What tunneling and undermining mean
Tunneling wound care deals with a wound that is larger under the skin than it appears on top. Two words describe the hidden part.
Tunneling is a narrow channel that runs from the wound into deeper tissue in one direction, like a passage. You may also hear it called a sinus tract. Undermining is a wider space under the wound edge, where tissue beneath the skin has broken down and the skin overhangs it like a shelf. A wound can have either or both.
If you are looking for help with this wound close to home, start with our overview of wound care in St. Louis.
How clinicians measure and describe them
A clinician checks for hidden space by gently exploring the wound with a sterile instrument, then records how far it extends in centimeters. To show where it is, they use the face of a clock. Twelve o’clock points toward the person’s head and six o’clock toward the feet.
A note might read “tunnel at 2 o’clock” with a depth, or “undermining from 9 to 12 o’clock.” Comparing those numbers at every visit shows whether the space is filling in. Our guide to understanding wound measurements explains the other numbers in a wound note, and the page on wound assessment and measurement describes the visit itself.
Why a wound tunnels or undermines
Several things can open space under the skin. The treating clinician works out which ones apply.
- Pressure combined with sliding or dragging forces, as in many pressure injuries
- Infection, or the space left after an abscess is drained
- A surgical incision that has separated beneath the skin
- Something in the wound that should not be there, such as a retained stitch
- Less often, a problem in deeper tissue or bone that the clinician will want to rule out
Why follow-up matters
A flat, open wound shows you most of what it is doing. A tunneling wound does not. Drainage and bacteria can sit in the hidden space, and the surface can narrow or close while the deeper part is still open. Fluid may then collect underneath, and the wound can break open again.
Regular measurement is the only reliable way to see the trend. If a tunnel is not getting shorter over several visits, the clinician looks again at the cause and the plan. That review may include tests, imaging, a change in dressings or a referral to a surgeon.
What care can involve
The treating clinician decides the plan for each wound. Depending on the cause, it may include:
- Dressing material placed lightly in the space so it can fill in from the deepest point outward
- Dressings chosen to handle the drainage and protect the surrounding skin
- Debridement, the removal of dead tissue that slows healing
- Negative pressure wound therapy for some wounds
- Pressure relief, repositioning and attention to sliding in the bed or chair
- Evaluation and treatment of infection
If a family member changes the dressing between visits, ask the clinician to demonstrate and to write the steps down. Tell the clinician if dressing material that went into the wound cannot be found at the next change.
Changes to report and when to call 911
Contact the treating clinician about:
- More drainage than usual, or drainage that turns thick, cloudy or foul-smelling
- New or increasing pain, especially deep, throbbing pain
- Redness, warmth, swelling or firmness spreading around the wound
- Fever, chills or feeling suddenly unwell
- A new opening in the skin near the wound
- The surface closing quickly while the area beneath stays tender or swollen
Call 911 for heavy bleeding that does not stop with firm pressure, or for confusion, fast breathing, fainting or a rapid heartbeat along with signs of infection.
How Gateway coordinates care for tunneling wounds
Gateway arranges wound care with partner clinicians in private homes, skilled nursing facilities, assisted living and other settings across Greater St. Louis and the Metro East. We coordinate the request, scheduling, records, clinician orders, supplies and follow-up, and we keep the rest of the care team informed. The treating clinician makes every clinical decision.
These wounds depend on consistent visits, so we work to keep the schedule and supply orders on track. To ask about a visit, call 314-325-0126 or use the request care form. You do not need a referral, and we confirm availability for your location and care setting.
Common questions
Is a tunneling wound serious?
It deserves close attention, because its true size is hidden and problems can develop below the surface before anyone sees them. How serious it is depends on the cause, the depth, what lies beneath and the person’s overall health. Some tunneling wounds are managed with regular wound care visits, and some need tests or a surgical opinion. Ask the treating clinician which applies to yours.
Can I tell whether my wound has a tunnel by looking at it?
Usually not. Clues include a small opening that produces more drainage than you would expect, drainage that appears when nearby skin is pressed, or a wound that shrinks on top yet stays sore. These are reasons to call the clinician. Do not put anything into the wound to check for yourself, since that can injure tissue and carry bacteria deeper.
Why does the clinician place dressing material inside the wound?
An empty space under the skin tends to collect fluid, and the surface may close before the deeper part has filled in. Material placed in the space absorbs drainage and helps the wound heal from the inside out. The clinician chooses the type and amount for your wound. If you help with dressing changes, use only what was ordered.
Will a wound with tunneling need surgery?
Some do, and many do not. Surgery may be considered when a tunnel does not improve, when there is a deep pocket of infection, or when the clinician suspects a problem in deeper tissue. That decision belongs to the treating clinician and the surgeon. If a referral is ordered, Gateway can help with specialist referral coordination so records and appointments line up.
Related pages
General information to help you talk with your own clinician. It is not medical advice, and the treating clinician makes every clinical decision. For a medical emergency, call 911.