A practical guide for the diagnosis of primary enteric nervous system disorders.

OBJECTIVE: Primary gastrointestinal neuropathies are a heterogeneous group of enteric nervous system (ENS) disorders that continue to cause difficulties in diagnosis and histological interpretation. Recently, an international working group published guidelines for histological techniques and reporting, along with a classification of gastrointestinal neuromuscular pathology. The aim of this article was to review and summarize the key issues for pediatric gastroenterologists on the diagnostic workup of congenital ENS disorders. In addition, we provide further commentary on the continuing controversies in the field. RESULTS: Although the diagnostic criteria for Hirschsprung disease are well established, those for other forms of dysganglionosis remain ill-defined. Appropriate tissue sampling, handling, and expert interpretation are crucial to maximize diagnostic accuracy and reduce interobserver variability. The absence of validated age-related normal values for neuronal density, along with the lack of correlation between clinical and histological findings, result in significant diagnostic uncertainties while diagnosing quantitative aberrations such as hypoganglionosis or ultrashort Hirschsprung disease. Intestinal neuronal dysplasia remains a histological description of unclear significance. CONCLUSIONS: The evaluation of cellular quantitative or qualitative abnormalities of the ENS for clinical diagnosis remains complex. Such analysis should be carried out in laboratories that have the necessary expertise and access to their own validated reference values.

A recessive contiguous gene deletion causing infantile hyperinsulinism, enteropathy and deafness identifies the Usher type 1C gene.

Usher syndrome type 1 describes the association of profound, congenital sensorineural deafness, vestibular hypofunction and childhood onset retinitis pigmentosa. It is an autosomal recessive condition and is subdivided on the basis of linkage analysis into types 1A through 1E. Usher type 1C maps to the region containing the genes ABCC8 and KCNJ11 (encoding components of ATP-sensitive K + (KATP) channels), which may be mutated in patients with hyperinsulinism. We identified three individuals from two consanguineous families with severe hyperinsulinism, profound congenital sensorineural deafness, enteropathy and renal tubular dysfunction. The molecular basis of the disorder is a homozygous 122-kb deletion of 11p14-15, which includes part of ABCC8 and overlaps with the locus for Usher syndrome type 1C and DFNB18. The centromeric boundary of this deletion includes part of a gene shown to be mutated in families with type 1C Usher syndrome, and is hence assigned the name USH1C. The pattern of expression of the USH1C protein is consistent with the clinical features exhibited by individuals with the contiguous gene deletion and with isolated Usher type 1C.

Loss of functional KATP channels in pancreatic beta-cells causes persistent hyperinsulinemic hypoglycemia of infancy.

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a disorder of childhood associated with inappropriate hypersecretion of insulin by the pancreas. The pathogenesis of the condition has hitherto remained controversial. We show here that insulin-secreting cells from a homogeneous group of five infants with PHHI lack ATP-sensitive K+ channel (KATP) activity. As a consequence, PHHI beta-cells are spontaneously electrically active with high basal cytosolic Ca2+ concentrations due to Ca2+ influx. Our findings define the pathogenesis of this disease as a novel K+ channel disorder.

Therapy for persistent hyperinsulinemic hypoglycemia of infancy. Understanding the responsiveness of beta cells to diazoxide and somatostatin.

The neonatal disorder persistent hyperinsulinemic hypoglycemia of infancy (PHHI) arises as the result of mutations in the subunits that form the ATP-sensitive potassium (KATP) channel in pancreatic beta cells, leading to insulin hypersecretion. Diazoxide (a specific KATP channel agonist in normal beta cells) and somatostatin (octreotide) are the mainstay of medical treatment for the condition. To investigate the mechanism of action of these agents in PHHI beta cells that lack KATP currents, we applied patch clamp techniques to insulin-secreting cells isolated from seven patients with PHHI. Five patients showed favorable responses to medical therapy, and two were refractory. Our data reveal, in drug-responsive patients, that a novel ion channel is modulated by diazoxide and somatostatin, leading to termination of the spontaneous electrical events that underlie insulin hypersecretion. The drug-resistant patients, both of whom carried a mutation in one of the genes that encode KATP channel subunits, also lacked this novel K+ channel. There were no effects of diazoxide and somatostatin on beta cell function in vitro. These findings elucidate for the first time the mechanisms of action of diazoxide and somatostatin in infants with PHHI in whom KATP channels are absent, and provide a rationale for development of new therapeutic opportunities by K+ channel manipulation in PHHI treatment.

