Incontinence-Associated Dermatitis-Like Skin Changes Induced by the Application of Absorbent Pads Containing Bacteria and Artificial Urine in Rats

Incontinence-associated dermatitis (IAD) is one of the most serious complications in older people with incontinence. Controlling urine property in absorbent pads could be effective for preventing IAD caused by bacterial urine. However, no animal model has been established to evaluate their effectiveness. This study aimed to induce IAD-like skin changes using absorbent pads containing bacterial urine and to confirm their pathophysiology in rats. Hairless Wistar Yagi rats were divided into the bacteria-containing urine (BU) and the bacteria-free urine (U) groups. A 10-h-attachment of absorbent pads containing artificial urine with/without bacteria to the skin pretreated with sodium lauryl sulfate was performed repeatedly for 5 days. Macroscopic findings and skin barrier function were examined every day, and histological changes, inflammatory responses and bacterial quantification in tissue samples were examined on Day 5. The BU group exhibited significant skin redness from Day 3, significant elevation of transepidermal water loss from Day 1, and histological changes, including significantly thickened epidermis, abnormal keratinocyte differentiation and erythrocyte leakage. Inflammation, confirmed by higher myeloperoxidase-positive cells, elevated tumour necrosis factor-α expression, and vascular endothelial damage, indicated by CD31 and pentraxin 3-positive cells, were observed in the BU group. The bacterial quantification showed no significant difference between the groups. IAD-like skin changes including histological changes and inflammation were suggested to be caused by urine properties altered by bacteria. This study proposed a new animal model for evaluating the effectiveness of absorbent pads in controlling the urine properties of bacterial urine on preventing IAD.