Surgery Flashcards
What are the advantages of open castration?
Testicular/vaginal tunics entered and reflected, allowing palcement of ligatures directly onto vascular cord and ductus deferens, minimising chance of ligature slippage or loosening
What are the disadvantages of open castration?
- Indirect opening into peritoneal cavity created (however under aseptic technique, infection should not be a major issue)
- Operation time slightly longer
Describe the method for open castration
- Incise skin and subcut tissue on prescrotal midline
- Advance one testicle towards incision
- Incise speratic fascia to reach parietal vagina tunic
- Fenestrate spermatic fascia, place clamp across ligament of tail of epididymis
- Divide ligament and fascial attachments above clamp
- Wipe spermatic cord with gauze sponge to retract fascial layers
- Double or triple clamp, ligate testicular vein and artery together proximally to animal, ligate ductus deferens
- Place second encircing ligature around vascular cord and ductus deferens
- Transect cord between 2 haemostatic clamps
- Release cord under control of thumb forceps
- Observe for haemorrhave, replace within tunic
- Repeat with second testicle
- Dense fascial layers apposed with interrupted or continuous suture, subcut tissues with simple interrupted or continuous absorbable sutures, intradermal or subcuticular sutures placed instead of skin sutures, or close skin in routine fashion
Describe semi-closed castration
- Same as open, except that the vaginal tunic is ligated at the end of the procedure
- Commonly used in rodents
- Vaginal tunic cut proximally then closed using 3-0 or 4- absorbable suture
How can herniation of abdominal contents into the tunic following semi-closed castration be avoided?
Minimise the size of the tunic before closure
What are the advantages of closed castration?
- Vaginal tunics not entered
- Reduced risk of bleeding from incised vaginal tunics
- Rapid, easy
- Reduced risk of infection as there is no opening into peritoneal cavity created
- No possibility of seeding local wound with tumour cells as tunics and testicle remain in tact
What are the disadvantages of close castration?
- No tension must be placed on spermatic cord during clamping or ligation
- Extra care when placing ligatures since vessels supplying testicles are indirectly ligated
- More risk of catastrophic bleeding if ligatures are not secure
Describe the method for close castration in the dog
- Pre-scrotal midline incision
- Advance testicle towards incision
- Do not incise tunic
- Push testicle out of wound
- Hold scrotum in place under drape, pull testicle firmly up to break down spermatic fascia and gubernaculum and expose at least 8cm of cord
- wipe spermatic cord with gauze sponge to retract fascial layers and strip loosely adhered fat
- place 3 clamps on cord
- Ensure cord is loose so vessels are not under tension
- Flatten cord with finger, separate cremaster from vessels
- Apply transfixing encircling ligature closest to proximal clamp around spermatic cord
- Pass needle through cord, around vessels, 2 throws on vessels side, 4 on other side
- Transect cord 0.5cm distal to transfixing ligature
- Release cord under control of thumb forceps, observe for haemorrhage, replace within wound
- Close subcut tissue with simple interrupted or continuous absorbable sutures
- Can place intradermal sutures or route percutaneous sutures
What are the advantages of cruciate mattress sutures?
- Quick to place
- Allows for good skin apposition and control of tension across the wound
What are Ford Interlocking sutures used for?
Closure of skin incisions in farm animal species
What is cytology?
The study of cell number and type in a tissue mass or fluid accumulation, to investigate it’s cause
What can be gained from cytological examination?
- Differentiation of different fluids
- Differentiation of types of inflammation
- Detect presence of neoplasia (and indicate type)
What are the advantages of cytology?
- Sampling is quick, safe, inexpensive
- Can often be safely retrieved from lesions near vulnerable structures in conscious animals, so anaesthesia and surgical biopsy is unnecessary
- Quick results
- Little equipment and limited skill for sampling
- Simple blood stain and microscope can give idea of pathological process
How might false negatives in the detection of neoplasia occur in cytology?
- Poor exfoliation of neoplasm
- Failure to sample tumour tissue
- Extensive necrosis/inflammation present hiding tumour cells
- Neoplasm may not be well differentiated enough to allow accurate diagnosis
How might false positives in the detection of neoplasia occur in cytology?
