Small Animal Surgery Flashcards
What are the Halstead’s Principles?
- Haemostasis
- Approximation of tissues
- Adequate blood supply
- Strict asepsis
- Tension free close
- Tissue handled atraumatic
- Dead space reduced
What is the Anatomy of the Abdomen?
Linea Alba
Widest at the cranial abdomen
Composed of: External & internal abdominal obliques and transverse abdominal muscles
Attaches: To pubis via prepubic tendon (Cr Pubic ligament)
Prepubic Tendon
Dog: Attaches to pectineus, rectus abdominis & Aponeurosis of abdominal obliques
Cats: Doesn’t exist – is instead separate attachments of the pectineus & abdominal m.
What are Hernias?
Any full thickness defect or weakness in the abdominal wall that allows protrusion of abdominal contents
Composed of:
a) Ring – Anatomic limits of wall defect
–> True Defect: May be within a true aperture in body wall – covered by mesothelial membrane
–> False Defect: Made by blunt trauma – no sac & has risk of adhesions
–> Acquired Defect: Iatrogenic, e.g., surgery – no sac & has risk of adhesions
b) Sack – Mesothelial membrane (e.g., peritoneum)
c) Protruding contents
Locations:
- Cranio-Ventral Mid: Umbilical, substernal
- Lateral: Parasternal, dorsal lateral
- Caudal: Congenital scrotal, inguinal
- Traumatic: Prepubic, femoral
What is the Sequelae to Hernias?
a) Space occupying effects:
Abdominal wall becomes tightened as it adapts to the organ displacement
Issues: Abdominal compartment syndrome, tension on repair, acute pulmonary issues
b) Incarceration:
Luminal obstruction of hollow organs, usually by small inelastic rings (Femoral, scrotal)
Bladder: Usually entrapped within perineal, ventral, inguinal & traumatic – decompress*
Intestine: High mortality if hernia is ~ same size
Uterus: Only issues if pyometra or gravid
c) Strangulation:
Herniated contents are incarcerated and undergo devitalisation – may be delayed in traumatic hernias due to adhesions
Reversible: Early venous obstruction Irreversible: Arterial strangulation causing necrosis
What are the Aims and approach to hernia repair?
- Return contents
- Close ring to prevent recurrence
- Remove redundant tissue
- Use patients own tissue if suitable
Dx:
- Reduction of contents & palpation
- Radiograph (Abdominal strip)
- CT
- US to rule out DDx
Surgical Approach:
Hernial sac is ligated/amputated as close to canal or ring as possible
a) Over Hernial Ring: If uncomplicated & no evidence of obstruction or strangulation
b) Midline Celiotomy: If due to trauma or risk of strangulation/obstruction
Describe Ventral Abdominal Hernias (Do not breed)
Cause:
- Failure of embryogenic folds (Cephalic, caudal, lateral)
- Polygenic inherited character
Associated with:
- Fucosidosis
- Cryptorchidism
- Ectodermal dysplasia
- Incomplete caudal sternal fusion
- Concomitant diaphragmatic hernia
Omphaloceles
Large midline defects cause abdominal organs to protrude from the body in a transparent sac. Hard to repair and are usually PTS (put to sleep)
Umbilical:
Most common type. May be acquired via excess traction at birth but is RARE
Dx: Palpation in dorsal recumbency at umbilical scar
Tx:
- <2-3mm: Treat conservatively
- Larger: Surgical repair usually at ovariohysterectomy, tension free using Linea alba
- Spontaneous closure can occur ~6m
- Resect all irreversibly damaged organs
- Recurrence is uncommon
- Neuter all patients
Prognosis: Good. Guarded if strangulated, open at birth or multiple hernias
Causes of Caudal Abdominal Hernias?
- Congenital defect of Inguinal ring
Scrotal hernia - Indirect *Emergency
Viscera enters the vaginal process
Host: Young male dogs, increased with cryptorchidism
Consequence: Narrow inguinal canal causing high incidence of strangulation (GIT!)
