The child with polyuria and polydipsia
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Transcript of The child with polyuria and polydipsia
The child with polyuria and polydipsia
Detlef Bockenhauer
Objectives
• To provide an overview of polyuria/polydipsia by giving case scenarios
• Aetiology
• Assessment
• management
?
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
Case 1: examination
• Unremarkable examination: weight: 5.54 kg (<0.4th 5ile), height: 62.5 cm (>0.4th), OCF: 42.5 cm (<9th %ile)
• BP: 94 mmHg systolic• Normal renal US
biochemistries Plasma Urine unit
Sodium 157 <5 mmol/l
creatinine 0.03 1.1 mmol/l
osmolality 319 83 mosmol/kg
Diagnosis?
• Diabetes insipidus (central or nephrogenic)
Further investigations
• Admission for iv DDAVP test• Max urine osm: 83 mosm/kg
Diagnosis?
• Nephrogenic diabetes insipidus
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)
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
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
Case 2: examination
• Unremarkable examination: weight, height, OCF: all around 9th %ile
• BP: 100/52 mmHg• Normal renal US
biochemistries Plasma Urine unit
Sodium 141 15 mmol/l
creatinine 0.03 2.5 mmol/l
osmolality 288 55 mosmol/kg
Diagnosis?
• (partial) Diabetes insipidus (central or nephrogenic) based on max Uosm of 482
• Habitual polydipsia
Further investigations
• Admission for water deprivation /iv DDAVP test
• Max urine osm: 630 mosm/kg (normal plasma Na throughout), 639 mosm/kg after DDAVP
Diagnosis?
• ?(partial) Diabetes insipidus (central or nephrogenic)
• Habitual polydipsia
Case 2: discussion• not documented normal urine concentrating capacity
(>800 mosm/kg) ?washout• Urine osmolality on spot samples always well below
(<100 mosm/kg) documented concentrating capacity (>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
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 Osmolality baseline 101
maximum 254
biochemistries Plasma Urine unit
Sodium 141 15 mmol/l
creatinine 0.03 2.5 mmol/l
osmolality 288 55 mosmol/kg
Diagnosis?
• Nephrogenic diabetes insipidus• Treated with Indometacin and thiazide
• “Presentation is unusually mild”
Family history of polyuria & polydipsia
Mother,III13: insulin dependent diabetes mellitus
Grandmother,II8: “cranial” DI
Maternal uncle,III1: nephrogenic DI
Maternal uncle,III10: nephrogenic DI
Maternal g’aunt II1: nephrogenic DI
Maternal g’aunt II4: nephrogenic DI
Maternal g’grandfather I1: history of severe polyuria
Nephron Physiol 114(1), p1-p10
III13
III10III1
II1 II4II8
I1
Case 3 continued
• Aged 5y, remained very well• Treated with Indometacin and
bendroflumethiazide• Excellent growth Ht 75th, Wt 25th centiles• Normal plasma biochemistry• Never admitted
IV1: repeat DDAVP test: 2mcg IM
Blood Baseline 20mins 2 h 3 h 4 h 5 h
Na 142 141
Osm 291 289
Urine
Na 14 38 62 76 61 43
Osm 117 232 370 416 570 280
Mutation analysis
tested x x
All tested carry a mutation in AVPR2 : V88M
Diagnosis?
• Partial NDI
• Now treated with desmopressin at night
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
History
• Parents are first cousins, mother 24 y old primigravida
• History of maternal polyhydramnion and s/p 2 amnioreductions
biochemistries Plasma Urine unit
Sodium 157 45 mmol/l
creatinine 0.047 0.9 mmol/l
osmolality 318 197 mosmol/kg
Diagnosis?
Bartter Syndrome
Treatment of Bartter Syndrome
• COX-inhibitors
• Salt and potassium supplementation
Surprise!
Indomethacin (1 mg/kg/d) was startedChemistries the next day as follows:
Na 150 mmol/lK 4.8 mmol/lCl 119 mmol/lHCO3 21 mmol/lOsmolality: 311 mosm/kg
Urine Na: <5 mmol/lUrine osmolality: 76 mosm/kg
A case of Diabetes Insipidus?
DDAVP 0.05 mcg im was given. Chemistries 4 hours later:Na 140 mmol/lOsmolality 290 mosm/kg
Urine Na 7 mmol/lUrine osmolality 63 mosm/kg
Bartter? or DI?
Off Indomethacin - Bartter
Na 159
K 2.9
HCO3 24
Urine Na 82
Urine osmolality253
Back on Indomethacin - DI
Na 142
K 4.8
HCO3 20
Osmolality299
Urine Na 5Urine osmolality76
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
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)
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