- Dysplasia can mimic neoplasia and may occur in inflammatory diseases
- e.g. mesothelial cells can develop atypical morphology and proliferative changes caused by inflammation, revert back to normal if irritant is removed
Describe fine needle capillary sampling
- FNA with no suction
- No syringe attached
- Cells drawn into needle via capillary action
- Less traumatic to cells
- Less likely to draw blood and dilute sample
Describe fine needle aspirates
- Minimal suction
- used in cysts or failed FNCS
- Need to ensure are not applying suction pressure when removing the needle from the animal
- Some risk of cell destruction
List the different sampling techniques for cytology
- FNA and FNCS
- Lavages
- Thoraco/abdominocentesis
What are lavages/washes in cytology?
- Using sterile saline, cells washed from nasal, bronchoalveolar and urinary bladder mucosae
- Retrieved by immediate aspiration of the lavage fluid
Outline abdomino/thoracocentesis
- Small amount of fluid is normal, usually too little for collection except in horses
- Marked hypoproteinaemia is common pathological cause of excess body cavity fluid
- May use needle alone, needle with syringe or needle with a 3-way tap
Outline transtracheal lavage
- Catheter passed through wide gauge needle in a conscious dog
- Fluid flushed into airway and quickly aspirated
- Smears made from centrifuged sediment
Outline bronchoalveolar lavage
- Fluid lavaged through catheter which has been passed through endo-tracheal tube in anaesthetised animal
- Can be done using a bronchoscope
What is the advantage of using a bronchoscope in cytological sampling?
Can visualise lesion and directly remove cells from it using a small brush
What 4 basic tests are applied to fluid samples?
- Gross appearance
- Total protein content
- Nucleated cell count (TNCC)
- Cell type/s content (sediment smear under microscope)
Describe aspirate smear preparation
- Blood sample (“wedge”) method or flat slide method
- Smear dried rapidly by waving in the air, holding in front of fan or hair dryer
- Dry slides stained and examined, or stored in slide holder and packed for postage to commercial laboratory
- Never put wet slides in carrier box
- Attach description of mass including size, location, texture and growth rate
Describe the preparation of cytology fluids
- If turbid, make direct smears
- If clear, centrifuge and smear deposit (ordinary centrifuge at low speed for short period, or special cytocentrifuge)
- Air dry rapidly and stain
- Sediment smears with wedge or flat slide method
What samples can touch imprints be made with?
Biopsy or necropsy tissue
Outline the use of touch imprints in cytological examination
Rapid preliminary diagnosis while waiting for results from histopathology of tissue sample
Describe how to produce a touch imprint from a tissue sample
- Grasp small piece of tissue with forceps
- Dab off excess blood
- Imprint onto several clean glass slides
- Air dry quickly, stain with blood stain, examine immediately
Describe the preparation of core and tru-cut biopsies
Roll core along side for cytology, then place in formalin pot for histology
Outline the staining of cytological samples
- Usually romanowsky blood stain e.g. Diff-Quik, Dip-Quik, Wright’s, Giemsa, Leishman
- Simple, quick, familiar colouration of cells
- can use special stains e.g. methylene blue, toluidine blue (mast cell granules) periodic acid Schiff (PAS)
- If microorganisms are suspected: Gram’s, Modified Ziehl Nielsen, PAS or Fontana’s stain
Name the different types of effusions
- Transudate
- Exudate
- Haemorrhage
- Lymphorrhage
Outline lymphorrhage
- Can be chylous or non-chylous
- may be due to rupture of bile duct or blockage
Explain how effusions may occur
- Increased hydrostatic pressure
- Increased cardiac pressure (will increase the hydrostatic pressure)
- Inflammation
- Decreased colloid pressure in the vessels
How may inflammation lead to effusions? Describe its contents
- Makes vessel walls permeable and leaky
- Fluid loss out of the spaces
- Will contain cells as well as protein
Describe the characteristics of transudate (gross appearance, protein content, nucleated cell content, cell types)
- Clear, watery appearance
- Protein poor (<20g/L) or protein rich (3-35g/L)
- Nucleated cells <5x10^9/L
- Cell types: few RBCs, small mixed nucleated cell population (neutrophils up to 60%, lymphocytes, monocytes, macrophages, mesothelial cells)
How may transudate occur?
