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Risk of incomplete pyloromyotomy and mucosal perforation in open andlaparoscopic pyloromyotomyNigel J. Hall a, , Simon Eaton a , Aaron Seims b, Charles M. Leys b, John C. Densmore c, Casey M. Calkins c,Daniel J. Ostlie d, Shawn D. St Peter d, Richard G. Azizkhan e, Daniel von Allmen e, Jacob C. Langer f ,Eveline Lapidus-Krol f , Sarah Bouchard g, Nelson Piché g, Steven Bruch h, Robert Drongowski h,Gordon A. MacKinlay i, Claire Clark i, Agostino Pierro a, f

a UCL Institute of Child Health & Great Ormond Street Hospital for Children, London, UK b Riley Hospital for Children, Indianapolis, IN c The Children's Hospital of Wisconsin, Medical College ofWisconsin, Milwaukee, WI d

Children's Mercy Hospital, Kansas City, MOe Cincinnati Children's Hospital Medical Center, Cincinnati, OH f Hospital for Sick Children and University of Toronto, Toronto, Canadag Hospital Sainte-Justine, Montreal, Canadah University of Michigan, Ann Arbor, MI i Royal Hospital for Sick Children, Edinburgh, UK

a b s t r a c ta r t i c l e i n f o

Article history:Received 4 July 2013Received in revised form 7 October 2013Accepted 7 October 2013

Key words:Pyloric stenosis

PyloromyotomyMinimally invasive surgeryInfant

Background: Despite randomized controlled trials and meta-analyses, it remains unclear whetherlaparoscopic pyloromyotomy (LP) carries a higher risk of incomplete pyloromyotomy and mucosalperforation compared with open pyloromyotomy (OP).Methods: Multicenter study of all pyloromyotomies (May 2007 – December 2010) at nine high-volumeinstitutions. The effect of laparoscopy on the procedure-related complications of incomplete pyloromyotomyand mucosal perforation was determined using binomial logistic regression adjusting for differences amongcenters.Results: Data relating to 2830 pyloromyotomies (1802 [64%] LP) were analyzed. There were 24 cases of incomplete pyloromyotomy; 3 in the open group (0.29%) and 21 in the laparoscopic group (1.16%). Therewere 18 cases of mucosal perforation; 3 in the open group (0.29%) and 15 in the laparoscopic group (0.83%).The regression model demonstrated that LP was a marginally signi cant predictor of incompletepyloromyotomy (adjusted difference 0.87% [95% CI 0.006 – 4.083]; P = 0.046) but not of mucosal perforation(adjusted difference 0.56% [95% CI − 0.096 to 3.365]; P = 0.153). Trainees performed a similar proportion of each procedure (laparoscopic 82.6% vs. open 80.3%; P = 0.2) and grade of primary operator did not affect therate of either complication.Conclusions: This is one of the largest series of pyloromyotomy ever reported. Although laparoscopy isassociated with a statistically signi cant increase in the risk of incomplete pyloromyotomy, the effect size issmall and of questionable clinical relevance. Both OP and LP are associated with low rates of mucosalperforation and incomplete pyloromyotomy in specialist centers, whether trainee or consultant surgeonsperform the procedure.

© 2014 Elsevier Inc. All rights reserved.

Since its introduction two decades ago, the laparoscopic approachto pyloromyotomy has gained popularity and has been implementedby many centers. During this period, a number of groups havereported comparative outcomes between the traditional openprocedure and the laparoscopic procedure. Such studies initiallytook the form of retrospective comparative reports, but there havesince been at least ve prospective randomized controlled trials

(RCTs) [1– 5]. Furthermore, there are three published systematicreviews with meta-analysis covering this topic [6– 8]. The reportedbene ts (as de ned by the attainment of statistical signi cance[P b 0.05]) in these RCTs and meta-analyses include shorter time toachieve full feeds [3,6,8], shorter postoperative time in hospital [3,6],less postoperative vomiting [1], less pain [1,3,4], fewer woundcomplications [6], better cosmesis [2] and improved cost-effective-ness [9]. Despite these bene ts, there remain concerns that thelaparoscopic approach may subject patients to a higher risk of thespeci c procedure-related complications of incomplete pyloromyot-omy and mucosal perforation [4,6,7,10] . Although a statistically

Journal of Pediatric Surgery 49 (2014) 1083 – 1086

Corresponding author at: Surgery Unit, UCL institute of Child Health, 30 Guilford St,London, WC1N 1EH, UK. Tel.: +44 207 9052 641; fax: + 44 207 4046 181.

