Megarectum surgery in the management of constipation

Definition of encopresis, soiling and constipation

Encopresis is soiling with a small amount of faeces into the clothes of a toilet trained child, involuntarily, The term encopresis has been used to describe the ‘diagnosis’ of the patients, but, like the word ‘constipation’, the term does not define a disease, as it is merely a description of events; it does not identify a cause. Van der Plas et al., in their study to improve the understanding of what constitutes a megarectum, define encopresis as the loss of a normal amount of stool in the underwear of a child after the age of 4 years, without any underlying organic disorder.¹ Benninga et al.² and Chiarioni et al., in assessing a megarectum in children manometrically, restated the definition used by van der Plas et al., highlighting that encopresis is in the absence of organic disorder.³ Alberto Pena suggested that the encopretic child does not even have spontaneous bowel motions.⁴ Whether the amount of stool passed is ‘normal’ or not differs between authors.

Benninga et al. note the important difference between encopresis and soiling as the amount of faeces lost, with soiling being the lesser of the two.² They note that the terms are inappropriately used indistinguishably in published work. Faecal soiling represents the staining of underwear and is often associated with faecal impaction. They were adamant that, by definition, there is no faecal mass palpable in the encopretic child, a group they appropriately considered would respond to behaviour treatment.² They go on to assert that encopresis can occur in the absence of constipation.

Nixon, a paediatric surgeon of repute from Great Ormond Street Children’s Hospital, explained that constipation means incomplete emptying; encopresis is not overflow and there is no marked constipation or megarectum.⁵ Constipation is defined in many ways, but most accept that constipation is a term that does not equate to a diagnosis, but does imply infrequent stools, incomplete emptying, firm stools, straining at stool, pain on defaecation and abdominal pain or a combination of some or all of these. Certainly, there is no literature support for a boy presenting with a rectum loaded with faeces, occupying most of the width of the pelvis, as never having had constipation as claimed by some. According to Coccorullo et al., treatment of constipation is still largely based on clinical experience rather than on evidence-based studies.⁶

Many authors provide comment and evidence that refute of the claims of patients who state, ‘[they] didn’t feel it’ when they soil, is not due to a lack of perianal sensation. Oppe, as early as 1967, noted that ‘another aspect of denial is the claim made by the child that he is unaware of soiling or the presence of the faeces in the rectum’,⁷ which anyone involved in the management of faecal and urinary incontinent children should be very conversant with – i.e. child with any form of incontinence usually says ‘I didn’t feel it’.

Definition of megarectum

Before discussing megarectum, let me explore the presence of dilated segments of other parts of the internal anatomy to help understand how we might, appropriately, approach the dilated bowel from lessons learnt from other body systems. For example, the renal pelvis is considered to require resection if found to be baggy when it has been dilated by obstruction, rather than just the obstruction being operated on. Children with a kidney that can be distended to up to 3 L, and not uncommonly in developing countries, up to 1 L, must have resection of part of the dilation for the kidney to drain.

Likewise, the oesophagus and duodenum are plicated as part of the management of those congenital anomalies, which was clarified in 1990, by Dewan and Guiney who described the case of a girl with segmental dilatation of the duodenum, who presented with failure of pubertal development which was resolved by resection of the dilated component.⁸ Adrian Bianchi, from Manchester, has provided a technique for dealing with ectatic segments of small bowel⁹ and Swenson and Rathauser, in 1959, presented the first three cases of segmental dilatation of the colon and rectum,¹⁰ which were treated with resection. A later case of proximal colonic segment dilatation was presented in a 3-year-old in 1980.¹¹ In 2008, Al-Salem reviewed 12 cases of segmental dilatation, noting that 10 of the 12 cases included were operated on at less than 10 years of age, and provided images of a case of a megarectum.¹² Thus, the renal pelvis, the oesophagus, the duodenum, the small bowel, and the colon have been demonstrated to be either removed or narrowed if significantly dilated. So, what about megarectum?

