developabnormal defecation dynamics.On the CBCL we observed that children

with paediatric constipation and enco-

presis/soiling had a significantly higher inci-dence of behaviour problems than a normativesample of non-referred Dutch children.Loening Baucke et al 58 and Wald et al 22

showed similar high percentages for behaviourproblems in children with constipation andencopresis in 500 o and 450 respectively.Currently a prospective study is beingconducted, using the CBCL before and aftertreatment, to analyse whether constipation or

encopresis, or both, leads to behaviouralproblems or vice versa.

This study illustrates the importance of theinterpretation of clinical symptoms, the use ofmarker studies, and the value of anorectalmanometry in children with defecation dis-orders. Not all children will present withinfrequent painful defecation associated withabdominal pain and poor appetite. This studyindicates that children reporting encopresiswith normal defecation frequencies, withoutassociated symptoms of constipation, withnormal CTTs and normal threshold of analsensation probably form a distinct entity

among children with defecation disorders. Inour, as yet, limited experience these childrenrespond favourably to behavioural treatmentssuch as biofeedback training.

We are grateful to G W Akkerhuis of the department of childpsychiatry for analysis of the child behaviour checklist.

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