Table 1. pertinent biochemistries of the four cases.

Shown are biochemistries from plasma and urine during episodes of dehydration and after administration of vasopressin analogues (shown is the result from the aliquot with the highest osmolality obtained within 3 hours after an intravenous injection of 0.3 mcg/kg DDAVP). Note that urine osmolality remains well below plasma osmolality during dehydration, as well as after DDAVP, consistent with NDI. In case 2 the NDI appears to have developed with time, as urine osmolality at the age of 6 years was above that of plasma. Case 4 recovered urinary concentrating ability after treatment of her AME. ND: not determined

Case 1: cystinosis		Dehydration episodes			DDAVP
					pre	post
Age (years)		2.5	3.5		3.5
Plasma	Na (mmol/l)	165	182		148
K (mmol/l)		4.4	3.8		3.7
Osmolality (mosmol/kg)		344	365		296
Creatinine (µmol/l)		1068	113		89
Urine	Na (mmol/l)	33	45		8
Ca (mmol/l)		ND	ND		ND
Osmolality (mosmol/kg)		114	125		52	57
Case 2: nephronophthisis			Pitressin 0.9 units		DDAVP
					pre	post
Age (years)		6	6		9
Plasma	Na (mmol/l)	146	146		144
K (mmol/l)		4.2	ND		ND
Osmolality (mosmol/kg)		303	306		ND
Creatinine (µmol/l)		53	ND		98
Urine	Na (mmol/l)	ND	ND		39
Ca (mmol/l)		ND	ND		ND
Osmolality (mosmol/kg)		360	396		130	151
Case 3: Bartter syndrome			DDAVP
			pre	post
Age (years)		7	8
Plasma	Na (mmol/l)	148	137
K (mmol/l)
Osmolality (mosmol/kg)		304	291
Creatinine (µmol/l)		33	25
Urine	Na (mmol/l)	33	15
Ca (mmol/l)		2.8	ND
Osmolality (mosmol/kg)		191	205	167
Case 4: apparent mineralocorticoid excesss			DDAVP		Post AME treatment
			pre	post
Age (years)		1.2	2.2		2.3
Plasma	Na (mmol/l)	146	136		136
K (mmol/l)		3.7	2.3		5.0
Osmolality (mosmol/kg)		307	293		ND
Creatinine (µmol/l)		42	43		45
Urine	Na (mmol/l)	21	8		156
Ca (mmol/l)		ND	1.52		0.6
Osmolality (mosmol/kg)		145	107	129	705