Case Study 3: Diabetes Insipidus – Flashcards

Checking hormones levels - problems with pituitary or adrenal gland Blood test to check for hormone levels Measure urination quantity Physical exam for hydration status, checking blood pressure Perform a prostate examination Giardia does not cause increased urination, may be due to excessive consumption of water Have not ruled out diabetes, could perform sugar urine test as well as blood sugar

Decreased reabsorption of water due to osmosis flow, results in more urination

Specific gravity - shows whether the urine is diluted or not; ratio of the density of a substance to the density (mass of the same unit volume) of a reference substance Used to rule out structural defects of kidneys, UTI Urine normally has a specific gravity between 1.003 and 1.035. Low specific gravity = dilute urine Blood normally has a specific gravity of ~1.060.

Measurement of urinary osmolarity Low osmolarity = more water = dilute urine High osmolarity = less water = concentrated urine

Should be between 800-2000 mL Elevation above this value is known as polyuria

Overhydration - excess fluid intake Kidney failure - inability to excrete excess fluid Malfunctions with ADH hormone - inability to reabsorb water (remains in the collecting tubule) Infection of the bladder or kidney - Post Streptococcal glomularnephritis Renal tubular necrosis

Diabetes insipidus - excess urine output, typically dilute urine; usually blood glucose levels aren't changed Nephrogenic DI - insensitivity to ADH despite release from CNS Neurogenic DI - affecting the hypothalamus, lack of ADH

no secretion of aldosterone, therefore no Na+ or H20 reabasorption, leads to decreased urine osmolarity

increased ACTH levels, which increases cortisol secretion. Increased glucose levels in blood draws H20 out and decreases reabsorption of water, leading to decreased urine osmolarity

Constant sensation of dry mouth, urge to consume water, could be due to medications

Constant urine output regardless of water consumption, due to hormonal regulations instead of water consumption urges

Following doctor's instructions to refrain water intake for 24 hours, urine collection levels should eventually decrease near the end of the 24 hour cycle. Osmolality should increase and stabilize

Neurogenic / Central DI Nephrogenic DI Dipsogenic DI

Decreased production of ADH Results from damage to the pituitary gland Could be caused by head trauma / infectious process Medication used for depression

Insensitivity to ADH release

Defect to thirst mechanism in hypothalamus Inability to trigger ADH secretion

Results from damage to the pituitary gland - metastatic pituitary hypothalamic tumor Could be caused by head trauma / infectious process - destruction of hypothalamus or some part of the supraoptic hypothalamic tract leading to the posterior pituitary gland Medication used for depression that the patient did not inform the physician of Vascular autoimmune infection (sarcoidosis) Genetic disorders may play small role

Insensitivity to ADH Could be lithium medication complication Genetic disorder - V2 class of vasopression receptors, lack of aquaporin receptors to reabsorb water Chronic disorders - polycystic kidney disease, sickle cell disease, amyloidosis, inherited genetic disorders Kidney failure Hypercalcemia

Desmopression - synthetic hormone, used to treat neurogenic DI (mimics ADH) Medication does not work in nephrogenic DI since body is insensitive to ADH Measure levels of ADH: Would be decreased in neurogenic DI compared to nephrogenic DI, complete by using hormone blood test Head MRI - examination of potential malfunctions or damage of the pituitary gland / hypothalamus

Mimics ADH function Structural analog to vasopression, works through second messenger system by initially binding to a V2 receptor on the basolateral surface Results in phosphorylation of proteins, frees aquaporin receptors from enclosed vesicle within the luminal cell Aquaporin receptors transported to apical membrane of the collecting duct, allows for reabsorption of water Decreases urine output Typically in the nephron, hormones function near the distal end of the tubular system (collecting ducts)

Lack of ADH results in decreased water reabsorption Hypothalamus recognizing increased sodium levels, results in activation of thirst mechanism, kidneys attempting to reabsorb remaining water By consumption of chips and his underlying condition without medication, the patient will become extremely dehydrated

Avoid excess salts within IV fluid Recommended to give hypotonic saline solution Negative side effect - destruction of nerve cells by lysis IV drip possibility, continual assessment of the patient, several blood samples. Attempts to correct low blood volume / blood pressure