draining tract sa

Investigations

·    Solitary swelling? Pyrexic? – abscess

·    FNA

o  Neutrophils – abscess

o  Pyogranulomatous inflammation + adipocytes = panniculitis

·    Cytology of exudate

o  Macrophages, neutrophils, RBCs – furunculosis

o  Lymph node – plasma cells, amastigotes, nuclear streaming, degenerate neutrophils

·    Deep skin scrapes/hair plucks – rule out demodex

·    Wedge biopsy – stain and culture

·    Microbial culture

Management

·    Deep pyoderma

o  Furunculosis – topical chlorhex shampoo, 4-8w antibiotics (based on C+S)

·    Control inflammation once infection controlled – topical/systemic glucorticoids +/- ciclosporin

·    Address any underlying predisposing factors, e.g. reduce weight, analgesia if pain

·    Abscess – lance/drain, analgesia, systemic abx if pyrexic

·    Cellulitis – systemic amoxiclav

·    Mycobacterial infections – 6m course of abx based on C+S

·    Leishmaniasis – allopurinal, meglumine antimoniate

Causes

Infectious:

·    Bacteria

o  Deep pyoderma – furunculosis (pyogranulomatous reaction to folliculitis)

§ Clinical manifestations: chin/muzzle, nasal furunculosis, ID furunculosis, aural lick dermatitis, post-grooming

§ Can be secondary to allergies, ectoparaises, infections, immunosuppression

o  Abscess/cellulitis – caused by trauma, FBs

§ Abscess – supprative material in dermis, well defined

§ Cellulitis – ill-defined inflammation involving deep subcut connective tissue

o  Bacterial granulomatous dermatitis – traumatic implantation of saprophytic organisms

§ Mycobacterial granulomas/pyogranuloms – M. bovis, M. microti, M. tuberculosis

§ Non-filamentous bacterial granulomas

§ Filamentous bacterial granulomas

·    Subcutaneous (deep) fungal infections – see cutaneous papules and subcut nodules

o  Subcutaneous dermatophytic granuloma

o  Saprophytic subcutaneous fungal infection

o  Sporotrichosis – ZOONOTIC

·    Protozoa/parasites

o  Leishmaniasis – see exfoliative dermatitis (silver scales), ulcerative dermatitis

o  Demodicosis

Non-infectious:

·    Immune-mediated/autoimmune

o  Anal furunculosis

o  Metatarsal fistulation

o  Pansteatitis

o  Sterile nodular panniculitis – inflammation of subcutaneous fat

o  Dermoid sinus