Diabetes Insipidus

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Diabetes Insipidus

Diabetes insipidus (DI) is a disorder of water metabolism characterized by polyuria, urine of low specific gravity or osmolality (so-called insipid, or tasteless, urine), and polydipsia.

 

PATHOPHYSIOLOGY

  • Central DI—deficiency in the secretion of ADH
  • Nephrogenic DI—renal insensitivity to ADH

 

SYSTEMS AFFECTED

  • Endocrine/Metabolic
  • Renal/Urologic

 

INCIDENCE/PREVALENCE

  • Central DI—rare
  • Nephrogenic—rare

 

SIGNALMENT

Species

Dog and cat

 

Breed Predilections

None

 

Mean Age and Range

  • Congenital forms < 1 year
  • Acquired forms (e.g., neoplastic, traumatic, and idiopathic), any age

 

Predominant Sex

 

None

 

SIGNS

  • Polyuria
  • Polydipsia
  • Incontinence—occasional

 

CAUSES

  • Inadequate Secretion of ADH
  • Congenital defect
  • Idiopathic
  • Trauma
  • Neoplasia
  • Renal Insensitivity to ADH
  • Congenital
  • Secondary to drugs (e.g., lithium, demeclocycline, and methoxyflurane)
  • Secondary to endocrine and metabolic disorders (e.g., hyperadrenocorticism, hypokalemia, pyometra, and hypercalcemia)
  • Secondary to renal disease or infection (e.g., pyelonephritis, chronic renal failure, pyometra)

 

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

  • Polyuric Disorders
  • Hyperadrenocorticism
  • Diabetes mellitus
  • Liver disease—portosystemic shunt
  • Hyperadrenocorticism
  • Pyometra
  • Pyelonephritis
  • Hyperthyroidism—cats
  • Hypercalcemia
  • Psychogenic polydipsia
  • Renal failure

CBC/BIOCHEMISTRY/URINALYSIS

  • Usually normal, hypernatremia in some patients
  • Urinary specific gravity low (usually < 1.012, often < 1.008)

 

OTHER LABORATORY TESTS

Plasma ADH

 

IMAGING

MRI or CT scan if a pituitary tumor is suspected

 

DIAGNOSTIC PROCEDURES

  • Modified water deprivation test (see Appendix II-A for protocol)
  • ADH supplementation trial—therapeutic trial with synthetic ADH (DDAVP); a positive response (water intake decreases by 50% in 3–5 days)
  • Rule out all other causes of PU/PD before conducting an ADH trial.

 

PATHOLOGIC FINDINGS

Degeneration and death of neurosecretory neurons in the neurohypophysis (CDI)

 

TREATMENT

APPROPRIATE HEALTH CARE

Patients should be hospitalized for the modified water deprivation test; the ADH trial is often performed as an outpatient procedure.

 

ACTIVITY

Not restricted

 

DIET

Normal, with free access to water

 

CLIENT EDUCATION

Review dosage of DDAVP and administration technique

Importance of having water available at all times

 

SURGICAL CONSIDERATIONS

N/A

 

MEDICATIONS

DRUG(S) OF CHOICE

CDI—DDAVP (1–2 drops of the intranasal preparation in the conjunctival sac q12–24h to control PU/PD); alternatively, the intranasal preparation may be given SC (2–5 μg q12–24h). An oral preparation of DDAVP is available in 0.1–0.2 mg tablets with each 0.1 mg comparable to 1 large drop of the intranasal preparation

NDI—hydrochlorothiazide (2–4 mg/kg PO q12h)

 

CONTRAINDICATIONS

None

 

PRECAUTIONS

Overdose of DDAVP can cause water intoxication.

 

FOLLOW-UP

PATIENT MONITORING

  • Adjust treatment according to the patient’s signs; the ideal dosage and frequency of DDAVP administration is based on water intake.
  • Laboratory tests such as PCV, total solids, and serum sodium concentration to detect dehydration (inadequate DDAVP replacement)—usually not necessary

 

PREVENTION/AVOIDANCE

Circumstances that might markedly increase water loss

 

POSSIBLE COMPLICATIONS

Anticipate complications of primary disease (pituitary tumor).

 

EXPECTED COURSE AND PROGNOSIS

  • The condition is usually permanent, except in rare patients in which the condition was trauma induced.
  • Prognosis is generally good, depending on the underlying disorder.
  • Without treatment, dehydration can lead to stupor, coma, and death.

 

MISCELLANEOUS

ASSOCIATED CONDITIONS

N/A

 

AGE-RELATED FACTORS

  • Congenital CDI and NDI usually manifest before 6 months of age
  • CDI related to pituitary tumors is usually seen in dogs > 5 years old

 

PREGNANCY/FERTILITY/BREEDING

N/A

 

SYNONYMS

  • Central diabetes insipidus
  • Cranial diabetes insipidus
  • ADH-responsive diabetes insipidus
  • Nephrogenic diabetes insipidus

 

SEE ALSO

Hyposthenuria

 

ABBREVIATIONS

ADH = antidiuretic hormone

CDI = central diabetes insipidus

DDAVP = brand name of desmopressin

DI = diabetes insipidus

MRI = magnetic resonance imaging

NDI = nephrogenic diabetes insipidus

PCV = packed cell volume

PU/PD = polyuria/polydipsia

 

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