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Previous exam questions Flashcards

1
Q
  1. How are bronchopulmonary sequestration classified?
  2. What are associated CT findings?
  3. Name 3 associations with BPS.
A

Bronchopulmonary sequestration refers to a mass of non-functioning lung tissue that is supplied by an anomalous systemic artery and does not have a bronchial connection to the native tracheobronchial tree. Thought to develop from a supranumerary lobe from abnormal budding early in foregut embryogenesis.

  • Intralobar versus Extralobar bronchopulmonary sequestration.
    • Intralobar sequestration occurs when the abnormal bud forms before the development of the pleura.
    • Extra lobar occurs after the development of the pleura, has its own pleural covering.
  • CT findings: abnormal tissue, anomalous arterial supply (usually off aorta). May be sub-diaphragmatic.
  • BPS associated with:
    • Congenital diaphragmatic hernia (5% have BPS)
    • Congenital heart disease
    • Vertebral anomalies
    • Recurrent pneumonia/abscess
    • Pleuropulmonary blastoma
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2
Q

How is bladder compliance defined?

How is it measured on urodynamics?

A

Bladder compliance is measured as change in pressure/change in volume.

Urodynamics (cystometry) measure compliance via a pressure probe on an intravesical catheter. As bladder is filled (increasing volume), the pressure probe measures the change in bladder pressure (detrusor pressure) at various volumes (measured in cm H20)

Detrusor pressure = vesical pressure - abdominal pressure = cm H20

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3
Q

What is AFP, where is produced, and what is it used for?

A
  • Alpha-foetoprotein is a protein produced in the foetal liver (similar to albumin) and the yolk sac.
    • It is thought to have several functions in the foetus:
      • Transporter for oestrogen, bilirubin
      • Growth factor
      • Immunosuppression
  • Used for:
    • Antenatal screening
      • Elevated in gastroschisis, exomphalos, teratoma, neural tube defects.
      • Decreased in Trisomy 21.
    • Post natal
      • Monitoring teratoma, hepatoblastoma, yolk sac tumours, germ cell tumours.
  • Average AFP for term baby 40000 ng/mL, half life 5-7 days in neonatal period. (Much higher in premature)
    • Should be less than 10 by 1yr of age (adult level < 6)
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4
Q

Describe three differences between the child and adult abdomen (6). How is this clinically relevant in blunt abdominal trauma?

A
  • Paediatric abdomen:
    • Relatively small size of abdomen - single force distributed across multiple organs.
    • Abdominal wall is relatively thin - less subcutaneous fat and muscle to dissipate blunt force.
    • Ribs are more pliable, provide less protection to upper abdominal organs.
    • Liver and spleen are relatively large - occupy significant proportion of abdomen.
    • Diaphragm is flatter in children, effectively lowers liver and spleen into abdomen.
    • Bladder is intra-abdominal, more prone to injury.
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5
Q

What are the features of Currarino triad (3)?

A

Pre-sacral mass

Anorectal malformation

Hemisacrum

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6
Q

What are the physiological factors that contribute to gastro-oesophageal competence?

A
  • Lower oesophageal sphincter
    • Lower oesophageal sphincter below the diaphragm (supported by the phreno-oesophageal ligament) - when abnormal, reflux can occur (hiatal hernia).
    • Lower oesophageal sphincter pressure and length of lower oesophageal sphincter directly proportional to effectiveness of sphincter.
  • Angle of His
    • Acute angle of His creates effective anti-reflux valve (obtuse angles are more likely to result in reflux).
      • Abnormalities such as seen with gastrostomy placement or OA/TOF repair → reflux.
  • Length of intra-abdominal oesophagus
    • Shorter intra-abdominal oesophageal lengths are more likely to result in reflux.
  • Intra-abdominal pressure
    • Persistently high intra-abdominal pressure associated with risk of developing GORD
      • Neurological - retching, increased tone (CP)
      • Physiological - coughing (cystic fibrosis), obesity, ascites, PD
      • Anatomical abnormalities - gastroschisis, exomphalos, CDH
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7
Q

Describe three skin features of occult spinal anomalies

A
  1. Sacral pit
  2. Hairy patch
  3. Haemangioma
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8
Q

What is Beckwith-Wiedemann Syndrome?

Name 3 solid tumour manifestations of BWS (5)

A

Beckwith-Wiedemann is an overgrowth syndrome characterised by (macroglossia, visceromegaly, hemihypertrophy, abdominal wall defects, hyperinsulinism, various tumours). Associated with defect at chromosome 11p15.

Associated solid organ tumours:

  • Wilms tumour (most common tumour in BWS) - usually occurs by age 7.
  • Hepatoblastoma - usually occurs by age 2
  • Rhabdomyosarcoma, adrenocortical carcinoma, neuroblastoma (all rare)
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9
Q

What is type 3b atresia?

What are two long term risks/conditions associated with it?

A

Type 3b atresia - apple peel atresia, distal limb is arranged in a helical pattern around a single blood vessel (usually ileocolic or right colic artery). Perfusion is retrograde. May be associated with significant loss of bowel length, usually significant mesenteric loss.

Long term risks: short gut syndrome/intestinal failure, gut ischaemia secondary to single retrograde end-arterial flow, difficulties if develops right sided colonic malignancy in adulthood.

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10
Q

What is the incidence of pyloric atresia?

Name two associated conditions?

A
  • Pyloric atresia a rare form of congenital gastric outlet obstruction - 1 per 100 000 (accounts for 1% of all atresias)
  • Associated with:
    • Gastric duplication cysts
    • Epidermolysis bullosa (most common)
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11
Q

List 3 syndromes (5) and 3 genetic mutations (7) associated with Hirschsprung Disease

A
  • Syndromes:
    • Trisomy 21 - associated with RET
    • Smith-Lemli-Opitz
    • Waardenburg-Shah (type IV) - SOX10, Endothelin 3, EDNRB
    • Congenital central hypoventilation syndrome (HADDAD Syndrome) - RET, PHOX2B, Endothelia 3, GDNF
    • Neurofibromatosis
  • Genes
    • RET proto-oncogene
    • GDNF (glial cell line derived neurotrophic factor)
    • Endothelin 3
    • Endothelin B
    • EDNRB
    • SOX10
    • Hedgehog-Notch
    • Phox2B
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12
Q

Name three pathological findings on liver biopsy associated with biliary atresia (5)

A
  1. Bile duct proliferation
  2. Bile plugs.
  3. Expansion of the portal tracts
  4. Portal stromal oedema
  5. Features of fibrosis/cirrhosis.
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13
Q

Name four extra-hepatic manifestations of hepatic haemangiomas

A
  • May be associated with haemangiomatosis
    • Cutaneous haemangiomas
    • Gastrointestinal haemangiomas (PR bleeding)
  • Multi-focal and diffuse hepatic haemangiomas of infancy often associated with hypothyroidism (secondary to high levels of 3-iodothyronine deiodinase (deactivates circulation thyroid hormones)
  • Can be associated with high output cardiac failure (if macrovascular shunts)
  • Occasionally associated with thrombocytopaenia
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14
Q

What are the layers of the adrenal cortex and what do they produce?