CS: Dark swelling of caudal scrotum, pain, inflammation, hydrocoele, cord-like swelling
DDX: Orchitis, abscess – can rule out hernia if spermatic cord is normal size
Tx:
- Castration recommended
- +- Scrotal ablation
- +- Laparotomy if strangulated
- No post op Ab unless hollow lumen
- Suture both int. & ext. rings (Simple interrupted to allow spermatic cord, pudendal & n.)
Inguinal Hernia - Direct:
Less common, organs pass through inguinal rings
Host: Mature females – wider/shorter inguinal canal which ↑ by obesity & hormones
Consequence: Large w/ low incidence of strangulation
DDx: Lipoma, mammary tumour, fat, LN’s - DO NOT FNA unless US first
CS: Soft painless swelling in inguinal region, uni or bilateral
Tx:
- Bilateral: Midline approach
- Suture inguinal opening partially
- +- enlargement of cr. ring to reduce
- Traumatic
Tx: Require sutures at inguinal lig., ext. rectus fascia & int. oblique abdominal
What is Femoral Hernias?
Location: Protrusion through the femoral canal, lateral to the inguinal canal, usually caudomedial to the femoral vessels. Femoral ring is located at the inguinal ligament
Composed of:
a) Muscular lacuna: Femoral n. within iliopsoas m.
b) Vascular lacuna: Craniomedial to muscular lacuna – contains Saphenous n., femoral a. & v.,
Causes:
- Iatrogenic transection of pectineus m.
- Blunt trauma = avulsed cr. Pubic & inguinal lig
Dx: Palpate caudal to the inguinal ligament
Tx: Approach parallel to inguinal lig., or midline. Sutures placed btwn. Inguinal lig. & pectineal fascia
What is a Traumatic Hernia (False Hernia)
Associated w/: Diaphragmatic hernia or pelvic fracture due to increased abdominal pressure
CS: May be masked by signs of trauma, migration of contents may change site of swelling
- Acute: Painful, Chronic: non-painful
- Bulging mass & asymmetry
- Swelling ↑ with ab contraction
Dx: Assess abdominal strip for break & chest rads +-US if fluid
Tx: Acute: Midline approach Chronic: Over hernia to avoid adhesions +- enlarge ring
Aftercare: Encourage standing +- hobbles
Complications: Seroma, haematoma, infection,
skin dehiscence – recurrence is uncommon
What is an Incisional Hernia?
When abdominal suture is disrupted. May be acute (<7d) or chronic (wks → years)
Pathogenesis:
- ↑ intra-ab pressure (Pain, preg, obesity)
- Entrapped fat btwn hernia
- Inappropriate suture material
- Chronic steroid treatment
- Poor post-op care
CS: Wound oedema/inflam, serosanguinous drainage, +- evisceration by patient
Tx:
Acute:
- Early aggressive supportive therapy
- Sterile bandages +- E-collar
- Superficial: Close ab wall defect
- Deep wounds: Open peritoneal drainage
- Use monofilament abs or non-abs
- DON’T debride edges
Chronic:
- Debridement
- Reconstructive surgery
Prognosis:
- Good if no complications & limit exercise (2wks)
- Shock/contamination ~<40% mort
- ↑ hospitalisation: Small body, high lactate, evisceration
What is a Perineal Hernia?
Failure of pelvic diaphragm due to weakness or separation causing dilation of rectum and protrusion of prostate, bladder, intestine, rectal flexure, retroperitoneal fat/omentum, periprostatic cysts into perineum
Hosts: Males (89-93%) cf. females, middle-age to old dogs
CS: Constipation, obstipation, tenesmus, perineal swelling, +- UT signs ass. w/ bladder retroflexion
Describe the Pelvic Diaphragm
Functions: Maintain ab contents in abdomen & provide structure for rectum & other structures that transverse the pelvic canal
Muscles:
- Coccygeus m.
- Levator ani *Most common fault
- Ext. anal sphincter m.
- (Int. obturator m.)
Location:
- Most common: Between levator ani, ext. anal sphincter & internal obturator (Caudal Perineal)
- Least common : Between Bulbospongiosus, ischiourethral, ischiocavernous m.
