Diagnostic Tests for Autoimmune Diabetes Insipidus
Autoimmune Diabetes Insipidus Tests: Book Excerpts
Home Diagnostic Testing
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Autoimmune Diabetes Insipidus Diagnosis: Book Excerpts
Diagnostic Tests for Autoimmune Diabetes Insipidus: Online Medical Books
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POLYDIPSIA:
DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)
The basic workup includes a CBC, sedimentation rate, urinalysis, 24-hr urine volume, a serum and urine osmolality, a thyroid profile, and x-rays of the skull and long bones.
The diagnosis of hyperparathyroidism may be assisted by ordering a serum parathyroid hormone level. Also, a 24-hr urine collection for calcium may be done to help diagnose this condition. Microscopic examination of the urinary sediment will help diagnose renal disease, as will renal biopsies. If pituitary diabetes insipidus is suspected, a CT scan of the brain and blood tests for serum growth hormone, FSH, LH, ACTH, and TSH may be done. The Hickey-Hare test and monitoring intake and output before and after vasopressin (Pitressin®) will be useful in differentiating pituitary diabetes insipidus from nephrogenic diabetes insipidus. The concentrations of circulating vasopressin may be measured by immunoassay.
An endocrinologist should be consulted before ordering these expensive diagnostic tests.
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Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
Polydipsia:
History and physical examination
(Handbook of Signs & Symptoms (Third Edition))
Obtain a history. Find out how much fluid the patient drinks each day. How often and how much does he typically urinate? Does the need to urinate awaken him at night? Determine if he or anyone in his family has diabetes or kidney disease. What medications does he use? Has his lifestyle changed recently? If so, have these changes upset him?
If the patient has polydipsia, take his blood pressure and pulse when he’s in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/
minute from the supine to the sitting or standing position may indicate hypovolemia. If you detect these changes, ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor. Infuse I.V. replacement fluids, as needed.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Signs & Symptoms (Third Edition), 2006
Polydipsia:
History and physical examination
(Professional Guide to Signs & Symptoms (Fifth Edition))
Obtain a history. Find out how much fluid the patient drinks each day. How often and how much does he typically urinate? Does the need to urinate awaken him at night? Determine if he or anyone in his family has diabetes or kidney disease. What medications does he use? Has his lifestyle changed recently? If so, have these changes upset him?
If the patient has polydipsia, take his blood pressure and pulse when he’s in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/minute from the supine position to the sitting or standing position may indicate hypovolemia. If you detect these changes, ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor. Infuse I.V. replacement fluids as needed.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Signs & Symptoms (Fifth Edition), 2006
Polydipsia:
Physical examination
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
A thorough general physical examination, including vital signs, is helpful in making the diagnosis, but the emphasis is on the neurologic examination (i.e., visual fields, cranial nerve deficits, oculomotor palsies, and reflexes). Signs of recent weight loss or presence of peripheral neuropathy is helpful in making the diagnosis of DM (Chapters 2.13 and 4.6).
Testing
A. Clinical laboratory tests. A urinalysis needs to be performed to look for glucosuria of DM or the low specific gravity associated with DI. A chemistry panel is helpful in checking for elevated serum glucose levels of DM or an elevated creatinine seen with renal disease or nephrogenic DI. A calcium level could be useful if hypercalcemia is suspected (Chapter 17.4). Serum and urine osmolality are useful in differentiating between DI, which presents with increased serum osmolality and in an appropriately low urine osmolality (specific gravity < 1.005), and excessive water intake, which presents with low or normal serum osmolality and an appropriately low urine osmolality. Normal serum values are between 285 and 295 mOsm/L.
B. Diagnostic imaging. Magnetic resonance imaging (MRI) of the head may be indicated to exclude pituitary or hypothalamic tumors. In neurogenic DI, MRI is quite specific because the normal bright spot of a functioning pituitary gland will be absent (3).
C. Water deprivation test. This indirect test may be useful in making the diagnosis of DI and to differentiate between neurogenic and nephrogenic DI by determining the effects of water deprivation (mild dehydration) on ADH secretion by measuring serum, urine osmolality, urine-specific gravity, and serum sodium in a controlled environment (3). This test needs to be carefully supervised by someone able to treat severe hypertonic dehydration if necessary. Patients with mild polydipsia are placed on fluid restriction starting at midnight prior to testing, but fluids are restricted in those with severe polydipsia during the day only. Baseline body weight, plasma osmolarity, serum sodium, and urine osmolarity are determined. Urine osmolarity and weight are assessed on an hourly basis. Adequate dehydration is noted by a decrease in body weight by 5% and serum osmolarity by more than 275 mOsm/L. A normal response would show normal plasma osmolarity and sodium concentration with decreased urine output and increasing urine osmolarity to more than 800 mOsm/L (i.e., two to four times greater than the plasma). In contrast to healthy patients, patients with DI cannot concentrate their urine in response to dehydration. Patients with central DI respond to desmopressin (a synthetic analog of vasopressin) administered intranasally, whereas patients with nephrogenic DI do not (4). Sometimes patients do not fall into definite categories (e.g., partial central DI). The direct form of testing where ADH levels are measured after infusing hypertonic saline is rarely performed.
