Rectum

The rectum in children with ARM is usually dilated and does not shrink very much after the establishment of a colostomy. Its voiding function is reduced due to the impairment of parasympathetic nerve fibers and, in a few cases, of the intramural nerve plexus. A dilated bowel segment is not usually able to

Table 25.3 Pathologic conditions for stool continence in anorectal malformations. ARM Anorectal malformations, AG Agangliono-sis, HG hypoganglionosis, IND intestinal neuronal dysplasia

Anatomical site

Pathological condition

Rectum

Blind-ending, dilated rectal pouch Malformation of extramural nerve supply -tethered cord, spinal dysraphism, caudal regression, over-distension of cholinergic nerve fibers, damage, and atypical course of the erigentes nerves Malformations of intramural nerve plexus and bowel wall structures

-AG, HG, IND, desmosis, absence of interstitial cells of Cajal Reduced fixation of the rectum in the small pelvis after pull-through: disposition for rectal prolapse

Pelvic floor

Hypoplastic striated muscle complex, frequently not in direct contact with external sphincter muscle fibers and much better developed close to the sacrum than at the side of the anal dimple No clearly visible anorectal angle

Internal anal sphincter

Reduced number and weaker smooth muscle fibers localized around the fistula and not always at the deepest point of the blind pouch, with the exception of ARM without fistula

External anal sphincter

Hypoplastic and sometimes malpositioned muscle fibers Hemorrhoidal plexus on a higher level No longitudinal muscle fibers of the rectal muscle coat running through the external anal sphincter into the anal skin: disposition for mucosal prolapse No anoderm: reduced sensibility

Table 25.3 Pathologic conditions for stool continence in anorectal malformations. ARM Anorectal malformations, AG Agangliono-sis, HG hypoganglionosis, IND intestinal neuronal dysplasia contract. The slow waves are disturbed and the evocations of spike potentials are reduced [15]. This is a well-known phenomenon in other diseases like ileus, segmental dilatation of the small bowel loops, and jejunal atresia. However, rectal dilatation in ARM does not usually need tapering like jejunal obstructions. Partial resection might be necessary only in a very few cases of inert rectum that are resistant to washouts. However, one always has to keep in mind that patients with ARM need a certain degree of constipation to become clean with washouts.

In 1997, Rintala [13] demonstrated that total colonic transit is significantly prolonged in patients with ARM and even more prolonged in high types (median 24% prolonged transit) than in low types and healthy individuals (median 10% prolonged transit). However, Nagashami et al. in 1992 [28] found no difference in either contractile or myoelectric activity (spike bursts and slow waves) of the rectum between the two groups. Heikenen et al. [29] observed highamplitude propagating contractions in severely constipated children with ARM soiling after repair. The same phenomenon is found in children with myelo-meningocele [13,24,30]. Thus, overflow incontinence in ARM seems mainly to be a motility disturbance of the rectum and not a problem of the anorectal sphincters. This can also be concluded by comparing the functional situation in ARM with that of patients with Hirschsprung's disease. In Rehbein's procedure it is permitted to leave 4-5 cm of aganglionic anorec-tum in situ. However, chronic constipation occurred postoperatively in only 7.9% of these patients [31]. The frequency of postoperative chronic constipation in children after megacolon repair is lower than in children after PSARP for imperforate anus. In addition, hypoganglionosis of the lower most part of the blind pouch represents the normal ganglion cell distribution in the internal anal sphincter in healthy individuals.

Motility disturbance could theoretically also result from malformations of the parasympathetic nerve supply to the rectum. Christensen pointed out that the large intestine receives its extrinsic nerve supply through the vagus nerves, from the pelvic nerves and from the mesenteric nerves [16]. The vagus nerves provide a parasympathetic innervation to the whole gastrointestinal tract and to the rostral end of the large intestine. The pelvic nerves also distribute cholinergic fibers, the sacral component of the craniosacral outflow, to the whole of the large intestine. They form the pelvic plexus from which colonic nerve branches pass to the large intestine. The mesenteric-

adrenergic nerves emerge from the three prevertebral ganglia, which send branches along the three arteries to the gut. The vagal branches extend no further than about the middle of the transverse colon. The pelvic nerves distribute nerve fibers to the remainder of the large intestine. Branches of these colonic nerves extend rostrally in the myenteric plexus as far as the transverse colon. These are called ascending nerves of the colon. They may well overlap to some degree with that of the vagus nerve and vary widely.

In children with ARM this descending, ascending, and intramural nerve supply could be disturbed and its stimulating influence diminished leading to the varying degree of constipation observed in these children. This aspect is supported by studies of Mandhan et al. [32] showing that the imunoreactivity of neuron-specific enolase, vasoactive intestinal peptide, NSE, VIP, and nuclear protein SP-100 is markedly reduced in the rectum and fistulous tract of high ARM and slightly reduced in low ARM compared with controls. Intramural nerves immunostained with VIP and SP-100 antisera are decreased in both types of ARM, indicating that both inhibitory and excitatory motor neural elements are affected. This may also explain the distal colonic dysmotility seen postoperatively in both high and low ARM.

However, the degree of rectal dysmotility varies widely. Kayaba et al. [33], performing fecoflowmetric studies in 16 patients after repair of ARM, demonstrated that 7 out of 16 children exhibited periodical contractions of the rectum synchronized with relaxations of the anal canal during saline infusion, as did controls, and had significantly better clinical scores than other patients. Only two children with severe chronic constipation lacked rectal contraction. The fecoflow parameters, such as the maximum flow, average flow, and tolerable volume of saline infused into the rectum, were significantly lower in the patients with poor clinical scores than those of controls. The maximal squeeze pressure and resting anal pressure were not significantly different between the patients and controls. This also indicates that anorectal dysfunction in patients with ARM is more a problem of dysmotility of the rectum than of anal sphincter incompetence. However, a low anorectal pressure barrier might be an additional problem leading to overflow incontinence. This is supported by the studies of Heikenen et al. [29]; they performed motility studies in 13 children with repaired ARM and fecal soiling and found high-amplitude propagating contractions with an average of 80% propagation into the neorec-tum. Internal sphincter resting pressure was low in six out of ten patients. Internal sphincter relaxation was also present in six out of ten children. Only one out of five patients was able to cooperate and therefore capable of generating a normal squeeze pressure. The authors conclude that fecal soiling in patients with repaired ARM is a multifactorial problem including propagation of excessive numbers of high-amplitude propagating contractions into the neorectum as well as internal sphincter dysfunction. However, high-amplitude contractions are a typical electromanometric sign of chronic constipation [34]. In addition, in 20% of Heikenen's patients the rectum was "lazy", showing no motility. These patients probably needed rectal resection [29].

Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

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