A

Three layers - Zona glomerulosa, zona fasciculata, zona reticularis.

  • Zona glomerulosa - mineralocorticoids
  • Zona fasciculata - glucocorticoids
  • Zona reticularis - sex steroids
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15
Q

Name 5 potential lead points for intussusception

A
  • Meckel diverticulum
  • Polyp
    • Juvenile
    • Familial adenomatous polyposis syndrome
  • Duplication cyst
  • Peutz-Jehger (hamartomas)
  • Small bowel tumour
    • Benign
      • Haemangioma
    • Malignant
      • Lymphoma
      • Carcinoid
  • Thickened small bowel associated with Henoch-Schonlein Purpura.
  • Cystic fibrosis associated with higher rates.
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16
Q

Give 3 gastrointestinal associations for duodenal atresia (6)

A
  • Annular pancreas (30%)
  • Malrotation (30%)
  • VACTERL
    • TOF/OA - 5-10%
    • ARM - 5%
  • Biliary
    • Gallbladder agenesis
    • Biliary atresia
    • CBD stenosis
  • Concurrent distal atresia (only 1%)
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17
Q

Describe 3 paediatric surgical issues associated with Trisomy 21 (11)

A
  • Gastrointestinal:
    • Increased rates of OA/TOF - especially type A.
    • Duodenal atresia (up to 50% of DA associated with Trisomy 21).
    • Higher rates of Hirschsprung disease, more likely to have episodes of Hirschsprung associated enterocolitis.
    • Anorectal malformations (most commonly Anorectal atresia without fistula)
    • Infantile hypertrophic pyloric stenosis
    • Achalasia
  • Respiratory:
    • Congenital diaphragmatic hernia
  • Abdominal wall
    • Exomphalos
  • Genitourinary
    • Prune Belly Syndrome
  • Oncology
    • Increased rates of leukaemia
  • Other
    • Lymphatic malformations
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18
Q

What is the cellular defect associated with cystic fibrosis? What are three organ systems affected by CF (12)?

A
  • Cystic fibrosis associated with a defect in the CFTR gene (cystic fibrosis transmembrane conductance regulator) on delta F508.
  • Organ systems involved:
    • Gastrointestinal
      • Meconium disease (meconium ileus, meconium cyst, meconium peritonitis)
      • Pancreatic insufficiency (chronic obstruction of pancreatic ducts leads to pancreatic autodigestion by exocrine secretions → pancreatic insufficiency
      • Distal intestinal obstruction syndrome (DIOS)
      • Biliary system - cholelithiasis in 25%, also associated with biliary cirrhosis due to inspissated bile obstructing bile ductules → inflammatory response, activated stellate cells → further inflammation and fibrosis.
      • Gastro-oesophageal reflux disease
      • Intussusception
      • Rectal prolapse
    • Respiratory
      • Associated with bronchiectasis (impaired muco-ciliary clearance, bacterial colonisation, chronic inflammation/infection.
      • Mucus plugging.
    • Genitourinary
      • Bilateral absence of vas deferens
      • Male infertility
      • Female sub fertility.
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19
Q

What is the immune complex associated with Henoch-Schonlein Purpura and how does it cause paediatric surgical issues?

A

IgA

IgA deposition in the tissues (renal, gastrointestinal, scrotal) → vasculitis, inflammation and pain.

Examples:

Abdominal pain, intussusception.

Acute scrotum → scrotal oedema.

GI bleeding (vasculitis and mucosal inflammation)

Non surgical - IgA nephropathy (macroscopic haematuria)

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20
Q

What is the definition of short bowel syndrome?

What are the most common causes in paediatric surgery (5)?

A
  • Multiple definitions:
  • Short bowel syndrome is defined as insufficient intestinal length/absorptive capacity to sustain adequate enteral nutrition.
  • Short bowel syndrome = intestinal failure secondary to insufficient length of intestine to support nutritional homeostasis, growth and hydration.
  • Short bowel syndrome - residual small bowel length less than 25% of that predicted for gestational age OR TPN > 6 weeks.
  • Most commonly caused by:
    • Necrotising enterocolitis (35%)
    • Congenital atresias (25%)
    • Gastroschisis (particularly vanishing) (18%)
    • Malrotation and volvulus (14%)
    • Long segment Hirschsprung disease (2%)
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21
Q

What are the three components of Prune Belly Syndrome?

A

Deficiency of abdominal wall musculature (maximal midline, inferiorly)

Renal tract dilatation (megacystis - smooth walled, enlarged, hydroureteronephrosis, Megalourethra (dilated anterior urethra)

Undescended testes

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22
Q

Explain the different approaches for a coin and a button battery lodged within oesophagus.

A
  • Button battery extremely high risk - if lodged within the oesophagus can form circuit and generate a severe alkali burn (within 15 minutes) → liquefactive necrosis and vascular thrombosis, full thickness injury → erosion into adjacent structures (i.e. aorto-oesophageal fistula, trachea-oesophageal fistula).
    • Endoscopic should be immediate.
    • Once removed - remain high risk during reparative phase due to thinning of oesophagus.
      • Stages: liquefactive necrosis, reparative phase (days 5-7), scar contraction (>14 days).
    • Oral feeding delayed until - tolerating secretions, risk of fistula deemed low.
  • Coin ingestion - lower risk as mechanism of injury is secondary to pressure necrosis.
    • If tolerating secretions, can attempt spontaneous passage.
    • If not tolerating secretions, or present > 24 hours should offer endoscopic removal.
      • Post operative feeding will depend on whether significant injury or not (unlikely).
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23
Q

What is Kasabach-Merrit phenomenon? When does it occur?

A
  • Kasabach-Merritt phenomenon is characterised by the following:
    • Rapidly expanding vascular tumour (usually Kaposiform haemangioendothelioma, or tufted angioma)
    • Profound + refractory thrombocytopaenia (due to consumption of platelets in rapidly expanding tumour)
    • Microangiopathic haemolytic anaemia
    • Consumptive coagulopathy
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24
Q

What is the most common presentation for persistent Müllerian duct syndrome?

A
  • Persistent Müllerian Duct Syndrome (PMDS) - aka Hernia uteri inguinale
    • Normal mesonephric duct derivatives but also persistent paramesonephric duct structures in a 46XY with normal male phenotype.
      • Has bilateral testes (often undescended), vas deferens BUT ALSO Fallopian tubes, uterus.
  • Most commonly presents with the finding of a Fallopian tube in the a hernia sac whilst performing orchidopexy.
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25
Q

What are three non-malignant histological changes associated with cryptorchid testes (6)?

