The difference between sinus tract and undercover

Sinus tracts and undermining are two common and complex conditions in chronic wound care, and accurately distinguishing between them is crucial for developing the right treatment plan. Many patients and even healthcare professionals confuse the two, but their formation mechanisms and treatments are fundamentally different.

What is a sinus?

Sinus tracts are abnormal passages between deep tissue and the skin surface, typically tubular structures with separate openings. These passages may lead to deep foci of infection, dead spaces, or sites of foreign body entrapment. Sinus tract walls are composed of fibrous tissue and lack a normal epithelial covering, a primary reason for their chronic resistance to healing. Sinus tracts are often deeper than they are long, reaching several centimeters and sometimes even extending into bone or hollow organs. Discharge is typically purulent, serous, or bloody, varying in volume and sometimes possessing a distinctive odor.

What is stealth?

Undermining refers to the loss of tissue beneath the wound edge, forming a pocket-like cavity. This cavity lies beneath intact skin and is connected to the main body of the wound, but lacks a separate external opening. Undermining can be thought of as a tunnel at the wound edge, potentially extending deeper and wider than what is visible on the surface. The walls of the undermining cavity are composed of damaged subcutaneous tissue and are often accompanied by accumulation of necrotic tissue or exudate. This condition is particularly common in pressure injuries and infected wounds.

How to distinguish the two based on clinical manifestations?

Observing the wound's appearance is the most straightforward way to distinguish them. A sinus tract appears as a separate opening, and the surrounding skin may be red, swollen, or hyperpigmented. Undermining tracts lack a separate opening, and the underlying cavity is only revealed when the wound edges are lifted. Probing also differs in feel. When probing a sinus tract with a sterile cotton swab, a distinct tubular channel is felt, with a relatively fixed direction. When probing an undermining tract, the swab can be moved freely beneath the wound edge, covering a wider area but at a relatively shallow depth.

The characteristics of the discharge also vary. Sinus discharge is usually persistent, and the amount correlates with the extent of the underlying infection. Undercurrent discharge tends to accumulate within the cavity and may increase suddenly with changes in body position or pressure on surrounding tissues. Sinus discharge is often accompanied by deep tenderness or dull pain, whereas undercurrent discharge may only cause discomfort during probing.

What are the differences in formation mechanisms?

Sinus tract formation is often associated with deep infection or foreign bodies. Postoperative suture retention, dead bone formation, and ruptured deep abscesses can all contribute to sinus tracts. Undermining is more often related to mechanical factors. Sustained pressure or shear forces cause necrosis of subcutaneous tissue, forming cavities. Spread of infection to the periphery can also cause tissue dissolution, leading to undermining. Impaired circulation can prevent wound edges from healing properly, leading to the gradual development of undermining.

What is the difference in treatment methods?

The key to sinus management is eliminating the underlying cause. Adequate drainage is essential, and packing with alginate or silver dressings is essential to maintain patency. Deep infections require the use of sensitive antibiotics based on susceptibility testing. Surgical resection of the sinus tract and affected tissue is necessary if necessary. Enhanced nutritional support is also crucial to promote tissue repair.

The key to successful wound management is to eliminate cavities. Pack with appropriate dressings to prevent accumulation of exudate. Reduce local pressure by changing body position or using pressure relief devices. Remove necrotic tissue to promote healthy granulation. Maintain open wound edges to prevent premature epidermal closure.

What should I pay attention to when using dressings?

For sinus tracts, a dressing with drainage function should be selected. Alginate dressing strips absorb exudate and maintain adequate moisture. Silver-containing dressings can help control infection. The dressing should not be overly tight, as this may impair drainage and granulation growth. Dressings should be changed regularly, and changes in sinus tract depth should be recorded.

When treating undermining wounds, the dressing must be properly packed to the deepest part of the cavity. Foam dressings cut into appropriate shapes can effectively fill the cavity. Hydrocolloid dressings can promote autolytic debridement. Dressing changes should be performed gently to avoid damaging new tissue.

When do you need to seek professional help?

If a wound shows no significant improvement after two weeks of standard care, seek medical attention promptly. Systemic symptoms such as fever and increased pain suggest a worsening infection. A sudden increase in wound exudate or a foul odor requires professional evaluation. If a sinus tract exceeds 5 cm or continues to expand, seek specialist treatment. Patients with underlying medical conditions such as diabetes or immunocompromise should seek professional care promptly. For more information on Innomed® Alginate Dressing, refer to the Previous Articles. If you have customized needs, you are welcome to contact us; you wholeheartedly. At longterm medical, we transform this data by innovating and developing products that make life easier for those who need loving care.

Editor: kiki Jia