Pilonidal Cyst and Sinus Differential Diagnoses

Updated: Nov 14, 2022
  • Author: Alex Koyfman, MD; Chief Editor: Gil Z Shlamovitz, MD, FACEP  more...
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Diagnostic Considerations

Location of the disease process is the best way to confirm the diagnosis of pilonidal disease, although several other disease entities should be considered:

Anal fistula and hidradenitis suppurativa: Several surgical studies mention the difficulty in differentiating pilonidal disease from anal fistula and hidradenitis suppurativa. [11] Pilonidal disease may result in sinuses that reach the perianal region and simulate an anal fistula. A valuable clinical observation in establishing diagnosis of anal fistula is palpation of the tract leading to the secondary opening to the anus. When no primary opening is observed and no tract is palpable, the possibility of an extra-anal source of the infection must be considered. [12] Consider hidradenitis suppurativa, a chronic inflammatory disease of the apocrine sweat glands in which folliculitis and local friction also play a role, in patients aged 30 years or older, especially with comorbidities such as diabetes and obesity. This disease often affects the groin, axillary, perianal, perineal, and inframammary regions. These patients need surgical referral because this condition is likely to be a long-term concern. [13]

Congenital abnormalities: In some congenital lesions, a continuous tract with the central cord of the spinal cord may occur, and discharge of CSF fluid may be present. It is likely that diagnosis of this variant will have occurred before an ED presentation. [4]

Inclusion dermoid/teratoma: Differentiation and post-primary presentation referral to a surgeon are critical, as treatment of a sacrococcygeal teratoma is en bloc excision and appropriate oncologic care.

Perirectal abscess: Location of the lesion is the best means to differentiate this entity from pilonidal disease. Perirectal abscesses frequently require surgical consultation in the ED for formal drainage in the operating room.

Pyoderma gangrenosum: Pyoderma gangrenosum is an ulcerative lesion also generally seen in the fourth decade of life with other comorbidities.

The following are other problems to consider:

  • Primary presacral or sacrococcygeal sinus
  • Furuncle or carbuncle
  • Syphilitic granuloma
  • Tuberculous granuloma

All of the above are rarely seen but should be considered in the face of atypical or variant history or physical examination findings. Readers are left to explore all these topics in further detail as indicated.

Differential Diagnoses