Diabetes insipidus in pregnancy TOG 2018 Flashcards
What is the incidence of diabetes insipidus in pregnancy?
Similar to general population 2-4/100,000 (rare)
Symptoms of diabetes insipidus?
Excessive thirst and polyuria
Drink @ night and pass large volumes of dilute urine >3/L a day
?Weakness/confusion/seizures
Usually raised in 3rd trimester and remits 4-6 weeks PP.
What is normal plasma osmolality outside pregnancy? How does this change in pregnancy?
Non preg: 285-295
Pregnancy: 270
So normal non pregnant levels considered abnormal in pregnancy.
What are normal sodium levels in pregnancy
Reduced 4-5mmol/l in pregnancy
(135-145 outside preg)
What is the pathogenesis of diabetes insipidus
Deficiency in ADH (produced from posterior pituitary)
Central: Underproduction, idiopathic/pituitary adenoma/sheehans/trauma
Nephrogenic: ADH resistance, CKD/lithium/high Ca
Transient: Increased vasopressinase production from placenta (higher in multiple pregnancy) which metabolises ADH. The liver metabolises vasopressinase, therefore anything that impacts liver function - PET/HELLP/AFLP can exacerbated Sx.
Psychogenic: Excessive drinking of water
How to Dx diabetes insipidus in pregnancy?
Rule out cases of polyuria - diuretics, hyperglycaemia, hypercalcaemia, hypokalaemia
Do not performed water deprivation test in pregnant
Paired osmolality
Plasma: >285 mOsmol/kg, serum sodum >145mmol/l
Urine: <300 mOsmol/kg
How does the urine to plasma osmolality help you in diagnosis?
If U:P is more than 2:1 and plasma osmolality >295 - DI can be excluded.
If U:P ratio < 2 consider DI
Especially if Na high
?Hx PPH/neurogenic causes
Effects of pregnancy on DI
May unmask previous subclinical DI, 50% will experience deterioration
- Increased GFR
- Placental production vasopressinase
- Antagonism of ADH by prostaglandins
Effects DI on pregnancy
Severe dehydration/electrolyte disturbance - seizures and Oligohydramnios
If Tx no adverse effect on prengnacy
How to treat DI in pregnancy?
New onset - Ix PET and AFLP
DDVAP - resistant to vasopressinase. 1-4ug daily
What is the treatment of nephrogenic DI outside in pregnancy, what is given in pregnancy?
Outside - chlorpropamide (causes fetal hypoglycaemia)
Inside - Good water intake, consider thiazides, NSAIDS, carbamazipine
What are signs of hypernatraemia
Weakness, altered mental state
seizure coma
How quickly can correct hypernatraemia?
1 mol/l/hour
Risk osmotic brain injury
Impact DI on spinals
Reduced intravascular volume can Redner spinal inappropriate, consider epidural
