1. The child with polyuria and polydipsia Detlef Bockenhauer

2. Objectives To provide an overview of polyuria/polydipsia by giving case scenarios Aetiology Assessment management

3. ?

4. Case 1: History A 6-month old boy is referred because of failure-to- thrive and vomiting No other significant past or family history, born at 37 weeks gestation, normal pregnancy

5. Case 1: examination Unremarkable examination: weight: 5.54 kg ( 0.4 th ), OCF: 42.5 cm (<9 th %ile) BP: 94 mmHg systolic Normal renal US biochemistriesPlasmaUrineunit Sodium157<5mmol/l creatinine0.031.1mmol/l osmolality31983mosmol/kg

6. Diagnosis? Diabetes insipidus (central or nephrogenic)

7. Further investigations Admission for iv DDAVP test Max urine osm: 83 mosm/kg

8. Diagnosis? Nephrogenic diabetes insipidus

9. NDI: management Dietetic advice: restricting solute load to 15 mosm/kg/d but providing appropriate calories and RDA for protein Each gram protein is metabolised to appr. 4 mmol of urea Each gram of salt constitutes appr. 18 mosm (9 each for sodium and chloride) Lipids and carbohydrates do not generate solute load (hence maxijul fortified milk)

10. NDI: medications Indometacin: enhances (?) proximal tubular sodium uptake. NOT by chemical nephrectomy Thiazide: enhances proximal tubular sodium uptake As PT is permeable for water, enhanced sodium uptake results in enhanced water reabsoprtion, thus less water is transported to CD, where it cannot be reabsorbed. Medications can often be discontinued with increasing age

11. Case 2: History A 3-year old boy is referred because of long- standing polyuria/polydipsia (since age 10 months) He drinks about 2.5 to 3 litres of fluid per day He gets up once or twice at night to drink Local assessment: normal growth and biochemistries Water deprivation test (age 18 m): unable (screams constantly for water) After DDAVP: generalised convulsion with Na of 125 mmol/l. Max urine osm: 482 msom/kg No significant past or family history

12. Case 2: examination Unremarkable examination: weight, height, OCF: all around 9 th %ile BP: 100/52 mmHg Normal renal US biochemistriesPlasmaUrineunit Sodium14115mmol/l creatinine0.032.5mmol/l osmolality28855mosmol/kg

13. Diagnosis? (partial) Diabetes insipidus (central or nephrogenic) based on max Uosm of 482 Habitual polydipsia

14. Further investigations Admission for water deprivation /iv DDAVP test Max urine osm: 630 mosm/kg (normal plasma Na throughout), 639 mosm/kg after DDAVP

15. Diagnosis? ?(partial) Diabetes insipidus (central or nephrogenic) Habitual polydipsia

16. Case 2: discussion not documented normal urine concentrating capacity (>800 mosm/kg) ?washout Urine osmolality on spot samples always well below ( 600 mosm/kg) Assuming an osmol load of 20 mosm/kg, urine output with urine of 600 mosm/kg in a 20 kg child would be 0.67 litres/day Polyuria thus likely secondary to polydipsia Hyponatraemic seizure during DDAVP highly suspicious of habitual polydipsia

17. Case 3 An 8-month old boy with excess polyuria and polydipsia from newborn period (1200 ml/d) Normal growth, normal feeding DDAVP test at age 11-month (1 mcg IM injection): Urine Osmolalitybaseline 101 maximum254 biochemistriesPlasmaUrineunit Sodium14115mmol/l creatinine0.032.5mmol/l osmolality28855mosmol/kg

18. Diagnosis? Nephrogenic diabetes insipidus Treated with Indometacin and thiazide “Presentation is unusually mild”

19. Family history of polyuria & polydipsia Mother,III 13 : insulin dependent diabetes mellitus Grandmother,II 8: “cranial” DI Maternal uncle,III 1: nephrogenic DI Maternal uncle,III 10: nephrogenic DI Maternal g’aunt II 1 :nephrogenic DI Maternal g’aunt II 4 :nephrogenic DI Maternal g’grandfather I 1 :history of severe polyuria Nephron Physiol 114(1), p1-p10 III 13 III 10 III 1 II 1 II 4 II 8 I1I1

20. Case 3 continued Aged 5y, remained very well Treated with Indometacin and bendroflumethiazide Excellent growth Ht 75 th, Wt 25 th centiles Normal plasma biochemistry Never admitted

21. IV 1 : repeat DDAVP test: 2mcg IM BloodBaseline20mins2 h3 h4 h5 h Na142141 Osm291289 Urine Na143862766143 Osm117232370416570280

22. Mutation analysis tested xx  All tested carry a mutation in AVPR2 : V88M

23. Diagnosis? Partial NDI Now treated with desmopressin at night

24. Case 4: Bartter A 4-months old ex-26 wk premie is referred because of persistent polyuria (up to 12 ml/kg/h) and intermittent hypernatraemia

25. History Parents are first cousins, mother 24 y old primigravida History of maternal polyhydramnion and s/p 2 amnioreductions biochemistriesPlasmaUrineunit Sodium15745mmol/l creatinine0.0470.9mmol/l osmolality318197mosmol/kg

26. Diagnosis?

27. Bartter Syndrome

28. Treatment of Bartter Syndrome COX-inhibitors Salt and potassium supplementation

29. Surprise! Indomethacin (1 mg/kg/d) was started Chemistries the next day as follows: Na 150 mmol/l K4.8 mmol/l Cl119 mmol/l HCO321 mmol/l Osmolality: 311mosm/kg Urine Na: <5mmol/l Urine osmolality:76mosm/kg

30. A case of Diabetes Insipidus? DDAVP 0.05 mcg im was given. Chemistries 4 hours later: Na140 mmol/l Osmolality290 mosm/kg Urine Na7 mmol/l Urine osmolality63 mosm/kg

31. Bartter? or DI? Off Indomethacin - Bartter Na159 K2.9 HCO324 Urine Na82 Urine osmolality253 Back on Indomethacin - DI Na142 K4.8 HCO320 Osmolality299 Urine Na5 Urine osmolality76

32. Discussion case 4 Bartter syndrome classically associated with isosthenuria About 20% of cases (Bartter 1 and 2) have hyposthenuria (NDI) Mechanism unclear (hypercalciuria?) Treatment quandary: to give or not to give salt

33. Polyuria: causes Non-renal Excess water intake Increased solute load (DKA, mannitol) Renal Impaired water reabsorption in CD (NDI) Impaired concentration gradient (Bartter, NPHP, TIN)

34. conclusions Polyuria can be water (NDI, polydipsia) or solute driven (Bartter, DKA, Mannitol etc.) Urine osmolality can help in assessment: (Uosm<Posm in water diuresis; Uosm≥Posm in solute diuresis) Clear distinction not always possible (e.g. secondary NDI in Bartter) Maximal Uosm can be impaired in Habitual polydipsia (“medullary washout”) Careful observation mandatory during DDAVP test