A
  1. Peritubular fibrosis
  2. Reduced/absent spermatogenesis (post pubertal)
  3. Atrophy of seminiferous tubules
  4. Increased microliths in seminiferous tubules
  5. Sertoli cell nodules - nodules of immature, elongated Sertoli cells, may contain microliths.
  6. Leydig cell hyperplasia
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26
Q

Name 3 benign testicular masses

A
  • Germ cell
    • Teratoma (benign in prepubertal)
    • Epidermoid cysts (previously classed as epithelial, now considered germ cell).
  • Stromal
    • Leydig Cell tumour - may secrete testosterone (associated with precocious puberty)
    • Granulosa Cell tumours
    • Sertoli cell tumour (benign in prepubertal)
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27
Q

Name 3 conditions or syndromes associated with increased risk of skin malignancies (10).

A
  1. Neurofibromatosis
  2. Previous history of Hodgkin Lymphoma (chemotherapy induced)
  3. Retinoblastoma
  4. Xeroderma pigmentosum (10000 fold risk of skin cancer, 2000 fold risk of melanoma).
  5. Organ transplant recipients (immunosuppression).
  6. Congenital melanocytic naevi
  7. Fitzpatrick 1 pigmentation
  8. Familial melanoma
  9. Werner syndrome
  10. Li Fraumeni (p53)
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28
Q

Describe the process of infection in the intussusceptum

A
  1. Intussusceptum (usually terminal ileum) is drawn into the intussuscipiens, including the mesentery.
  2. Obstruction of lymphatic drainage → oedema to intussusceptum → becomes stuck.
  3. Progressive venous obstruction → secondary arterial ischaemia → necrosis/infarction.
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29
Q

What is the definition of short gut?

What are the 3 most common causes of short gut in paediatric surgery?

A
  • Short gut syndrome refers to inadequate intestinal length to maintain electrolyte homeostasis, hydration and growth on enteral nutrition alone.
  • Short gut most commonly due to:
    • Necrotising enterocolitis (35%)
    • Intestinal atresia (25%)
    • Gastroschisis (18%)
    • Malrotation and volvulus (14%)
    • Total colonic Hirschsprung disease (2%)
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30
Q

What are the newborn findings in Beckwith-Wiedemann Syndrome in a newborn?

A
  • Physical:
    • Macroglossia
    • Hemi-hypertrophy
    • May be associated abdominal wall defect - exomphalos
    • Organomegaly
  • Biochemical:
    • Neonatal hypoglycaemia
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31
Q

What are the three components of Prune Belly (Triad) syndrome?

A
  1. Deficiency of abdominal wall musculature - worse in midline, inferiorly.
  2. Renal tract dilatation (megacystis, hydroureteronephrosis, dilated urethra)
  3. Bilateral undescended testes
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31
Q

What are the conditions associated with hepatoblastoma?

A
  • Beckwith Wiedemann Syndrome
  • Trisomy 18 (Edwards Syndrome)
  • Polyposis coli
    • Familial Adenomatous Polyposis
    • Gardner Syndrome
  • Budd-Chiari Syndrome
  • Very low birth weight
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32
Q

List 3 differential diagnoses for a pre-sacral 3cm solid mass in a 2yr old male

A
  • Neoplastic:
    • Sacrococcygeal teratoma
      • Currarino syndrome (pre sacral mass, sacral agenesis, ARM)
    • Neuroblastoma
    • Ganglioneuroma
    • Schwannoma
    • Nerve sheath tumour
    • Ewing sarcoma
  • Congenital:
    • Rectal duplication
    • Myelomeningocoele
    • Dermoid cyst
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33
Q

What are the blood volumes of a preterm baby, a term baby, a 3 month old, and an older child?

A
  • Preterm = 100ml/kg
  • Term = 90ml/kg
  • Infant = 80ml/kg
  • Older child = 70-80ml/kg
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34
Q

What is a hamartoma?

List 3 examples

A
  • A hamartoma refers to a disorganised collection of benign cells native to the area.
    • Examples include:
      • Fibrous hamartoma of infancy - usually solitary mass on the limb, trunk, sacrum, scrotum.
      • Mesenchymal hamartoma (liver) - second most common benign tumour in children.
      • Pulmonary hamartoma
      • Hartomatous polyposis syndromes
        • Juvenile polyposis syndrome
        • Cowden disease (affects all three germ layers)
        • Peutz-Jegher Syndrome
          • Polyps are hamartomas of the muscularis mucosa, they demonstrate strands of smooth muscle fibres that divide the polyp into sectors.
35
Q

What is Horner’s Syndrome?

What are examples of causes of Horner’s syndrome in the paediatric population?

A
  • Horner’s syndrome refers to a triad of symptoms associated with injury or damage to the sympathetic pathway to supply the head, neck face and eye (1st order, 2nd order or 3rd order).
    • Ptosis (drooping of upper eyelid due to loss of sympathetic function of Muller’s muscle)
    • Miosis (pupillary constriction) - loss of sympathetic function of iris dilator muscle.
    • Anhydrosis - loss of sweating from ipsilateral side.
  • Horner’s most commonly occurs with damage to second or third order sympathetic nerves.
    • Mediastinal
      • Neuroblastoma
      • Teratoma
      • Lymphoma
    • Neck
      • Thyroid tumours
36
Q

List genes and their associated conditions, implicated in Hirschsprung disease.

A
  • Genes/Conditions:
    • RET mutation associated with:
      • Trisomy 21
      • Congenital Central Hypoventilation Syndrome (+ Endothelin 3, glial derived neurotropic factor, Phox2B)
      • MEN2A
    • Endothelin 3 associated with:
      • Congenital central hypoventilation syndrome
      • Waardenburg-Shah Syndrome (+ SOX10, EDNRB)
    • SOX10
      • Waardenburg-Shah Syndrome
    • Endothelin B
    • Hedgehog-Notch
    • GDNF
  • RET proto-oncogene (encodes tyrosine kinase receptor). Similarly neurturin and glial cell line -derived neurotrophic factor (GDNF)
    • Whilst these genes are often found to be impaired in HD, their contribution to aganglionosis is unclear. Assumption is they contribute to early neuronal cell death.
  • Endothelin-3 and endothelin-B with SOX-10 genes have also been shown to be involved in HD.
    • These are believed to trigger early maturation or differentiation of neural crest cells.
37
Q

What is acetylcholinesterase staining used for in paediatric surgery and what does a positive result mean?

A
  • Acetylcholinesterase staining is used in the diagnosis of Hirschsprung Disease.
    • On rectal biopsies of HD, acetylcholinesterase staining is increased. This represents increased cholinergic innervation - as seen in HD.
38
Q

What are the three most common causes of PR bleeding in a 3 month old infant?

A
  1. Anal fissure (most common cause in children <2years)
  2. Meckel Diverticulum
  3. Intussusception
  4. Infectious diarrhoea
  5. Lymphonodular hyperplasia
  6. Allergic proctocolitis (inc cows milk colitis)
39
Q

Why does small arterial bleeding stop with pressure?