E-mail address: nigel.hall@ucl.ac.uk (N.J. Hall).

http://dx.doi.org/10.1016/j.jpedsurg.2013.10.014

0022-3468/© 2014 Elsevier Inc. All rights reserved.

Contents lists available at ScienceDirect

Journal of Pediatric Surgery

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signi cant difference in incidence of these complications has not beendemonstrated in any of the RCTs, none was large enough to detectsuch a difference because of the low incidence of these complications.In meta-analysis there is a trend toward a higher incidence of incomplete pyloromyotomy using the laparoscopic technique thatapproaches statistical signi cance ( P = 0.06) [6,7] although thevalidity of this gure has been questioned owing to concerns overthe statistical techniques used [10,11] .

Thedif culty in determining whether there is really a difference inthe incidence of incomplete pyloromyotomy and mucosal perforationbetween laparoscopic and open pyloromyotomy lies in the samplesize required to demonstrate a difference, if one truly exists. Even inpublished meta-analyses, the total number of patients available(owing to the limited number of RCTs included and their individualsample sizes) remains limited at approximately 500 [6– 8]. We havepreviously estimated that a sample size of approximately 1250patients would be required to demonstrate a statistically signi cantdifference in the incidence of incomplete pyloromyotomy betweenlaparoscopic and open procedures of 2.5% (the unadjusted differencein incidence obtained from the raw data included in meta-analysis[10] ). Such a large study collecting data from individual patients hasnever been reported in the eldof pediatricsurgery to our knowledge.Therefore, we aimed to perform a study large enough to overcome thesample size limitations of previous studies with adequate power todetect small differences in the incidence of these complicationsbetween open and laparoscopic approaches.

1. Methods

We performeda retrospective studyin ninehigh-volume specialistpediatric surgical centers in the UK, USA and Canada. IRB/ethicalapproval was obtained for each center. Centers were invited forinclusion following a mailshot and selected only if they performed atleast 15 laparoscopic pyloromyotomies per year. The study period ranfrom 1st May 2007 to 31st December 2010. This start date was chosenas being the date following which the last patient was randomizedinto a previous RCTof open versuslaparoscopic pyloromyotomy [3] toexclude duplication of reporting. Data relating to all pyloromyotomiesfor infantile hypertrophic pyloric stenosis performed in this periodwere recorded including patient demographics (age, gender), oper-ativeapproach (openor laparoscopic), conversion rate of laparoscopy,and grade of operating surgeon (trainee under supervision orconsultant). Grade of operating surgeon was recorded because aprevious RCT reported that a signi cantly higher proportion of laparoscopic procedures were performed by consultants than wereopen procedures [3]. Although grade of operating surgeon had noin uence on the primary outcomes of that RCT, the effect of grade of primary operator on the primary outcomes of this study remainsunknown. The primary outcomes for this study were the speci cprocedure-related complications of (i) incomplete pyloromyotomyand (ii) mucosal perforation. A mucosal perforation was de ned as

breach of the mucosal barrier during pyloromyotomy which waseither identi ed at the time of the myotomy and repaired immedi-ately, or became apparent in the postoperative period and wasreexplored and repaired. An incomplete pyloromyotomy was de nedas an inadequate myotomy requiring another procedure. Redoprocedures following incomplete pyloromyotomy were excludedfrom the analysis.

1.1. Statistical analysis

A binomial multivariate logistic regression modelwas generated tocalculate incidence of primary outcomes taking into account differ-ences in rate of complications between different centers and grade of primary operator. Analysis of patient demographics revealed a

statistically signi cant difference in age at surgery between open

and laparoscopic groups. Furthermore an initial univariate analysisalso demonstrated that age at surgery, but not gender, was asigni cant determinant of IP. Therefore age at surgery was includedin the nal multivariate model. Non-parametric data were comparedusing a Mann – Whitney U test and proportions were compared usingchi-square test. SPSS version 18 was used for all analyses.

1.2. Sample size

Based on data from previous RCTs and meta-analyses wecalculated that to detect statistically signi cant differences in theincidence of incomplete pyloromyotomy and mucosal perforationwould require a total sample size of approximately 1250 and 390,000respectively. Given the impossibility of achieving the second of thesesample sizes (and therefore a near-impossible chance that there is aclinically signi cant difference) we designed a study aiming for asample of at least 1250 patients, and selected centers and a time scalein order to achieve this.