Unfortunately, megarectum is a term that is used across a wide spectrum of abnormality, a little like the term constipation or bronchospasm. The ‘constipation’ term alone does not define the nature of the problem, the prognosis, nor the therapy for the individual patient. There are several authors who have defined a megarectum on barium study, the first being Preston, who concluded that a rectal diameter of greater than 6.5 cm in the lateral view was the lower limit above which the rectum was abnormal in adults.^13,14 In Preston et al.’s study they investigated 50 controls, 18 women with slow transit constipation and 20 idiopathic colon patients. Those with slow transit constipation had a normal rectum, neither the controls, nor the slow transit constipation group had a rectal diameter above 6.5 cm. The rectal width was measured from true lateral pelvic radiographs along a line drawn perpendicular to the body to S2. The bowel width was measured perpendicular to the lumen at the pelvic brim.¹³ In particular, the rectal diameter should be measured on a line extending perpendicular to the second sacral segment. Gladman et al. highlight that the rectal diameter should be measured at 90° across the widest transverse diameter at the pelvic brim.¹⁵ Several authors have since concurred on the definition of megarectum,^3,16 while others suggest 6.1 cm as the upper limit of normal^17,18 or add consideration of the extension of the megarectum from the pelvis:¹⁹ the younger the child, the lower the expected upper limit of the rectal size. Appropriately, the absolute size of the rectum is not considered a good guide in paediatric patients, thus a recto-pelvic ratio of 0.61 is considered abnormal.¹ Some authors maintain that rectal function seems severely deranged due to the atonic state of the rectum that sometimes adapted to a capacity of over 800 mL.³

There are several studies that have diagnosed and treated children with anorectal anomalies and a megarectum^20–24 and many studies that have provided surgical care for adults with a diagnosis of chronic constipation and a megarectum,^25–27 in doing so there has not only been evidence accumulated as to a radiological and manometric diagnosis, but also a histological confirmation. Brent and Stephens provide histologic evidence for primary rectal ectasia,²⁸ and in 1997, Gattuso et al. reported on the histology of idiopathic megarectum in cases of rectal only or combined colonic dilatation, showing significant thickening of the megarectum muscularis mucosae (median 78 μm vs 73 μm, P < 0.005), circular muscle (1000 μm vs 633 μm, P < 0.005), and longitudinal muscle (1083 vs 303 μm P < 0.005), despite rectal dilatation. The density of neural tissue in the longitudinal muscle seemed to be reduced in patients with idiopathic megarectum compared to normal controls.¹⁴ Despite thickening, the rectum of the megarectum sufferer tends to be atonic, able to tolerate large volumes that are too large to be defaecated.³ In patients with faecal impaction the rectal wall develops myohypertrophy to overcome chronic faecal loading.¹

One of the points of confusion is when can the diagnosis of a congenital anomaly be made, some erroneously suggesting that the older patients only ever have secondary changes in the bowel.

Differential diagnoses

This paper is not meant to be exhaustive on the topic of the differential diagnosis of idiopathic megarectum, but will make the point of the importance of ultra-short segment Hirschsprung disease as a differential diagnosis, and highlight why a diagnosis of Hirschsprung could be possible at the end of an operation, but not at the start. It also intends to indicate the inappropriateness of protracted medical management in the presence of likely failure of non-surgical treatment.

Megarectum is commonly treated as functional constipation or confused with Hirschsprung disease.¹² Far too much has been made of this differential diagnosis, which can be ascertained by rectal biopsy and anorectal pressure studies, but the studies are only indicated when sufficiently likely to warrant the investigations.^29,30

In a case description in 1990, which described a 3 year old with segmental dilatation, Al-Salem and Grant state that the barium enema examination shows distension of the rectal ampulla and colon in idiopathic megacolon, but the same radiographic picture may exist also in short-segment Hirschsprung,³¹ which is discussed again later.