Cloning of HOXD1 from unfertilised human oocytes and expression analyses during murine oogenesis and embryogenesis.

We describe the cloning of HOXD1 in human unfertilised oocytes and detailed expression analyses during mouse oogenesis and embryogenesis. The cDNA of 1991bp has an open reading frame of 987bp encoding a protein of 329 amino acids. A comparison of the amino acid sequence with the mouse homologue revealed an overall homology of 85.5% with 99% identity within the homeodomain. Expression was detected in unfertilised human oocytes and 2-, 4-, 8-cell and blastocyst stage embryos. Expression analyses in mature mouse ovaries, early embryos and isolated gut revealed expression in the oocytes of the primary and secondary ovarian follicles, and in embryonal mesodermal derivatives such as dermatomes, urogenital tubercle, tail bud, kidney, ovaries, testes and enteric mesoderm adjacent to the caecum where expression was up-regulated in vitro in response to increasing doses of retinoic acid. Our observations indicate a possible role for HOXD1/Hoxd1 in the ovarian oocytes and the establishment of mesodermal derivatives during embryogenesis.

Effects of chronic vitamin E deficiency on vascular function--a study of sympathetic nerves, smooth muscle and endothelium of the mesenteric arterial bed of the rat.

1. Male rats were deprived as weanlings of dietary vitamin E for 2, 4, 6, 10 and 12 months. Mesenteric arterial beds from these rats and from age-matched controls were isolated and perfused with Krebs solution at a constant flow rate (5 ml min-1). The function of perivascular sympathetic nerves, smooth muscle and endothelium was assessed. 2. At 12 months vitamin E deficient rats exhibited the characteristic symptoms of vitamin E deficiency, namely poor coat condition, muscle wasting, kyphoscoliosis and impaired gait. In the isolated mesenteric arterial bed electrical field stimulation (EFS) of perivascular nerves (4-32 Hz, 90 V, 1 ms, for 30 s) elicited frequency-dependent vasoconstrictor responses which were unaffected by vitamin E deficiency except at 12 months, at which age responses were significantly greater than those of the controls at 24 and 32 Hz (P < 0.01). 3. Exogenous noradrenaline (NA; 0.15-500 nmol) elicited dose-dependent vasoconstriction which was similar in vitamin E-deficient and control preparations at all ages. Potassium chloride (0.15 mmol) also produced similar vasoconstrictor responses in vitamin E-deficient and control preparations at each age. 4. Tone of the preparations was raised by continuous perfusion with methoxamine (4-70 microM), producing similar increases in perfusion pressure in vitamin E-deficient and control preparations at each age. Endothelium-dependent dose-dependent vasodilatation to adenosine 5'-triphosphate was significantly impaired in mesenteric arterial beds from 12 month-old vitamin E-deficient rats compared with the controls (P < 0.05). Relaxation to acetylcholine was not significantly different at any age. 5. Endothelium-independent vasodilatation to sodium nitroprusside was similar in vitamin E-deficient rats and age-matched controls. 6. These results suggest that long term (12 months) deprivation of dietary vitamin E may impair endothelial function in mesenteric arteries of the rat. Sympathetic perivascular nerve constrictor function was increased at 12 months. There were no functionally expressed changes in the vascular smooth muscle, which appears to be more resilient to the effects of oxidative stress in vitamin E deficiency.

Effects of chronic vitamin E deficiency and a high polyunsaturated fatty acid diet on rat mesenteric arterial function.

