Fig. 6 | Algorithm for the management of persistent obstructive symptoms and soiling. Persistent obstructive symptoms and soiling are the two main complications after pull-through in children with Hirschsprung disease.

a, In children with obstructive symptoms, a mechanical obstruction should be searched for using a contrast enema and a rectal examination. Moreover, a transition zone pull-through should be excluded by reviewing the pathology from the pull-through resection and performing a biopsy. After excluding a mechanical obstruction or transition zone pull-through, hypertonic internal anal sphincter is the likely aetiology and may be improved by performing an intra-sphincteric botulinum toxin injection. Botulinum toxin injections are now used by up to 27% of paediatric surgeons148,232. Although prospective

and large cohort studies are lacking, several small cohort studies have shown that botulinum toxin injections may decrease obstructive symptoms and the

occurrence of enterocolitis after pull-through233. b, In order to investigate persistent soiling after pull-through, sensation and sphincter function should first be assessed using physical examination, anorectal examination under anaesthesia and anorectal manometry. This should allow patients with altered sensation and sphincter function, who suffer from true incontinence (which should be managed using an enema programme or ostomy), to be distinguished from patients with pseudo-incontinence, which is the most frequent finding. In patients with pseudo-incontinence, a contrast enema, possibly associated with colonic manometry, will allow determination

of whether the patient suffers from obstruction or hypermotility, and introduction of the most adapted treatment. ACE, antegrade continence enema. Part a adapted from ref. 169, Springer Nature Limited. Part b adapted from ref. 170, Springer Nature Limited.

has been reported164–166. Therefore, the appendix should not be relied upon for diagnosis. To ensure the complete removal of the transition zone, intraoperative frozen section analysis of the entire bowel circumference (‘donut’ section) should be performed at the proximal end of the resection or ostomy site141.

Postoperative surgical pathology.Surgicalspecimenscollectedfrom patientswithHSCRincludetheremainingtissuefromtheintraoperative frozensectionandtheresectedbowelsegments.However,studieshave described discrepancies between the frozen section analysis and final pathological analysis, with reported rates as high as 3–11%167,168. The purpose of the pathological evaluation is to confirm the intraoperative interpretations, estimate the length of the aganglionic segment and ensure that the most proximally resected bowel is free from any importanthistopathologicalcharacteristics,suchasthetransitionzone. Toachievethis,full-circumferencesectionsfromthedistalandproximal surgical margins and one or more longitudinal strips along the entire length of intervening bowel can be taken from the resected bowel141.

Postoperative complications

Each pull-through technique has its own distinctive complications. For example, Duhamel pull-through can result in a leak on the rectal stump, requiring a stoma diversion and peritoneal lavage. Swenson pull-through and Yancey–Soave pull-through can become complicated with a coloanal anastomotic leak, which may lead to peritonitis or perineal abscess and will require a diverting stoma and local wound care. In cases of anastomotic leakage or refractory stenosis despite serial dilatations, a diverting stoma may be necessary.

Some children may experience ongoing obstructive symptoms, such as abdominal distension, severe constipation, enterocolitis and/or ongoing soiling, which have several possible causes, including mechanical obstruction, abnormal pathology in the pull-through bowel, internal sphincter achalasia, dysmotility of the proximal bowel or stool withholding behaviour169,170 (Fig. 6). The pathology from the patient’s original pull-through resection should be reviewed whenever possible to exclude transition zone histology at the proximal margin.

A twisted pull-through is possible, especially after a total transanal approachwithoutlaparoscopicview.Diagnosiscanbechallenging,and a contrast study or a transanal examination under general anaesthesia is rarely conclusive. Endoscopy or laparoscopy is often required to confirm the diagnosis. A transanal redo pull-through is feasible, with resection and anastomosis after untwisting the bowel171.

Residual aganglionosis or transition zone may require a redo pull-through, which can be performed by a transanal approach with a

SwensonprocedureorbyswitchinganinitialSwensonpull-throughtoa Duhamelprocedurebykeepingtheinitialpulled-throughcolon172.How- ever, studies have found similar results for non-operative treatment of transition pull-through173. Cases of secondary vanishing ganglionic cells may also require a redo pull-through174.

After a Yancey–Soave procedure, persistent obstructive symptoms may be owing to a tight muscular cuff. To avoid this complication, the cuff has been reduced over the last decade and divided posteriorly. If obstructive symptoms persist, the cuff may be divided by laparoscopy if it was not done during the initial surgery or may be removed and a redo pull-through performed. After a Duhamel procedure, recurrent obstructive symptoms may be due to a spur, which may be divided during redo surgery. The posterior sagittal approach may be ideal for long ischaemic colonic stenosis, which may be suspended above a non-stenotic coloanal anastomosis175.

The three main causes of soiling are poor sphincter tone, poor sensation, hyperperistalsis of the pull-through and faecal retention170 (Fig. 6). Following transanal approaches, over-stretching of the anal sphincter may cause partial tear and irreversible lesions, resulting in soiling or faecal incontinence. Reconstruction of the sphincter has been reported to improve functional outcomes with promising results176.Redosurgerymayberequiredincaseofimmediate,mid-term orlong-termcomplications.Adivertingstomaisoftennecessarytocre- ate a more favourable situation and allow the child to recover and gain satisfactory nutritional status before performing a redo pull-through.

Postoperative HAEC. In approximately one-third of patients with HSCR, at least one episode of postoperative HAEC will occur after pull-through, and recurrent HAEC after pull-through requires additional evaluation to determine whether a surgically correctable cause can be identified105 (Fig. 6). Although HAEC is most frequent during the first2yearsoflife,itcanoccuratanytimeduringfollow-up177,178.Despite theidentificationofseveralriskfactors,suchastrisomy21,totalcolonic aganglionosis or malnutrition, the pathophysiology of postoperative HAEC remains poorly understood. A combination of intestinal dysmotility, intestinal barrier dysfunction, impaired mucosal immunity and abnormal microbiota is believed to underlie the pathogenesis of postoperative HAEC177,179–182. Each episode of HAEC should be assessed and treated according to its severity, and might require medical or surgical treatment. In some cases, no cause may be identified and the child may not improve despite botulinum toxin injections or bowel management. In patients with recalcitrant HAEC, a diverting stoma may be necessary to avoid short-term and long-term complications such as sepsis, bowel perforation and failure to thrive.