Abscess

Etiology and pathways of infection entry

Abscesses are most commonly caused by Staphylococcus aureus (Staphylococcus aureus), although mixed microbial flora (staphylococcus combined with Escherichia coli, streptococcus, or Bacteroides) is also possible.

Infection can enter tissues via several routes:

• Exogenous: microorganisms penetrate from the external environment. This is the most frequent scenario, facilitated by skin contamination, excessive sweating, and poor hygiene.
• Endogenous: spread of infection from adjacent structures or distant organs (metastatic abscesses in sepsis).
• Iatrogenic (aseptic): occurs due to accidental or erroneous introduction of concentrated solutions into tissues (e.g., 25% magnesium sulfate or 50% metamizole sodium). The drugs cause tissue necrosis, which subsequently suppurates.

Pathogenesis and wall formation

The process begins with the development of suppurative inflammatory infiltration. This is followed by tissue necrosis, sloughing (formation of sequestra), and subsequent enzymatic liquefaction.

Morphologically, an abscess cavity can be either simple and rounded or complex, featuring numerous internal pockets. A crucial stage in the evolution of an abscess is the formation of its wall. Initially, it is lined only with purulent-fibrinous deposits and fragments of dead tissue. Gradually, an inflammatory zone develops along the periphery, ultimately forming a pyogenic membrane composed of dense connective tissue. It serves as a barrier preventing the spread of infection.

Clinical presentation and diagnostics

When an abscess is superficial (e.g., in subcutaneous tissue), classical local symptoms of inflammation are clearly manifested:

1. Redness (Hyperemia).
2. Swelling (Edema).
3. Pain (Dolor).
4. Local temperature elevation (Calor).
5. Loss of function (Functio laesa).

At the onset of the disease, a painful nodule forms, which rapidly turns into a dense infiltrate. After 10–15 days, softening appears in the center of the infiltrate. A positive sign of fluctuation (undulation) is a key diagnostic indicator that fluid (pus) has accumulated inside.

The appearance and odor of the exudate help suggest the type of pathogen:

• Staphylococcus: thick pus of a characteristic yellow-green color.
• Pseudomonas aeruginosa: a blue-green tint and a specific sweetish odor.
• Putrefactive flora: dirty-gray mass with a sharp, foul odor.

Outcomes of an abscess

The development of an abscess can follow several scenarios:

• Favorable: spontaneous rupture outward (typical for mastitis, paraproctitis, subcutaneous abscesses). The cavity empties, the walls collapse, and scarring occurs.
• Unfavorable (chronic course): if evacuation was incomplete, the process may become chronic with the formation of a persistent purulent fistula.
• Complicated: rupture of pus into closed cavities (joints, pericardium) leads to severe arthritis, pericarditis, and peritonitis. Rupture into hollow organs (bronchi, intestines) is also possible.

Principles of surgical treatment

The main rule of abscess surgery: the abscess must be incised, evacuated, and drained. An exception is made for "cold" abscesses of tuberculous etiology — they must not be incised due to the high risk of superinfection. Small, well-defined abscesses with a dense capsule can be excised entirely.

Surgical technique:

1. Access: the shortest route is chosen, attempting to make the incision near the lower pole of the abscess for adequate passive drainage driven by gravity.
2. Incision along the needle: the cavity is first punctured, and then tissues are dissected along the needle tract. The surgical field is thoroughly isolated with drapes.
3. Cavity revision: pus is removed by suction, after which the surgeon explores the cavity with a finger. It is necessary to break down septa and pockets, and remove tissue sequestra. Important rule: manipulations must be gentle so as not to destroy the pyogenic membrane.
4. Completion: the cavity is washed with antiseptics and drains are placed (tubes, enzyme-soaked tampons). If drainage through the main incision is insufficient, a counter-incision (secondary incision) is made.

In the postoperative period, antibiotic therapy (guided by antibiogram), plasma transfusions, and specific immunization (staphylococcal toxoid, $\gamma$-globulin) are administered.

Class and exam questions

What else to study on this topic

• Features of the clinical presentation and treatment of internal organ abscesses (liver, lungs)
• Types and techniques of draining purulent cavities
• Specific immunotherapy for staphylococcal infections
• Chronic abscesses and principles of treating purulent fistulae
• Purulent hidradenitis as a specific case of abscess formation

Other topics from the section "CHAPTER 11. SURGICAL INFECTION (PURULENT-INFLAMMATORY DISEASES)"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.