A boy with water-like urine

Transcription

1 ANNUAL SCIENTIFIC MEETING 2018 HONG KONG PAEDIATRIC NEPHROLOGY SOCIETY A boy with water-like urine Dr Alvin Hui (Paediatrics, QEH) Dr MT Leung (Chemical Pathology, QEH)

2 Case history M/37 days Full term with uneventful perinatal course Non-consanguineous couple No significant family history

3 Case history Presented with one day history of fever Associated with vomiting of undigested milk of 4-5x/day; there was no diarrhoea Usual feeding EBM/AF ml x 7 Also given water 10-30ml of 3-4x/day UO up to 10x/day. Described to be clear or light yellowish in colour No history of drug intake/herbs intake Mother took 1/52 of antibiotics after discharge

4 Physical examination Appropriate growth OFC: 38cm (50 th -75 th percentile) BH: 53cm (25 th percentile) BW: 4.3kg (25 th 50 th percentile) Afebrile Hydration: slightly on dry side No dysmorphic features No evidence of mid-line defect No signs of increased intracranial pressure Systemic examination: unremarkable

5 Initial Investigations Biochemistry Reference Intervals Sodium mmol/l Potassium mmol/l Urea mmol/l Creatinine 35 <37 µmol/l Glucose 4.5 mmol/l CRP <1 <5.0 mg/l Bedside urine dipstick showed a specific gravity <1.005 and Glucose -ve

6 Progress Initial impression was hypernatraemic dehydration Started IV fluid using D10: NS solution Sepsis workup was performed and empirically started on ampicillin and cefotaxime (Refused LP by parents) 7 hours later Na: 160 -> 164mmol/L K: 4.9mmol/L; Cl: 125mmol/L and HCO3 25mmol/L Urea 4.5mmol/L and creatinine 37umol/L Other tests: Serum osmolality 322 mosmol/kg (Ref: ) Urine sodium < 20 mmol/l Urine osmolality 143 mosmol/kg CT brain: Unremarkable; No structural brain lesion

7 Progress Transferred to PICU Reduce IVF [Na] to 77mmol/L and later to 40mmol/L Simultaneous polyuria up to 10ml/kg/hour Required isotonic fluid boluses to correct his volume deficit Combination of Hypernatraemia Polyuria Low urine osmolality Clinical diagnosis was diabetes insipidus (DI)

8 Walmsley, R. N., Watkinson, L. R., & Cain, H. J. (1999). Cases in chemical pathology : a diagnostic approach. Singapore ; River Edge, N.J. : World Scientific, c1999.

9 Bockenhauer, D. and Bichet DG. Nat. Rev. Nephrol. 2015;11:

10 Bockenhauer, D. and Bichet DG. Nat. Rev. Nephrol. 2015;11:

11 Progress Desmopressin (10 microgram) was first given orally Later continuous vasopressin infusion up to 2 milliunits/kg/hr Continued to have polyuria and serum Na continued to rise Peak [Na] = 186mmol/L (D2 of admission) Serum [Cl] >140mmol/L Serum osmolality 366 Osm/kg and paired urine osmolality 146 Osm/kg

12 Progress Vasopressin was then stopped Oral indomethacin, hydrochlorothiazide and amiloride were started A low sodium diet was prescribed Serum [Na] was then gradually stabilised Urine output reduced to ~3-4ml/kg/hour

13 Courtesy: Dr JKK Sit

14 Nephrogenic DI - Aetiologies Congenital X-linked nephrogenic DI (~90%) Autosomal recessive (~9%) / autosomal dominant (~1%) Acquired Drugs e.g. lithium, demeclocycline, antimicrobials (amphotericin B, foscarnet), methoxyflurane, etc. Osmotic diuresis e.g. hyperglycaemia Tubular disease: Bartter or apparent mineralocorticoid excess Associated with hypokalaemia and hypercalciuria Renal disease e.g. polycystic kidneys, sickle cell

15

16 Prevalence Exact prevalence of NDI is not known but is assumed to be rare 8.8 in 1,000,000 males in Quebec, Canada A higher incidence of NDI is also found in Utah due to the prevalence of the Cannon mutation Nephrogenic Diabetes Insipidus. GeneReviews. Last Update: June 14, Bockenhauer, D. and Bichet DG. Nat. Rev. Nephrol. 2015;11:576 88

17 Clinical Features Polyuria, polydipsia Hypernatraemia, dehydration Vomiting, lethargy, failure to thrive Seizure, mental retardation Heterozygous female carriers of X-linked NDI have variable degrees of symptoms because of skewed X-chromosome inactivation

18 Diagnosis Traditionally making the diagnosis relies on water deprivation test and DDAVP challenge However in neonates or very young infants with documented hypernatraemia together with low urine osmolality, the test is usually not performed Administration of desmopressin with baseline and regular measurement of serum [Na] and urine osmolality Diagnosis can be made if the urine osmolality does not increased >100 osmo/kg over baseline Bichet DG. UptoDate 2018

19 Diagnosis Other diagnostic approach Serum AVP level Copeptin level C-terminal glycoprotein moiety of pro-avp Stable surrogate marker of vasopressin secretion Molecular testing

20 Molecular testing by Chemical pathologist

21 Progress

22

23 Progress As the patient is growing older Able to indicate thirst and drink water by himself Titrate the dose of medications No acute crisis episode Recently increase the dose of medications to reduce polyuria for social reason

24

25 Any questions?