A
  1. Application of pressure causes collapse of the bleeding vessel.
  2. Reduced blood flow/stasis
  3. Combination of platelet clumping at site of injury and vasospasm cause bleeding to stop when pressure released.
40
Q

What does 99m Tc-Mercaptoacetyltriglycine measure?

A
  • 99m Tc-Mercaptoacetyltriglycine (MAG-3) is a radioisotope used in dynamic renal scintigraphy.
    • Injected into the blood, taken up by proximal tubules = assessment of perfusion/function (given as differential function)
    • MAG-3 is then secreted in the distal proximal tubule = assessment of drainage of the kidney.
41
Q

For what diagnostic purpose is 99m-Tc-Pertechnotate used in paediatric surgery?

What particular histologic feature determines its usefulness?

A
  • 99m-Tc-Pertechnotate is the radioisotope used in the Meckel scan.
    • It is taken up by parietal cells in gastric mucosa.
    • Positive scan in Meckel diverticulum is dependent upon the presence of ectopic gastric mucosa within the the Meckel diverticulum
42
Q

Explain the role of the spleen in infections

A
  • Spleen made up of white pulp and red pulp. White pulp mostly involved in infections.
    • White pulp made up of macrophages and T-lymphocytes arranged around a central arteriole.
    • Splenic immune response occurs in the white pulp when antigens come into contact with the macrophages and helper T-cells.
      • T cells initiate cytokine synthesis and activated T cells circulate to modulate the response.
    • Antigen presenting cells (APC - dendritic cells, macrophages) present antigen to T cells in white pulp.
      • Activated T cells migrate to follicle and present to follicular B cells.
      • B-cells then convert to plasma cells and begin making antibodies (IgG or IgM) to combat the antigen.
  • Red pulp macrophages involved in phagocytosis of opsonised pathogens only.
43
Q

List 3 organisms that pose increased risk to asplenic individuals

A
  • Asplenic individuals are at risk from encapsulated bacteria:
    • Streptococcus pneumonia
    • Neisseria meningitis
    • Haemophilus influenzae B
44
Q

What is OPSI and what organisms cause it?

A
  • Overwhelming post splenectomy infection - rapidly progressing infection usually caused by encapsulated bacteria.
    • Streptococcus pneumoniae
    • Haemophilus influenzae B
    • Neisseria meningitidis
45
Q

List 5 pathologies that could present as PR bleeding in childhood

A
  • Newborn
    • Anal fissure (most common cause of PR bleeding in <2yrs)
    • Cows milk protein intolerance
  • Infant
    • Anal fissure
    • Meckel diverticulum
    • Intussusception
    • Haemangioma
    • Infectious diarrhoea
    • Malrotation with volvulus
  • Older child (>1 yr)
    • Anal fissure
    • Polyp (most common cause of PR bleeding in children aged 2-5yrs
    • Infectious diarrhoea
    • Inflammatory bowel disease
46
Q

Give two examples of causes of adenomatous polyps and two for hamartomatous polyps

A
  • Adenomatous polyps in paediatrics (3% of all polyps)
    • Familial adenomatous polyposis (FAP)
    • Gardner syndrome (FAP plus extra colonic manifestations)
    • Turcut syndrome (FAP plus extra colonic tumours)
    • Peutz-Jehger Syndrome (predominantly hamartomas but adenomatous polyps can co-occur).
  • Hamartomatous polyps (80% of paediatric polyps)
    • Juvenile polyps (isolated)
    • Peutz-Jehger Syndrome -
    • Cowden syndrome - hamartomas contain all 3 germ cell layers - associated with increased risk of breast, thyroid, endometrial neoplasia
    • Juvenile Polyposis Syndromes
      • Diffuse juvenile polyposis syndrome of infancy (first few months of life)
      • Diffuse juvenile polyposis (6m to 5yrs)
      • Juvenile polyposis coli (5yrs to 15yr) - associated cleft palate, malrotation, polydactyly, abnormalities of the heart and cranium.
47
Q

What is biliary atresia splenic malformation syndrome?

A
  • Syndromic biliary atresia - associated with Chromosomal 22 aneuploidy = 10 to 20% of biliary atresia
    • Associated with:
    • Polysplenia
    • Intestinal rotational anomalies
    • Aberrant venous anatomy
      • Interrupted vena cava
      • Pre duodenal portal vein
    • Heterotaxy
      • Situs inversus,
    • Cardiac defects
48
Q

What histological feature of the portal plate is described as a prognostic indicator in biliary atresia?

A
  • Patients with the best prognosis have portal plate that is similar to a normal portal plate:
    • Low degree of bile duct proliferation
    • Number of bile duct structures
    • Length of bile duct structures at portal plate
49
Q

What are the pancreaticobiliary consequences of cystic fibrosis?

A
  • Cystic fibrosis - mutation in the CFTR gene on delta 508.
    • Results in decreased Cl secretion (water usually follows) → thickened, inspissated secretions.
      • Pancreas:
        • Thickened secretions associated with pancreatic duct obstruction → stasis of exocrine secretions → pancreatitis and auto digestion → pancreatic insufficiency.
      • Biliary:
        • Thickened bile → obstruction of intrahepatic bile ducts → biliary cirrhosis.
        • Associated with increased rates of cholelithiasis
          • Increased cholelithiasis → increased risk of choledocholithiasis +/- gallstone pancreatitis.
50
Q

Describe the Todani classification

A
  • Type Ia = cystic dilatation of the CBD.
  • Type Ib = fusiform dilatation of the CBD.
  • Type II = Diverticulum off CBD
  • Type III = choledochocoele (dilation of terminal CBD within duodenal wall)
  • Type IVa = Multiple intra and extra-hepatic cysts.
  • Type IVb = Multiple extra-hepatic cysts
  • Type V = Caroli disease (intrahepatic cysts only)
51
Q

Name 5 causes of intra-abdominal cyst in a female foetus

A
  • Genitourinary
    • Kidney
      • Multicystic dysplastic kidney (MCDK)
      • Polycystic kidney disease (PCKD)
      • Hydronephrosis/PUJ obstruction
    • Bladder
      • Megacystis (isolated megacystis, Prune Belly Syndrome (uncommon in females)
      • Ureterocoele
      • Urachal cyst
    • Vagina/Uterus
      • Hydrometrocolpos
    • Ovary
      • Ovarian cyst
  • Gastrointestinal
    • GI duplication cyst
    • Duodenal atresia
    • Mesenteric cyst
    • Omental cyst
  • Hepatobiliary
    • Choledochal cyst
    • Cystic biliary atresia
  • Neoplastic
    • Teratoma (SCT)
  • Spinal
    • Anterior myelomeningocoele
52
Q

What are the theories of the aetiology of choledochal cysts?

