Congenital disorders Flashcards by Lucy Butler

What can congenital dz be due to?

Due to developmental failure during gestation

Which may be a result of:
- inherited disorder
- nutritional deficiency or excess in gestation
- dz in gestation

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - what is it?

= hyposomatotropism

Congenital growth hormone (GH) deficiency

Abnormal development of the pituitary gland
- hormone-producing cells fail to differentiate during gestation

Inherited dz (simples autosomal recessive)
- German shepherds most commonly affected
- KC scheme for Tibetan terriers introduced 2021
- rare in cats

Other pituitary hormones may be affected: thyroid stimulating hormone (TSH), prolactin, gonadotropins
- adrenocorticotropin hormone (ACTH) unaffected?

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - presentation

Animal may appear normal until about 2m/o
- stunted growth, delayed dentition
- puppy coat (primary ‘guard’ hairs don’t develop), bilateral symmetric alopecia
- abnormal reproductive development (cryptorchidism, anoestrus)

Affected dogs will have shortened lifespan
- prognosis guarded with tx, poor without

How well did you know this?

Not at all

Perfectly

‘Stunted growth’: Differentials

GI
- malnutrition (including parasitism)
- malabsorption dz

Endocrine
- pituitary dwarfism
- congenital hypothyroidism
- juvenile DM
- EPI
- hypoadrenocorticism

Hepatic
- portosystemic shunt
- other liver dz

Iatrogenic
- glucocorticoids

Renal
- aplasia, dysplasia
- other renal dz

Metabolic
- storage dz (lysosomal, glycogen)

Skeletal
- skeletal dysplasia ‘dwarfism’

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - diagnostic options

biochemistry
thyroid hormones
growth hormone / insulin-like growth factor 1 (IGF1)
GH stimulation test
advanced imaging
genetic testing

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - diagnostics - biochemistry

Elevated creatinine
- GH deficiency impacts renal development
- TSH deficiency reduces GFR

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - diagnostics - thyroid hormones

low thyroxine (T4)
low TSH

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - diagnostics - growth hormone / insulin like growth factor-1 (IGF-1)

Low (but can be low in normal animals)
- IGF-1: indirect evaluation of GH

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - diagnostics - GH stimulation test

Definitive for GH deficiency

Requires a GH stimulant (plasma GH should increase after 20-30mins)
- GH-releasing hormone
- alpha-adrenergic drugs (clonidine, xylazine)
- human ghrelin

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - diagnostics - advanced imaging

May reveal cyst (thought to be secondary)
- may be found incidentally in brachycephalic

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - diagnostics - genetic testing

GSD
Tibetan terriers

How well did you know this?

Not at all

Perfectly

Pituitary dwarfism - tx

Problem = insufficient GH, solution = supplement GH?

Cats: ideal tx unknown

Growth hormone
- porcine GH
- difficult to acquire
- canine GH not available
- DM risk: monitor GH, IGF-1, glucose

Progestagens
- medroxyprogesterone
- stimulates GH in mammary glands (ineffective in cats)
- risk of DM, mammary tumours, acromegaly, CEH
– spay females prior to tx

Supplement thyroxin (levothyroxine)

Prognosis still guarded even with tx
- progressive pituitary dysfunction and renal dz, cyst enlargement

How well did you know this?

Not at all

Perfectly

Congenital hypothyroidism - what is it?

Congenital thyroxine deficiency

Primary = abnormality of the thyroid glands
- dysmorphogenesis - anatomical abnormality
- dyshormonogenesis - abnormality in hormone synthesis (fox terriers, rat terriers)

Secondary = abnormality of the pituitary
Tertiary = abnormality of the hypothalamus
Secondary & tertiary = ‘central’ CH (CCH), rare (<5% of cases)

Rare in both dogs and cats
- potentially misclassified as ‘fading puppy’

How well did you know this?

Not at all

Perfectly

Congenital hypothyroidism - presentation

Disproportionate dwarfism
- wide skull
- macroglossia (tongue too large for mouth)
- delayed dentition

Signs of adult hypothyroidism

Affected dogs at risk of OA due to epiphyseal dysgenesis (joint abnormalities)

Only 3.6% of dogs diagnosed

How well did you know this?

Not at all

Perfectly

Congenital hypothyroidism - diagnostics

Biochemistry
- hypercholesterolaemia

Haematology
- Non-regenerative anaemia

Thyroid hormones
- definitive: low T4 with high TSH
Low T4
- interference of non-thyroidal illness
- age-related interference (4.5x higher in healthy puppies up to 3mo)
High TSH
- will be low if CCH: thyrotropin-releasing hormone (TRH) functional test

Thyroid scintigraphy
- diagnostic
- decreased or absent radionuclide uptake

How well did you know this?

Not at all

Perfectly

Congenital hypothyroidism - tx

Problem = insufficient thyroxin

Levothyroxin

Prognosis guarded
- contrast with good prognosis for acquired?
- age of diagnosis may limit additional growth

How well did you know this?

Not at all

Perfectly

What does aplasia mean?

failure to develop

How well did you know this?

Not at all

Perfectly

What does hypoplasia mean?

Study These Flashcards

incomplete or under-development

What does atrophy mean?

Study These Flashcards

something may have developed, but now its deteriorating e.g. autoimmune dz

Pancreas - islet cells vs acinar cells

Study These Flashcards

Islet cells
- produce insulin
- endocrine

Acinar cells
- produce digestive enzymes
- exocrine

EPI - what is it?

