Surgery of the acute abdomen

Question 1

Definition of the acute abdomen

Answer 1

Any disease process resulting in acute onset of clinical signs referable to intra-abdominal pathology

Question 2

Differential diagnoses for acute onset of clinical signs referable to intra-abdominal pathology

Answer 2

Main ddx: spinal pain

Peritonitis (septic and bile most common)

Haemoabdomen

Uroabdomen

Etc.

Question 3

Aetiology of primary peritonitis

Answer 3

Definition = ‘Spontaneous inflammation of the peritoneum without a pre-existing intra-abdominal cause.’

This form is rare in small animals and the best example is feline infectious peritonitis due to coronavirus infection (FIP).

Question 4

Definition of secondary peritonitis

Answer 4

‘Inflammation of the peritoneum due to an identifiable intra-abdominal disease process.’

This type of peritonitis may be aseptic or septic.

Question 5

Aetiology of aseptic peritonitis

Answer 5

Mechanical/FB e.g. surgical swab, glove powder

Chemical
§ Endogenous: sterile bile or urine, pancreatic enzymes
§ Exogenous: barium, other contrast agents.

Question 6

Aetiology of septic peritonitis

Answer 6

GI leakage
§ Most common – 60% of cases
§ Typically due to dehiscence of a surgical wound
§ Other = perforating intestinal FB, rupture of neoplastic lesion, ulceration etc.

Infected urine or bile

Ruptured pyometra

Intra-abdominal abscess: prostate, liver, spleen etc.

Penetrating abdominal wounds

Question 7

Pathophysiology of septic peritonitis

Answer 7

Typically polymicrobial - two predominate
- Bacteroides fragilis (anaerobic)
- E. coli (gram negatice enteric bacteria)

Intense inflammatory reponse
- influx of neutrophils and macrophages, mast cell degranulation, activation of complement system, increased vascular permeability

Question 8

What does the intense inflammatory response in septic peritonitis lead to?

Answer 8

Abdominal pain, impaired ventilation

Ileus which predisposes to bacterial translocation, sepsis and endotoxaemia

Outflowing of protein rich fluid. Massive surface area affected (150% greater than skin). Effect is analogous to severe burns.

Question 9

Clinical signs of septic peritonitis

Answer 9

Vomiting/diarrhoea

Anorexia/depression

Abdominal pain – guarding, praying position

Abdominal distension due to effusion (‘fluid thrill’ may be present)

Ileus: non audible gut sounds

Hypovolaemic shock

Question 10

Laboratory findings in septic peritonitis

Answer 10

Usually a neutrophilia with a left shift, but if high numbers of neutrophils have been sequestered in the abdominal cavity/consumed, may be neutropaenia, but still with left shift/toxic changes

Increased haematocrit, total protein and azotaemia may be associated with dehydration

Hypoalbuminaemia may be present due to huge third space losses

Hypoglycaemia is common

Acid/base and electrolyte abnormalities

Question 11

Radiographs of septic peritonitis

Answer 11

Fluid: Loss of serosal contrast

Free gas: (normal following previous abdominal surgery), tends to accumulate between diaphragm and stomach

Signs consistent with ileus: generalised accumulation of gas throughout GI tract

Pleural effusion: when present, risk of death is increased 3.3 times

Question 12

Ultrasonography of septic peritonitis

Answer 12

Confirms the presence of free fluid and may help identification of cause e.g. pyometra

Question 13

Abdominocentesis of septic peritonitis

Answer 13

The most important diagnostic test!

Butterfly or hypodermic needle, 19 or 21G, one inch length.

Ultrasound guided or ‘blind’ abdominocentesis

Fluid is collected into both EDTA (cytology) and plain (culture) pots

Question 14

Diagnostic peritoneal lavage for septic peritonitis

Answer 14

Infuse 20 ml/kg of warm crystalloid, roll from side to side, then drain (just need enough for sample, don’t worry about getting it all out).

Question 15

Cytology of peritoneal fluid in septic peritonitis

Answer 15

Degenerate neutrophils with intracellular bacteria are diagnostic for septic peritonitis.

This differs from a standard post-surgical sample which will contain non-degenerate neutrophils and perhaps extracellular bacteria.

Bile pigment is seen in bile peritonitis.

Organic debris may be seen with rupture of the GI tract.

Question 16

Biochemistry of peritoneal fluid with septic peritonitis

Answer 16

NB The blood sample must be taken at the same time as the fluid sample!

