Endo - ix Flashcards
DI ix
Water deprivation test (8h) + desmopressin (ADH analogue) administration
- Conc after water deprivation - should be >700mOsm/kg
- Conc after water deprivation in DI pt - <400 mOsm/kg
- plasma osmolality >300 mOsm/kg + urine osmolality <600 mOsm/kg
DDAVP administration
- Cranial DI - concentrated urine after ADH administration [urine osmolatrity increases by >50%]
- Nephrogenic DI - urine remains dilute [urine osmolatrity increases by <45%]
Before test consider whether there is true polyuria (>3L/24h) !!!!
Test is only performed if patient’s sodium is in the normal range + urine osmolarity is <300 mOsm/kg [Normal urine osmolarity following fluid depletion should be >850mOsm/kg]
It’s a dangerous as hypovolaemia can cause AKI
- monitor patients weight throughout test and if it drops >3% stop test
- Urine dipstick
To exclude DM, UTI
- Urine osmolarity - Low
- Serum osmolarity/Na - High
- 24h urine collection - >3L
- MRI of hypothalamus, pituitary, surrounding tissues
- Serum calcium
- Serum potassium
(Hypercalcaemia + hypokalaemia can cause nephrogenic DI)
(in DI you get hypernatraemia)
Fluid restriction + desmopressin administration contraindications
This test is carried out to assess whether the DI is cranial or nephrogenic
Contra-indications
- Renal insufficiency
- Co-existing adrenal/thyroid hormone insufficiency
- Uncontrolled DM
- Hypovolaemia
Autoantigens associated w T1DM
- GAD (glutamic acid decarboxylase)
- Insulin
- Insulinoma-associated protein 2
- Cation efflux zinc transporter
- Islet cell antibodies
HLAs associated with T1DM
- HLA DR3
- HLA DR4
- Islet cell antibodies
T1DM Ix
- Fasting plasma glucose >7mM
- Random plasma glucose >11.1mM
- OGTT >11.1mM
- HbA1c - >6.5%, >48 mmol/mol*
- MSU - ketonuria, glycosuria, microalbuminuria
Ix to consider
- Plasma C-peptide (low <0.2nanomol/L)
- Autoimmune markers (autoantibodies to GAD, insulin, insulinoma associated protein 2, cation efflux zinc transporter, islet cell antibodies)
- reflects exposure to glucose/degree of hyperglycaemia over the last 3 months
therefore in a newly diabetic patient it is likely to be normal
also not accurate in haemolytic anaemias, haemoglobinopathies
T2DM Ix
- Fasting plasma glucose >7mM
- Random plasma glucose >11.1mM
- OGTT >11.1mM
- HbA1c - >6.5%, >48 mmol/mol
To differentiate between T1DM/T2DM
- Plasma C-peptide
Will be low in T1DM (<0.2 nanomol/L)
Will be high in T2DM (>1 nanomol/L)
Glucose tolerance test (OGTT)
Values for fasting + 2h after 75g oral glucose tolerance test
Normal
Prediabetes
Diabetes
Normal
- Fasting 4-5.9mmol/L or <6.1mmol/L
- 2-h/OGTT <7.8mmol/L
Pre-diabetes- Fasting
- 6.1-6.9 mmol/L- 2h/OGTT
- 7.8-11.0 mmol/L
Diabetes
- Fasting >7 mmol/L
- 2h/OGTT >11.1mmol/L
Histological features in diabetic kidney disease
Glomerular mesangial sclerosis
- Glomerular sclerosis
- Mesangial expansion
- BM thickening
DKA ix
- Urinalysis
Glucose, ketones - FBC
Increased plasma glucose
Increased plasma ketones (>3mmol/l)
WCC might be increased in the absence of infection
-ABG
Metabolic acidosis (pH <7.3, HCO3 <15mmol/L)
Large anion gap (>13 mmol/L)
Hyperkalaemia
- Plasma osmolarity - high
Higher in HHS
>290 mOsm + ketonaemia/ketonuria- DKA
>320 mOsm + no ketanaemia/ketonuria - HHS
Why do we check U+Es in secondary hyperparathyroidism?
Because CKD can cause osteomalacia
Primary hyperparathyroidism Ca PO43- PTH Vit D ALP
Ca - increased PO43- - decreased PTH - increased or inappropriately normal Vit D - normal ALP - increased or normal
Secondary hyperparathyroidism Ca PO43- PTH Vit D ALP
Ca - decreased or normal PO43- Increased if CKD Decreased if Vit D deficiency PTH - increased Vit D - decreased ALP - increased
Imaging investigations in primary and secondary hyperparathyroidism
X-ray/CT - extent of bone disease
CT KUB - renal stones
Cervical US - before surgery
DEXA scan
Primary HPT
- pepper pot skull
- brown tumours
- rugger jersey spine
- subperiosteal bone resorption in phalanges + long bones
Secondary HPT - Rickets Bone bossing Rachitic rosary Bowed legs Knock knees - Looser's pseudofractures - vascular + visceral calcification - soft tissue calcification - osteopenia - coarse trabeculae - codfish vertebrae
Vitamin D deficiency/osteomalacia ix
Bloods
• N/low Ca
• High PTH
• low 25-hydroxyvitamin D
o Major circulating form of vitamin D used to determine vitamin D status
• Phosphate
o high in CKD (because kidneys are not working to excrete the phosphate)
o low in vitamin D deficiency (because as a response to vitamin D deficiency, more PTH is released which increases the excretion of phosphate)
• Increased ALP
Imaging - Rickets Bone bossing Rachitic rosary Bowed legs Knock knees - Looser's pseudofractures - vascular + visceral calcification - soft tissue calcification - osteopenia - coarse trabeculae - codfish vertebrae
Paget’s disease Ix
- Increased ALP - The only abnormality
- Everything else is normal - Except if immobilised - immobilisation can lead to hypercalcaemia
• Xray
o Enlarged deformed bones with mixed lytic/sclerotic appearance
o Lack of distinction between cortex and medulla
o Skull – osteoporosis circumscripta, enlargement of frontal + occipital areas associated with a “cotton wool” appearance (suggests multifocal sclerotic patches)
o Lytic lesions (radiolucency)
o Incomplete fractures
o Thickened bone cortices
o Later stage – sclerotic picture predominates over osteolytic
o Blade of grass lesion – classical V shaped pattern between healthy + diseased long bones
o Cotton wool pattern – in skull, suggests multifocal sclerotic patches
• Radionuclide bone scans (Tec99)
o Not specific for dx
o To assess the extent of skeletal involvement
o Pagetic bone lesions - focal areas of markedly increased uptake (hot spots)
o Hot spots = lytic areas
• Bone biopsy
o Confirmatory diagnostic test
o To exclude malignancies
o Rarely indicated
• CTX (serum C-terminal propeptide of type 1 collagen)
o Used as a marker of bone resorption
o Used as an index for treatment response
o Initially elevated, treatment may normalise values
• Urine hydroxyproline
o Used as a marker of bone resorption
o Used as an index for treatment response
o Initially elevated, treatment may normalise values
• P1NP (serum procollagen 1 N-terminal peptide)
o Used as a marker of bone formation
o Used as an index for treatment response
o Initially elevated, treatment may normalise values