Study These Flashcards

exocrine pancreatic hormone deficiency (e.g. trypsin)

EPI in dogs

Study These Flashcards

most commonly pancreatic acinar atrophy (PAA)
believed to be autoimmune
complex heritability
may have concurrent DM

EPI in cats

Study These Flashcards

most commonly chronic pancreatitis

Juvenile diabetes mellitus - what is it?

Study These Flashcards

= insulin deficiency (usually absolute)
- DM diagnosed <6m/o
- uncommon

Variable aetiology
- congenital islet cell atrophy, aplasia or hypoplasia
- not usually auto-immune
- insulin receptor defects possible but not reported
- Keeshond’s may have heritable dz

Juvenile diabetes mellitus - presentation

- stunted growth - other hallmarks of DM including cataracts

Juvenile diabetes mellitus - diagnostics

- fasting hyperglycaemia - glucosuria - fructosamine - glucose curves

Juvenile diabetes mellitus - tx

Treatable with insulin therapy possibly but challenging

Porto-caval & portosystemic shunt (PSS) - what is it?

Structural defect: foetal vascular structure fails to close (or forms during development)

Porto-caval & portosystemic shunt (PSS) - types of shunt

When the shunt develops: congenital vs acquired - congenital: usually single, persistent foetal structure - acquired: usually multiple/complex, cirrhosis, portal hypertension Number of shunts: single vs multiple/complex - single e.g. persistent ductus venosus - multiple e.g. cirrhosis, portal hypertension Location: intra vs extra hepatic - intra = most common congenital PSS of large dogs - extra = most common congenital PSS of cats and small dogs

Porto-caval & portosystemic shunt (PSS) - presentation

Neurological signs - hepatic encephalopathy (HE) - depression - head pressing - blindness - ataxia - seizure (may occur soon after a meal) GI signs - hypersalivation - d+ - v+ Urinary signs - ammonium bitrate crystalluria - dysuria - pollakiuria - haematuria - stranguria Stunted growth Acquired shunts: - ascites

Porto-caval & portosystemic shunt (PSS) - haematology

- leukocytosis - microcytic anaemia

Porto-caval & portosystemic shunt (PSS) - biochemistry

Increased bile acid (fasting in some cases, postprandial in all) - highly suspect in young animal with signs of HE Increased ALT, ALP - ALP may be age-related (rather than cholestasis) Other hepatic markers: - hypoglycaemia - hypoalbuminaemia (may be normal in cats) - low urea Hyperammoniaemia - dynamic testing: Ammonia tolerance test

Porto-caval & portosystemic shunt (PSS) - urinalysis

- low USG - ammonium biurate crystalluria

Porto-caval & portosystemic shunt (PSS) - imaging

*Diagnostic* Radiography: may see micro hepatic, renomegaly US: may be challenging, esp extra hepatic shunts CT angiography Scintigraphy: technetium circulates more rapidly to heart and lungs

Porto-caval & portosystemic shunt (PSS) - tx

Problem = persistent/abnormal vascular structure Surgery - close the structure - ideal for single congenital - ligation: may be abrupt, risk of complications - constriction: gradual - aneroid constrictor, thrombogenic coil Medical management - not all can be closed (complexity, finances) - lactulose: acidifies colonic contents, trapping ammonia - antibiotics (e.g. amoxicillin): reduces colonic bacteria that produce ammonia - protein restricted diet: reduce ammonia production

Vascular ring anomaly: persistent right aortic arch (PRAA) - what is it?

Structural defect: foetal vasculature fails to close 6 embryonic paired aortic arches surround the foregut - arches either involute or persist to become adult structures - embryonic foregut becomes oesophagus and trachea 4th right aortic arch can persist (abnormally) and lead to compression of the oesophagus. PRAA is the most common of up to 9 types of VRA identified.

Vascular ring anomaly: persistent right aortic arch (PRAA) - presentation

Regurgitation - soon after weaning More common in dogs than in cats - may be heritable e.g. GSDs

Vascular ring anomaly: persistent right aortic arch (PRAA) - diagnostics

Radiography - leftward deviation of trachea Barium study - oesophageal dilation CT angiography - surgical planning

Vascular ring anomaly: persistent right aortic arch (PRAA) - tx

- surgical closure - prognosis can be good if carried out before development of chronic oesophageal dilation or other complications (aspiration pneumonia)

Congenital renal dz - what is it?

Structural anomalies of the kidneys Developmental abnormalities - dysplasia/hypoplasia - aplasia/agenesis - renal fusion Some types of cystic dz (e.g. polycystic kidney dz [PKD] may be congenital) - autosomal dominant heredity in Persian & DLH cats

Congenital renal dz - dysplasia

= kidney(s) fail to develop normally - kidney(s) hypoplastic with subnormal cortex - unilateral cases usually develop hypertrophy of contralateral kidney - histologic abnormalities e.g. immature glomeruli: CRF may be identified between 6m-2y/o - rare in cats

Congenital renal dz - aplasia/agenesis

= kidney and ureter fail to develop - unilateral cases may have same-sided reproductive abnormality - bilateral = death - other kidney may function normally (incidental finding)

Congenital renal dz - renal fusion

= kidneys fuse during development - horseshoe kidney - function often normal

Congenital disorders Flashcards

(43 cards)