It appears that in patients with idiopathic megarectum, impaired motility is a result of chronic retention and overstretching of the bowel, whereas the opposite is true in patients with primary rectal ectasia.²² That is, there is a different disease in each patient and there is a spectrum of each disease, which concurs with Pena’s view that, ‘the concept of a spectrum of disease cannot be over emphasized … standard therapeutic protocols that render good results in a percentage of cases but always leave a group of patients who do not respond’.⁴

Fuacheron, in investigating 154 patients, reported on 12 cases of megarectum, which they considered as one form of akinesia,³² which in effect fits with the functional disruption suggested by others, and the range of pathology proffered by Pena.⁴

Megarectum investigations

Types of surgery for constipation

A wide range of surgical therapies exist for assistance with the management of patients with constipation. Obviously, all have a limited role, but the presentation of the option of colostomy for idiopathic constipation, while an extreme undertaking is none-the-less one of the options that a surgeon should consider in the armamentarium for the care of the constipated patient, particularly given the latter discussion on life threatening complications of constipation; and the recent death in Victoria. Highlighting that a failure to diagnose and treat constipation sufficiently aggressively in children can result in significant life-threatening complications.

The surgical options that have been recommended in adults, children or both include:

To understand the appropriateness of the decision to operate and what operation to perform for the constipated child, we need to work through the above options, particularly the invasiveness of the formation of a colostomy and the potential complications of the Malone antegrade enema option that some regard as an innocuous alternative.

Firstly, let me discuss the literature related to surgical alternatives for resection of the bowel in constipated patients, which ranges from total colectomy to permanent colostomy. The surgery ranges from evacuation of the bowel,¹⁷ which does not have any significant surgical risk, then rectal biopsy, then myomectomy,^21,29 which are not without the risk of bleeding and infection. Pena considers the latter alternative less than satisfactory.⁴ The formation of a catheterisable stoma into the right colon, known at the Malone stoma^18,38,40,42 is supported by many, or to the left colon, known as the Lace,¹⁸ supported by some.

Longitudinal reduction of the diameter of the rectum can be achieved by rolling the segment to enable coaptation of the inner walls, in a process known as imbrication,⁴³ or the lumen is reduced in size longitudinally by removing part of the circumference of the intestine, known as vertical reduction rectoplasty.^16,27 There are a large number of publications that advocate the use of resection and anastomosis, using procedures that perform a resection focused on removal of the sigmoid colon,^22,35 both during an open operation and laparoscopically. Levitt and Pena, having considered that sigmoid resection was sufficient, published in 2009 that they preferred a transanal approach where they performed the same procedure in 15 children with idiopathic megarectum. They reported using a sigmoid resection technique in 17 children previously.²⁴ Amano treated 6 of 20 children with a megarectum with resection²⁰ and advocated anterior resection for the treatment of mega rectosigmoid as a safe and effective procedure for the management of a megarectum.⁴⁴

Others have used another operation initially devised for Hirschsprung surgery, the Duhamel procedure,^12,19,25,31 with colectomy of various degrees being mentioned by others.^16,26,33,36

Colostomy and ileostomy have been used for the treatment of constipation, which seems extreme, but is obviously within the realm of reasonable care given that papers from noted institutions have been published in peer reviewed journals, including the paper by Woodward on 10 children.^17,36,45,46 But stomas could possibly be avoided by more proactive treatment in early childhood.

