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Medicine

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Endocrine

Question
7 out of 9
 

True about nephrogenic diabetic insipidus is (LQ)



A Serum Na is increase

B Urine osmolality is reduced

C No effect after ADH administration

D All of the above

Ans. D

All of the above

(Ref. Hari 18th ed., pg. 2905.)

Regarding – desmopressin/Exogenous vasopressin is used in the treatment and not the ADH is true.

1). Water deprivation test is useful for diagnosis

2). ADH per se is not used in its treatment

3). Can be induced by certain drugs

4). It is mandatory to treat when serum osmolality > 288 mmol/dL

Drugs causing DIABETES INSIPIDUS:

1). Lithium

2). Demeclocycline

3). Methoxyflurane

4). Amphotericin B

5). Aminoglycosides

6). Cisplatin

7). Rifampin

8). Foscarnet

Diagnosis

The water deprivation test.

1). In this test patient is hospitalized and his water intake is stop completely.

2). If patient urine output is reduce that indicates psychogenic cause of polyuria.

3). If still urine output is high then injection ADH is given.

4). Now If patient’s urine output is reduce that indicate cranial cause of diabetes insipidus.

5). If still urine output is high than it is most likely nephrogenic diabetes insipidus. In that case treat the basic cause.

Laboratory differentiation of polyuria

Lab parameters

Psychogenic Polydipsia

Central DI

Nephrogenic DI

Osmotic Diuresis

Serum Na

Posm

Uosm

Plasma ADH

Uosm after ADH

Increase

Increase

Nil

Slight increase

How to approach a cause of Polyuria (>3L / 24 hrs)

Urine osmolality (Should be first to be checked in cases of polyuria)

1). Urine osmolality < 250 mosmol = diabetes insipidus

a. Low serum sodium, · Plasma osmolality Normal or Low = Psychogenic polydipsia

b. Increased serum sodium, Increased plasma osmolality

i. plasma ADH & no response in urine osmolality after ADH administration = Nephrogenic DI

ii. plasma ADH & increase in urine osmolality after ADH administration = Central DI

2). Urine osmolality (>300 mosm/kg) = Solute Diuresis

Serum Sodium / Serum Osmolality is usually increased

During solute diuresis more water is lost than sodium thereby causing hypernatremia and hypertonicity.

Solute Diuresi

1). Glucose (Diabetes Mellitus)

2). Mannitol (Osmotic Diuretic)

3). Urea (High protein feeding)

4). Resolving ATN

5). Medullary Cystic Disease

Treatment

1). Cranial DI: desmopressin, a synthetic analogue of ADH.

2). Nephrogenic: Treat the cause- Treatment with conventional doses of a thiazide diuretic and/or amiloride in conjunction with a low-sodium diet and a prostaglandin synthesis inhibitor (e.g., indomethacin) usually reduces the polyuria and polydipsia (Ref. Hari-18th ed., Pg-2907)

Endocrine Flashcard List

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