A
  • Congenital vs acquired.
    • Congenital
      • Result of prenatal structural defect in the bile duct (reduced ganglion cells on histology)
    • Acquired (type I, type IV) - 90%
      • Long common channel (pancreaticobiliary malunion)
        • Allows reflux of pancreatic secretions into the CBD → inflammatory damage to epithelium and mural weakness.
        • Distal CBD stenosis/obstruction creates high pressure CBD → dilatation.
53
Q

Child with pigmentation around the lips and intussusception.

What is the condition?

What mutation causes this?

What is the pattern of inheritance?

A
  • Melanocytic pigmentation around lips with associated intussusception is suggestive of Peutz-Jehger syndrome.
  • Peutz-Jehger is an autosomal dominant polyposis syndrome (hamartomas) associated with mucocutaenous melanin pigment macules around the mouth.
    • Associated with mutation of tumour suppressor gene STK11 (serine/threonine kinase 11)
54
Q

What are 5 potential lead points in intussusception?

A
  • Idiopathic - associated with children 2months to 2 years)
    • Lymphoid hyperplasia (associated with viral illness - rotavirus, adenovirus).
  • Pathological - associated with children <2 months or > 3years
    • Meckel diverticulum
    • Neoplastic
      • Benign
        • Polyp
          • Peutz-Jehger Syndrome (STK11 mutation) - autosomal dominant
          • Juvenile polyps or polyposis syndrome
          • Lymphoid polyp
          • Adenomatous polyp
      • Malignant
        • Lymphoma
    • Inflammatory lesion
      • Henoch-Schonlein Purpura - IgA deposition → inflammation → lead point for intussusception.
    • GI duplication
    • Cystic fibrosis.
55
Q

What are the causes of gynaecomastia in an adolescent boy?

A
  • Physiological - 70% of males develop gynaecomastia approaching puberty
  • Chromosomal
    • Associated with Klinefelter’s (47XXY)
  • Medications
    • Ranitidine/Omeprazole
    • Metronidazole/Minocycline
    • Digoxin/Frusemide/Spironolactone
    • Antidepressants - TCA, SSRI
  • Metabolic conditions resulting in excess oestrogen or deficient androgen.
  • Feminising and adrenal testicular tumours.
56
Q

What are three gastrointestinal associations with duodenal atresia?

A
  • Gastrointestinal:
    • Rotational anomalies (30%)
    • OA/TOF (5-10%)
    • Anorecal anomalies (5%)
    • Annular pancreas
  • Chromosomal
    • Trisomy 21 (50% of DA associated with trisomy 21)
  • Cardiac anomalies (25-65%)
    • Congenital heart disease
  • Genitourinary anomalies (5-15%)
  • Skeletal malformations (5%)
57
Q

What are 3 paediatric surgical issues associated with Trisomy 21 (17)?

A
  • Trisomy 21:
    • Trisomy 21 and anaesthesia
      • 10% have Perioperative complications.
        • Smaller calibre trachea
        • Tracheal stenosis common due to presence of complete tracheal rings below cricoid.
        • 50% have significant congenital heart disease (ASD, VSD, tetralogy of Fallot)
        • Difficult airway:
          • Atlanto-axial instability
          • Macroglossia
    • Risk factor for:
      • CDH
      • Achalasia
      • Exomphalos
      • Prune Belly Syndrome
      • Congenital chylothorax, Chylous ascites
      • Leukaemia
      • Haemangiomas
    • Disease specific associations with Trisomy 21:
      • Hirschsprung disease
        • Higher incidence among patients with Trisomy 21
        • High incidence of Hirschsprung associated enterocolitis.
      • OA/TOF:
        • Strong association with Type A oesophageal atresia
      • Duodenal atresia
        • Strong association with duodenal atresia.
      • Anorectal malformation
        • Many have anorectal atresia without fistula (50% of this defect have Trisomy 21).
58
Q

What is tetanus?

Which injuries predispose to tetanus?

How do you prevent tetanus?

A
  • Tetanus caused by infection with gram positive, spore-forming, anaerobic bacteria (bacillus) - Clostridium tetani
    • Clostridium tetani is found in soil, dust and animal faeces.
    • Anaerobic environment allows spores to germinate into mature organisms that produce neurotoxins.
      • Tetanospasmin → affects peripheral nerves → uncontrolled muscle spasms.
      • Tetanospasmin → affects brain → autonomic instability.
      • Tetanolysin → causes tissue damage
  • Tetanus can be caused by any dirty wound, ulcer, abscess or wounds with non-viable tissue.
    • Risk is increased when wound closure delayed.
    • Risk in unvaccinated
  • Tetanus can be prevented by:
    • Routine immunisation against tetanus, with associated boosters.
    • Early washout +/- closure of wounds
59
Q

How do you classify ovarian tumours?

A

Classification of ovarian tumours are as follows:

  • Primary vs secondary
  • Benign vs malignant
    • Malignancy very rare in children < 5yrs.
  • Germ cell vs sex cord-stromal vs epithelial-stromal
    • Majority of tumours are germ cell.
  • Germ Cell Tumours:
    • Teratoma - most common (composed of one or more germ layers)
    • Yolk sac tumour - most common malignancy
    • Dysgerminoma (aka seminoma in males)
    • Choriocarcinoma
    • Mixed germ cell tumours
  • Sex cord - stromal tumours:
    • Granulosa cell tumours
    • Sertoli-Leydig cell tumours
    • Theco-sibroma tumours
  • Epithelial-stromal:
    • Serous carcinoma
    • Mucinous carcinoma
    • Endometroid carcinoma
60
Q

What are the three elements associated with Wilms tumour?

What does triphasic mean?

A
  • Wilms tumour are made up of three components - blastemal, stromal and epithelial
  • Triphasic tumours contain all three components.
    • Favourable histology (accounting for 90%) of all Wilms tumours.
61
Q

What is massive transfusion?

What blood products does massive transfusion protocol include?

A
  • Massive transfusion refers to:
    • 40mL/kg of blood within 12hrs, or 70-80ml/kg within 24 hours (depends on age of child/estimated blood volume)
    • Transfusion of 50% of expected total blood volume within 3 hours.
    • Transfusion of 100% of expected total blood volume within 24 hours.
    • Ongoing blood loss >10% per hour despite ongoing transfusion.
  • Massive transfusion protocol includes - 1:1:1
    • Packed red blood cells
    • Fresh frozen plasma
    • Platelets
62
Q

What is the pathophysiology of appendicitis? Include a timeline of events.

A
  • Appendicitis is a caused by an obstruction of the appendices lumen (lymphoid hyperplasia, faecolith, tumour etc).
    • Mucosa secretes mucous, bacteria proliferates, appendix dilates (patient experiences visceral pain).
    • Stretch in appendix wall obstructs lymphatics → secondary venous obstruction → arterial obstruction.
    • Mucosal ischaemia + bacterial translocation → transmural inflammation (contact with peritoneum → localised pain) - within 12-24 hours of onset.
    • Ischaemia + translocation → necrosis and perforation (24-48 hours from onset).
      • Perforation may be contained as peri-appendiceal abscess.
      • Appendix may be walled off by momentum → if left will form phlegmon (approx 7 days).
      • Perforation may result in fulminant peritonitis → sepsis.
63
Q

What are 3 signs and 3 physiological mechanisms for cardiac tamponade?

