Draining sinus tracts 1 Flashcards
Introduction & non-infectious causes
What is a sinus?
= tract from skin surface to a deeper, but abnormal, focus, usually in the dermis or subcutis
What is a fistula?
= tract between two epithelium-lined structures (e.g. skin and a hollow organ)
2 fistulae seen in dermatology
- Anal furunculosis – sometimes referred to (inaccurately) as ‘perianal fistulae’ - actually are sinuses
- Fistulae of the feet – tract between the dorsal and palmoplantar aspects of the foot
Why do sinus tracts usually form?
- due to an attempt to reject material from dermis or subcutis
Material sets up an inflammatory/foreign body reaction → bulla → ruptures → draining tract
How does material reach the dermis/subcutis? (i.e. different types of sinus tracts)
- Penetration from surface
– e.g. foreign body, mycobacterial/ opportunistic fungal infections - Breakdown of the hair follicle (furunculosis), e.g.
– deep pyoderma
– demodicosis
– dermatophytosis - Systemic routes
– e.g. systemic mycoses - Formed within skin
–e.g. immune-mediated/autoimmune
What do draining tracts usually reflect?
▪ Deep infection
▪ Foreign body
▪ Immune-mediated/autoimmune disease
Non-infectious causes of draining sinus tracts
Immune-mediated/autoimmune
- Anal furunculosis (perianal fistulae)
- Metatarsal fistulation
- Sterile panniculitis (inflammation of s/c fat, with no underlying infectious cause)
▪ Steatitis (‘yellow fat disease’)
▪ Sterile nodular panniculitis
- Dermoid sinus
General investigative approach to draining sinus tracts
Signalment, history, clinical examination ▪ Site of lesion
▪ Solitary/multifocal
▪ Palpable underlying nodule?
▪ Nature of exudate
▪ Lifestyle of patient
▪ Other clinical signs (dermatologic/systemic)
Diagnosis
▪ Cytology of exudate
▪ Deep skin scrapes/hair plucks
▪ Biopsy for histopathology and tissue culture – frequently required
▪ Microbial culture
▪ Other tests, as indicated
– E.g. Serology (leishmaniasis, sporotrichosis), fluorescent in situ hybridization for microbes
Diagnosis - Cytology of exudate
▪ FNA from bulla, if present
▪ Touch impression of sinus tract contents
Often pyogranulomatous/granulomatous. May see organisms (Diff Quick + Gram if possible)
Diagnosis - Deep skin scrapes/hair plucks
- if demodicosis suspected
Diagnosis - Biopsy for histopathology and tissue culture
- Do not shave or cleanse first
- Biopsy erythematous skin adjacent to tract and go deep enough to include dermis and subcutis–need wedge, not punch. Multiple samples/locations.
- May need special stains( e.g. for mycobacteria, Actinomyces, Nocardia, fungi)– notify pathologist of your d/ds
Diagnosis - Microbial culture
▪ Tissue culture best – tissue with drop of sterile saline in sterile universal container
▪ If tissue grains present in exudate, submit for culture also – often many organisms
▪ Swabs in transport media?
– more prone to contamination – best from FNA of bulla or deep in sinus tract ▪ Request
– Aerobic + anaerobic bacterial culture
– Fungal culture (not just dermatophytes)
NB Notify lab of d/ds – re safety and selection of appropriate culture requirements
Other points
▪ If unsure whether culture needed, chill or freeze additional deep tissue samples (not in formalin!)
pending histopathology results → microbial isolation later, if needed
▪ Freeze fresh tissue samples when submitting biopsies for histopathology from any cutaneous/subcutaneous mass in a cat
– Mycobacteria very hard/slow to grow - can do mycobacterial PCR on fresh frozen tissue
Anal furunculosis - Aetiology & pathogenesis
- The cause is unknown but is suspected to involve an immune-mediated mechanism with a genetic predisposition
- A broad-based tail with low tail carriage may predispose to bacterial infection and chronic inflammation of the perianal skin, but this is likely a contributing factor and not a cause
- The draining tracts are lined with chronic inflammatory tissue and may extend to the lumen of the rectum and anus
- Infection may spread to deeper structures involving the external anal sphincter and, therefore, should be treated promptly.