Many papers have reported the use of surgery for constipation. A number of centres use the Malone stoma alone, but there is often not good definition of the differences between patients.^18,38,40,42 Lee et al. form a Malone stoma at the time of the resection of the megarectum, which is only used for a period of 12 months,²² which I would argue is seldom necessary after appropriate patient selection, and appropriate extent of surgery: adding the Malone stoma adds associated, unnecessary risks. The original paper on the Malone stoma used the technique of attaching the appendix to the skin to facilitate regular washout in only five patients from October 1989 including three children with a myelomeningocele and two who were born with an anorectal anomaly.⁴⁷ However, the Malone stoma, while a good part of the surgical armamentarium, is not the innocuous, universally successful tool, suggested by some, with 69% of Hutson’s group having recurrent soiling after the formation of the access port.⁴⁰

Hutson’s group published a report of late follow-up of 56 children with a Malone stoma for the management of constipation, with only an 81% success rate, with 71% having symptoms at some stage during the course of using the washouts.⁴⁰ Complications were common in the use of the Malone stoma as shown in Hutson’s paper,⁴⁰ including Granulation tissue (79%), Anxiety about the Ace (50%), Stomal infection (43%), Stomal leakage in at least 38%, Embarrassment (36%), Dislike (29%), Stomal pain (26%), Stomal stenosis (19%), Behaviour disturbance (17%), Stomal prolapse (14%), Stomal bleeding (14%), Limited activity (10%), Weight loss (5%), Perforation (5%). Poirier et al. recorded their complications of the Malone stoma for 18 patients, with only 78% success. They had 10 patients with 12 complications, including two with appendix perforation.⁴² Herndon et al. had a short mean follow-up with 13 stomal revisions in 117 patients and major complications such as caecal volvulus, small bowel obstruction, shunt infection but more importantly four patients who elected to not use the stoma due to intractable cramping with irrigation, which is a common complaint.³⁸

Timing of surgery for constipation

The argument that surgery should only be used after extensive medical management is trite at best. Surgery should be part of a package of options that is considered in all conditions that may require an operation. Obesity, for instance, should rarely require surgery, yet it is widely used, and there are many procedures where surgery and medicine provide complementary options that the patient may prefer one over the other. There are many other examples where conservative, medical and surgical options should be balanced with the need to treat and the preferences of the patient. There is argument that a failure to intervene surgically and continue with unsuccessful medical treatment in the light of a clear indication that a surgical solution will benefit the patient, resulting in a long period of psychologic damage, is unacceptably deleterious, and again highlighted by the death from constipation of an 11 year old in Victoria in 2022.

Many support the view that delaying appropriate treatment can have a devastating impact. Hutson and colleagues, writing from the Royal Children’s Hospital in Melbourne maintains that 30% of children fail conventional medical management of constipation and develop long-term symptoms. His team go on to claim that ‘as 90% of faecal incontinence episodes are due to chronic constipation, there may be devastating effects on children’s emotional and social development’.^40,41 Coccorullo et al. also highlight the adverse impact of chronic constipation suggesting that the condition significantly interferes with a child’s emotional growth and development.⁶

There have been several publications that support a regime that identifies the nature of the pathology as the guide to the time of the surgery, rather than just the outcome of a particular sequence of medical treatments in a particular order over a particular duration. To highlight the acceptability of a short time from diagnosis to surgical treatment in the presence of appropriate pathology, let us look at the time in a number of studies. Al-Salem, operated on four patients for removal of their megarectum, one of whom had a barium study, with his patients ranging in age from 1.3 to 7 years, with a mean 3.9 years.¹² Woodward et al., whose 10 patients had a permanent colostomy created ranged in age from 2 to 15 years, 5 of whom were less than 9 years. The 2-year-old was described as ‘a changed little boy’.⁴⁵

Obviously, the patients at the lower end of the above-mentioned ranges did not have extended periods of medical management, but they had a combination of medical and surgical care directed at the specifics of their pathology. Notably the surgical services at the Children’s Hospitals in Sydney and Melbourne have operated on patients with constipation at a young age. In 2005, King et al. reported the formation of Malone stomas in patients as young as 37 months,⁴⁰ while Gera et al. reported on 15 cases having laparoscopic resection of the rectosigmoid as young as 7 months.³⁵

