A245 DETERMINING THE PREVALENCE OF DELAYED GASTRIC EMPTYING IN PEDIATRIC PATIENTS WITH CONSTIPATION USING NUCLEAR SCINTIGRAPHY

Background

Gastrointestinal motility is coordinated by complex neurohormonal circuits existing between different segments of the gastrointestinal tract. It has been hypothesized that one of these pathways, the “cologastric brake,” acts as a negative feedback system to inhibit gastric motility when there is loading of stool within the colon in conditions such as constipation.

Aims

To assess gastric emptying in pediatric patients presenting with constipation using whole-gut nuclear scintigraphy. We hypothesize that children with constipation are likely to exhibit delayed gastric emptying due to neurohormonal pathways such as the cologastric brake.

Methods

A retrospective review of all patients under 18 years of age who underwent a whole-gut nuclear scintigraphy study for the work-up of constipation at The Hospital for Sick Children between January 2014 and May 2021 was completed. Demographic and clinical data at the time of presentation was summarized. The proportion of patients with delayed gastric emptying and delayed small and large bowel transit were calculated. Exploratory univariable analyses were performed to identify clinical predictors of delayed gastric emptying.

Results

This study identified 140 patients meeting inclusion criteria of whom 72 were male (51.4%), (meanage = 10.04 ± 4.79). The prevalence of patients with delayed gastric emptying was 61.9% (n = 86). Despite this, only 5.0% (n = 7) and 21.8% (n = 29) had delayed small and large bowel transit respectively. Children with delayed gastric emptying were significantly younger (meanage = 9.15 ± 4.60) than those with normal gastric emptying (meanage = 11.53 ± 4.79), p = .01. A chi-square test of independence showed that there was no significant relationship between use of a promotility agent and delayed gastric emptying ( p = .48). There was also no significant association between the presence of upper gastrointestinal symptoms and delayed gastric emptying ( p = .79).

Conclusions

We found that children with constipation have a high prevalence of delayed gastric emptying. However, only a small proportion of these patients have delayed bowel transit. This supports the idea that delayed gastric emptying in children with constipation is likely not due to intrinsic neuromuscular defects of the gut but rather, secondary to a neurohormonal “cologastric brake.” This is important information for clinicians as it suggests that a key step in managing delayed gastric emptying in this scenario is to treat patients’ constipation as opposed to initiating therapies, such as prokinetic agents, which attempt to directly improve gastric emptying.

Funding Agencies

None

Simulation of radionuclide atmospheric dispersion and dose assessment for inhabitants of Tehran province after a hypothetical accident of the Tehran Research Reactor

Radiological dose assessment is one of the main categories of safety assessment for nuclear reactors and facilities. The radiation risks to the public and to the environment that may arise from these facilities have to be assessed and, if necessary, controlled. The main objective of this paper is the assessment of radiation doses to residents of Tehran province after a hypothetical accident of the Tehran Research Reactor (TRR) including the determination of any protective actions that might be needed for the benefit of people's health. The concentration of radionuclides in air and deposited on the ground surface as a result of a hypothetical radionuclide release from the TRR, following a hypothetical accident scenario, have been calculated by the HYSPLIT computer code. Simulations were performed using selected source terms taken from the TRR Final Safety Analysis Report (FSAR). Meteorological data of the Air Resources Laboratory of the National Oceanic and Atmospheric Administration (NOAA) have been used in these calculations. The simulation results indicate that maximum annual total effective dose equivalent values for the residents of the Tehran province are less than the protective action dose limits. Thus, it is concluded that during this hypothetical accident in the TRR, required safety due to public radiation is achieved and the residents of Tehran province are safe under a TRR accident condition.

The value of 18F-FDG PET in pediatric patients with post-transplant lymphoproliferative disorder at initial diagnosis

PTLD is a serious complication of both solid organ and BMT. This study assessed whether (18) F-FDG PET, when added to CT scan, had additional value in the initial evaluation of PTLD in pediatric patients and whether PET/CT at baseline can reliably guide biopsy. This retrospective study evaluated 34 consecutive pediatric patients (14 female), aged 3.5-17.0 yr (mean age: 9.9 yr, s.d.: 4.9 yr), who had undergone (18) F-FDG PET/CT from May 2007 to December 2014 at initial diagnosis of PTLD following heart (n = 13), lung (n = 8), kidney (n = 4), liver (n = 3), liver and bowel (n = 3), and bone marrow (n = 3) transplantation. PTLD was diagnosed histopathologically in 33 patients and was based on clinical findings, elevated EBV, and imaging and follow-up results in one patient. On lesion-based analysis, (18) F-FDG PET showed more lesions than conventional CT scan (168 vs. 134), but CT revealed 22 lesions negative on PET. On per patient analysis, PET detected more lesions in 13 patients, CT identified more abnormalities in seven, and both showed the same number of lesions in 14. Adding (18) F-FDG PET to CT scans upstaged the disease in seven patients (20.5%). A combination of (18) F-FDG PET and CT was also useful in guiding biopsy, being positive in 36 of 39 samples (92.3%). These findings indicated that (18) F-FDG PET and CT are complementary at initial staging of pediatric PTLD and that (18) F-FDG PET/CT scanning can guide biopsies.

Tunneling transport in topological insulator normal metal/insulator/d-wave superconductor junctions

We investigate the tunneling conductance in a normal metal/insulator/d-wave superconductor (NM/I/d-wave SC) junction with a barrier of thickness d and with an arbitrary gate voltage V(0) applied across the barrier region, formed on the surface of a topological insulator, using the Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk (BTK) formalism. We find that the tunneling conductance as a function of both d and V(0) displays an oscillatory behavior whose amplitude decreases with increase of V(0). We also find that when the Andreev resonant condition is met, the tunneling conductance approaches a maximum value of 2G(0), independent of the gate voltage V(0).