1. Male rats were deprived as weanlings of dietary vitamin E and fed on a high polyunsaturated fatty acid (PUFA) diet for 6 months. Rats fed on a high PUFA or on an untreated diet served as controls. Mesenteric arterial beds were isolated and perfused at a constant flow rate (5 ml min-1) and the function of sympathetic nerves, smooth muscle and endothelium was assessed. 2. Electrical field stimulation (4-32 Hz, 90 V, 1 ms, for 30 s) elicited frequency-dependent vasoconstriction of the mesenteric arterial preparations. Response curves were similar between untreated control and PUFA-fed control groups. Maximum vasoconstrictor responses (at 24 and 32 Hz) were significantly attenuated in rats deprived of vitamin E and on a high PUFA diet compared to the PUFA-fed controls (P < 0.05). 3. Exogenous noradrenaline (NA; 0.15-500 nmol) elicited dose-dependent constriction of the mesenteric arterial beds. Preparations from rats fed on a high PUFA diet elicited significantly smaller responses compared to the control group. There was no significant difference in constrictor responses of PUFA rats deprived of vitamin E compared to the PUFA controls. Vasoconstrictor responses to doses of adenosine 5'-triphosphate (ATP) (5-5000 nmol) were significantly impaired in vitamin E-deficiency with a high PUFA diet compared to a high PUFA diet alone (P < < 0.001). Constrictor responses to potassium chloride (0.15 mmol) were significantly impaired in vitamin E-deficient PUFA rats compared to the PUFA-fed control group (P < 0.05). 4. Vasodilator responses were assessed in preparations in which tone was raised by continuous perfusion with methoxamine (4-25 microM). Mesenteric arterial beds from PUFA-fed rats deprived of vitamin E acquired significantly less tone, 59.8 +/- 4.6 mmHg (n = 7), than PUFA-fed controls 116.9 +/- 7.6 mmHg (n = 7) (P < 0.001) and were refractory to further increases in tone with further additions of methoxamine. Methoxamine-induced tone of PUFA-fed controls was greater than in P that in the untreated controls (83.9 +/- 7.4 mmHg; n = 5) (P < 0.05). Responses to the endothelium-dependent vasodilators acetylcholine (ACh) and ATP were significantly reduced in preparations from rats fed on the vitamin E-deficient high-PUFA diet compared to PUFA controls. Vasodilator responses to ACh were greater in PUFA controls than in untreated controls and this reached statistical significance at 5 nmol ACh. 5. Vasodilator responses to sodium nitroprusside, which acts directly on the vascular smooth muscle, were similar in untreated control and PUFA control groups. Responses were significantly attenuated in vitamin E-deficient PUFA rats compared to the PUFA control group (P < < 0.001). 6. These results indicate that a combination of a high PUFA diet and vitamin E deficiency impairs mesenteric arterial function at the level of the vascular smooth muscle. A high PUFA diet alone attenuates responses to NA and augments endothelium-dependent vasodilation. The detrimental effects of loss of antioxidant activity due to vitamin E-deficiency on vascular function may be exacerbated by a high PUFA diet.

LFA-1 and ICAM-1 molecule expression in jejunal mucosa from children with autoimmune enteropathy.

The expression of adhesion molecules by cells of the small intestinal mucosa was compared in gut biopsies from children with autoimmune small intestinal enteropathy and normal controls and related to HLA-DR expression by the same tissue. Jejunal biopsies were stained by IFL with monoclonal antibodies to LFA-1 (TS1/22 and CD11a/25.3.1) and ICAM-1 (RR1/1 and 84H10) molecules. LFA-1 and ICAM-1 positive cells were observed in the lamina propria in all cases and the counts were increased in autoimmune enteropathy compared with controls. In addition, in 4 of 7 cases of autoimmune enteropathy crypt enterocytes were positives for ICAM-1 when stained with RR1/1 and 3 of the 4 were also positive for LFA-1 when stained with both LFA-1 reagents. We speculate on the role of adhesion molecule expression in autoimmune enteropathy.

