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Large Animal Surgery > Equine Skin Diseases & Disorders > Flashcards

Equine Skin Diseases & Disorders Flashcards

1
Q

What are sarcoids? What are the 4 most common places?

A

locally invasive, non-metastatic cutaneous fibroblastic tumor (most common skin tumor in horses)

  1. head, legs, ventral abdomen
  2. eyes, ears, muzzle
  3. areas of previous trauma/wounds
  4. penis
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2
Q

What horses are most commonly affected by sarcoids?

A

young adults 2-9 y/o

1/3 will have multiple lesions

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3
Q

What are 4 possible etiologies of sarcoids?

A
  1. bovine papilloma virus - viral E5 protein associated with malignancy
  2. trauma - common at wound sites
  3. direct contact/vector-borne - eyes, ears, distal limbs
  4. genetics - AQH > TB > SB
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4
Q

What are 4 typical characteristics of sarcoids on histopathology?

A
  1. epidermal acanthosis
  2. hyperkeratosis/hyperplasia
  3. dermal fibroblastic tissue with immature fibroblasts - arranged in a whorl pattern
  4. mitotic figures
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5
Q

What are occult sarcoids? What can it be confused with?

A

earliest form of sarcoid where there is a circular, hairless area of thickened skin (may stay unchanged for years)

ringworm —> more thickened, won’t respond to treatment, hair samples come back negative

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6
Q

What are verrucous sarcoids? What is characteristic?

A

grey, scaly, warty sarcoid that can develop local ulceration or have small nodules below the skin (flat, no longer smooth)

occult halo - lack of hair around the rim

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7
Q

Occult sarcoid:

A

flat, hairless

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8
Q

Verrucous sarcoid:

A

grey, scaly, warty

+/- nodules

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9
Q

What are nodular sarcoids? Where are they most commonly located?

A

discrete, firm nodule under the skin that can ulcerate +/- firmly attached

  • eyelid
  • axilla
  • inner thigh
  • groin
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10
Q

Nodular sarcoid

A

+/- firmly attached

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11
Q

What are fibroblastic sarcoids? What leads to further ulceration/infection?

A

fleshy and aggressive in appearance that can have a narrow pedicle attaching it to the body and may invade past

attractive to flies

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12
Q

Where are mixed sarcoids most commonly found?

A

areas of repeated trauma (tack rubbing) or inappropriate treatments

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13
Q

What are malignant/malevolent sarcoids?

A

rare type of sarcoid that can extensively spread through skin and underlying tissues

  • aggressive local invasion, NOT internal organs
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14
Q

What sarcoids are most likely to spontaneously regress? Which ones progress to malignancy?

A

occult > verrucous

verrucous/occult —> fibroblastic

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15
Q

What is avoided when diagnosing sarcoids?

A

biopsy —> most commonly already know what it is and risk making it worse

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16
Q

What does the treatment of choice for sarcoids depend on?

A
  • type
  • anatomic location
  • extent and number
  • duration
  • previous interventions
  • facilities
  • DVM expertise
  • cost of treatment
  • owner/horse compliance
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17
Q

How is sharp excision of sarcoids best done? What is the most common development following surgery?

A

when combined with other therapy

VERY hard to define margins —> recurrence is common, must change gloves and rinse with saline frequently

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18
Q

How does laser excision compare to scalpel excision? What complication is associated?

A

better success - less likely to seed tumor to normal surrounding skin

higher rate of wound dehiscence due to thermal damage —> only use in areas that allow second intention healing

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19
Q

How does cryosurgery work? What types of tumors does it work best on?

A

necrosis of the tumor through three freeze/thaw cycles from -20 to -30 degrees C to room temperature

superficial tumors —> limited by size and location

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20
Q

What are 3 options for chemotherapy to treat sarcoids?

A
  1. TOPICAL - Acyclovir or 5-fluorouracil cream
  2. INTRALESIONAL - Cisplatin or 5-fluorouracil
  3. ELECTROCHEMOTHERAPY - high voltage electric pulses and chemo to increase the dose directly reaching the cells (requires GA and 4-8 treatments, very effective with low recurrence)
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21
Q

What are 3 options for immunotherapy to treat sarcoids?