2. Results

Overall there were 2830 pyloromyotomies; 1028 were performedopen and 1802 laparoscopically. The distribution of cases between thenine centers is shown in Table 1 . Patients operated on laparoscopicallywere slightly older (difference in median age 2 days) and weighedmore (difference in median weight 0.14 kg); these differences werestatistically signi cant ( Table 2 ).

Thirty- ve laparoscopic procedures (1.9%) were converted to anopen procedure for reasons including inability to complete theprocedure laparoscopically, suspected mucosal perforation and forrepair of con rmed mucosal perforation. However, not all instancesof mucosal perforation in laparoscopic cases were converted to an openprocedure. All such conversions were analyzed in the laparoscopicgroup on an intention-to-treat basis.

In total there were 24 cases of incomplete pyloromyotomy; 3 inthe open group (0.29%) and 21 in the laparoscopic group (1.16%).There were 18 cases of mucosal perforation; 3 in the open group(0.29%) and 15 in the laparoscopic group (0.83%). The binomiallogistic regression model demonstrated a signi cantly higher inci-dence of incomplete pyloromyotomy with laparoscopic surgerycompared with open (adjusted difference 0.87% [95% CI 0.006 –

4.083]; P = 0.046) but no signi cant difference in the incidence of mucosal perforation ( Table 3 ). The distribution of mucosal perforationand incomplete pyloromyotomy among centers is shown in Table 4 .At least one complication occurred in each center and there wasno signi cant relationship between predominant procedureperformed at each center (laparoscopic or open) and distributionof complications.

The proportion of laparoscopic and open procedures performed bytrainees was similar (laparoscopic 1446/1749 [82.6%] vs. open 465/

Table 1Distribution and description of cases between centers.

Center N Age (days) Weight (kg) Male

Median IQR a Median IQR a n %

A 414 36 29 – 48 3.92 3.48 – 4.40 350 84.5B 350 34 27 – 45 3.90 3.46 – 4.32 292 83.4C 389 36 27 – 47 3.96 3.44 – 4.44 329 84.6D 502 34 27 – 45 3.83 3.46 – 4.50 424 84.5E 179 35 27 – 47 4.10 3.50 – 4.55 140 78.2F 373 34 26 – 46 4.00 3.56 – 4.50 298 79.9G 108 38 30 – 49 3.80 3.35 – 4.30 83 76.9H 344 35 27 – 49 4.10 3.60 – 4.56 285 82.8I 171 36 29 – 47 3.76 3.40 – 4.30 146 84.9Total 2830 35 27 – 47 3.90 3.50 – 4.44 2347 82.9a

Interquartile range.

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579 [80.3%]; P = 0.2; data unknown for 502 procedures, 1 center).Grade of operating surgeon had no effect on the incidenceof either incomplete pyloromyotomy (adjusted difference trainee vs.consultant − 0.438% [95% CI − 1.198 to 1.483]) or mucosalperforation (adjusted difference trainee vs. consultant − 0.677%[95% CI− 1.183 to 0.8]).

3. Discussion

Despite high-quality RCTs and meta-analyses, until now it has

remained unknown whether laparoscopic pyloromyotomy carries ahigher incidence of incomplete pyloromyotomy or mucosal perfora-tion than the open procedure. In this multicenter review, comprisingone of the largest series of pyloromyotomy ever reported, we haveidenti ed a small (0.87%) but statistically signi cant ( P = 0.046)increase in the incidence of incomplete pyloromyotomy in thelaparoscopic group compared with the open group. Although this isa statistically signi cant difference, we believe that the size of theclinical effect it describes should be carefully considered. Thedifference in incidence of incomplete pyloromyotomy of 0.87%indicates that the number of children that would need to be treatedlaparoscopically in order for one additional episode of incompletepyloromyotomy to occur is 115. While there is a higher proportion of children in the laparoscopic group who will require a repeatprocedure, this marginally higher rate of repeat procedure must bebalanced against previously documented advantages of laparoscopicpyloromyotomy over the open procedure [1,3,6]. Furthermore, itshould be noted that previous studies reporting shorter recoverytime following laparoscopy have included patients who have hadan incomplete pyloromyotomy [3,6,8]. Thus the low incidenceof an extended postoperative recovery period from incompletepyloromyotomy does not offset the advantage of laparoscopy forthe population.

