Molecular viscosity and diffusivity effects in transitional and shock-driven mixing flows.

This paper investigates the importance of molecular viscosity and diffusivity for the prediction of transitional and shock-driven mixing flows featuring high and low Reynolds and Mach number regions. Two representative problems are computed with implicit large-eddy simulations using the inviscid Euler equations (EE) and viscous Navier-Stokes equations (NSE): the Taylor-Green vortex at Reynolds number Re=3000 and initial Mach number Ma=0.28, and an air-SF_{6}-air gas curtain subjected to two shock waves at Ma=1.2. The primary focus is on differences between NSE and EE predictions due to viscous effects. The outcome of the paper illustrates the advantages of utilizing NSE. In contrast to the EE, where the effective viscosity decreases upon grid refinement, NSE predictions can be assessed for simulations of flows with transition to turbulence at prescribed constant Re. The NSE can achieve better agreement between solutions and reference data, and the results converge upon grid refinement. On the other hand, the EE predictions do not converge with grid refinement, and can only exhibit similarities with the NSE results at coarse grid resolutions. We also investigate the effect of viscous effects on the dynamics of the coherent and turbulent fields, as well as on the mechanisms contributing to the production and diffusion of vorticity. The results show that nominally inviscid calculations can exhibit significantly varying flow dynamics driven by changing effective resolution-dependent Reynolds number, and highlight the role of viscous processes affecting the vorticity field. These tendencies become more pronounced upon grid refinement. The discussion of the results concludes with the assessment of the computational cost of inviscid and viscous computations.

Pyloric balloon dilation for delayed gastric emptying in children.

Delayed gastric emptying may manifest with symptoms of epigastric pain, early satiety and delayed vomiting, and at times may be associated with failure to thrive. These symptoms and signs may improve following surgical pyloroplasty. To determine whether pyloric balloon dilation (PBD) is an effective therapy for children with these symptoms, hospital records of all children who underwent endoscopic PBD between October 1991 and March 1994 at British Columbia's Children's Hospital were reviewed. Excluded were children with chromosomal abnormalities, neurological disorders and erosive esophagitis. Through-the-scope balloons of diameter 15 or 18 mm were positioned in the pyloric channel and inflated with air to 2334 or 1815 mmHg respectively, for 2 min. Nineteen children with a mean age of 3.75 years (range eight months to 10 years) who presented with symptoms for more than three months (mean 11 months) were identified. Eleven children presented with failure to thrive, 14 with delayed vomiting and 10 with early satiety. Results of gastric emptying tests at 90 min ranged from 8% to 75% (mean 32%). The pylorus was difficult to intubate in 11 of 19 children, and in two the pylorus could not be passed before PBD. No complications were experienced with PBD. Thirteen children had complete resolution of symptoms, and five had transient improvement lasting four to eight weeks after PBD with subsequent complete resolution of symptoms following surgical pyloroplasty. One child continued to have mild symptoms after PBD but did not have further treatment. This study suggests that PBD is a safe and effective therapeutic option in children with symptoms and signs associated with delayed gastric emptying.

Effect of long-term omeprazole treatment on antral G and D cells in children.

BACKGROUND: Long-term omeprazole therapy is associated with hypergastrinemia. In the antrum, gastrin secretion from G cells is inhibited in a paracrine manner by somatostatin secreted from D cells. Omeprazole may alter the ratio of G to D cells; however, there are limited data concerning such an effect in humans and none in children. The authors studied the effect of long-term omeprazole therapy on antral G- and D-cell numbers in children. METHODS: Six children received omeprazole for 4 to 7 years for erosive reflux esophagitis. Endoscopic antral biopsy specimens obtained at baseline and at 1, 4, and 7 years of omeprazole administration were immunostained to assess G and D cell numbers per antral gland. The G- and D-cell numbers were also assessed in an age-matched control group consisting of 24 healthy children from six different age groups. RESULTS: The mean G-cell number per unit area showed a significant increase at 4 years (85 +/- 5.7 years) and at 7 years (89 +/- 6.8 years) on omeprazole compared with baseline (56 +/- 4.8 years) ( P < 0.01). D-cell numbers did not change. The ratio of G to D cells increased progressively, and the change from baseline was significant at 7 years taking omeprazole ( P < 0.02). In the control group, G- and D-cell numbers did not differ significantly within the six age groups. CONCLUSIONS: Long-term omeprazole therapy is associated with a significant increase in G-cell numbers and in the ratio of G to D cells in children. These changes reflect the effect of omeprazole because there was no change in these parameters in the age-matched control group.