A
  1. BCG - Mycobacterium bovis cell wall immunostimulant to increase B and T cell response to tumor antigens
  2. Imiquimod (Aldera) - immunomodulator applied 3x a week for several months
  3. autologous vaccination - use bits of sarcoid frozen in liquid nitrogen and implanted into the neck to create a vaccine for numerous lesions not amenable to surgery
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22
Q

What 4 things are required for BCG to work? What tumors does this work best on?

A
  1. patient must be able to create an immune response
  2. immune response to BCG must correspond to tumor cells
  3. debulk before application
  4. multiple injections

small, periorbital, or fibroblastic tumors

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23
Q

What 2 complications are associated with BCG immunotherapy?

A
  1. anaphylactic shock
  2. severe local tissue swelling
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24
Q

What are 5 options for radiotherapy in treating sarcoids?

A
  1. Iridium-192
  2. Gold-198
  3. Cobalt-60
  4. Radon-222
  5. Radium-226

(locally implanted)

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25
Q

Why is radiotherapy rarely used?

A
  • expensive
  • hazardous
  • requires general anesthesia
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26
Q

What topical may aid in treatment of sarcoids? When are they most commonly used?

A

blood root/zinc chloride mixtures (Xxterra)

less aggressive sarcoids - can make aggressive ones worse

27
Q

What 3 things affect the prognosis for sarcoids?

A
  1. number of treatments - more treatments that don’t work = worse prognosis
  2. location - worse prognosis on limbs and periocular region
  3. type - more “angrier” = worse prognosis
28
Q

What treatment is best in this situation?

A

LEAVE IT ALONE

  • treatment/biopsy makes it worse
29
Q

What treatment is best in this situation?

A

<10 cm = topical Aldara, topical Xxtera, intralesional Cisplatin, embedded Cisplatin beads

> 10 cm = debulk, cryotherapy OR embed Cisplatin beads at margin

30
Q

What treatment is best in this situation?

A

<10 cm = topcial Aldara, intralestional Cisplatin, implant marginal Cisplatin beads

> 10 cm = debulk, cryotherapy OR implant marginal Cisplatin beads

31
Q

What treatment is best in this situation?

A
  • do anything you can
  • plan on it taking a long time
  • plan on using multiple therapies

(unlikely to completely clear)

32
Q

What is a dentigerous cyst? How is it treated?

A

ear tooth - cystic lining around a tooth in an abnormal location that presents as a draining tract near the ear

remove cyst lining and tooth

33
Q

What is nodular necrobiosis? What are 2 possible causes?

A

eosinophilic granulomas for 0.5-1 cm firm nodules often on the withers/back

  1. trauma (found under the saddle)
  2. insect hypersensitivity
34
Q

Is treatment necessary for nodular necrobiosis? What can be done?

A

no —> cosmetic

inject steroids (triamcinolone, methylprednisolone) into lumps —> recurrence = multiple treatments

35
Q

What is the general rule for margins in equine mass removals?

A

> 5mm margins (~1 cm)

36
Q

What techniques are used for mass removals on limbs?

A
  • tourniquet to minimize hemorrhage
  • immobilize post-removal, especially at joints
  • graft - not enough elastic skin to close
37
Q

What techniques are used for mass removals near eye or rectal orifices? What can interfere with function?

A
  • reconstruct area to maintain function
  • partial closures
  • +/- grafts

scarring

38
Q

How are masses on the body left to heal?

A

second intention - not commonly need to close

+/- graft

39
Q

How are equine skin grafts used in wound healing? Is this considered the best option for healing?

A

modify the appearance of a wound or surgical site

primary closure is ALWAYS best when possible

40
Q

What are 3 indications for applying equine skin grafts?

A
  1. extensive tissue loss causes there to be insufficient amount for closure
  2. excessive granulation tissue prevents wound contraction
  3. contraction/epithelialization will be insufficient to close defect
41
Q

What are 5 requirements for success of equine skin grafts?

A
  1. good vascular supply - will not work over exposed bone, tendons, ligaments, or fat
  2. free from infection
  3. competent post-graft care - proper bandaging
  4. flat, healthy bed of granulation tissue - remove proud flesh
  5. no motion - bandage or cast
42
Q

What bacteria can interfere with grafting? How do other bacteria affect grafting?

