What are the typical physical examination findings of a pilonidal sinus?

Physical Examination Findings of Pilonidal Sinus

The typical physical examination of a pilonidal sinus reveals one or more midline pits or openings in the natal cleft (intergluteal region), often with visible hair protruding from the opening, and may include lateral secondary openings with purulent or serosanguineous discharge when infected.

Primary Examination Features

Location and Appearance

• The primary pit is located in the midline of the natal cleft, representing the initial site where a hair follicle has become infected and serves as the entry point for loose hairs 1, 2.
• The sinus typically presents in the sacrococcygeal region as the most common anatomical location 2.
• Multiple pits may be present, with additional sinuses frequently having lateral openings off the midline 2.
• The primary opening is lined by stratified squamous epithelium and may appear as a small dimple or pit 2.

Hair Characteristics

• Visible hair tufts protruding from the sinus opening are a characteristic finding, though the hair often originates from the scalp rather than local follicles 3.
• The presence of loose hairs within the tract is pathognomonic when the sinus is explored 4, 1.

Clinical Presentation Spectrum

Asymptomatic Disease

• Asymptomatic pits without signs of infection may be discovered incidentally and do not require immediate treatment 2.

Acute Infection

• Painful, swollen, erythematous mass in the sacrococcygeal area indicates acute abscess formation 2.
• Purulent or serosanguineous discharge from one or more openings is common during active infection 5, 1.
• Tenderness to palpation over the affected area is present during acute episodes 2.

Chronic Disease

• Recurrent drainage from sinus openings with periods of quiescence and exacerbation 3, 1.
• Indurated tissue surrounding the sinus tract in chronic cases 2.
• Multiple secondary openings lateral to the midline may develop over time 2.

Examination Technique

Inspection

• Examine the entire natal cleft with the patient in prone position with buttocks separated 1.
• Look for midline pits as the primary pathognomonic feature 1, 2.
• Identify any lateral openings that may represent secondary sinus tracts 2.
• Assess for visible hair protruding from openings 4, 1.

Palpation

• Palpate for induration and subcutaneous tracts extending from the primary pit 2.
• Assess for fluctuance if abscess formation is suspected 2.
• Evaluate tenderness which indicates active infection 2.

Atypical Presentations

Rare Locations

• While sacrococcygeal location is standard, pilonidal sinuses can occur in any hairy area subject to friction, including axillae, groin, anterior chest wall, and even the nasal dorsum 4, 5.
• Hair-containing fistulas in unusual locations should raise suspicion for pilonidal disease, particularly in hirsute individuals 4, 5.

Critical Pitfalls to Avoid

• Don't dismiss asymptomatic pits in young adults, as they represent early disease that may become symptomatic 2.
• Don't confuse with other midline lesions such as dermoid cysts; the presence of hair within the tract and the acquired nature (rather than congenital) distinguishes pilonidal disease 5.
• Don't overlook lateral openings which are frequently present and represent secondary tract formation 2.
• Don't assume all hair-containing lesions are dermoid cysts; histopathological examination should be performed to confirm pilonidal sinus, especially in atypical locations 5.