Diabetes Insipidus

Diabetes insipdus

Q. 1

Which of the following is true about nephrogenic diabetes insipidus

 A

Renal tubule is unresponsive to ADH

 B

There is central decrease in secretion of ADH

 C

Serum sodium is low

 D

Urine osmolality is increased after administration of ADH

Q. 1

Which of the following is true about nephrogenic diabetes insipidus

 A

Renal tubule is unresponsive to ADH

 B

There is central decrease in secretion of ADH

 C

Serum sodium is low

 D

Urine osmolality is increased after administration of ADH

Ans. A

Explanation:

Answer is A (Renal tubule is unresponsive to ADH):

Nephrogenic Diabetes Insipidus is charachterized by resistance of action of ADH on Renal tubules or unresponsiveness of renal tubules to the action of ADH or Renal Hyposensitivity to action of ADH.

Serum sodium is typically high (increased), urine osmolality is low and fails to increase after exogenous administration of ADH /vasopression.


Q. 2

Which of the following statements about Diabetes Insipidus is true:

 A

Urine osmolality should be > 300 mosm/L

 B

Plasma osmolality should be < 280 mmol/L

 C

Water deprivation test is required

 D

Plasma osmolality should be > 300 mosm/L prior to H2O Deprivation

Q. 2

Which of the following statements about Diabetes Insipidus is true:

 A

Urine osmolality should be > 300 mosm/L

 B

Plasma osmolality should be < 280 mmol/L

 C

Water deprivation test is required

 D

Plasma osmolality should be > 300 mosm/L prior to H2O Deprivation

Ans. C

Explanation:

Answer is C (Water deprivation test is required) :

Diagnosis of diabetes insipidus often requires a water deprivation test.

Water deprivation test is used to establish the diagnosis of diabetes insipidus and to differentiate Central and Nephrogenic forms of Diabetes Insipidus.

Patients with diabetes insipidus have a normal or increased plasma osmolality (> 280 mosm/l) and decreased urine osmolality (<300mosm/1). 'Water deprivation test' typically demonstrates an increase in plasma osmolality with failure of urinary osmolality to increase (no change) during H20 deprivation in cases of diabetes insipidus thereby suggesting the diagnosis.

Diabetes Insipidus is associated with plasma osmolality > 280 mosm/kg and urinary osmolalitv < 300  mosm /kg

In normal subjects the plasma osmolality ranges from 275-295 mosm /kg while the range of urine osmolality is wide, from 40 to 1000 mosm/kg depending on the state of hydration. After water deprivation the urine osmolality will normally rise to exceed 800 mosm/kg while the plasma osmolality remains below 295 mosm/kg (U/P >2)

In Diabetes Insipidus subjects the plasma osmolality ranges from normal to high (>275 mosm/kg) while the urine osmolality is typically < 300 mosm/1. After water deprivation plasma osmolality rises to > 295 mosm/kg while urinary osmolality fails to rise appropriately (Fails to rise to >300 mosm/kg) (U/P Ratio < 2.0)

Water deprivation test is often required to establish a diagnosis of Diabetes insipidus

Water deprivation test is indicated in patients with hypotonic polyuria (Uosm < 300 mosm/kg) and a plasma osmolality 410 within the normal range (Posm = 275 — 295 mosm/kg) to establish the diagnosis of diabetes insipidus and differentiate central & nephrogenic forms.


Q. 3

Nephrogenic diabetes insipidus is caused by all of the following except:  

March 2008

 A

Toxicity of lithium

 B

Amyloidosis

 C

Hypocalcemia

 D

Hypokalemia

Q. 3

Nephrogenic diabetes insipidus is caused by all of the following except:  

March 2008

 A

Toxicity of lithium

 B

Amyloidosis

 C

Hypocalcemia

 D

Hypokalemia

Ans. C

Explanation:

Ans. C: Hypocalcemia

Nephrogenic diabetes insipidus is characterized by a decrease in the ability to concentrate urine due to a resistance to ADH action in the kidney. The 24 hour urine volume is more than 50 mL/kg body weight and the osmolarity is less than 300 mosmol/ L.

Nephrogenic diabetes insipidus can be observed in:

  • Drugs:

-Lithium toxicity

-Demeclocycline

-Methoxyflurane

-Amphotericin B

  • Metabolic

Hypercalcemia,

-Hypokalemia,

iii.Infiltration:

-Amyloidosis

  1. Tubulointerstitial diseas
  2. Rarely, diabetes insipidus may be hereditary

Quiz In Between



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