Rodent Surgery Flashcards
Rodents urinary/repro anatomy ?
Have sepratae urinary and vaginal openings - can determine if discharge is from urinary or reprod tract
Scent glands ?
Ventral scent gland dwarf hamsters and gerbils vs FLNAK in syrian hamsters
What patient factos to consider in rodent surgery?
- Relatively small lung volume compared to body size
- Ideally elevate head -> reduces abdominal contnts pushing against diaphragm
Wha surgical equipment/ haemostasis considerations?
- Fine tipped equipment
- sterile cotton tip applicatos
- Artery forceps
HAEMOSTASIS in rodents?
in healthy animals total blood volume 7% of BW
- 10% of this can be drawn for blood sampling
- 0.5-0.7ml/100g max amount of blood loss
to calculate = each cotton tipped applicator holds 0.1ml blood
What initial assessment of rodents?
- Full CE
- Sabilise & get BW
- Pre-op assess - RR & HR
- Rodents don’t vomit => unnecessary to withold food &fasting inc risk of GI disturbanceds
- Minimise stress
Pain in rodents?
- Newcastle grimace scale - rats and mice
- Hunched? hiding?
-Belly pressing? - contracted abd muscles
- loss of appetite
- Chage of HR, RR and deph
surgical skin prep in rodents?
Iodine/chlorhex & good contact time
- Warm surgical scrub first
- Avoid excess alcohol due to evaporative losses
Iv placement where?
- caphalic/saphenous in GP
- Tail vein in rats
Intraosseous placement where?
- Femur -> through trochanteric fossa
- Tibia -> through tibial crest
What is fluid mainenance rate for most rodent species?
3-4ml/kg/hr
During surgery - considerations?
- HYPOTHERMIA! - warm theatre, bubble wrap, warm fluids,
- Prevent HYPOXIA! - oxygen admin
Post op considerations?
● Monitor & supportive care.
● Maintain body temperature
● Analgesia essential
○ Traumatising surgical site
● Fluid and nutritional support
○ Assist feeding ASAP.
● Therapeutic laser therapy
● Phovia
What reasons for skin surgery?
- Lump removal - neoplastic /cystic
- Absess surgery - thick, caseous material within a thick capsule
- wound management
- Scent gland hyperplasia/ neoplasia
Describe Trichofolliculoma in Guinea pigs
- usually located over the dorsum, may ischarge keratinous or haemorrhagic material from a central pore
- Surgical approach similar to lump removal
- excision curative
Describe Ventral sent gland tumour surgery in gerbils and dwarf hamsters ?
- In gerbils, neoplasia (SCC, adenomas, adenoCs)
- wide excision aroudn scent gland
- Most rodents have moderate to extensive amount of loose skin
Pregnancy prevention ?
- Sexual maturity in mice/ rats/ gerbils = 6-8 weeks
- sexual maturity in GP = 4-6 weeks (female) and 9-10 weeks (male)
Disease prevention for reproductive management ?
- significant reduction in mammary tumours developing if ovariectomy performed in rats before 90 days
What non surgical options of reproductive management?
- separation of sexes but welfare implications & fighting in same sex!
- Medical management (implants -> NOT effective, CI in GPs) & Hormonal injections (not effective)
What surgical approaches to neutering?
- Traditional, ventral abdominal midline
- Flank (GP and rats) -> bilat or unilar
- Combination approaches
What considerations for elective neutering ?
- Small nodular ovaries
- Ovaries locate dinf at
- Confilcting advice in lit regarding type of uterus tat some rodents have - clinically no difference
What advantages of Flank approach?
- Less invasive
- Quick recovery time
- Less risk of infection
- Less risk of suture disruption and complications
- Less risk of evisceration secondary to dehisence
- Bilat or unilat
Flank (more lumbar) approach -> describe part 1
- Find landmarks (spine, last rub, pelvis)
- Incise bulge in midle
- Blunt dissect trough muscles (external oblique & internal laminar muscles)
Describe flank approach part 2
- retract fat until you can see the distal uterine horn and ovary
- Ligate the ovarian pedicle
- Often a bilat flank approach
Describe ventral midline approach
- Similar to dog
- Much fat on ovaries located at caudal pole of kidneys
- BE CAREFUL WITH ADHESIONS! -> gentle handling, haemostasis, don’t use dry swabs, irrigate tissues & don’t use catgut sutures
What signs of ovarian and uterine dx ?
- Infertility
- wbdo distention
- Weight loss
- Poor BCS
- Vaginal discharge
- on speicfic
- Pain
What signs of mammary dx?
- Development opf masses
- swollen glands
- Discharge
- Pyrexia
- Non specific
What ddx for surgical uterine dx?