A
  • Cardiac tamponade occurs when there is external compression on the heart limiting filling and resulting in obstructive shock.
  • Physiologic mechanisms:
    • Pericardial effusion - associated pericarditis
    • Haemopericardium (traumatic)
    • Tension pneumothorax
    • Neoplasm
      • Lymphoma
  • Signs:
    • “Beck’s triad:
      • Distended neck veins (raised JVP)
      • Hypotension
      • Muffled heart sounds
    • Pulsus paradoxus
    • Tachycardia
64
Q

Regarding cardiac shunts, what is meant by left to right shunts and what is meant by right to left shunts?

Give examples of each.

A
  • Left to right shunts:
    • Oxygenated blood from left side of the heart (systemic circulation) re-entering the pulmonary circulation.
      • VSD
      • ASD
  • Right to left shunts:
    • Poorly oxygenated blood from the right side of the heart bypassing the pulmonary circulation and entering the systemic circulation.
      • Multiple right to left shunts in the foetal circulation
        • Foramen ovale - right atrium to left atrium.
        • Ductus arteriosus - pulmonary artery to distal aortic arch.
          • May persist into neonatal period.
          • Protective in CDH with severe lung hypoplasia.
65
Q

Describe 4 types of shock and give an example of each.

A
  • Distributive shock: septic shock (peripheral vasodilation), anaphylaxis
  • Hypovolaemic shock: severe dehydration, haemorrhage.
  • Cardiogenic shock: failure of muscle pump - reduced contractility (hypoaxamia and acidosis)
  • Obstructive shock: cardiac tamponade, tension pneumothorax
66
Q

What conditions/syndromes are associated with an increased risk of skin malignancy?

A
  • Conditions/Syndromes associated with melanoma (most common skin malignancy in paediatrics)
    • Congenital melanocytic naevi (especially giant)
      • 20% risk of melanoma in giant CMN, 1-5% in small CMN (if multiple small CMN, higher risk).
    • Maternal melanoma during pregnancy
      • Transplacental transmission.
    • Loss of p53 tumour suppressor gene (i.e Li Fraumeni)
    • Xeroderma pigmentosum
    • Dysplastic naevi syndrome (CDK4 gene mutation) → Presence of > 100 naevi
    • Fitzpatrick 1 (fair skin, fair hair, blue/green eyes), UV radiation
    • Immunosuppression/Immunodeficiency
    • Neurofibromatosis (NF1)
    • Previous malignancies (Leukaemia/Lymphoma) - chemotherapy/radiotherapy cause increased risk
    • BRAF mutation
    • NRAS mutation
67
Q

What are the factors involved in nocturnal enuresis?

A
  • Nocturnal enuresis refers to involuntary loss of urine whilst sleeping at night.
    • Children > 5yrs, duration > 3 months
    • Primary enuresis (never been dry) VS Secondary enuresis (previously dry > 6months)
  • Factors:
    • Significant genetic component (autosomal dominant)
    • Increased nocturnal urine production - thought secondary to vasopressin deficiency.
      • Rx: Desmopressin
    • Reduced nocturnal functional bladder capacity - possibly nocturnal detrusor overactivity.
    • Difficulty with sleep arousal (hard to wake) - younger children have ‘deeper’ sleep, also seen in children with OSA.
      • Rx: Wetting alarm.
68
Q

What is the aetiology of renal tumours in children?

A
  • Renal tumours:
    • Wilms tumour (nephroblastoma) - most common renal malignancy in children
      • Favourable histology (triphasic)
      • Unfavourable histology - anaplasia (focal vs diffuse)
        • WT is an embryonal malignancy - disruption during differentiation and maturation of intermediate mesoderm → metanephric mesenchyme → epithelium.
    • Congenital mesoblastic nephroma (Harmatoma) - most common renal tumour in neonatal period.
    • Renal cell carcinoma (RCC) - 2-6% - most common in children > 15yrs
    • Clear cell carcinoma (CCSK) - 2-4% - presents aged 2-3yrs.
    • Rhabdoid tumour of the kidney (RTK) - presents 10-18 months of age
    • Cystic renal tumour
    • Angiomyolipoma
69
Q

Explain why skin discolouration is seen in jaundice

A
  • Jaundice is the clinical sign associated with hyperbilirubinaemia
    • Unconjugated hyperbilirubinaemia (usually associated with haemolysis (i.e newborn transition from HbF)
      • Breakdown of RBCs (into haem + globulin, then haem broken down into Fe2+ and unconjugated bilirubin) exceeds immature livers ability to conjugate bilirubin (glucuronic acid) for excretion in the gut.
        • Serum unconjugated bilirubin increases and becomes deposited in skin and mucous membranes → icteric discolouration.
    • Conjugated hyperbilirubinaemia
      • Obstruction of the outflow of bile (biliary atresia, choledochal cyst, choledocholithiasis, tumour) results in back pressure of bile into the liver → reabsorbed in the blood and deposited in the tissues.
70
Q

What is the differential diagnosis for torticollis?

A
  • Torticollis caused by either birth trauma or ‘tumour’ of SCM.
    • DDx:
      • Vertebral anomalies
      • Clavicle fracture
      • Plagiocephaly
      • Craniosynostosis
      • Ocular pathology
      • CND lesion
71
Q

Which structures are passing through the umbilicus at 12 weeks gestation?

A
  • Right umbilical vein
  • Umbilical arteries (left and right)
  • Allantois
  • Physiological hernia may persist (usually returns to abdomen between weeks 10-12)
72
Q

What is the pathophysiology of pilonidal sinus?

A
  • Pilonidal sinus is an acquired inflammatory condition.
    • Associated with ingrowth or forcefully deposited into the skin → foreign body reaction → inflammation and granuloma formation.
      • Hairs have sharp tips → pierce the skin.
      • Have hooks and unidirectional scales which encourage the hair to embed further.
73
Q

Explain the zones of penetrating neck trauma and management of these.