In agreement with previous smaller studies [1,3,4] we have notidenti ed a statistically signi cant difference in incidence of mucosalperforation between open and laparoscopic pyloromyotomy.

The reason for the higher incidence of incomplete pyloromyotomywith laparoscopic procedure is not immediately apparent. While it ispossible that the lack of tactile feedback during laparoscopy results ina less precise pyloromyotomy, St Peter and colleagues [1] haveimpressively demonstrated in an RCT that by ensuring a pyloromyot-omy of adequate length, this complication can be avoided altogether.By ensuring a pyloromyotomy of minimum length 2 cm (measured

intraoperatively with an intracorporally placed length of string)they achieved a zero incidence of incomplete pyloromyotomyduring laparoscopic procedure. These results were available to allcenters prior to the rst patient in this study being treated, yet stilloverall a higher incidence with laparoscopy was encountered. Otherfactors that cannot be controlled for outside the strict con nes of anRCT in a “ real-world ” setting may be contributory. Our resultstherefore describe the rates of complication applicable to patientsoutside an RCT.

We have also demonstrated that grade of primary operator(trainee under supervision or consultant/attending) has no signi canteffect on the incidence of either incomplete pyloromyotomy ormucosal perforation. A previous RCT comparing open and laparo-scopic pyloromyotomy also reported no signi cant effect on primaryoutcomes attributable to grade of primary operator [3]. However, themajority of laparoscopic procedures were performed by a consultantsurgeon while the majority of open procedures were performed by asupervised trainee. In comparison, the majority of both open andlaparoscopic procedures in this series were performed by a traineeunder supervision. The fact that these results are valid for proceduresperformed predominantly by trainees under supervision clearly hasimportant implications for service delivery as well as for surgicaltraining. These results demonstrate that equally good outcomes canbe achieved from open and minimally invasive surgery withinpediatric surgical training institutions where the majority of pro-cedures are performed by trainees.

The main strength of this study is its size. This is one of the largestseries of pyloromyotomies ever reported. This high number of cases,combined with the multicenter nature of the study, allows us to drawreliable conclusions applicable to a large number of similar centersworldwide. This study demonstrates that to detect small differencesin treatment outcomes large, multicenter collaborations are essential.This study has demonstrated a statistically signi cant difference inincidence of incomplete pyloromyotomy when smaller RCTs havefailed to do so because of sample size limitations. These data also

come from a “ real-life ” setting; that is all patients were includedand inclusion in the study was not limited by the eligibility criteria of an RCT.

A potential limitation to this study is that data were collectedretrospectively. From the outset, we considered whether to perform asecond, larger, multicenter randomized study as a follow-on from ourprevious trials [1,3] or a retrospective review. In general terms,prospective studies are preferred as they reduce the in uence of biases on the results of a study. A study in which any of the outcomesare subjective or consist of a continuous variable may be particularlyprone to the in uence of bias in this way. However,a study suchas thecurrent one that uses well-de ned, objective, categorical endpoints ishighly unlikely to be in uenced by the sources of bias that exist in atypical retrospective study. In addition, the procedure-related

complications analyzed in this study are diagnosed either during the

Table 2Demographic details of infants undergoing open or laparoscopic pyloromyotomy.

Operative approach P

Open Laparoscopic

Age at surgery (days) a 34 (27 – 45) 36 (28-48) 0.003 b

Weight at surgery (kg) a 3.85 (3.43 – 4.40) 3 .99 (3.50 – 4.47) 0.002 b

Male, n (%) 864 (84%) 1483 (82%) NSc

a Data are median (interquartile range).b

Mann–

Whitney U test.c Chi-square test.

Table 3Rates of procedural complications of pyloromyotomy.

Operative approach Adjusted difference a,(%) (95% CI)

P *

Open Laparoscopic

Mucosal per foration (%) 0.29 0.83 0.56% ( − 0.096 to 3.365) 0.153Incomplete

pyloromyotomy (%)0.29 1.16 0.87% (0.006 to 4.083) 0.046

* Binomial logistic regression analysis.a

Adjusted for center and age.

Table 4Distribution and description of complications between centers.

