Effect of various mediums on water bead expansion in acidic and neutral solutions

Ingestions of expanding water beads by young children may result in proximal small bowel obstruction and even death. We sought to explain a mechanism for these unusual obstructions and explore potential interventions.

A single brand of polyacrylamide expanding water beads were placed in a hydrochloric acid solution (pH 2.0) and water (pH 6.0) to simulate the stomach and duodenal environments. Six stomach and duodenal simulant samples were made and one in each group served as controls. An intervention was added to five samples including polyethylene glycol, orange juice, whole milk, vegetable oil, or 25 g of activated charcoal. Three water beads were added to each beaker and measurements taken from 0 h to 120 h. In a second study, seven water beads were placed in pH 2.0 solution for 3 h, then transferred to pH 6.0 solution for 9 h to simulate movement from the stomach to duodenum.

The largest water bead in the gastric simulant control group expanded to 14.6 mm at 6 h and to 19.5 mm with whole milk added. The largest water bead in the duodenal simulant-only group expanded to 33.2 mm in 6 h. The beads in orange juice and milk-containing groups in duodenal simulant expanded to 18.6 mm and 20.4 mm in 6 h, respectively. Results from the second study showed the mean rate of water bead expansion was greater in duodenal simulant than gastric simulant at 0.96 mm/h and 2.47 mm/h, respectively (P <0.05).

Water bead expansion was less in gastric simulant compared to beads in duodenal simulant. The addition of either whole milk or orange juice in the duodenal simulant groups blunted bead expansion.

The development of proximal small bowel obstruction from expanding water beads may be explained by changes in the acid-base environment of the gastrointestinal tract.