A
  • Three zones of neck trauma
    • Zone 1: Clavicles to cricoid cartilage
    • Zone 2: cricoid cartilage to angle of the jaw
    • Zone 3: angle of the jaw to base of skull.
  • Zones are further differentiated into anterior and posterior triangles
    • Anterior triangle → anterior border of SCM to midline.
    • Posterior triangle → posterior border of SCM to anterior border of trapezius.
  • Management:
    • Hard signs → surgical exploration (expanding haematoma, severe haemorrhage, shock, neurolgical deficit, haematemesis, massive haemoptysis, air bubbling through wound)
    • In the absence of hard signs:
      • Zone 1 and 3 are associated with difficult surgical access
      • Zone 2 should be explored if the injury extends deep to platysma.
74
Q

Explain the different approaches to a coin and a button batter lodged within the oesophagus

A
  • Impaction of a button battery in the oesophagus is surgical emergency and should be removed ASAP.
    • Forms circuit with mucosa → low voltage burn.
    • Releases free radicals that cause severe and rapid caustic burn (liquefactive necrosis)
      • Can cause full thickness necrosis within 15 mins of ingestion.
    • May be associated with acquired tracheo-oesophageal fistula, aorto-oesophageal fistula = high mortality.
    • Post removal, must be kept NBM and perform axial imaging to assess for extent of injury.
  • Impaction of a coin in the oesophagus causes injury by pressure necrosis only (in addition to aspiration risk).
    • Can trial period of observation → medical management (glucagon, carbonated drink)
    • Remove within 24hrs.
75
Q
  1. Explain the stages of empyema (short answer)
  2. Discuss the stages of empyema. Outline causative organisms and how they affect pathophysiology and presentation (essay)
A
  • Four stages of empyema:
    • Pre-collection stage - pneumonic associated with development of inflammation of the pleura (pleuritis).
    • Exudative stage - development of parapneumonic effusion.
    • Fibrinopurulent stage - cell count in effusion (large numbers of polymorphonuclear cells and fibrin) increases, fibrinous septations develop (due reduced fibrinolysis).
    • Organising stage - thick rind/exudate forms on the surface of the lung (associated with fibroblast invasion) and can cause restrictive lung pathology.
  • Associated with organisms that typically cause pneumonia
    • Strep pneumoniae (most common) - associated with higher risk of pneumatocoele formation
    • Staph aureus - associated with higher risk of lung abscess
    • Haemophilus influenzae B - associated with higher risk of pneumatocoele formation
    • Mycobacterium tuberculosis
  • Presentation:
    • Fevers, tachypnoea, cough → respiratory failure.
    • In immunocompromised child → may develop fungal or atypical infection.
76
Q

What is the differential diagnosis for testicular mass by age?

A
  • Germ cell tumours account for majority of testicular tumours.
    • Pre-pubertal (75% benign):
      • Germ cell tumours
        • Teratoma (most common germ cell tumour in prepubertal)
        • Yolk sac tumour (most common malignancy in prepubertal) - presents between 6m and 2yr.
        • Epidermoid
        • Gonadoblastoma (DSD only)
      • Stromal tumours
        • Leydig cell - aged 5-10yrs → precocious puberty.
        • Granulosa cell tumours (most common < 6months)
        • Sertoli cell tumours (most commonly present 6 months)
    • Post pubertal (75% malignant) - usually mixed non seminomatous GCT
      • Germ cell tumours
        • Teratoma (more likely to be malignant)
        • Embryonal carcinoma (post pubertal)
        • Seminoma (associated with hx UDT)
77
Q

Name 3 benign testicular masses

A
  • Testicular masses are more likely to be benign when they present pre-pubertally.
    • Majority of testicular masses are germ cell tumours
      • Teratoma most common (unlikely to be malignant pre-pubertal period)
      • Epidermoid cysts
    • Stromal tumours
      • Leydig cell tumours (universally benign)
      • Granulosa tumours (universally benign)
      • Sertoli cell tumours (unlikely to be malignant in prepubertal).
78
Q

What is the normal progression of AFP levels from birth to 12 months of life?

A
  • AFP is grossly elevated at birth (physiologically) - average 40000
    • Half life 5-7 days initially (varies with age - half life approx 30 by 3 months of age)
      • Normally AFP < 10 by 1yr.
79
Q

What is epignathus?

A
  • Epignathus refers to a teratoma protruding from the mouth.
    • Usually arises from the palate.
    • May be associated with obstruction of the oropharynx → polyhydramnios
    • May be associated with respiratory difficulties at birth.
80
Q

List the biochemical abnormalities associated with pyloric stenosis.

A
  • Classically associated with hypochloraemic, hypokalaemic metabolic alkalosis (elevated HCO3-).
    • Also associated:
      • Hyponatraemia
      • Hypovolaemia
      • May be associated with hypoglycaemia
81
Q

What is SCIWORA and how do you diagnose it?

A
  • SCIWORA = spinal cord injury without radiographic abnormality
    • Diagnosis:
      • Presence of neurological signs or symptoms in the absence of radiographic abnormality (X-rays and CT)
      • MRI spine now limits this as has a higher sensitivity for soft tissue injury
82
Q

What is a teratoma? Name a syndrome associated with increased risk.

A
  • Teratoma is a germ cell tumour composed of the all 3 germ layers (ectoderm, mesoderm, endoderm).
    • Klinefelter syndrome (47XXY) associated with mediastinal teratomas (strong), retroperitoneal teratomas.
      • Mediastinal teratoma in Klinefelter often associated with choriocarcinoma within teratoma → HCG induced precocious puberty.
83
Q

What are the long term outcomes in Hirschsprung disease? How do you assess bowel function? ESSAY

A
  • Long term outcome measured by:
    • Obstructive symptoms
      • 5 causes of obstructive symptoms
        • Mechanical obstruction (i.e. stricture, spur)
        • Persistent aganglionosis
        • Colonic dysmotility
        • Internal sphincter achalasia
        • Functional megacolon
    • Soiling
      • 3 causes
        • Abnormal sphincter function
          • Sphincter injury during operation
          • Previous sphincterotomy.
        • Abnormal sensation
          • Loss of sensation of full rectum
          • Loss of ability to differentiate solid and liquid stools
            • May occur due to anastomosis being below the dentate line.
        • “Pseudoincontinence” = severe constipation
  • Hirschsprung associated enterocolitis.
  • Outcome also affected by comorbidity.
    • Long segment
    • Trisomy 21
    • Associated syndromes such as congenital hyperventilation syndrome
    • Congenital heart disease.
  • Assessment:
    • Assessment of mechanical obstruction/stricture
      • EUA rectum
      • Contrast enema
    • Assessment of persistent aganglionosis
      • Repeat rectal biopsy
    • Assessment of colonic motility
      • Colonic transit study
    • Trial of intrasphincteric botox
      • Success suggests internal sphincter achalasia.
    • Assessment of sphincter function
      • Anorectal manometry
      • Endoanal ultrasound.
    • Assessment of sensation
      • EUA rectum – assess whether anastomosis is below dentate line.
84
Q

Describe Hirschsprung associated enterocolitis pathophysiology and relate this to risk factors for it (ESSAY)