High prevalence of celiac disease in patients with type 1 diabetes detected by antibodies to endomysium and tissue transglutaminase.

OBJECTIVE: To establish the prevalence of celiac disease (CD) in children with type 1 diabetes in British Columbia. PATIENTS AND METHODS: Two hundred thirty-three children with type 1 diabetes were prospectively screened for CD using blind testing with the current 'gold standard', immunoglobulin A endomysium antibody (EmA), and the novel immunoglobulin A tissue transglutaminase (tTG) antibody. Those children with positive results were offered small bowel biopsy; a gluten-free diet was recommended if CD was confirmed. RESULTS: Nineteen children were positive for EmA and had an elevated tTG level. One patient from this group was already known to have CD, and the other 18 patients consented to biopsy. One biopsy was normal, three biopsies demonstrated elevated intraepithelial lymphocyte counts with normal morphology and 14 biopsies had morphological changes consistent with CD. Growth parameters were normal in all patients, and nine of 19 children who were positive for EmA were asymptomatic. Seven patients had mild elevation of tTG levels alone. Two children from this latter group had normal biopsies, and five declined biopsy. CONCLUSIONS: At least 14 new cases of CD were detected in addition to four known cases, yielding an overall biopsy-confirmed prevalence of CD of 7.7% (18 of 233). The present study confirms that CD is as prevalent in the pediatric type 1 diabetic population in British Columbia as it is in Europe. Serological screening of these children is important because many children have no symptoms or signs suggestive of CD. This study suggests that tTG serology may also be useful in monitoring response and compliance with a gluten-free diet.

Omeprazole maintenance therapy for gastroesophageal reflux disease after failure of fundoplication.

BACKGROUND: Recurrence of gastroesophageal reflux (GER) in children after failed fundoplication poses a therapeutic challenge. The authors report the experience with long-term omeprazole for children with severe GER after failed fundoplication. METHODS: The authors reviewed the charts of all children who were treated with omeprazole for GER subsequent to failed fundoplication from 1990 to 1999. All underwent endoscopic and clinical assessment of the treatment at baseline, at 3-5 months, at 6-9 months, and annually. RESULTS: Eighteen children presented with GER, after a total of 27 fundoplications. Ten had corrected esophageal atresia, 6 had neurologica impairment, and 2 had hiatal hernia. The mean age of presentation of children with recurrence of GER was 7.8 years, and symptoms of GER occurred 4.9 years (range, 0.6-13) after last fundoplication. Fifteen patients had a mean follow-up of 4.4 years for omeprazole. Ten patients had grade III/IV esophagitis and 5 had grade II esophagitis at presentation after fundoplication. Marked improvement was noted in symptoms of GER and severity of esophagitis while taking omeprazole. Remission of esophagitis was maintained while the patient was taking omeprazole and none had further surgery. There was no recurrence of peptic strictures in eight of nine children on omeprazole, after initial esophageal dilatations. Except for benign gastric polyps in three patients, no clinical adverse effects were observed. CONCLUSIONS: Omeprazole is an effective long-term drug for gastroesophageal reflux disease after failed fundoplication in children. Omeprazole was well-tolerated by all children and should be tried before subsequent surgical intervention.

Increased prevalence of celiac disease in girls with Turner syndrome detected using antibodies to endomysium and tissue transglutaminase.

