Diagnostic dilemma: A woman started eating foam from her chair while receiving dialysis

The patient: A 31-year-old woman in the U.K.

The symptoms: The patient had a history of type 1 diabetes, mild learning difficulties and end-stage kidney failure. For the last condition, she was receiving dialysis three times a week.

This treatment fills in for the kidneys by clearing waste and excess fluid from the bloodstream, and patients are advised to restrict their fluid and salt intake between sessions. If they don't, fluid can build up in the body because the kidneys aren't filtering it out of the blood, leading to weight gain and strain on the heart.

In this case, the woman consistently experienced this excessive fluid buildup between appointments, "despite several interventions" aimed at helping her manage it.

What happened next: Over time, the patient could no longer tolerate long dialysis sessions, so she would start and end each session above her target weight due to all the fluid buildup. She also reported experiencing occasional constipation.

After one dialysis session, a nurse cleaning the chair the woman had been sitting in noted that it felt "rather light." Upon inspection, she noted large chunks of foam — specifically low-density polyurethane foam — were missing from the chair.

The diagnosis: The woman's medical team discovered this was a case of pica, in which people develop a habit or compulsion to eat non-food items.

"We were surprised to discover that our patient had been eating the foam and had increased her fluid intake with the assumption that it would absorb excess water in the stomach and thus prevent systemic absorption," her doctors wrote in a report. "This was evidently not the case." In other words, she hoped the foam would act like a sponge and soak up the excess fluid she was retaining.

Pica is sometimes associated with nutrient deficiencies, such as a lack of iron or zinc, leading some scientists to theorize that these deficiencies lead to unusual cravings. Alternatively, some think that people with pica may be drawn to the sensations — the tastes, textures or smells — of non-food substances. The condition is sometimes associated with pregnancy or sickle cell anemia, as well as certain mental health disorders and medications.

In this case, the woman’s doctors ran tests and ruled out nutritional deficiencies as a factor. They also didn't uncover any "acute psychosocial triggers for her behaviour," and she had no past history of pica. They suspected that her known learning difficulties may have played a role.

The treatment: The patient was advised about the consequences of eating foam and received regular guidance from a dietitian with a speciality in helping patients with kidney dysfunction. Her family also became more closely involved in her treatment. Other cases of pica are typically treated with behavioral therapies, but the case report didn't note whether any such options were explored.

She additionally received a laxative treatment to help her pass the foam she'd already eaten without any complications. At the time the case report was published in 2010, she was continuing to undergo dialysis three times a week.

What makes the case unique: Cases of pica have been reported among kidney disease patients in the past, but they typically involve patients craving and eating clay, dirt, aspirin, flour, baking soda or ice. The effects can range from benign to severe; in the latter case, a person may experience toxic effects, dental problems, bowel obstruction or malnutrition, for example.

The woman's doctors searched the medical literature for cases of kidney disease patients eating polyurethane foam and didn't find any, but they did find a few cases of people without renal disease eating the material.

"This case highlights a recognised but under-diagnosed phenomenon in renal patients, known as pica," the doctors wrote. "While the ingestion of ice, aspirin, clay and baking soda has been reported in haemodialysis patients, this case is unique in that the patient resorted to eating foam from her dialysis chair."