- MAINLY right > left side
Important Structures: Sacrotuberus lig (Sciatic n. runs close, do NOT ligate)., Int. pudendal a/v/n., Caudal rectal n., Caudal gluteal a., Sciatic n., AND semitendinosus m., sup. Gluteal m., pelvic diaphragm
Explain the aetiology and consequences of of Perineal Hernia
Aetiology:
1. Congenital Predisposition
2. Rectal Abnormalities *RRRGRANP
- Rectal deviation (100%)
- Rectal dilatation (40%)
- Rectal diverticulum (Rare)
- Gender related differences
- Neurogenic atrophy
- Prostatic disease
3. Hormonal Imbalance: Androgens (2.7x risk if entire), relaxin
4. Prostatic Enlargement
Results in straining to defecate against a potentially weakened diaphragm
5. Structural Weakness of Pelvic Diaphragm
Short tail breeds w/ under developed levator ani & coccygeus
Surgical Importance: Poor suture holding power & absence of suture points
6. Chronic Straining
Consequences:
- Dilation/deviation of terminal rectum
- Faeces impaction
- Diverticulum
- Retroflexed Bladder: (20-30%), +- azotaemia, Hyperk – Emergency (Catheter, cystocentesis, cystopexy)
Diagnosis and Treatment of Perineal Hernia?
Dx:
- Rectal Exam: Lack of support (Finger lateral inside anus), check prostate/straining causes
- Radiography
- Cystography
- Barium meal
- US
Tx:
*Requires combination of techniques
- Pre-op
Bloods, urinalysis, Ab’s, remove faeces, empty anal sacs, pack rectum w/ gauze, purse string suture butthole
+- urinary catherer. CONTRAINDICATED: Enemas - Standard Technique
Reappose m. of pelvic diaphragm – preplace all sutures before tying
Sternal recumbency – PRESERVE the pudendal n. overlying int. obturator
Problems: Suturing degenerate tissue, tension on repair - Transposition of Internal Obturator
Provides good support ventrally, used in combination w/ other techniques - Prosthetic Mesh Repair
Used when severe atrophy is present – polypropylene - Transplantation of Semitendinosus
Used for ventral midline defects, particularly after bilateral repair - Transplantation of Superfial Gluteal
Used to reinforce standard repair dorsally – in combo with int. obturator flap
BUT increased incision & trauma - Cystopexy/Vas Defernsopexy
Used when bladder is retroflexed, usually pexy colon at same time → PH 1wk later
Vas deferns connects to prostate, pull it forward and pexy - Castration
Important in prostomegaly (4-6wk healing) but also lower recurrence rate - Alternatives
Porcine SIS, Porcine dermal collagen, Fascia lata autograft/allograft, tunica vaginalis fascia post castration
Post-Op:
- Remove purse string
- Digital rectal support check
- Medication to ↓ strain
- Low residue diet
- +- Antimicrobial
Complications:
- Wound infection
- Faecal incontinence
- UT malfunctions
- Tenesmus
- Sciatic n. paralysis
- Recurrence
What are Diaphragmatic Hernias?
- Musculotendinous partition
- Strong central tendon (21%)
- Muscles: Par sternalis (D & V), Pars costalis (L), Paired lumbar crura (R > L– L, I, M)
–> Right is larger than left
Divided into lateral intermediate and medial - Nerves: Splanchic N. & Sympathetic trunk – btwn lateral crus & 13th rib bilaterally
Openings:
1. Aortic Hiatus (Dorsal): Aorta, azygos, hemiazygos, lumbar cistern thoracic duct
2. Oesophageal Hiatus: Oesophagus & blood supply, dorsal & ventral vagal trunks
3. Caval Foramen (Ventral): Vena cava
Cause: Trauma - Direct or indirect (Sudden ↑ IAP w/ glottis open)
IAP: Intra Ab Pressure
Location: Costal > Central tendon; Cats: Circumcostal (59%),
Dogs: Radial (40%), Circumcostal (40%)
- Most commonly herniated organ: Liver (88%)
CS: *Depends on system affected
- Obstruction, cardiorespiratory, incarcerated
- Dyspnoea!
Causes: Compression/atelectasis, hypoventilation, V/Q, dysrhythmia, pleural/peritoneal pressure equalises, pain/mechanical
- Pleural effusion: Mostly liver, thin cranial vena cava & hepatic V. walls, lymphatic distension
- Strangulation: Via adhesion bands; Ischaemia, perforation, abscessation, cranial vena cava (CVC) pressure (rare)
How to diagnose and treat Diaphragmatic Hernias?