- Neoplasia
- polyps
- Infection
- hydrometra
- Endometrial hyperplasia
- Torsion
- Endometrial aneurysms
What vaginal/vulval dx can be surgical ?
- Congenital
Neoplasia - Prolapse
- vulvitis?
What species specific considerations - gerbils ?
- High incidence of ovarian dx -> cysts, neoP
CLS: abd distention, bilat alopecia, weight loss, dec appetite, respiratory effort
Dx: cls, imaging
Ventral midline approach
Pyometra or not - syrian hamsters?
Off-white, stringy discharge after ovulation on day 2 of oestrus cycle -> completely normal!
Pyometra in hamsters/ gerbils?
- Do not misinterpret in hamsters!
Dx: cls, US, cytology
What type of ammmary tumours do rats get?
Often benign fibroadenomatous mammary tumours
What is thought to play a part in mammary tumours?
Prolactin
Where an mammary tumours develop?
tissue extensive! -> from peri-anal to shoulder region!
What prevention against mammary tumors?
Early age Ovariectomy (<90days)
What charcateristics of male reprod tract ?
Histricomorphs (GPs) o not have a distinct scrotum
- Testicles located in inguinal region
- Testicles large for body size
- inguinal canals remian open -> funcitonal cremaster muscle to move in and out of abdo cavity
Who’s inguinal ring closes?
Rabbits and rodents -> stays OPEN
What approaches to ‘catsration’ do we have in rodents?
- Scrotal -> open, closed, open/closed mix
- Prescrotal - open, closed, open/closed mix
- Abdominal approach
Vasectomy
Describe Abdominal approach castration (GPs, and small rodents)
- 1-2 cm incision between umbilicus and pubis
- Start incision caudal to umbilicus
- Incise Linea Alba
- Exteriorise bladder & reflect caudally
- Visualise testicle fat pad & exteriorise testicle
- Break tunic attachment and place 1 clamp
- Place encircling lig
- Remove testicle and check stump for bleeding
Describe Pre-scrotal/scrotal approach -> open-closed (modified open technique)
- Dorsal recumbency - lidocaine block & prescrotal or scrotal incision
- In cise tunica vaginalis & exteriorise testicle
- Detach from lig of tail of the epididymis
- Place lig proximal to incision in tunic to incorporate entier spermatic cord -> losing off tunic and external ring
What are rodents prone to post-castration?
Incisional infections and scrotal abscessation
How do we identify testicular dx?
- Change in testicular shape/ texture
- Change in libido
- Inflammation / papules/ ulcers
What kind of testicular dx do we see?
- Testiular neoplasia
- cryptochidism
- Orchitis
- Epididymitis
- Preputial/ testicular trauma - sometimes surgical
Describe fur ring in chinchillas and degus
- Fur ting traps penis causing paraphimosis -> large areas of self trauma can be visible due to pain
What GI dx are GPs prone to?
Bloat & GDV
(similar approach to dogs -> often see engorged gastric vessels and spleen)
How do we deal with GDV/ Bloat in GPs?
- Decompress stomach and careful reposition
- Perform gastropexy using monofilament suture
- Flush abdo with warmed steriel saline
- Routine closure
What GI (ish) dx do hamsters get?
Cheek pouch eversion -> bilat storage cheek pouches lined with a thin epithelium
How to treat cheek pouch eversion?
- Brief GA - clean pouch
- 1ml syringe to reduce and reposition pouch in mough
Place 1-2 mattress sutures, through the skin and cheek pouch and exit skin again - leave in for 2 weeks - Withhold normal diet for 3-5 days offer syringe soft feed to prevent use of pouch
What urinary tract dx do GPs get?
- Urinary calculi -> most common in males, urethral obstruction common
How to treat urinary calculi?
- Ventral midline incision caudal abdomen
- Identify bladder & place soaked swabs
- Place stay sutures at APEX of bladder & each side of proposed cystotomy incision
- Enter bladder in avascular area
- Remove uroliths (suction to prevent urine leakage)
- Collect samples
- lavage bladder
- Close (one layer - monoF absorbable
What orthopaedic surgery is routinely done in small rodents?
Degloving & Tail amputations
Who prone ot degloving/ tail amp?
Gerbils and degus
When is tail amputation recommended?
If loss of blood supply
How to do a tail amp?
- Make incision 1-2mm proximal to the location of skin loss
- Incise the dorsal skin more proximal than the ventral skin
- Tail incised between 2 vertebrae
- Ensure haemostasis of ventral coccygeal vessels
- Close via a Sc layer then intradermal suture layer or tissue adhesive
