Function of the Kidneys Homeostasis of Water, Sodium, potassium and pH

Homeostasis of Water ADH is primarily responsible for the reabsorption of water by the kidneys ADH produced by the hypothalamus; secreted by the posterior pituitary gland Secretion of ADH is stimulated by Dehydration High sodium intake Fall in blood volume

Homeostasis of Water ADH increases permeability to water of the distal convoluted tubules and collecting ducts Water is drawn out of the tubules by osmosis into a high salt concentration of fluid in the medulla and its capillaries Water returns to the blood Concentrated urine remains in the tubule to be excreted

Homeostasis of Water When the patients lack ADH – Diabetes Insipidus (DI) DI produce very large amounts of dilute urine and without treatment have difficulty drinking sufficient water to survive.

Homeostasis of Sodium When the amount of sodium increases, extra water is retained to preserve osmotic pressure An increase in sodium and water produces an increase in the blood volume and blood pressure When the BP increases, glomerular filtration increases, and extra water and sodium are lost Blood volume is reduced and returns BP to normal Reabsorption of sodium in the distal convoluted tubules is controlled by the hormones of the renin-angiotensin system

Homeostasis of Sodium Renin is secreted when BP or concentration of fluid in the distal convoluted tubule is low Renin is an enzyme and splits angiotensin I from angiotensinogen, converting to angiotensin II as blood flows through the lungs Angiotensin II, a potent vasoconstrictor, stimulates secretion of Aldosterone

Homeostasis of Sodium Aldosterone stimulates the distal convoluted tubules to reabsorb sodium and secrete potassium The additional sodium increases water reabsorption and increases blood volume and BP, returning the BP to normal; the stimulus for the secretion of renin is then removed

Homeostasis of Potassium Increases in potassium stimulate the secretion of aldosterone Aldosterone stimulates the distal convoluted tubules to secrete potassium; this acts to return the potassium concentration to normal Homeostasis of Acidity (pH) Blood pH is controlled by maintaining the concentration of buffer systems Carbonic acid and sodium bicarbonate form the most important buffer for neutralizing acids in the plasma

Homeostasis of Potassium Homeostasis of Acidity (pH)-continued The concentration of carbonic acid is controlled by the respiratory system The concentration of sodium bicarbonate is controlled by the kidneys Normal pH is 7.35 to 7.45, maintained to keep the ratio of concentrations of sodium bicarbonate to carbon dioxide constant at 20:1 Strong acids are neutralized by sodium bicarbonate to produce carbonic acid and the sodium salts of the strong acids; this process quickly restores the ratio and thus blood pH

Homeostasis of Potassium Homeostasis of Acidity (pH)-continued The carbonic acid produced dissociates into carbon dioxide and water; because the concentration of carbon dioxide is maintained at a constant level by the respiratory system, the excess carbonic acid is rapidly excreted Sodium combined with the strong acid is actively reabsorbed in the distal convoluted tubules in exchange for hydrogen or potassium ions; the strong acid is neutralized by the secretion of ammonia or potassium salts

Diagnostic Tests Refer to last lecture for normal values for renal function tests Urinalysis Perineal area should be cleaned Obtain 10 to 15 mls of first morning sample Know that refrigerated samples may alter SpGr If client menstruating, indicate this on requisition form

Diagnostic Tests Specific Gravity Determination Measures kidney’s ability to concentrate urine Dipstick Refractometer Urinometer

Diagnostic Tests Urine Culture and Sensitivity Urine test that identifies the presence of microorganisms and determines the specific antibiotics that will appropriately treat existing microorganism Clean perineal area and meatus with bacteriostatic solution Collect midstream in sterile container Send to lab immediately

Diagnostic Tests Creatinine Clearance Test A blood and timed urine specimen that evaluates kidney function Blood drawn at start of test and morning of the day that the 24-hour urine specimen collection is complete Encourage adequate fluids before and during (no forced fluids) Avoid tea, coffee and medications during test If taking corticosteroids or thyroid medication, check with physician regarding the administration of these meds during test

Diagnostic Tests Creatinine Clearance Test - continued Maintain urine specimen on ice or refrigerator and check with laboratory regarding the addition of preservative to specimen during collection

Diagnostic Tests Vanillylmandelic acid (VMA) test A 24-hour urine collection to diagnose pheochromocytoma, a tumor of the adrenal gland The test identifies an assay of urinary catecholamines in the urine Instruct the client to avoid foods such as caffeine, cocoa, vanilla, cheese, gelatin, licorice, and fruits for at least 2 days prior to beginning the urine collection and during the collection, and to avoid taking medications for 2 to 3 days prior to beginning the test, as prescribed

Diagnostic Tests Vanillylmandelic acid (VMA) test – continued Instruct the patient to avoid stress and to maintain adequate food and fluids during the test Save all urine, label the container, add preservative, and place the specimen on ice or refrigerate Check with the laboratory regarding med restrictions