The influence of Hox genes and three intercellular signalling pathways on enteric neuromuscular development.

Normal intestinal motility requires orderly development of the complex nerve plexuses and smooth muscular layers in the gut wall. Organization of these structures results, in part, from cell autonomous programmes directed by transcription factors, which orchestrate appropriate temporal and spatial expression of specific target genes. Hox proteins appear to function in combination to dictate regional codes that establish major structural landmarks in the gut such as sphincters and muscle layers. These codes are translated in part by intercellular signals, which allow populations of cells in the embryonic gut wall to alter the developmental fate of their neighbours. Some of the best characterized intercellular signalling pathways involved in enteric neurodevelopment are mediated by GDNF/GFRa1/RET, EDN3/ENDRB, and NETRINS/DCC. These signals affect enteric neural precursors as they colonize the gut, and perturbations of these molecules are associated with various types of intestinal neuropathology.

The histological appearances of Nissen-type fundoplication in the ferret.

Nissen fundoplication is of proven effectiveness in the surgical control of gastro-oesophageal reflux. However, our understanding of the effects of fundoplication upon foregut physiology is incomplete and post-operative symptoms are often poorly understood. This experimental study aimed systematically to characterize the tissue response to fundoplication in an animal model, to improve understanding of the effects of anti-reflux surgery upon foregut physiology. Nissen-type fundoplication was performed in the ferret, and the tissue response at 3 months examined histologically. Sham-operated animals that underwent laparotomy but no dissection or wrap, acted as controls. In fundoplicated animals, serosal fibrosis was observed in the gut wall, with patchy replacement of muscle by fibrous tissue. The ventral and dorsal vagal nerve trunks were identified intact within the wrap. In cases where the wrap had spontaneously disrupted, fibrosis was more extensive and there was evidence of nerve damage. This is the first systematic description of the histopathological response to Nissen fundoplication. In the intact wrap, the vagal trunks appear spared, but there is fibrosis in the serosa, extending into the muscularis of the distal oesophagus and region of the cardia. These findings are discussed in relation to the effects of Nissen fundoplication upon gastric physiology and postoperative symptoms.

Nissen-type fundoplication and its effects on the emetic reflex and gastric motility in the ferret.

Recurrent vomiting with failure to thrive is a common problem in neurologically impaired children. Many undergo fundoplication to control the underlying gastro-oesophageal reflux. The results of surgery are not always satisfactory and post-operative retching may be a major problem - a symptom indicative of activation of the emetic reflex. An animal model of antireflux surgery has been developed and used to investigate the effects of such surgery upon the emetic reflex and vagal influences on gastric motility. Following surgery, animals responded to a previously subemetic dose of a centrally acting opiate receptor agonist (loperamide), suggesting that fundoplication may sensitize the emetic reflex. A gastric vago-vagal reflex (tonic inhibition of corpus tone) and responses to direct stimulation of vagal motor efferents (both cholinergic and nonadrenergic noncholinergic responses) were not significantly affected by antireflux surgery. Mechanisms by which neural damage may sensitize the emetic reflex are discussed, together with the possible clinical implications for the management of post-operative symptoms in neurologically impaired children.

Counting the cost: hospital versus home central venous catheter survival.

We compared catheter survival and sepsis rates in a tertiary paediatric gastroenterology centre with those at home in the same patients. We examined whether there were differences in the safety in the two locations, and estimated the financial and opportunity cost implications of any difference. We used survival analysis to analyse differences. Surgical records were audited to determine venous access workload, and to estimate cost implications. Twenty patients with chronic intestinal failure but stable parenteral nutrition requirements, ranging from 0.04-15.83 years of age were studied. The duration of line survival and sepsis-free intervals and rates of re-operation for venous access were determined to estimate morbidity and costs. The study encompassed 28 patient-years in hospital and 48 patient-years at home. There was a significant reduction in the rate of sepsis at home compared with hospital (Z = 4.30, P < 0.00001), and a similar improvement in line survival (Z = 4.36, P < 0.00001). Line insertions accounted for 21% of minor surgery in our hospital, one third being reinsertions. We conclude that central venous catheter sepsis rates are greatly improved at home. If home results could be achieved in the hospital setting, considerable cost savings would be made.