- Altered hydraulic pressure e.g. increased alveolar capillary pressure, Na and water retention, portal hypertension
- Decreased pasma ocotic pressure
- Accumulation due to impaired lymphatic drainage
Explain how impaired lymphatic drainage can lead to transudate
Material coming into space not drained as quickly e.g. increased hydrostatic pressure in the posterior vena cava in venous congestion
Outline the causes of protein poor transudate
- Reduced plasma oncotic pressure (e.g. hypoalbunimaemia)
- Portal hypertension (pre-sinusoidal e.g. certain cirrhosis)
- Fluid that has not been sat around in the organ with high protein content
Describe protein rich transudate
- Proteins from interstitium rather than vasculature
- Varies by organ (2g/dl in subcutis, 6g/dl in liver)
- Caused by post-sinusoidal portal hypertension e.g. congestive cardiac failure
- May be referred to as modified transudate
Outline the appearance of mesothelial cells in transudate
- May appear neoplastic if are dysplastic
- Deeply basophilic cytoplasm, variable nuclear to cytoplasmic ratio, may be multinucleated, clumped chromatin, prominent nucleoli
- Apparent fringe of pink villi on some cells can help identify as mesothelial cells
- Seen singly or in clumps in all body cavity fluids
- may increase in number in irritation or inflammation
What are potential causes of exudate?
- Inflammation
- Infection
- Necrosis (including necrosis within tumours)
- Increased hydraulic pressure pushing protein rich fluid into interstitium, protein in interstitium then draws water out of vessels due to oncotic pressure
Describe the characteristics of exudate (gross appearance, protein content, nucleated cells, cell types)
- Turbid, bloody, purulent all possible
- Protein: >20g/L
- Nucleated cells >5x10^9/L
- Cell types: many RBCs, nucleated cells are mostly neutrophils (may be degenerate - karyolysis), bacteria may be present
Describe the cells found in ecudates
- May be neutrophils and macrophages only
- Or also lymphocytes
- Occasionally eosinoophils or lymphocytes predominate
Why is the cell count of exudate lower in FIP?
Because it is vasculitis rather than pleuritis
Describe the characteristics of neoplastic effusions (gross appearance, protein content, nucleated cell content, cell types)
- May be bloody and/or turbid
- Protein: often >35g/L
- Nucleated cells often 5-25x10^9/L
- Cell types: RBCs mixed with nucleated cell population, neoplastic cells may be seen
- Effusion may be directly from tumour or related to inflammation caused by the tumour
Describe the cell content of different neoplastic effusions
- Adenocarcinoma: morula of cells with characteristic appearance
- Lymphoma: mostly large round cells with malignant cells (as well as RBCs and neutrophils)
- Melanoma: mixed cell types and black granular material in fluid
Describe the characteristics of haemothorax/haemoperitoneum (gross appearance, PCV, protein content, nucleated cells, cell types present)
- Bloody but does not clot
- PCV variable, >0.03/L
- Protein: >20g/L
- Nucleated cells variable, similar to blood
- Cell types: RBCs, no platelets, mized nucleated and mesothelial cells, possible haemosiderophages
How can the proportion of blood in a fluid be calculated in a haemothorax?
- PCV on fluid
- PCV on blood
- Compare and calculate the proportion
Why are there no platelets in the fluid of a haemothorax?