Diagnostic assessment
Often important clues about the cause of polydipsia can be obtained with a directed clinical history with particular attention paid to the onset of symptoms, the presence of nocturia, and the medication history. The value of the physical examination is limited unless signs are evident of defects caused by a pituitary tumor (e.g., progressive headaches, visual field defects) or endocrinologic symptoms (e.g., amenorrhea, galactorrhea, acromegaly, Cushing’s disease). Often the diagnosis is made with routine laboratory tests. Sometimes a water deprivation test needs to be performed to make the diagnosis, but this test should be done in a hospital setting with the patient monitored closely for dehydration.
References
1. Greendyke RM, Bernhardt AJ, Tasbas HE. Polydipsia in chronic psychiatric patients. Neuropsychopharmacology 1998;18:272–281.
2. Olpade-Olaopa EO, Morley RN, Ahiaku ER, Bramble FJ. Iatrogenic polydipsia: a rare cause of water intoxication in urology. Br J Urol 1997;7:488.
3. Adam P. Evaluation and management of diabetes insipidus. Am Fam Physician 1997;55:2146–2153.
4. Blevins LS Jr, Wand GS. Diabetes insipidus. Crit Care Med 1992;20:69–79.>>
» READ BOOK EXCERPT ONLINE »
Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
Polydipsia:
Physical assessment
(Signs & Symptoms: A 2-in-1 Reference for Nurses)
If the patient has polydipsia, take his blood pressure and pulse when he’s in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/minute from the supine to the sitting or standing position may indicate hypovolemia. If you detect these changes, ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor. Infuse I.V. replacement fluids as needed.
» READ BOOK EXCERPT ONLINE »
Source: Signs & Symptoms: A 2-in-1 Reference for Nurses, 2007
Polyuria and Polydipsia:
Diagnostic Approach
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)
Polyuriamust be distinguished from small volume urinary frequency, whichis common in pediatric practice. Children with polyuria often havenocturia and are unable to sleep through the night without wakingup to urinate. Most children with urinary frequency do not havepolyuria or a defect in urinary concentrating ability. Common causesof isolated urinary frequency are habit, attention-seeking behavior,and urinary tract infection.Random sample of urine with specificgravity of >1.028 and absence of polyuria rules out a concentrationdefect. Even urinary specific gravity of >1.020 on randomor early morning sample indicates sufficient urinary concentrationsuch that symptomatic diabetes insipidus is unlikely. Children whohave urine with a somewhat lower than normal specific gravity butwho can sleep through the night without passing urine do not needfurther evaluation.Presence of polyuria, dehydration,and high urinary specific gravity is evidence for osmotic diuresis,which is most commonly caused by diabetes mellitus. Dilute urineassociated with polyuria suggests diabetes insipidus or psychogenicpolydipsia. If blood glucose and urea nitrogen are normal, high serumosmolality with hyposmolar urine suggests ADH deficiency or resistance.Low serum osmolality with hyposmolar urine suggests primary polydipsia.With either ADH deficiency or resistance,urine specific gravity rarely exceeds 1.005 and urinary osmolalityrarely exceeds 200 mOsm/kg. Water deprivation test thatdemonstrates inability to concentrate urine indicates diabetes insipidusand distinguishes it from primary polydipsia. If urine remains hypotonicwith dehydration, next step is to determine response to exogenousvasopressin, which distinguishes ADH deficiency from resistance.With ADH deficiency, administration of vasopressin causes diminishingof symptoms and increase in urine specific gravity, whereas no responseoccurs with ADH resistance.With suspected renal disease, certaintests should be performed: CBC and differential; UA; urine culture;serum electrolytes, calcium, phosphorus, and creatinine; blood ureanitrogen; hemoglobin electrophoresis; and renal U/S. Othertests (e.g., determination of serum and urinary amino acids, voiding cystourethrography,and renal biopsy) may be necessary to define specific renal abnormality.Psychosocial history of emotional disturbance,including episodes of compulsive water drinking and formation ofconcentrated urine with fluid deprivation, are evidence for psychogenicpolydipsia. This disorder may sometimes be difficult to distinguishfrom hypothalamic thirst defect, and consultation with a pediatricendocrinologist is recommended.
» READ BOOK EXCERPT ONLINE »
Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006
Polydipsia:
History and physical examination
(Nursing: Interpreting Signs and Symptoms)
Obtain a medical history. Find out how much fluid the patient drinks each day. How often and how much does he typically urinate? Does the need to urinate awaken him at night? Determine if he or anyone in his family has diabetes or kidney disease. What medications does he use? Has his lifestyle changed recently?
If the patient has polydipsia, take his blood pressure and pulse when he's in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/minute from the supine to the sitting or standing position may indicate hypovolemia. Ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor.
» READ BOOK EXCERPT ONLINE »
Source: Nursing: Interpreting Signs and Symptoms, 2007
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