The development of colonic transport mechanisms in early life: evidence for reduced anion exchange.

An anion exchange mechanism exists in colonic mucosa whereby chloride is absorbed and bicarbonate secreted. Using an in vivo non-equilibrium dialysis method we investigated rectal electrolyte movement in preterm neonates and older children. Our results show that anion exchange is poorly developed in infancy and appears to be absent in premature neonates, and suggest that complete maturation of this mechanism is not present until the end of the first year of life. This may render the young infant, and more especially the preterm infant, more susceptible to chloride depletion.

Gastrointestinal motility disorders in children.

The present state of knowledge regarding human gastrointestinal motility is summarized in this article. Areas that are of particular interest in childhood are highlighted. The relationship of this knowledge to disease states is discussed and areas where it might practically be applied indicated.

Intestinal motility during ontogeny and intestinal pseudo-obstruction in children.

From the fragmentary studies performed to date of both functional obstruction and the ontogeny of intestinal motility, several conclusions can be drawn. The development of motor activity that is primarily dependent on neuronal activity, such as sucking, swallow-induced peristalsis of the esophagus, and cyclic fasting small intestinal motor activity, occurs according to a timetable that is similar in all species studies is gestationally dependent, but its timing during gestation is species specific. Postprandial events, including gastric emptying and continuous postprandial motor activity in the small intestine, in contrast seem to be dependent on the nature of the humoral response to food, provided that the musculature of the gut and enteric nerves are able to respond to it. Although these activities are primarily determined by neuronal development, there is a limited amount of information to suggest that their appearance may be pharmacologically manipulated to advance the timing and rate of development. It is commonplace now for cortisol to be used to induce the production of surfactant in mothers of babies who are at risk of hyaline membrane disease. A limited amount of information suggests that cortisol may have similar effects in inducing duodenal motor activity, and, thus, it may be possible to advance the timing and rate of development of intestinal motility in the very preterm infant by its use. There are, however, no studies to date to prove this. It is now clear that intestinal pseudo-obstruction is a heterogeneous disorder associated with various pathologies, some of which are intrinsic to the gut, whereas others are multisystem diseases affecting the intestine. In addition, although intestinal pseudo-obstruction was originally thought to involve the small intestine, it is now realized that it may not affect only one region, as in achalasia or Hirschsprung's disease, but also it may present diffusely throughout the gut. The motility changes caused by the disease processes are nonspecific, although neuropathic and myopathic changes are distinct and due to the destruction of the particular motor control system involved. The mechanisms of the ontogenic and disease changes described in this article are, however, almost totally unexplored. The recent upsurge of interest in the area with the development of advances in cellular and molecular biology, at least the early events, is now beginning to unravel. At the present time, the stage is being set for probably the most exciting phase of understanding of the nature of the ontogeny of intestinal motor activity, which the author expects will enable us to manipulate motor activity in normal preterm infants and, it is hoped, congenital dysmotile states.

Acquired motility disorders in childhood.

Acquired motility disorders in childhood cause a number of gastrointestinal symptoms - principally, recurrent vomiting, abdominal pain and distension, constipation and loose stools. Gastrointestinal motility disorders result from disturbances of the control mechanisms of gut motor activity, which may be produced by organic disease involving enteric nerves and muscle, perturbation of the humoral environment of the nerves and muscle, and altered central nervous system input. In children, both congenital and acquired disease processes may produce these pathogenetic mechanisms, resulting in syndromes that vary in severity from chronic intestinal pseudo-obstruction to the irritable bowel syndrome.

The absorptive function of colonic aganglionic intestine: are the Duhamel and Martin procedures rational?