Other centres internationally have used various options for the management of constipation and faecal incontinence at a young age. Herndon, for example, treated 127 children from as young as 33 months with the formation of an antegrade enema stoma.³⁸ Lee et al. resected the bowel in a 9-year-old,²² and Godbole’s unit performed resections of dilated bowel in 22 boys and 7 girls aged 40 months to 14 years.¹⁹ The group operated on by Keshtgar et al., although born with anorectal anomalies, had effectively an isolated megarectum as their residual anomaly for which surgery was performed at an age range of 2–15 years. Those with normal sphincter and no neuropathy becoming continent in seven of the nine, despite the young age of some of the group.⁴⁸ Also, the duration of therapy before surgery obviously varies as indicated by the young ages, and evidence from groups such as Godbole et al., who used stimulant laxatives for as little as one month before surgery, is worth noting.¹⁹

The other side of the duration of medical care is the long period of unsuccessful medical management reflected in some studies, which could be construed as a failure of timely use of a surgical solution. Lee et al. consider that once the diagnosis of megarectum is made, operative intervention should not be delayed because conservative management not only fails but also may have significant psychological and physical morbidity.²² Fioretti et al. argued that even children who may have originally had a psychogenic cause of the constipation, subsequent regression results in an organic evolution independent of the original disturbance, so that surgery must be resorted to, as well as neuropsychiatric treatment.⁴⁹ And, in other studies the lack of intervention at an early age resulted in significant complications and long periods of unsuccessful treatment. For example, Brown and Shorthouse had two patients, one 16 and another 25 years old who had symptoms from early childhood.⁵⁰ These two were operated on as young adults even in the presence of low preoperative sphincter pressures with the existence of an idiopathic megarectum,⁵⁰ resolving their constipation. Stabiles group had one of seven who had distal dilatation from early childhood²⁵ and seven of Gattuso et al.’s chronic idiopathic constipation patients and a megarectum had surgery, some having unsuccessful medical treatment for up to 6 years.¹⁴ Likewise, Stabile et al. had a group of seven adults, five of whom had a good result from surgery for megarectum, but not before they had a difference between the median age of diagnosis and the median age of treatment of 14 years,²⁶ which seems unacceptable. Better definition of the pathology would enable the select few who require surgery to have the intervention without the need for lengthy periods of failed medical management.

Ó Súilleabháin et al. also note, as we have in PNG,^43,51,52 that dilated bowel does not involute once it has reached a certain degree of dilatation, despite diversion by a colostomy, in some cases for several years.³⁶ Lundy and Gadacz identify the complications from neglected patients with dilated bowel segments, recording the case of a 25-year-old who had perforation secondary to his megarectum.⁵³

The various other points to highlight the appropriateness of surgery are that patients in adult life will often have an idiopathic megarectum or megacolon whose onset of symptoms commenced much earlier in either childhood or adulthood and had been effectively under treated.²⁶ Ó Súilleabháin et al. argued that surgery was appropriate after the patient had had 6 months of their conservative management.³⁶ Williams et al. also mentioned the common feature of onset in childhood, but that there can be delayed onset,¹⁶ and Staiano et al. demonstrated the failure of conservative treatment in a group of 62 children, with 63% still suffering constipation at the end of a 5-year study.⁵⁴ It is interesting that any surgical adverse impact is readily and appropriately highlighted, yet medical management failure is so tolerated. The surgical literature clearly shows that surgery for a megarectum is successful, both when there is an underlying anorectal anomaly^48,52,55 and when there is idiopathic constipation associated with a megarectum.^12,16,19,24

The work of Levitt and Pena clearly supports the role of excision surgery in the management of chronic constipation, including both sigmoid and per-rectal rectosigmoid options, a view with which I concur, noting that surgery has a limited role, but limited by the pathology of an individual patient, not by the lack of surgical alternatives. The Cincinnati papers also attend to the limited role of preoperative investigations and display a sceptical view of the common Melbourne Children’s Hospital diagnosis of neuronal intestinal dysplasia.^24,55