A
  • Pathophysiology
    • Bacterial stasis + overgrowth -> epithelial/mucosal injury + bacterial translocation -> intramural inflammatory response + ileus -> coagulative necrosis of bowel -> ischaemia and infarction -> perforation and sepsis.
      • Intestinal wall inflammation:
        • Neutrophil infiltation into crypts → cryptitis.
        • Crypt dilatation and mucous trapping → crypt microabscesses → mucosal ulceration → transmural necrosis.
    • Hirschsprung disease results in an abnormal enteric nervous system (incorporates gut motility, secretion and immunity).
    • Pathophysiology broken down into:
      • Luminal factors
        • Motility
          • Reduced motility, dilation -> stasis, bacterial overgrowth, increased contact time with epithelium → translocation.
          • Reduced bacteriocidal effects of bile acids, gastric acids and pancreatic exocrine secretions.
        • Mucus
          • Mucus serves as scaffold for bactericidal or bacteriostatic proteins (provide barrier to invasion)
            • Mucin and immunoglobulin secretion is abnormal in patients with HD.
              • Less mucin, less effective mucin.
      • Gut wall factors
        • Immunity
          • Ineffective innate immunity → abnormal IgA transfer across mucosa.
        • Gap junctions
          • Sensitive to pro-inflammatory mediators -> dysfunction→ disrupted intestinal barrier.
          • Abnormal glial cell function/volume → regulate epithelial barrier function.
        • Immature mucosa → defective epithelial cell proliferation and differentiation.
      • Microbiome
        • Impaired intraluminal immunity (reduced IgA) → high risk of infection from C Difficile, Rotavirus
        • Reduced probiotic organism - lactobacilli, bifidobacteria
  • Risk factors
    • Trisomy 21
      • Impaired immunity
    • Long segment Hirschsprung disease
      • Worse colonic motility
    • Delayed diagnosis (more likely to present with HAE if diagnosis delayed beyond 1 week)
      • Prolonged exposure to noxious pathogens in dysfunctional gut.
    • Obstruction
      • Stricture
      • Internal sphincter achalasia
        • Both associated with stasis and gut dilation.
85
Q

Discuss the pathophysiology of NEC. Be sure to include consideration of risk factors (ESSAY)

A
  • Necrotising enterocolitis is an exaggerated immune response that an enteric pathogen that results in inflammation, bacterial overgrowth and coagulative necrosis. Can cause transmural gut injury and systemic inflammation or sepsis.
  • Risk factors:
    • Prematurity
    • Extreme low birth weight
    • Significant comorbidity (usually congenital heart disease)
    • Formula fed
    • Antibiotic use
    • Acid suppression
  • Pathophysiology:
    • Substrate/Luminal factors
      • Prematurity results in immature and ineffective gut secretions resulting in impaired gut protection from pathogens.
        • Gastric acid secretion is one of the first line defenses against enteric pathogens. Immature gastric acid production results in impairement of this defense. Gastric acid secretion matures at approx. 24/40.
        • Mucin secretion from goblet cells usually provides a scaffold for bacteriocidal and bacteriostatic proteins as well as a protective barrier to epithelial cells.
          • Mucin secretion is reduced in volume and effectiveness in premature infants.
      • Gut motility is reduced in prematurity
        • Allows for stasis of gut contents -> bacterial overgrowth and increased contact time between noxious stimuli and epithelial cells.
      • Formula fed babies
        • Associated with increased secretion of harmful bile acids which can damage mucosa.
        • Premature babies have low levels of IgA -> reliant on immunoglobulins from breast milk.
    • Impaired defences:
      • Gut wall immunity is impaired.
        • Reduced IgG (usually crosses placenta after 36/40)
        • Immature cellular immunity
          • Neutrophil stores reduced in premature neonates, unable to persistently supply neutrophils for ongoing infection/inflammation (neutropaenia associated with severe NEC).
        • Gut wall associated lymphatic tissue is impaired in size and function in neonates.
      • Increased toll like receptor 4 (TLR4) -> associated with exaggerated immune response.
        • Sensitive to lipopolysaccharides in bacterial cell wall (strong proinflammatory stimulus).
        • TLR4 response is to induce enterocyte apoptosis AND reduce mucosal repair mecanisms.
      • Immature tight junctions -> leaky and associated with increased permeability.
    • Microbiome
      • Microbiome affected by feeds and location (i.e. NICU)
      • Babies with NEC have lower gut flora diversity and tend to have a dominant organism which can be harmful.
      • Microbiome affected by antibiotic use (increased rates for premature neonates due to high risk of sepsis and concurrent comorbidities).
      • Acid suppression associated with increased rates of NEC due to alteration in microbiome.
      • Neonates have impaired immunity to gram negative bacteria such as E.Coli and salmonella.
    • Impaired intestinal barrier regeneration and repair.
      • Inflammatory mediators cause tissue injury and reduce cell repair (NO, PAF -> Oxygen free radicals -> apoptosis).
      • Lower amounts of protective epidermal growth factor in premature neonates.
    • Gut wall perfusion
      • Neonatal splanchnic perfusion is a low pressure, low resistance circulation. Complex and delicate interplay between endothelin-1 and NO (vasoconstriction and vasodilation).
        • Pro-inflammatory stimulus in NEC associated with reduced NO synthase -> impaired production of NO (vasodilator) -> vasoconstriction -> worsening ischaemia and necrosis.
      • Breast milk considered protective – Strongly enriched in NO precursor molecules, inhibits TLR4 signalling.
86
Q

Describe the biomarkers of NEC indicating severity and how they relate to pathophysiology

A
  • Biomarkers
    • Inflammatory markers
      • WCC
        • Non specific marker of infection/inflammation in the body.
        • Elevated in NEC due to inflammatory process and mobilisation of WCC to manage pathogens and inflammatory damage.
          • Neutropaenia associated with severe NEC and poor prognosis.
      • CRP
        • Non-specific inflammatory marker.
        • Elevations in NEC associated with severity and stricture formation.
        • Rapid elevation may accompany the clinical onset of NEC.
          • Can be used serially to monitor progression and complications.
    • Platelets
      • Drop in platelets usually occurs in NEC.
        • Severe, rapid onset thrombocytopaenia concerning for more significant NEC. Occurs due to inflammatory mediated endothelial damage -> platelet consumption.
  • VBG/ABG
    • Lactate
      • Marker of sepsis and tissue perfusion.
      • Raised lactate associated with significant impairment in perfusion.
      • pH
        • Acidosis occurs in sepsis.
    • Other
      • IFABP (intestinal fatty acid binding protein – enterocytes)
        • Marker produced by epithelial cell destruction.
          • Enterocyte destruction associated with release of IFABP into the blood -> cleared in the urine.
          • Samples can be taken from both urine and stools, can be used as a marker of NEC.
            • Faecal calprotectin
        • Marker of intestinal inflammation – released by neutrophils upon inflammatory activation in the gut.
        • Higher faecal calprotectin correlates to more severe (surgical NEC) – likely representing the extent of intestinal inflammation and injury.
      • IL-8
        • Inflammatory cytokine.
        • Has been shown to be higher in surgical NEC vs medical NEC.
          • Higher levels also seen in more severe surgical NEC (i.e. NEC totalis)
      • Platelet aggregating factor
        • Pro-inflammatory mediator

Pathophysiology (7 decks)

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