Discussion

Since the first reports in the late 1990s the transanal pull-through has become a popular procedure worldwide for Hirschsprung's disease management and the role of laparoscopy remains controversial.12 ,35 This meta-analysis identified only five eligible studies comparing TTERPT to LAPT. In general, these studies were of low quality, featuring heterogeneity with respect to outcome assessment, limited adjustment for potential confounders and inadequate long-term follow-up. The only outcome assessed, where there was a significant difference, was duration of surgery, with two studies demonstrating a significantly shorter duration of operation time for TTERPT compared with LAPT. This may be due to avoidance of time spent accessing the abdomen with a laparoscopically assisted procedure and concords with results from studies comparing open abdominal procedures with transanal pull-through.30 Unfortunately, these studies do not provide in-depth details of the reasons for the difference in operative time. As both studies included were retrospective observational studies and thus, likely to be subject to a degree of case selection, it is possible that cases with shorter, less-complicated disease segments were preferentially chosen for TTERPT.

The other relevant outcomes assessed were the incidence of Hirschsprung's associated enterocolitis (HAEC), and functional gastrointestinal outcomes. We found no evidence to suggest any difference in rates of postoperative HAEC between TTERPT and LAPT procedures. Incidence of HAEC ranged from 10% to 45% across studies; this compares to a reported incidence of 5–35% from previous studies.23 ,31 The variable rates of HAEC reported may relate to inconsistent definitions between studies. Kim et al25 used a previously validated scoring system to assess severity and utilised a Delphi score to ‘further secure uniformity’ of the diagnosis of HAEC. Van de Ven et al29 also used a Delphi score to diagnose HAEC. Neither Ishikawa et al27 or Dahal et al28 included definitions for the diagnosis of HAEC. We did not find evidence to suggest a difference in rates of faecal incontinence or constipation between TTERPT and LAPT groups. Of crucial importance in the assessment of incontinence and constipation is an adequate period of follow-up to allow assessment of children at an age when continence should be expected, and they have gained the necessary level of maturity and communication skills to report these outcomes. Follow-up durations were variable in the four studies that assessed these outcomes. Kim et al25 restricted their analysis to infants over 3 years of age and Ishikawa et al27 included only infants with three or more years of postoperative follow-up. Van de Ven et al29 included all infants with follow-up longer than 3 months. Dahal et al28 did not set a minimum follow-up period, with an age range from 6 to 171 months. In all studies, the methods used to assess faecal incontinence and constipation include an element of subjectivity. Kim et al25 employed a previously published parental telephone interview survey of bowel function with investigators blinded to the patient's operative arm. Ishikawa et al27 did not detail how follow-up data were obtained: constipation was defined as requiring anorectal myectomy and soiling as “greater than once per week at three years post-surgery.” Van de Ven et al29 defined constipation as “need for laxatives, enemas and/or bowel irrigations longer than 3 months,” but did not include data on faecal incontinence. Dahal et al28 did not define their terms ‘soiling’ or ‘constipation’, or the methods used to collect follow-up data.

The heterogeneity in outcome assessment methods and follow-up durations across these four studies must mandate caution in the interpretation of the finding that there was no evidence of a difference in faecal incontinence or constipation between the two surgical techniques. Of note is the fact that Kim et al25 found that differences in stool frequency between transanal pull-through and transabdominal procedures have converged by age 7 years. There is some evidence that bowel function following definitive surgery for Hirschsprung's disease continues to improve until adolescence.32 These findings reinforce our belief that longer durations of follow-up are vital to discover if apparent advantages of certain techniques persist as children develop. Since all the included studies were observational, there remains the possibility of uncontrolled confounding between the two treatment groups and thus, there are concerns regarding the comparability of both operative arms. All five studies were retrospective, with treatment selection occurring prior to inclusion in the study. Van de Ven et al reported on two units in which each performed one technique exclusively. While this reduces the risk of selection bias because patients are selected on a geographical basis rather than procedure technique, it introduces risks of confounding biases between sites.29 Four studies reported on a timeframe during which unit practice had altered, generally shifting towards greater utilisation of TTERPT. It is possible that improvements in non-operative areas, such as nursing care and preoperative diagnosis, may have had an effect on outcomes. In addition, Dahal et al28 acknowledge that the decision to utilise TTERPT or LAPT depended on results of barium enema, with longer segment disease more likely to be treated with a LAPT procedure. Reliance on a contrast enema to select patients for TTERPT introduces another potential difficulty for the surgeon, as recent reports suggest that 10–31% of infants have no radiologically identifiable TZ and a further 8–38% of reported TZs are discordant with the confirmed pathological length of aganglionosis.33 These difficulties may result in a surgeon inadvertently attempting to perform a totally transanal operation for an infant with long segment Hirschsprung's disease, in whom the procedure may be unsuitable due to the need for extensive colonic mobilisation. In addition, a staged approach with retro-rectal dissection (‘Long-Duhamel’ technique) may be preferred if the aganglionosis involves a large proportion of the colon.11 ,34

Several important outcome measures could not be assessed in this meta-analysis. One putative advantage of totally transanal approaches is the avoidance of intestinal adhesions leading to bowel obstruction. None of the studies reported any incidence of bowel obstruction but adhesions are a potentially lifelong complication that may take many years to manifest clinically. Rates of conversion from TTERPT to laparoscopy or laparotomy were not clearly reported across studies. Dahal et al included four patients where the planned TTERPT was converted to a laparoscopic procedure because of failure of colonic mobilisation; however, it is not clear whether these patients were analysed by intention to treat. Van de Ven et al29 report three cases where laparotomy was needed to treat colonic torsion following a TTERPT. Finally, other minimally invasive intra-abdominal techniques, such as umbilical incisions and minilaparotomies, were not assessed because these are outside the scope of this review.

Despite acknowledgement that more complicated and extensive disease segments require some form of intra-abdominal approach, including laparoscopy, minilaparotomy, umbilical incision or formal laparotomy,11 ,12 there is currently a lack of guidance to determine when it is unsafe to attempt a TTERPT. Therefore, it is vital that a number of measures are undertaken by the research community to improve the information available on the value of this approach. First, long-term follow-up studies are needed to fully understand the impact of TTERPT and LAPT techniques on bowel, urinary and sexual functions, including assessment of patient's satisfaction and late complications, such as intestinal obstruction secondary to adhesions. Despite widespread enthusiasm for newer procedures, it is important to note that virtually all data on bowel function in adulthood in patients with Hirschsprung's disease come from those operated on with a transabdominal Duhamel technique.32 Second, intention-to-treat analysis and reporting of comparative studies is vital, particularly in relation to the need to perform a laparotomy in a planned totally transanal procedure due to an unidentified long segment or total colonic aganglionosis. It is essential that authors accurately report such events, so that the true incidence of these occurrences can be gauged.

The issues we have raised regarding choice of operation would be best resolved by randomisation within a clinical trial of TTERPT versus LAPT approaches in patients with aganglionosis confined to the rectum and sigmoid colon on radiological assessment. However, this is unlikely to be feasible in a rare condition where individual clinician equipoise may be lacking. An alternative approach would be to conduct an expertise-based randomised controlled trial. In addition, multicentre data pooling, as exemplified by the BAPS-CASS programme in the UK,36 is needed to investigate long-term complications and effectively power evidence-based guidelines to identify patient groups in whom laparoscopic or other intra-abdominal assistance should be utilised.