Fluid glucose level lower than serum is suggestive of septic peritonitis

Fluid lactate concentrations higher than serum is suggestive of septic peritonitis

Fluid bile concentration 2x serum is seen with bile peritonitis

Fluid creatinine and fluid potassium higher than serum is seen with uroabdomen

Fluid lipase and amylase higher than serum is seen with pancreatitis

Question 17

Stabilisation of an animal with septic peritonitis

Answer 17

Fluids
- Aggressive initially, shock rates
- Albumin?
- 7% Hypertonic saline: rapid resuscitation, 4ml/kg
- May need to add glucose to treat hypoglycaemia

Antibiotics
- Gram positive: ampicillin, amoxicillin, 1st generation cephalosporin
- Gram negative: amikacin, gentamicin, fluoroquinolone
- Anerobic bacteria: metronidazole

Question 18

Surgery for septic peritonitis

Answer 18

Identify and correct source of contamination

Feeding tube (O or G)

Lavage (crystalloids)

Closure (primary if source removed/corrected, closed suction drainage if not)

Question 19

Post op care for septic peritonitis surgery

Answer 19

Monitoring

Nutrition

Analgesia

Additional medication

Renal support

IV fluids

Question 20

What do you need to monitor after surgery for septic peritonitis?

Answer 20

Clinical parameters

Blood pressure

Urine output

Fluid balance (ins: colloids, crystalloids, outs: drains, urinary catheter)

Haematology and biochemistry

Serial cytology on peritoneal fluid

Question 21

Nutrition post op for septic peritonitis

Answer 21

Absolutely vital due to massive protein loss and catabolic state

Oesophagostomy tube - no risk of leakage/peritonitis

Gastrostomy tubes and jejunostomy tubes - particularly if vomiting + give less risk of aspiration

Initially tube, then oral feeding 4d postop

Question 22

Analgesia post op for septic peritonitis

Answer 22

Very painful condition.

Mu agonist opioids (fentanyl, methadone, morphine) initially

Additional analgesia via CRI: ketamine, MLK (morphine, lidocaine, Ketamine), lidocaine (analgesia and prokinetic), medetomidine, dexmedetomidine

NSAID’s: contraindicated if hypovolaemic/hypotensive, may have a role later in recovery period.

Question 23

Additional medications used post op for septic peritonitis

Answer 23

Prokinetics for ileus: metaclopramide, ranitidine, lidocaine

Anti-emetics: metoclopramide, maropitant, ondansetron

Antibiotics

Question 24

Renal support post op for septic peritonitis

Answer 24

Frusemide, Dopamine if inadequate urine output

Question 25

Prognosis for septic peritonitis

Answer 25

Guarded, mortality generally accepted to be 30-50%

Patients will typically need a minimum of 3 days in ICU

Clients need to be counselled adequately on costs and prognosis before embarking on what will be very labour intensive and costly process. They have to be prepared for an expensive bill and a dead dog.

Prognosis often poorer in cats

Question 26

Aetiology of haemoabdomen

Answer 26

Traumatic
○ Damage to parenchymatous organ
○ Avulsion of major blood vessel

Non-traumatic
○ Intra-abdominal neoplasia
○ Splenic torsion
○ GDV
○ Liver lobe torsion
○ Coagulopathy
○ Post-surgical (e.g. post-spey)

Question 27

Clinical signs of haemoabdomen

Answer 27

Weakness/collapse

Tachycardia, pale mucous membranes, prolonged CRT, poor peripheral pulse quality

Cardiac arrhythmias

Tachypnoea

Distended abdomen

Palpable abdominal mass

Question 28

Laboratory findings of haemoabdomen

Answer 28

Anaemia & hypoproteinaemia
§ Note – PCV does not fall for approximately 6 hours therefore may be normal in an acute case.

Thrombocytopaenia

Azotaemia (likely pre-renal) – need urine SG to assess.

Coagulation profile to check clotting

Question 29

Diagnosis of haemoabdomen

Answer 29

Lab findings

Thoracic radiographs to check for mets

Echocardiography to check for right atrial HAS

Abdominal ultrasound

Abdominocentesis

Question 30

Stabilisation of animal with haemoabdomen

Answer 30

Intravenous fluids
○ Shock rates crystalloids, colloids or hypertonic saline
○ Note – try to avoid giving blood transfusion until bleeding under control
○ Autotransfusion in trauma cases?