OBJECTIVE: To establish the prevalence of celiac disease (CD) in girls with Turner syndrome (TS) in British Columbia. METHODS: Forty-five girls with TS were prospectively screened for CD using blinded testing with the current 'gold standard' - immunoglobulin A (IgA) endomysium antibody (EmA) and the novel IgA tissue transglutaminase antibody (tTG). Those with positive results were offered small bowel biopsies, and a gluten-free diet was recommended if CD was confirmed. RESULTS: One asymptomatic prepubertal East Indian girl was positive for EmA, had an elevated tTG concentration of 560 U/mL and histological evidence of CD. Seven girls were negative for EmA but had elevated tTG concentrations (175 to 250 U/mL); five were white, one was Asian and one was East Indian. Small bowel biopsies were performed on three girls, and the histologies were normal. The remaining four patients declined biopsy. CONCLUSIONS: One girl with TS was identified with CD from 45 screened, giving an overall biopsy-confirmed prevalence of 2.2%. This study confirms previous observations placing girls with TS at higher risk for CD and suggests a similar high prevalence in British Columbia.

Recombinant human erythropoietin for treatment of anemia of chronic disease in children with Crohn's disease.

We evaluated the efficacy and safety of and compliance with rH-EPO (150 U/kg three times a week subcutaneously for up to 12 weeks) for treatment of anemia in childhood Crohn's disease (n = 4). The mean hemoglobin level before rH-EPO therapy was 109 gm/L (10.9 gm/dl) (range, 103 to 115 gm/L). The mean hemoglobin level in the three compliant children increased to 138 gm/L (13.8 gm/dl) after treatment. Response time for the correction of anemia ranged from 6 to 12 weeks (mean, 9.5 weeks). Resolution of symptoms of lethargy, poor appetite, and irritability occurred with correction of the anemia. The only adverse effect observed was transient local pain at the injection site.

Effective 2-wk therapy for Helicobacter pylori disease in children.

UNLABELLED: Successful eradication of Helicobacter pylori infection in children has required long treatment regimens that may result in noncompliance with failure to eradicate this organism. Despite full compliance with shorter therapeutic regimens, such as amoxycillin and omeprazole for 2 wk, the H. pylori eradication rate is poor in children. OBJECTIVES: The aim of this study was to evaluate the efficacy of, and compliance with, a 2-wk treatment with metronidazole, omeprazole, and clarithromycin in eradicating H. pylori disease in children. METHODS: Over a 15-month period, children diagnosed to be H. pylori positive by Steiner's stain of gastric antral biopsy specimens were treated with metronidazole, omeprazole, and clarithromycin. Follow-up upper GI endoscopy was performed 6-8 wk after completion of therapy. RESULTS: Of 15 patients with H. pylori-positive antral gastritis, 11 had duodenal ulcer disease; three patients with severe abdominal pain and one with vomiting had H. pylori gastritis only. H. pylori eradication was seen in 11 of 11 (100%) patients with duodenal ulcer disease and in three of four (75%) with gastritis only; the overall success rate was 93%. Duodenal ulcer disease healed when H. pylori was eradicated in all but one patient, who at presentation had a penetrating ulcer with a duodenobiliary fistula. Fourteen of 15 patients (93%) were fully compliant, and no adverse reactions were reported. CONCLUSIONS: Two weeks of therapy with metronidazole, omeprazole, and clarithromycin is effective H. pylori therapy in children. It is well tolerated, and full compliance can be achieved.

Cyclosporine and 6-mercaptopurine for active, refractory Crohn's colitis in children.

