Examination of a Sinus or Fistula in Surgery

Definitions

Classification

Sinuses

Fistulae

History Taking

• Duration - congenital sinuses (e.g. preauricular) are present from birth
• Predisposing illness - tuberculosis, Crohn's disease, ulcerative colitis, actinomycosis, colloid carcinoma of the rectum
• Preceding abscess - most acquired sinuses and fistulae arise from a preceding abscess (osteomyelitic, ischiorectal, cold abscess)
• Previous surgery - sinuses/fistulae can be surgical complications (retained suture, anastomotic breakdown)
• Bone chips in discharge - suggests osteomyelitis with sequestrum
• Pain - points to active inflammation or blockage of the sinus opening
• Fever and redness - suggest inflammatory origin
• Family history - tuberculosis, Crohn's disease, ulcerative colitis, fistula-in-ano can run in families

Local Examination

A. Inspection

• Most fistulae are single
• Multiple sinuses/fistulae are seen in:
  • "Watering-can" perineum (multiple perineal openings from urethral stricture/disease)
  • Actinomycosis (always multiple sinuses)
  • Crohn's disease affecting the rectum and anal canal
  • Sometimes ulcerative colitis

• Preauricular sinus - at root of helix or tragus of pinna; tract runs upward and backward
• Branchial fistula/sinus - at lower third of neck, just anterior to sternocleidomastoid
• Pilonidal sinus - midline, posterior to anus (natal cleft)
• Tuberculous sinus - takes a position characteristic of the underlying node or bone
• Actinomycosis - multiple indurated sinuses in upper neck
• Osteomyelitic sinus - over irregular jaw suggests mandibular osteomyelitis

• Sprouting granulation tissue at the opening suggests a foreign body at the depth (sequestrum, retained drain, bullet, suture)
• Tuberculous sinus opening - wide mouth, thin bluish and undermined edges
• A biopsy should always be taken from the wall to exclude malignancy or specific infection

• Osteomyelitis - thick pus
• Tuberculosis - serosanguineous discharge
• Actinomycosis - pus containing sulphur granules (yellow, gritty particles)
• Fistulae - may discharge urine, faeces, bile, or intestinal content depending on internal communication

• Old scars - chronic osteomyelitis or healed tuberculous sinus
• Dermatitis and pigmentation - characteristic of Crohn's disease and actinomycosis

B. Palpation

1. Tenderness - inflammatory sinuses (e.g. osteomyelitic) are tender
2. Wall thickness - chronic sinuses develop a thick fibrotic wall; thickening on palpation indicates chronicity
3. Mobility - sinuses from osteomyelitis are fixed to the underlying irregular, thickened, and tender bone; mobile sinuses suggest no bony involvement
4. Surrounding lump - a lump near a sinus often indicates tuberculous lymphadenitis

C. Examination with a Probe

1. Direction and depth of the sinus or fistula
2. Foreign body (e.g. sequestrum) - felt as a gritty, moveable hard object at the base
3. Communication with a hollow viscus - in fistulae, the probe may enter the bowel, bladder, or other cavity
4. Fresh discharge produced on withdrawing the probe

Clinical principle: Never probe forcibly - a blunt malleable probe is used, following the natural direction of the tract.

D. Examination of Regional Lymph Nodes

General/Systemic Examination

Special Investigations

• Macroscopic, physical, chemical analysis
• Microscopy - sulphur granules for actinomycosis
• Bacteriology - culture and sensitivity

• Straight X-ray - shows sequestrum, osteomyelitic bone changes, or opaque foreign body
• Sinogram/Fistulogram - injection of radio-opaque contrast (Lipiodol or Hypaque) into the sinus or fistula tract; delineates the full course and identifies internal communications
• MRI - especially useful to differentiate pilonidal sinus from cryptoglandular fistula; preferred for complex anal fistulae
• CT scan - used when infection threatens major vessels (e.g. pharyngocutaneous fistula near carotid)

• Methylene blue instilled into the bladder - detected in vagina confirms vesicovaginal fistula
• Charcoal in food - detected in fistula discharge confirms upper GI fistula
• Pyridium (phenazopyridine) - excreted in urine, confirms urinary fistula if colour appears in discharge

• Proctoscopy, sigmoidoscopy for perianal fistulae
• Barium swallow to confirm closure of pharyngocutaneous or oesophageal fistula before resuming oral feeding

Key Principles of Management

• Sinus - directed at removing the underlying cause (sequestrum removal, excision of foreign body, treating tuberculosis); biopsy the wall always to exclude malignancy
• Fistula - directed at the underlying aetiology (treat Crohn's, close surgically, address nutritional/radiation status); conservative management (wound care, NPO with enteral feeding) may suffice for low-output fistulae
• A fistula will not heal if there is: distal obstruction, irradiation damage, foreign body, epithelialization of the tract, malignancy, or active infection (the FRIENDS mnemonic: Foreign body, Radiation, Infection/Inflammation, Epithelialization, Neoplasm, Distal obstruction, Short/High-output tract)