ICD-10-CM Code for Preauricular Pit Discharge
The correct ICD-10-CM code for a discharging preauricular sinus is Q18.1 (Preauricular sinus and cyst).
Primary Diagnosis Code
Q18.1 is the specific ICD-10-CM code designated for preauricular sinus and cyst, which encompasses both the congenital malformation and its complications including discharge 1, 2.
This code applies whether the preauricular sinus is presenting with active infection, persistent discharge, or recurrent episodes requiring medical attention 2, 3.
The preauricular sinus is defined as a congenital lesion where a small skin opening located anterior to the external ear communicates with a subcutaneous network of cysts 2.
Clinical Context for Coding
When the preauricular sinus presents with active infection or discharge, Q18.1 remains the primary diagnosis code because the discharge is a direct manifestation of the underlying congenital malformation 1, 2.
If there is documented cellulitis or abscess formation secondary to the infected preauricular sinus, you may add a secondary infection code (such as L03.211 for cellulitis of face or H60.10 for cellulitis of external ear), but Q18.1 should be listed as the primary or co-primary diagnosis 2.
The preauricular sinus is most commonly located at the anterior margin of the ascending helix, adjacent to the helicine crus, or adjacent to the tragus 3.
Laterality Considerations
Document laterality (right vs. left ear) in the clinical notes, as this is important for surgical planning even though the ICD-10-CM code Q18.1 does not have specific laterality modifiers 1.
In rare cases, bilateral preauricular sinuses can occur, and both should be documented clinically 1, 4.
Extremely rare variants include postauricular sinuses, which may co-exist with preauricular sinuses and should be documented separately in clinical notes 1.
Documentation Requirements
The diagnosis should specify whether the sinus is symptomatic (draining, infected) or asymptomatic, as draining sinus tracts prone to infection require surgical excision while asymptomatic sinuses may require no intervention 2.
Document the presence of purulent discharge, erythema, swelling, or tenderness to support medical necessity for treatment 2, 3.
Note any history of recurrent infections, as this influences treatment decisions and supports the need for definitive surgical excision 2, 5.
Common Coding Pitfalls
Avoid using nonspecific codes like L98.9 (disorder of skin and subcutaneous tissue, unspecified) when the preauricular sinus is the known diagnosis 2.
Do not code this as acquired fistula or sinus tract—Q18.1 specifically designates this as a congenital malformation inherited in an autosomal dominant pattern 3, 4.
When surgical excision is planned, ensure Q18.1 is documented as the indication for surgery to support medical necessity 2, 5.