OBJECTIVES: This prospective, open trial of treatment was conducted to determine whether cyclosporine A (CSA) is effective in inducing remission in children with severe, active Crohn's colitis refractory to other medical treatment and if remission may be maintained by 6-mercaptopurine (6-MP) and 5-aminosalicylic acid (5-ASA) after discontinuing CSA. METHODS: Ten children (five males, five females), ages 1.2-16 yr (mean 11), all had failed to respond to 4 wk of treatment with i.v. methylprednisolone and total parenteral nutrition/elemental diet; three were already receiving 6-mercaptopurine. CSA was initially given as a twice daily i.v. dosage and was switched to oral CSA when a clinical response was observed. At the same time, corticosteroids were switched to the oral route and tapered over the next 3 months. Patients were grouped by treatment outcome. "Responders" were those who achieved remission with i.v. CSA therapy, "relapsers" were those who achieved remission with i.v. CSA but relapsed later, and nonresponders had not achieved remission after 4 wk of i.v. CSA. Responders were given 6-MP with intent to discontinue CSA after 6 months and maintain remission by 6-MP and 5-ASA. RESULTS: There were seven responders to CSA. For all patients, the Pediatric Crohn's Disease Activity Index (PCDAI) (score range 0-100) had a mean value of 55 (range 40-65) just before treatment; PCDAI improved to a mean of 19 (range 5-42.5) after 2 wk of CSA therapy. Four of the seven responders discontinued CSA after 6 months and remain well on 6-MP and 5ASA alone for 22, 13, 8, and 3 months. One patient had massive GI bleeding (from active Crohn's colitis), which stopped within 48 h of CSA treatment. There were three relapsers (at 2-6 months of CSA), and three were nonresponders. Three patients who were already receiving 6-MP before CSA therapy either did not respond to CSA or relapsed while receiving it. The six nonresponders and relapsers required surgical resection. Transient side effects included hypertension responding to nifedipine in one child and hirsutism and tremors in another. CONCLUSIONS: We conclude that CSA offers a good remission rate for children with severe Crohn's colitis failing other medical treatment, although relapse was common especially if the child was already on 6-MP. In addition, CSA may offer "temporizing" therapy in severe, active Crohn's colitis; this may allow surgery to be performed electively, with time for psychosocial and nutritional preparation before surgery.

Prolonged use of gastrostomy for enteral hyperalimentation in children with Crohn's disease.

OBJECTIVES: To evaluate the safety of gastrostomy tube (G-tube) placement in children with Crohn's disease and the efficacy of prolonged enteral hyperalimentation in children with growth failure complicating Crohn's disease. METHODS: Twenty children with Crohn's disease and growth failure were offered enteral hyperalimentation via nasogastric tube (NG-tube) for treatment of growth arrest, with follow-up for complications, compliance, and response to nutritional support. The use of a G-tube was offered to children who refused to use the NG-tube. Medical and surgical management were provided as dictated by the disease activity. RESULTS: Thirteen children were started on NG-tube feeds, and five were started on G-tube feeds after refusal to use an NG-tube at the outset. Two children required surgery at the time of diagnosis and had a G-tube placed during the operation. Nine of 13 children found the use of an NG-tube too disruptive and were later changed to a percutaneous endoscopic gastrostomy (PEG) or surgically-placed G-tube. A total of 16 children had a percutaneous endoscopic gastrostomy (eight children) or a surgically-placed G-tube (eight children) for 6-29 months. Two of those children had endoscopic evidence of gastroduodenal Crohn's disease, and six had microscopic patchy chronic gastritis. Minor complications occurred in five of the 16, including external leakage, button dislodgement, local pain, and local wound infection. At this time, the G-tube has been removed from 13 children, 12 of whom had prompt and complete healing of the G-tube site and one of whom had a small gastrocutaneous fistula that required suture for successful closure. Poor compliance with G-tube feeds was observed in four of 16 children. During the period of nutritional support, there was resumption of normal growth rates for all; in addition, eight of 16 had catch-up growth. CONCLUSION: Nutritional therapy is important in the management of children with growth failure due to Crohn's disease, though it may not be the only factor affecting growth. G-tubes are safe and well tolerated by children with Crohn's disease and should be offered to those children who do not tolerate prolonged use of an NG-tube.