A

Pseudomonas spp. - creates exudate

make proteolytic enzymes that digest the fibrin needed to hold a graft

43
Q

What is a pedicle graft? Is this commonly used in horses?

A

graft connected to donor site by a vascular pedicle, including all skin components (gives a good appearance)

most cutaneous wounds are not suitable due to the inelasticity of equine skin

44
Q

What are free grafts defined by? What are the 2 types?

A

thickness

  1. split - epidermis and variable thickness of dermis
  2. full - epidermis and dermis without SQ tissue
45
Q

What is the difference between autografts, allografts, and xenografts?

A

graft from the same patient - most common and practical

graft from the same species - typically creates a strong immune response and rejection

graft from another species - biological dressings

46
Q

How do these wounds compare?

A

L = unhealthy with exudate

R = healthy, free from infection, not exuberant

47
Q

What is a pinch graft?

A

island graft where a small section of the skin in pinched or elevated with a needle and removed with a scalpel, then placed on a saline-soaked gauze before implantation —-> donor sites are left open or closed with a single suture

48
Q

How do pinch grafts affect healing?

A

split thickness at edges and full thickness in the center = variable hair growth

49
Q

What are 2 indications for pinch grafts?

A
  1. high motion areas (joints)
  2. buried into granulation tissue
50
Q

What are punch grafts? Where are they most commonly taken from?

A

full thickness island grafts taken using a biopsy punch to remove underlying SQ tissue

under mane on the neck, ventral abdomen, or thorax

51
Q

How is the recipient bed prepared for punch grafts? What is important for cosmetic results?

A

use a smaller biopsy punch to prep the area since the graft will likely shrink and want a tight fit + close each donor site with monofilament suture

direction of hair growth

52
Q

What are 2 indications for punch grafts?

A
  1. wounds over joints
  2. wounds less than 10 cm diameter
53
Q

What are tunnel grafts? What are the 2 types?

A

island graft tunneled about 6mm below the surface of granulation tissue and sutured on each side placed 2cm apart

  1. partial - dermatome
  2. full - parallel incisions 2 mm apart
54
Q

How do tunnel grafts heal? When are they most commonly used?

A

granulation tissue over them sloughs or is removed in 7-10 days

large wounds with thick granulation tissue —> good graft acceptance

55
Q

How are sheet grafts made? What 2 advantages do they have?

A

partial thickness pieces of skin are obtained with a dermatome (PAINFUL - needs general anesthesia), resulting in a sheet of skin that can be sutured into place

  1. prevents fluid accumulation
  2. improved graft acceptance
    (mesh turns large wound into lots of tiny ones)
56
Q

What are 3 options for limb immobilization for proper healing?

A
  1. sterile non-adherent pad
  2. compression bandage for distal limb wounds
  3. casting over areas of motion
57
Q

What is a major complication associated with casting for limb immobilization?

A

prevents examination of the wound

  • requires close monitoring for cast complications
58
Q

What are 6 causes of graft failure?

A
  1. poorly prepared recipient bed
  2. poor perfusion (bare bone, ligament, fat)
  3. hemorrhage displacing pinch or punch grafts
  4. motion
  5. fluid accumulation under graft = graft displacement
  6. bacterial infection causes excessive wound exudate and enzymatic destruction of fibrin responsible for holding graft into place
59
Q

What are the 2 most common bacterial causes of graft failure?

A
  1. Pseudomonas spp.
  2. beta-hemolytic Streptococcus spp
60
Q

How can infections of wound beds be avoided to prevent graft failure?

A

antibiotics —> powdered broad-spectrum Timentin (ticarcillin with potassium clavulanate)

61
Q

How can inflammation be controlled to prevent graft failure?

A

systemic NSAIDs - Phenylbutazone, Flunixin

62
Q

What are 5 options for decreasing movement to prevent graft failure?

A
  1. delay first bandage change to 4-5 days
  2. confine to stall
  3. non-adherent dressing
  4. immobilize limb with RJB or cast
  5. use techniques less affected by motion, like island grafts
63
Q

What are 2 options for decreasing fluid accumulation to prevent graft failure?

A
  1. use a meshed, tunnel, or pinch graft
  2. use hemostasis for punch grafts

Large Animal Surgery (32 decks)

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