seton
A few silk threads or horsehairs, or a strip of linen etc., introduced beneath the skin by a knife or needle, so as to induce suppuration; also, the issue so formed.
seton: a deliberate wound channel to drain infection
A seton is a thin cord or strip of material drawn beneath the skin to create a draining tract, typically in livestock. The material is inserted through a small incision using a seton needle (a large blunt needle with a flattened eye), and both ends are left protruding so the material can be withdrawn or replaced. The goal is to maintain an open channel that allows infected or inflammatory fluid to drain continuously, preventing abscess formation.
Historically, setons were made from silk thread, linen strips, or horsehair. In modern practice, veterinarians most commonly use cord made of cotton or synthetic material specifically manufactured for this purpose. The diameter is typically 3 to 6 millimeters. The material must remain slightly contaminated to sustain drainage without closing; if it becomes too cleanly healed, the channel will seal and the seton loses its function.
Application and duration
Setons are most often placed in the dewlap (the loose skin of the neck and throat) or along the shoulder and neck region where drainage can run freely. The procedure is performed under veterinary supervision in working animals such as cattle and horses. Depending on the severity of the condition, a seton may remain in place for two to eight weeks. It is checked regularly and kept clean; if the cord becomes plugged or infected with pathogenic bacteria, it must be cleared or replaced.
The practice reflects a deeper principle in older veterinary medicine: that controlled, managed drainage is preferable to sealed infection. Though antibiotics have reduced reliance on setons, they remain valuable in cases where antibiotic therapy is insufficient or where the infection is too deep or diffuse for conventional treatment. They are particularly useful in conditions such as fistulous withers or poll evil in horses, where infection tracks deep into tissue and resists topical or systemic treatment.
The term derives from the Latin seta, meaning bristle or hair, reflecting the original materials used. In practice, the seton itself is sometimes called a rowel or setone, and the tract it creates is the issue. Though less common than in previous centuries, setons remain part of the veterinarian's toolkit for managing chronic suppurative conditions in large animals where conventional drainage is impractical.