Dx:
- Thoracic palpation of apex beat to define side of hernia (80% accuracy)
- Radiographs: Partial loss of diaphragm line (66-97% - NOT DIAGNOSTIC)
- US (93% A)
- CT & MRI
- Contrast studies: Not indicated, false negatives (obstruction)
Sx Approaches:
- Midline Coeoliotomy:
Indications: Most traumatic & all congenital perito-pericardial hernias (UNLESS adhesions)
Adv: Don’t need to know position of tear
Dis: Adhesions difficult, hard to suture concave
- Median Sternotomy:
Allows extension of midline coeliotomy
Adv: Adhesions can be visualised - Lateral thoracotomy:
Performed on side of hernia CI: Bilateral hernia, perito-pericardial hernias
Tx:
Timing: Earliest opportunity in a stable patient
- Coeliotomy and examine for hernias
- Avoid kinking VC when repositioning liver
- +- Freshen chronic edges
- +- Chest drain
- Circumcostal: Sutures anchored on costal arch & ab wall
- Materials: Pig SIS, Silicone, Polypropylene, Fascia lata, Muscle flaps (Rectus & transverse ab)
- Pulmonary Reinflation: Lateral thoracostomy tube w/ gradual reinflation, esp. chronic or reperfusion issues – Pressure of 10mmH20
Issues:
a) Prolonged expansion: Valsalva effect = ↓ return of blood to heart
b) Over inflation: Ruptured parenchyma = haemorrhage, pneumothorax, pulmonary oedema
Post-Op:
- Expel residual air pre-close
- Radiographs
- IVFT
- +- Analgesia
- +- Ab if herniated liver/perforated viscous
- Monitor CV & RR: Pa02, MAP, CVP
- Inadequate RR: 02 sup, thoracostomy tube aspiration, auscultate thorax, blood gas analysis
- Intermittent/cont. suction of fluid/air
- Remove tube when <2-3ml aka ~6hr
Complications: (~50%)
- Death:
a) <24hrs: Haemo/pneumothorax, oedema, shock, pleural effusion, dysrhythmia
b) >24hrs: Rupture, obstruction, strangulation of GIT or unrelated disease
- Ascites
- Gastric ulceration
- Oesophagitis
- Megaoesophagus (Transient)
- Hiatal Hernia (↑IAP = ↑ Laxity)
- Recurrence
Px:
- Post-op 80-90% success
- 15% Mortality prior to presentation
- ↑ Mortality: Anaesthesia time, soft tissue injury, orthopaedic injury
What is the composition of the Peritoneum?
- Fluid:
Cell type: Acellular – Primarily macrophages (50%) and Lymphocytes (40%)
Composition: Small albumin, H20, low wt. molecules, SG <1.016 lacks fibrinogen
Role: Non-clotting surfactant, dilutes chem mediators, smooths mesothelial surfaces, removes particles, limits adhesions
Flow: From all surfaces to the diaphragm (lymphatic plexus for fluid collection)
- Micro layer:
a) Serous Layer: Has squamous cells with microvilli
b) Extensive lymphatics - Macro Layer:
a) Membrane: Clear, thin, translucent
b) Layers: Parietal & visceral
c) Peritoneal Cavity: Small volume of clear fluid
Explain lymphatic drainage
Movement: Through the mediastinal LN via passive diaphragm stretch & -ve intrathoracic pressure
Importance:
- Peritonitis is likely to form into bacteraemia <6mins
- ↑ Sternal LN suggest peri/retroperitoneum inflam/neoplasia as ONLY omentum can absorb particles & bacteria in the peritoneal cavity
Factors affecting matter clearance:
- Gravity
- Resp. movement
- GIT activity
- Diaphragm movement
- Intra-peritoneal pressure
- Particle size (<10um only)
Healing of Peritoneum
Timing: All defects close in 5-7d regardless of size
Mesothelial Cells Involved: Edges & depths of defects, adjacent mesothelial surfaces
Explain the formation and promotion of adhesions?