- Platelets will coagulate within a few minutes
- Helps differentiate between haemorrhage as part of disease process of as a result of sampling
Describe the characteristics of a uroperitoneum (gross apperance, protein content, nucleated cell content, cell types, creatinine and potassium)
- Serosanguinous, may be odour of urine (especially when heated)
- Protein: 10-30g/L
- Nucleated cells low at first, but with disease progress to 5-15x10^9/L
- Creatinine and potassium higher than in plasma if recent or ongoing
- Cell types: many RBCs, mixed nucleated cells (increased cell count due to inflammation)
Describe the characteristics of chylous effusions (gross appearance, protein content, nucleated cell content, cell types)
- Milky, white or pink
- Protein >20g/L
- Nucleated cells 5-20x10^9/L
- Cell types vary with age of lesion(mostly mature lymphocytes at first)
Describe the potential causes of chylous effusions
- Trauma/spontaneous rupture of thoracic duct (idiopathic chylothorax)
- Heart failure
- Cardiomyopathy
- Pericardial effusion
- neoplasia
- Lymphangectasia
- Obstruction of mior lymphatics by chronic inflammation etc
Non-thoracic duct origin chylous thoracic fluid is common in cats in what conditions?
- Cardiomyopathy
- Diaphragmatic hernia
How can fluid be confirmed as chyle?
Ether dissolves the turbidity after alkalinising it by adding NaOH
Compare the turbidity of chyle and non-chylous effusions
Chyle ++++
Non-chyle +++
Compare the triglyceride content in relation to plasma of chyle and non-chyle effusions
Chyle > plasma
Non-chyle < plasma
Compare the cholesterol content in relation to plasma of chyle and non-chyle effusions
Chyle < plasma
Non-chyle > plasma
Compare the Cholesterol:triglyceride ratio in chyle and non-chyle effusions
Chyle: low
Non-chyle: high
Compare the predominant cell type in chyle and non-chyle effusions
Chyle: lymphocytes
Non-chyle: neutrophils, macrophages
Describe the examination of synovial fluid
- Gross examinatino
- Viscosity (decreased in disease) assessed by pull test and acetic acid clotting (tight is norma)
- Total protein: smear should have proteinaceous background
- Total nucleated cell count: more than 10% neutrophils indicated inflammation
Describe the cytological findings in synovial fluid with degenerative joint disease
- Total protein, TNCC and cytology often normal
- Occasionally may find dysplastic synoviocytes
Describe the cytological findings in synovial fluid in non-septic inflammation of the joint
- Commonly immune mediated in dogs and cats
- Total protein and TNCC increased
- Neutrophils predominate
Describe the cytological findings in synovial fluid in a septic inflammation of the joint
- Common in horses and ruminants
- Total protein and TNCC increased
- Neutrophils predominate
- Bacteria visible or found on culture
Describe the normal cells found on bronchoalveolar lavage
- Ciliated columnar epithelial cells predominate
- <10% leukocytes
- Up to 25% eosinophils in cats
What findings in cytology of bronchoalveolar lavage indicate oropharyngeal contamination?
- Squamous epithelial cells
- Simonsiella bacteria
Describe cell types found from nasal lavage in inflammation
- Inflammatory cells
- Cell debris
- Mucus
- May see neoplasia
What conditions may be identified on tracheobronchial lavage?
- Inflammation (acute, septic/non-septic, eosinophilic, chronic)
- Pulmonary haemorrhage
- Neoplasia
Describe bone marrow examination
- Cellularity assessed: normal, decreased, increased?
- Evaluation of cell lineages: erythroid, myeloid, megakaryocytes
- Parasites present?
- Neoplastic cells present?
List Halstead’s principles of surgery
- Gentle tissue handling
- Strict asepsis
- Haemostasis
- Preservation of blood supply
- No tension on tissue
- Good approximation of tissues
- Obliteration of dead space
Identify the possible approaches for a laparotomy
- Ventral midline (most common)
- Flank
- Inguinal
- Paracostal
- Sublumbar
- Parapenile
Describe the paracostal approach to laparotomy
- Just behind last costal rib arch
- Often in combination with ventral midline to make approach bigger
Describe the sublumbar approach to laparotomy
- More common in large animals
- In small animals may be used to locate migrating foreign bodies or for spinal surgery
Describe the parapenile approach to laparotomy
- Common in dogs as sheath and prepuce are in the way of ventral midline approach
- Incision to the side of sheath, locate linea alba underneath
- Then make ventral midline incision through the linea alba
Why is a ventral midline incision cranial to the umbilicus preferable to caudally?