The Lester Martin modification of the Duhamel procedure is an accepted definitive operation for long-segment Hirschsprung's disease, in which considerable use is made of aganglionic bowel. Whether the aganglionic segment contributes to fluid and electrolyte reabsorption is not known. We have modified the technique of nonequilibrium dialysis of the rectum in order to obtain simultaneous measurements of electrolyte transport and transmural potential difference (PD) in 9 infants with Hirschsprung's disease (HD), prior to operation. Six age-matched infants were studied as controls. In the control group Na+ was absorbed electrogenically while K+ secretion was passive and greater than HCO3- secretion. In HD, both NA+ absorption and Cl- absorption were greater than in control children, with Cl- absorption exceeding Na+ absorption. PD was higher in HD infants than in controls, with an associated increase in K+ secretion. HCO3- secretion accounted for the difference between Na+ and Cl- absorption. These data clearly show that aganglionic colon transports electrolytes, and that in the Lester Martin modification of the Duhamel procedure the refashioned colorectum contributes to overall colonic salvage of electrolytes.

Brown bowel syndrome: a late complication of intestinal atresia.

Two children, aged 11 years, who originally had jejunal atresia corrected in the neonatal period, developed massive dilatation of the proximal small intestine. This resulted in circular muscular hypertrophy with lipofuscin deposits giving the typical appearance of "brown bowel." The condition was associated with malnutrition and vitamin E deficiency. Because of relatively short bowel, the condition was treated by limited resection and extensive tapering of the dilated segment, end-to-end reanastomosis, vitamin E supplementation, and intensive nutritional support.

Nissen fundoplication may induce gastric myoelectrical disturbance in children.

BACKGROUND: Recurrent vomiting with failure to thrive is a common problem in neurologically impaired children. Many undergo fundoplication to control the underlying gastroesophageal reflux, but the results of surgery are not always satisfactory, and postoperative retching may be a major problem. Retching is part of the emetic reflex and is associated with nausea, which is itself associated with disturbed gastric electrical control activity, resulting in a gastric dysrhythmia. METHODS: By recording gastric electrical control activity before and after Nissen fundoplication using the noninvasive technique of surface electrogastrography, the authors have shown that (1) Neurologically impaired children with gastroesophageal reflux more commonly have a preexisting gastric dysrhythmia (65% neurologically impaired v 20% neurologically normal children with gastroesophageal reflux, P<.05), (2) Children who retch preoperatively are three times more likely to retch postoperatively, and (3) 25% of neurologically impaired children may start to retch postoperatively for the first time. CONCLUSION: The authors propose that in neurologically impaired children, loss of central inhibitory mechanisms may result in inappropriate activation of the emetic reflex, which may be heightened by antireflux surgery.

Retching and vomiting in neurologically impaired children after fundoplication: predictive preoperative factors.

BACKGROUND/PURPOSE: In neurologically impaired children, retching and recurrent vomiting are common after Nissen fundoplication. The aim of this study was to identify whether there are preoperative factors that predict their occurrence. METHODS: Twenty neurologically impaired children (8 boys, 12 girls; age range, 3 months to 8 years) were studied prospectively by taking a detailed history of behaviors and symptoms associated with feeding before and after Nissen fundoplication for gastroesophageal reflux. RESULTS: Preoperatively, children could be classified into 2 groups. Children in group A had symptoms suggestive of only gastroesophageal reflux (effortless "vomiting" or regurgitation), whereas children in group B exhibited one or more features associated with activation of the emetic reflex (pallor, sweating, retching, forceful vomiting). Postoperatively 0 of 8 in group A retched compared with 8 of 12 in group B (P <.005, Fishers Exact test). CONCLUSIONS: Children at high risk of retching, and ultimately vomiting, after antireflux surgery may be identified clinically preoperatively. They have symptoms that are specifically caused by activation of the emetic reflex rather than to gastroesophageal reflux. In these cases, antireflux surgery could be considered inappropriate and hence be avoided.