Formation
- Initiated by: Peritoneal injury → inflammation
- Inflammatory cells & fibrin release → fibrinolysis in 3-4d assuming good perfusion
– Either:
A) Inflammation subsides: Adhesions may breakdown
B) Ischaemic tissues/persistent inflammation: Fibrin is infiltrated w/ fibroblasts producing collagen & permanent fibrinous adhesions persisting >4-5d
Promotion:
- Suturing peritoneum
- Endotoxemia
- Intestinal manipulation
- Bowel distension
- Desiccation of serosa
- Foreign body contamination
Prevention:
- Preventing desiccation
- Gentle tissue handling
- Haemostasis
- Precise sutures
- Lavage of clots & FB’s
Dissolution:
- Adequate mesothelial O2 & nutrition
- Lack persistent inflam
- Plasminogen activating substances
Advantages
- Increases blood supply in compromised tissue
- +- Limit leakage from viscus
Disadvantages
- Clinical disease via restrictive adhesions which compromise lumen and +- strangulate
Describe the components and uses of the Omentum?
Location: Inside of the peritoneal cavity
Components:
a) Lesser omentum: Attached to greater curvature of stomach & liver
b) Greater omentum: Attached to lesser curvature of stomach & pancreas (Has omental bursa)
Function:
- Isolates & seals source of infection/inflammation via adhesion
- Absorbs bacteria & other matter
- Rich blood supply
- Immune function (PMN, lymphocytes, macrophages, lymphatic drainage)
Use of Omentum
- Aid sealing of adhesions
- Highly movable, create flaps anywhere
- Through diaphragm for oesophageal healing
- Blood supply for non-healing wounds outside abdominal wall
Disadvantages:
- Causes adhesions on viscera → local abscesses/focal peritonitis (Can be good cf. general)
- Complicates ab tube drainage
- Obstruction of GI via adhesions
Describe Pathophysiology of Peritonitis
- Primary innate defence:
Complement system (C3a & C5a release) stimulates neutrophil chemotaxis & mast cell/basophil degranulation - Other innate defence:
Bacteria absorption via diaphragm lymph, phagocytosis, abscess formation & NK cell activity - Secondary specific defence:
Mediated by lymphocytes, provides a 2nd amplification system response to sepsis - Immunoglobulin production:
Produced by peritoneum assosciated. Lymphoid tissue & omental lymphoid tissue
Inflammatory response:
- ↑ protein rich fluid
- Neutrophils & macrophages
- Activation of complement
- Opsonisation
- Mast cell ↑ of perm
- Fibrinolytic inactivation
- Fibrin blocks stomata
- Peritoneal rel. lymphoid resp
Adjuvants:
- Gastric mucin: Anticomplement effects → Inhibits phagocytosis
- Haemoglobin: Interferes w/ chemotaxis, phagocytosis & intracellular killing (Provides iron)
- Bile salts: Lower surface tension & alter cell adhesion → RBC lysis & Hb release
- Barium
- Peritoneal fluid: ↑ bacteria, ↓ bacterial clearance, ↑ mortality rates
What are the results of peritonitis?
IRH MISS HIM
(I really have miss him)
- ↑ IAP
- ↑ Hypovolaemia - Impairs ventilation - Respiratory acidosis & hypoxaemia
- Via reflex diaphragmatic rigidity & ↑ IAP preventing ventilation - Hypoproteinaemia
- Protein fluid moves from IV to cavity - Metabolic acidosis
- Impaired oxygenation via respiratory acidosis - Intrahepatic cholestasis
- Alteration of bile flow → icterus - Severe catabolic state
- Via 25% increase in metabolic rate & massive protein loss into cavity - Septic shock
- Adrenergic stimulation → ↑ venous p. → injury to gut mucosa & translocation of flora - Hypovolaemia
- Protein fluid from IV to cavity - Fluid sequestration in bowel lumen via reflex ileus
- ↑ IAP → ↓ CO & return - Hypotension & ↓perfusion → metabolic acidosis/hypoxia - Impaired renal function
- Renal insufficiency → ↓ clearance of toxins → ARF - Myocardial depression
- Via hypoxic pancreas