- External sheath of rectus is between muscles
- Easy to visualise linea alba
Describe a ventral midline incision for laparotomy
- Midline incision through skin
- May need to remove some subcut fat to visualise midline clearly
- Grasp linea alba with rat toothed forceps, pull away from dog gently
- Use blade upside down to make nicks in the linea alba
- Then use push-cut technique to get through the LA
- May need to excise the falciform fat if are performing cranial abdominal surgery
Describe exploration of the abdomen in a laparotomy
- Good exposure critical so need to make incision long enough
- Use retractors e.g. Balfour (3 point), Gosset (2 point) or handheld
- Methodical examination esp. for GIT
Why are Balfour retractors preferable to Gosset retractors in abdominal surgery?
- Balfour are 3 point while Gosset are 2 point
- Gosset are therefore at risk of rotating within the incision site
List the structures that can be identified on laparotomy
- Liver and biliary tract
- Small intestine (duodenum, jejunum, ileum, iliocaecocolic junction)
- Pancreas (right limb and body alongside duodenum, left limb adjacent to the greater curvature of the stomach)
- Large intestine (caecum, colon)
- Urogenital tract
What does the suffix “otomy” mean?
Making a hole into a hollow organ or cavity
What does the suffix “ostomy” mean?
Making a permanent hole in an organ or cavity
What does the suffix “ectomy” mean?
Removal of an organ
What does enterotomy mean?
Making a small hole in the small intestine
What does enterectomy mean?
Removing a portion of the small intestine
What are the 2 techniques for a mesenteric dam?
- Duodenal or colonic manouvre
- Manipulate rest of GIT in order to allow better visualisation of dorsal structures when entering the abdomen ventrally
Describe the duodenal manouvre
- Duodenum sits ventrally on right side
- Retract across abdominally cavity, enabling small and large intestine to be retracted
- Exposes the right urogenital structures, vena cava and portal system
Describe the colonic manouvre
- Retraction of the descending colon
- Exposes the left side of the abdomen
What are the 4 layers of the bowel wall?
- Mucosal
- Submucosal
- Muscular (inner circular and outer longitudinal)
- Serosal
Which layer of the bowel wall forms the air and watertight seal?
The serosal layer
Outline the rules of GI surgery
- Submucosa must be incorporated into the surgical closure
- Gentle tissue handling
- Maintain good blood supply
- Prevent tension across the suture line
- Avoid spillage of contents by using laparotomy swabs
- Lavage and suction may be needed
- Peri-operative antibiotics may be needed in contaminated surgery
When might a gastrotomy be required?
In the removal of a foreign body
Outline the key considerations in a gastrotomy
- Stomach fixed at pylorus due to hepatogastric ligament so using stay sutures can manipulate bowel out of cavity and minimise contamination of abdominal cavity
- Surround with swabs
- Bacterial load of stomach low due to pH, but risk of acid scalding
When might surgery be required at the small intestine?
- Foreign body
- Intussusception (concertina-ing of bowel into itself, commonly oral end into aboral end)
What is a key consideration with small intestine surgery?
High bacterial load
When might an enterotomy be required?
- Removal of a foreign body
- Biopsy
Outline the enterotomy procedure for a biopsy
- Use non-crushing clamps to hold in place, but fingers often best
- Take full thickness small intestinal biopsy when animal has persistent diarrhoea +/- vomiting (may be immune mediated inflammatory bowel disease, only way to diagnose is biopsy)
What are the key points regarding enterotomy for the removal of a foreign body?
- Fluid build up on oral side of foreign body and empty bowel on aboral side
- Make incision on the antemesenteric side of the bowel
Outline the procedure for an enterectomy
- Use non-crushing and crushing clamps
- Crushing on the inside, non-crushing on the outside of the site to be removed
- Make incision for removal between the crushing and non-crushing clamps
- Anastomose ends that are left
Why might cystotomy be required?
- Removal of calculi
- Biopsy
- Tumour removal
Outline the key considerations for cystotomy
- Gentle handling to minimise oedema
- Place stay sutures in apex and draw bladder cranially
- Exteriorise and pack off bladder
- Drain
- Incise most convenient and avascular area (longitudinal incision on the ventral wall)
- Avoid trigone