Abdominal wrap
○ Vet wrap or Elastoplast used to tightly bandage whole abdomen to increase intra-abdominal pressure and stop/reduce bleeding.
○ Leave in place for 4-6 hours
○ Gradually cut approximately 1 inch at a time from CRANIAL to caudal to avoid release of large volume of inflammatory cytokines into the circulation.

Antibiotics
○ Blood is an excellent medium for bacterial growth & translocation of intestinal bacteria is common in compromised patients, thus broad-spectrum antibiotic cover given routinely.

Question 31

Surgery for traumatic haemoabdomen

Answer 31

Abdominal wrap alone may resolve the haemorrhage

Exploratory coeliotomy indicated in cases where bleeding continues after removal of the wrap.

Question 32

Surgery for non-traumatic haemoabdomen

Answer 32

If thoracic radiographs, echocardiography and abdominal ultrasound reveal no conclusive evidence of metastasis, exploratory coeliotomy is indicated.

Grossly there is no difference in appearance between haemangiosarcoma and a haematoma – histopathology is required to give a definitive diagnosis.

The abdomen is explored thoroughly for evidence of metastasis – euthanasia under general anaesthesia if metastasis certain e.g. multiple lesions throughout omentum.

Mass removed if possible – most commonly requiring splenectomy.

Question 33

Post operative acre for haemoabdomen

Answer 33

Blood transfusion may be indicated once bleeding stopped

Monitoring
○ Clinical parameters
○ Blood pressure
○ Urine output
○ PCV/TS

Antibiotics
○ Continue broad-spectrum cover for 5 days

Analgesia
○ Opioids
○ NSAIDs contraindicated until cardiovascular system stable

Question 34

Prognosis of haemoabdomen

Answer 34

Immediate
○ Good prognosis for discharge from the hospital

Long-term
○ Traumatic and post-surgical cases good prognosis
○ Benign neoplasia – good prognosis
○ Malignant neoplasia
HAS – Median survival 1-4 months postoperatively without additional treatment; 6-8 months with doxorubricin.

Question 35

Aetiology of uroabdomen

Answer 35

Rupture of an element of the urinary tract located within the peritoneal cavity (kidney, ureter, bladder, proximal urethra) resulting in accumulation of urine.

Bladder most common

Causes:
○ Spontaneous
○ Traumatic
○ Iatrogenic (e.g. following cystocentesis or surgery)

Question 36

Pathophysiology of uroabdomen

Answer 36

Urine within the abdominal cavity is usually sterile

Reabsorption of urea & creatinine results in marked postrenal azotaemia

Reabsorption of potassium is life-threatening

Bradycardia

Question 37

Clinical signs of uroabdomen

Answer 37

Weakness/lethargy

Vomiting/anorexia

Distended abdomen/pain

Dysuria?
○ Cannot rule out urinary tract rupture in animals seen to urinate normally!

Bradyarrhythmias

Poor pulse quality, pale or hyperaemic mucous membranes, prolonged CRT

Question 38

Diagnosis of uroabdomen

Answer 38

If RTA assess for other injuries

Lab findings

Survery radiographs

Abdominocentesis

Question 39

Lab findings in uroabdomen

Answer 39

Hyperkalaemia
Azotaemia
Acidosis

Question 40

Survey radiographs of uroabdomen

Answer 40

Loss of serosal detail
Absence of normal bladder outline

Question 41

Abdominocentesis of uroabdomen

Answer 41

Yellowish fluid

Biochemistry of fluid
§ MUST BE COMPARED TO BLOOD SAMPLE TAKEN AT THE SAME TIME!
§ Potassium fluid:blood ratio >1.4:1 and creatinine fluid:blood ratio >2:1 are diagnostic
§ Urea likely to be approximately the same in both samples due to rapid diffusion across the peritoneum and equilibration.

Question 42

Conrtast radiographs for uroabdomen

Answer 42

To document site of rupture
§ This may NOT be evident grossly at surgery, thus must be known prior to exploratory coeliotomy.
§ IVU reveals rupture of kidneys/ureters
§ Positive contrast urethrogram/vaginourethrogram reveals rupture of bladder or urethra.

Question 43

Postoperative care for uroabdomen

Answer 43

Urinary catheter to monitor output

Monitor:
- clinical parameters
- blood pressure
- Biochem

Analgesia
- opioid
- NSAIDs

Question 44

Prognosis of uroabdomen

Answer 44

Generally good provided adequate pre-operative stabilisation and postoperative care + resolution of the urinary tract rupture.

Ureter and urethral ruptures most difficult to repair – leakage may recur or strictures may form.