Diagnostic Tests Uric acid test A 24- hour urine collection to diagnose gout and kidney disease Encourage fluids and a regular diet during testing Place the specimen on ice or refrigerate, and check with the laboratory regarding the addition of a preservative

Diagnostic Tests KUB radiograph Kidneys, ureters, bladder x-ray Used to detect urinary calculi No specific preparation

Diagnostic Tests Bladder Ultrasonography A noninvasive method of measuring the volume of urine in the bladder May be performed for evaluating urinary frequency or inability to urinate

Diagnostic Tests Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI) Provide cross-sectional views of the kidney and the urinary tract

Diagnostic Tests Intravenous Pyelogram (IVP) The injection of a radiopaque dye that outlines the renal system Performed to identify abnormalities in the system Obtain consent form (injecting dye) Assess for allergy status, especially iodine, seafood, radiopaque dyes

Diagnostic Tests Intravenous Pyelogram (IVP) Pre-op Withhold food and fluids after MN on the night before Administer laxatives as prescribed Inform that sore throat irritation, flushing of face, warmth, or a salty taste may be experienced

Diagnostic Tests Post-procedure Implementation Monitor vital signs Instruct the patient to drink at least 1 liter of fluid unless contraindicated Assess the venipuncture site for bleeding Monitor urinary output

Diagnostic Tests Renal Angiography The injection of a radiopaque dye through a catheter for examination of the renal arterial supply Pre-Procedure Obtain a consent form Assess the patient for allergies to iodine, seafood, and radiopaque dyes Inform the patient about the possible burning feeling or the felling of heat along the vessel when dye is injected Withhold food and fluids after MN on the night before

Diagnostic Tests Renal Angiography Pre-Procedure (continued) Instruct the patient to void immediately before the procedure Administer enemas as prescribed Shave injection site Assess and mark the peripheral pulses

Diagnostic Tests Renal Angiography Post-Procedure Assess vital signs and peripheral pulses Provide bed rest and use of a sandbag at the insertion site for 4 to 8 hours Assess the color and temperature of the involved extremity Inspect the catheter insertion site for bleeding or swelling Force fluids unless contraindicated Monitor urinary output

Diagnostic Tests Magnetic Resonance Angiography (MRA) Combines MRI technology with angiography Cutting edge! You hear about it first, here! Look at that resolution!

Diagnostic Tests Renal Scan An IV injection of a radiopaque for visual imaging of renal blood flow Pre-procedure implementation Obtain a consent form Assess for allergies Assist with administering radiotope as necessary Instruct the patient that he or she will be required to remain motionless Instruct the patient that imaging may be repeated at various intervals before the test is complete

Diagnostic Tests Renal Scan Post-procedure implementation Encourage fluids unless contraindicated Assess the patient for signs of delayed allergic reaction, such as itching and hives Note that the radioactivity Is eliminated in 24 hours Follow standard precautions when caring for incontinent patients and double-bag patient linens per facility policy

Diagnostic Tests Cystometrogram (CMG) Pre-procedure Post-procedure A graphic recording of the pressures exerted at varying phases of the bladder Pre-procedure Inform the patient of the voiding requirements during the procedure Post-procedure Monitor the patient’s voiding after procedure

Diagnostic Tests Cystoscopy and Biopsy Pre-procedure The bladder mucosa is examined for inflammation, calculi, or tumors by means of a cystoscope; a biopsy may be obtained Pre-procedure Obtain a consent form Withhold food and fluids after MN on night before Administer enemas and medications as prescribed

Diagnostic Tests Cystoscopy and Biopsy Post-procedure Monitor vital signs Monitor for postural hypotension Force fluids as prescribed Monitor Intake and Output Encourage deep-breathing exercises to relieve bladder spasms Administer analgesics as prescribed

Diagnostic Tests Cystoscopy and Biopsy Post-procedure Administer sitz baths for back and abdominal pain Note that leg cramps are common because of the lithotomy position maintained during the procedure Assess the urine for color and consistency Note that pink-tinged or tea-colored urine is common Monitor for bright red urine or clots, and notify the physician if this occurs

Diagnostic Tests Renal Biopsy Pre-procedure Insertion of a needle into the kidney to obtain a sample of tissue for examination Pre-procedure Assess vital signs Assess baseline clotting studies Obtain a consent form Withhold food and fluids after MN

Diagnostic Tests Renal Biopsy During the procedure Position the patient prone with a pillow under the abdomen and shoulders

Diagnostic Tests Post-procedure Monitor vital signs Monitor hemoglobin and hematocrit Place the patient in the supine position and on bed rest for 8 hours as prescribed Provide pressure to the biopsy site for 30 minutes Check the biopsy site for bleeding Force fluids to 1500 to 2000mL as prescribed Instruct the patient to avoid heavy lifting and strenuous activity for 2 weeks