Anal furunculosis - CS
- tenesmus
- dyschezia
- diarrhea
- constipation
- fecal incontinence
- purulent discharge from the perianal region
Discomfort caused by the condition may lead to biting and licking of the perianal region.
Pain may also cause generalised depression or change in attitude and anorexia.
As the condition becomes chronic, anorectal stricture may result.
Anal furunculosis - diagnosis
- Based on physical examination and ruling out other causes of the signs
- In addition to the signalment and history, physical examination, including digital rectal examination, is a primary means of diagnosis
- Other causes of fistulisation (eg, anal sac disease, neoplasia) need to be ruled out
- Bacterial culture to identify organisms causing secondary infection may be needed
- Tissue biopsy is rarely indicated.
Anal furunculosis - tx
- Cyclosporine is the treatment of choice
Medical management is the primary mode of treatment. Cyclosporine (2–10 mg/kg, PO, every 12–24 hours, with monitoring) is the medication of choice. Higher dosages may be associated with improved outcome. After complete resolution of lesions (usually 8–12 weeks), cyclosporine is tapered to the least-effective dose that prevents relapse, which is common after stopping therapy. The concurrent use of ketoconazole allows for a lower dosage of cyclosporine and may reduce the cost of treatment.
Tacrolimus (0.1% ointment applied topically once or twice daily) may be used to treat mild lesions or as long term management after resolution of more severe lesions. Antimicrobials may be needed to treat secondary infections but are not effective as the primary or sole therapy for perianal fistulas.
Stool softeners and analgesics may be beneficial in dogs with significant tenesmus, dyschezia, or constipation.
Whereas once the mainstay of therapy, surgery is typically reserved only for cases refractory to medical management. Potential procedures include en bloc excision, anal sacculectomy, cryosurgery, and tail amputation. Complications of surgery can include wound dehiscence, fecal incontinence, anal stricture, persistence of clinical signs, and recurrence of fistulas.
Anal furunculosis - primary breed it affects
GSD
Pansteatitis - cause
- Vitamin E deficiency and/or excessive dietary unsaturated fatty acids
- The inadequate vitamin E:unsaturated fatty acid ratio results in oxidative damage to adipocytes and subsequent lipid peroxidation.
- Cats that eat a fish only diet are at increased risk of developing this disease
- Other unbalanced, meat-based diets have also been implicated in the development of pansteatitis.
Pansteatitis - CS & clinical features
- Clinical signs include subcutaneous nodules, draining tracts, lethargy, inappetence, fever, pain and reluctance to move
- Haematological abnormalities may also be present
- Affected adipose tissue has an unusual yellow–orange colour.
Pansteatitis - diagnosis
- The dietary history and clinical signs will strongly suggest pansteatitis
- However, a skin biopsy (being careful to include adipose tissue in the biopsy) with special stains for infectious agents is necessary to confirm the diagnosis and rule out infectious causes of inflammation of the fat
- Plasma tocopherol levels of <300 mg/100 ml further confirm the diagnosis.
Pansteatitis - tx
- Affected cats should receive supportive care including pain medication and parenteral fluid therapy, depending on the severity of their condition
- Affected cats should be fed a high-quality, properly balanced diet
- Additional α -tocopherol supplementation (50 mg/kg po q24 h) may also be helpful to speed recovery
- Full recovery may take several weeks
-mIt is imperative that affected cats continue to consume a balanced diet even after resolution of clinical signs.
Pansteatitis - how it affects multicat households
- Cats have different abilities to tolerate diets high in unsaturated fatty acids and/or deficient in vitamin E
- Some cats will develop pansteatitis and others will not even when fed the same diet
Metatarsal fistulation - definition
= an uncommon condition where draining tracts occur in the skin of the plantar metatarsal area
