Feline Aural Hematoma Study Guide

Overview and Clinical Importance

Aural hematoma (also called auricular hematoma) is a blood-filled subcutaneous fluctuant swelling on the pinna formed when traumatic rupture of capillaries and separation of the auricular cartilage and skin occurs. While more common in dogs, aural hematomas in cats present unique clinical considerations due to feline pinna anatomy and the higher likelihood of Otodectes cynotis (ear mite) infestation as an underlying cause. The condition is a sequela of ear pruritus or trauma, not a primary diagnosis.

In cats, the relatively thin auricular cartilage is more sensitive to inflammation, and scarring is more severe than in dogs. Untreated hematomas in cats are more likely to form a permanently narrowed ear canal, potentially leading to chronic ear infections and permanent disfigurement ("cauliflower ear").

Relevant Anatomy

Feline Pinna Structure

The feline pinna has a relatively uniform triangular appearance across breeds (unlike the variable conformation seen in dogs). It consists of three key layers: skin on both concave and convex surfaces, auricular cartilage sandwiched between, and dermis containing blood vessels.

The skin on the concave (inner) surface is tightly adherent to the underlying auricular cartilage, while the skin on the convex (outer) surface is more loosely attached. The cutaneous marginal pouch (Henry's pocket) is present on the posterior margin of the pinna in most cats.

Vascular Supply

Pathophysiology

Aural hematoma formation occurs through the following mechanism: ear irritation (infection, parasites, allergy, or foreign body) causes pruritus and head shaking, which leads to shear forces that cause capillary rupture and cartilage fracture. Blood then accumulates between the tightly adherent concave skin and the underlying cartilage.

In the early stages, the hematoma contains fresh blood with sero-hemorrhagic fluid. If left untreated, the clot is converted to granulation tissue through fibroblastic and capillary ingrowth. The hematoma cavity eventually fibroses, and the cartilage may ossify, leading to permanent disfigurement. In cats specifically, the thinner pinnae may deviate medially and obstruct the external acoustic opening, further exacerbating the inciting otitis externa.

Etiology

Primary and Secondary Causes of Otitis Leading to Aural Hematoma

Feline-Specific Considerations

Otodectes cynotis is the most common primary cause of feline otitis externa, implicated in 53-85% of clinical cases. Mites are commonly found in young cats and outdoor cats, though older cats can also be affected. The characteristic clinical finding is dark, crumbly, "coffee-ground" ceruminous debris in the ear canal.

Unlike dogs, atopic dermatitis does not appear to be as common a trigger for feline otitis. Unilateral otitis in cats should prompt investigation for inflammatory polyp, foreign body, or neoplasia.

Exam Focus: When you see a question about a young cat with intense ear pruritus, head shaking, dark crumbly ear discharge, and aural hematoma - think Otodectes cynotis FIRST. Remember: Unilateral = polyp, foreign body, or neoplasia. Bilateral = parasitic, allergic, or autoimmune.

Clinical Signs and Presentation

Physical Examination Findings

Diagnosis

The diagnosis of aural hematoma is typically straightforward based on physical examination. However, identifying the underlying cause is essential for successful treatment and prevention of recurrence.

Diagnostic Approach

• Otoscopic Examination: Evaluate ear canal for erythema, discharge, masses, polyps, foreign bodies, and tympanic membrane integrity. May require sedation if painful.
• Ear Cytology: Collect debris with cotton swab; examine under microscope for bacteria, yeast (Malassezia), and ear mites. Mites may wash off during staining - use unstained mineral oil preparations.
• Fine Needle Aspiration (optional): Confirms blood in the hematoma; cytology shows RBCs. Not always required if diagnosis is clinically obvious.
• Skin Scraping (if indicated): Pinna skin scraping for Demodex, Sarcoptes, or Notoedres if suspected.
• Additional Testing: Allergy testing, culture and sensitivity, or imaging (radiographs, CT) if indicated based on history and otoscopic findings.

Differential Diagnoses

• Pinnal abscess (may follow bite wound)
• Pinnal cyst
• Neoplasia (squamous cell carcinoma in white cats)
• Inflammatory polyp (if mass present on otoscopy)

Treatment

Treatment goals include: (1) identifying and treating the underlying cause; (2) providing adequate drainage; and (3) maintaining apposition between skin and cartilage. Both medical and surgical approaches are used, with surgery generally preferred for larger or recurrent hematomas.

Treatment Options Comparison

Medical Management Protocol

Indications: Small hematomas, early onset (less than 24-48 hours), or when anesthesia is contraindicated.

Procedure Tip: Use a 19-21 gauge butterfly needle with line attached - this allows drainage, flushing with sterile saline, and steroid instillation through a single puncture site, minimizing patient discomfort and repeated skin puncture.

Surgical Technique

Indications: Large hematomas, recurrent hematomas, chronic cases with fibrin, or when medical management fails.

• Preparation: General anesthesia; clip both surfaces of pinna; aseptic preparation; place cotton in ear canal
• Incision: Make longitudinal or S-shaped incision on CONCAVE surface through skin only (not cartilage)
• Drainage: Express blood and fibrin clots; flush with sterile saline
• Suture Placement: Place multiple staggered mattress sutures (3-0 or 4-0 nylon) PARALLEL to long axis of pinna and auricular vasculature, 8-10 mm apart
• Post-operative Care: Bandage pinna over head for 1-2 weeks; Elizabethan collar; sutures remain 2-3 weeks

Treating the Underlying Cause

Otodectes cynotis Treatment Options

Important: Treat ALL in-contact animals. Systemic products are preferred over otic preparations in cats as they also treat ectopic mites and improve client compliance. Cats are highly fastidious and may have irritant reactions to topical otic medications.

Prognosis and Complications

Prognosis: Good to excellent with appropriate treatment of both the hematoma AND the underlying cause. Recurrence is uncommon if the underlying etiology is properly addressed.

Potential Complications

• Cauliflower ear deformity: Permanent disfigurement from fibrosis and cartilage contraction
• Ear canal obstruction: Scarred pinna may deviate medially and obstruct external acoustic opening (more common in cats)
• Chronic otitis: Secondary to narrowed ear canal
• Recurrence: If underlying cause not addressed
• Avascular necrosis: If sutures placed perpendicular to auricular vessels

Memory Aid

HEMATOMA = H.E.A.R

• Head shaking causes it
• Ear mites (Otodectes) are the #1 cause in cats
• Address underlying cause or it recurs
• Run sutures PARALLEL to vessels