Pilonidal Sinus
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Direct answer
Jeep disease, as pilonidal sinus was nicknamed after afflicting second-world-war drivers, is a hair-driven foreign-body condition of the natal cleft: shed body hairs drill into the moist, deep intergluteal fold through midline skin pits, creating a sinus that tracks laterally and presents in a young hirsute, sedentary man either as recurrent abscesses or as a chronic discharging sinus. The midline pits are the entry; the lateral opening is the exit; the cavity between them contains granulation tissue and nests of hair — and the anatomy explains every treatment. An acute abscess is simply drained (off-midline where possible), while the definitive operation removes the pits and tract and closes the wound away from the midline — Bascom's pit excision, Karydakis flap or rhomboid (Limberg) flap — because midline wounds in this crease heal poorly and recur. Post-operative and lifelong hair removal from the cleft, with hygiene and avoidance of prolonged sitting, halves recurrence risk.
What you must remember
- Demographic: young adult males, hirsute, obese, sedentary occupations (drivers, IT professionals), deep natal cleft; rare after about 40 years of age.
- Pathogenesis: acquired, not congenital — hair with scales barbing it backwards works into follicle-free midline pits with friction and suction of the gluteal cleft, forming a foreign-body sinus.
- Presentation triad: midline pits in the intergluteal fold, lateral discharging sinus opening, and episodes of tender abscess; hair tufts may protrude from the pits.
- Acute abscess rule: incision and drainage first (off-midline incision preferred), definitive sinus surgery electively once inflammation settles — draining and definitive excision in the same sitting has higher failure.
- Definitive options: laying open (Bascom) with marsupialisation for simple sinuses; excision with primary off-midline closure (Karydakis); rhomboid/Limberg fasciocutaneous flap for recurrent or extensive disease; excision leaving the wound open (healing by secondary intention) for gross sepsis, at the cost of long dressing care.
- Why off-midline: the midline crease is moist, tensile and hair-attracting — flattening and lateralising the scar removes the niche that recreates the disease.
- Recurrence prevention: laser or razor depilation of the cleft until healing and periodically after, hygiene, weight reduction and breaks from prolonged sitting.
- Differential on presentation: infected sebaceous cyst, hidradenitis suppurativa (multiple axillary and inguinal lesions), anal fistula (internal opening in the anal canal at the dentate line).
A typical exam case
A 24-year-old call-centre employee has had two drained abscesses at the top of his natal cleft and now presents with a chronic lateral opening discharging serosanguinous fluid 4 cm from the midline, with two visible midline pits. Examination under the pattern: probing the lateral sinus tracks cephalad towards the pits, hairs emerge on gentle pressure, the anal canal and sacrococcygeal region are otherwise normal. Because there is no active sepsis, a definitive procedure is offered — Bascom pit excision with lateral sinus extraction, or a Karydakis excision-with-advancement closing the wound lateral to the midline. He is counselled realistically: any procedure can recur, so he must keep the cleft hair-free by shaving or laser until healed, maintain meticulous hygiene and take standing breaks at work. Had he arrived febrile with a hot fluctuant swelling, the answer that day would be drainage alone — the elegant flap is an elective operation on a quiet field, never a salvage in pus.
How the FMGE frames it
The question trio is constant: abscess first (drainage, not definitive surgery), treatment of choice for the uncomplicated sinus (excision with off-midline primary closure — Karydakis/Limberg in recurrent disease), and the recurrence-prevention lifestyle answer (hair removal). Examiners also test the pit-versus-fistula discrimination — a pilonidal sinus never has an internal opening in the anal canal, which is the single best discriminator from a fistula-in-ano in a hairy, confused posterior examination.
Frequently asked questions
What causes pilonidal sinus — congenital or acquired?
It is acquired: loose hairs penetrate midline pits of the natal cleft aided by friction, suction and moisture, setting up a foreign-body reaction — the congenital theory is obsolete.
How is an acute pilonidal abscess treated?
By incision and drainage, ideally through an off-midline incision, with definitive sinus surgery deferred until the acute inflammation resolves.
Why are off-midline closures preferred after excision?
Midline scars sit in a moist, hair-attracting, mobile crease and heal poorly; lateralising the closure (Karydakis, Limberg flaps) flattens the cleft and lowers recurrence.
Which patients are most at risk?
Young hirsute men with deep natal clefts, obesity and sedentary occupations — classically drivers, hence "jeep disease".
How is recurrence prevented after surgery?
Keeping the natal cleft hair-free by shaving or laser depilation, meticulous hygiene, weight reduction and avoiding prolonged sitting during healing.