Center Open Laparoscopic Total, n (%)

n MP IP n MP IP MP IP

A 86 0 0 328 2 9 2 (0.48%) 9 (2.17%)B 265 1 3 85 1 1 2 (0.57%) 4 (1.14%)C 0 – – 389 1 1 1 (0.26%) 1 (0.26%)D 449 1 0 53 0 0 1 (0.19%) 0 ( – )E 2 0 0 177 1 0 1 (0.56%) 0 ( – )F 118 1 0 255 4 1 5 (1.34%) 1 (0.27%)G 15 0 0 93 4 3 4 (3.70%) 3 (2.78%)H 89 0 0 255 1 5 1 (0.29%) 5 (1.45%)I 4 0 0 167 1 1 1 (0.58%) 1 (0.58%)Total 1028 3 3 1802 15 21 18 (0.64%) 24 (0.84%)

MP, mucosal perforation; IP, incomplete pyloromyotomy.

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operation or soon after it, and patients are treated in the same center.This reduces the chance of these complications being missed from theanalysis and not reported. We therefore justify this retrospectivestudy which hasthe added advantage of providing data to the surgicalcommunity more rapidly than a prospective study. Interestingly, ageat surgery and weight at surgery were signi cantly higher (by 2 daysand 140 g respectively) in the group undergoing laparoscopicpyloromyotomy than the group undergoing open pyloromyotomy inthis study. Although this is a potential confounding factor (and sourceof bias), we have controlled for age at surgery in the analyses byincludingage in our regression model. We did not additionally controlfor weight in the regression analysis, as age and weight are highlycorrelated as expected and controlling for both age and weight wouldyield an overadjusted model.

A further observation is that these data were obtained from high-volume, specialist pediatric surgical centers. Whether the results of this study are generalizable and applicable to smaller or nonspecialistunits is not known. There is a recognized association between patientoutcomes and both high volume and specialization [12,13] . Overallthe procedural complication rates reported in this study are amongthe lowest reported for either open or laparoscopic procedures, afactor that we suspect is at least partly caused by volume andspecialization. While Langer and To [14] have shown improvedoutcomes after open pyloromyotomy done by a pediatric Surgeoncompared with that by a general surgeon and Haricharan andcolleagues [15] have shown an increased rate of complicationswhen laparoscopic pyloromyotomy is performed by a general surgicalresident rather than a pediatric surgery resident, it is also true that Aliand colleagues [16] have demonstrated that laparoscopic pyloro-myotomy can be safely and effectively performed by a non-specialistgeneral surgeon in a non-specialist center.

These data may be interpreted differently by different groups of surgeons. Laparoscopic enthusiasts may regard the difference in rateof incomplete pyloromyotomy between laparoscopic and openapproaches to be so small as to be of questionable clinical signi cance.This, combined with the previously reported bene ts of laparoscopy,may be viewed as continued justi cation in support of the use of thelaparoscopic approach. Conversely, surgeons who favor open pylor-omyotomy may focus on the statistically higher incidence of incomplete pyloromyotomy with laparoscopy. We believe that thisstudy demonstrates that the rates of incomplete pyloromyotomy andmucosal perforation at high-volume pediatric surgical centers are lowduring both open and laparoscopic procedures and justify thecontinued use of both procedures in such institutions. However, wewould recommend that particular attention be paid to the length of

the pyloromyotomy during laparoscopy especially in young orsmall infants.

4. Summary

Open and laparoscopic pyloromyotomies have similar rates of mucosal perforation and incomplete pyloromyotomy. Both ap-proaches to pyloromyotomy are safe and carry an acceptable rate of

these complications in high-volume, specialist centers.

References

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[12] Safford SD, Pietrobon R, Safford KM, et al. A study of 11,003 patients withhypertrophic pyloric stenosis and the association between surgeon and hospitalvolume and outcomes. J Pediatr Surg 2005;40:967 – 72.

[13] Chowdhury MM, Dagash H, Pierro A. A systematic review of the impact of volume of surgery and specialization on patient outcome. Br J Surg 2007;94:145 – 61.

[14] Langer JC, To T. Does pediatric surgical specialty training affect outcome afterRamstedt pyloromyotomy? A population-based study. Pediatrics 2004;113:1342 – 7.

[15] Haricharan RN, Aprahamian CJ, Celik A, et al. Laparoscopic pyloromyotomy: effectof resident training on complications. J Pediatr Surg 2008;43:97 – 101.

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