Super-Absorbent Polymers (SAP) Ingestion

Foreign body ingestion is particularly common in children, especially those younger than 5 years old. Although the vast majority pass through the GI tract uneventfully; some will require endoscopic removal, and a few will necessitate surgical intervention due to bowel obstruction.

The Missouri Poison Center has recently received several calls concerning pediatric ingestion of Super-Absorbent Polymers (SAP). These are basically fragments of dry hydrogels that expand dramatically in size by absorbing liquid. SAPs have multiple applications in the home setting, including floral arrangements, gardening, disposable diapers, and as toys. They come in the form of granules, beads, and balls which vary in starting size from a coarse powder to marbles.

Once in contact with sufficient liquid, the small dry fragments quickly grow to many times their original size to become large, rubbery masses. The most rapid growth occurs over the first few hours, but proceeds up to 12 hours or longer with continued exposure to liquid. One common brand of beads advises that a teaspoon of dry balls added to water will produce approximately 2 cups of hydrated beads over a 3-4 hour period.

MECHANISM OF TOXICITY

Colorful SAPs can mimic the appearance of candy to a young child; they are easily swallowed when dry and expand after ingestion. Luckily, the hydrogel fragments do not attract each other at any stage of their hydration, and remain individual units. Risk of obstruction can therefore be assessed by the final hydrated size of individual beads. Those that exceed the diameter of the small intestine of a young child (approximately 25-30 mm or about 1 inch) may obstruct the bowel.

Dry SAP fragments smaller than a pea are not considered an obstruction risk, although they may cause transient symptoms of nausea, vomiting, and abdominal pain.

However, dry balls that are 8 mm (nearly half the diameter of a dime) can swell to 32 mm or more (slightly larger than the diameter of a half dollar). Such large SAP balls were recalled in December 2012 by the Consumer Product Safety Commission, although some may still be found in homes.

Symptoms of bowel obstruction are repeated vomiting, abdominal distention, and abdominal pain or tenderness.

QUICK SIZE CHECK

Ask parents/caregivers to bring samples of the dry and/or hydrated SAPs with them to the ED, if available.

A quick size check can be made by placing a dry bead on a penny, on top of Lincoln’s face, and looking down on it from straight overhead. If any of his hair or beard can be seen, the bead is likely to be smaller than 8 mm and therefore relatively safe.

Another quick size check is placing a fully hydrated bead on a quarter and looking straight down on it. If any of the quarter is visible, it is unlikely to cause obstruction, although transient GI symptoms are possible.

DIAGNOSIS AND MANAGEMENT

Radiological tracking of hydrated SAP balls is difficult because SAPs are radiolucent. Abdominal x-ray may show dilated loops of bowel; ultrasound or abdominal CT may show an intraluminal mass.

If there was a witnessed, recent ingestion of an SAP whose dry size is larger than a pea (8 mm) early endoscopy may successfully retrieve the partially hydrated mass before it travels to the distal small bowel. Decisions to perform prophylactic laparoscopic removal of partially or fully-hydrated masses should be based on an assessment of the hydrated size, which determines the risk of obstruction, as well as the patient’s clinical condition and any informative imaging results.

Observation is recommended until 6 hours have passed since the ingestion, in case obstructive symptoms develop as the beads hydrate. This can be conducted at home if SAP fragments were smaller than a pea.

Management decisions for pediatric ingestion of SAPs can be challenging, primarily if the original size is unknown. Our advice is to call the Missouri Poison Center. Our specially trained nurses, pharmacists, and medical toxicologist can provide you with the most up-to-date treatment advice.