17 Diagnostic Tests for Renal System

Normal Renal Function Values

  • Blood urea nitrogen level, 8 to 25 mg/dL
  • Serum creatinine level, 0.6 to 1.3 mg/dL
  • Serum uric acid level, 2.5 to 8.0 mg/dL

Determination of serum creatinine level

Description:

  • A test that measures the amount of creatinine in the serum. Creatinine is an end product of protein and muscle metabolism.

Analysis

  • Creatinine level reflects glomerular filtration rate.
  • Renal disease is the only pathological condition that increases the serum creatinine level.
  • Serum creatinine level increases only when at least 50% of renal function is lost.

Determination of blood urea nitrogen (BUN) level

Description:

  • A serum test that measures the amount of nitrogenous urea, a byproduct of protein metabolism in the liver.

Analysis

  • BUN levels indicate the extent of renal clearance of urea nitrogenous waste products.
  • An elevation does not always mean that renal disease is present.
  • Some factors that can elevate the BUN level include dehydration, poor renal perfusion, intake of a high-protein diet, infection, stress, corticosteroid use, gastrointestinal (GI) bleeding, and factors that cause muscle breakdown.
  • When the BUN and serum creatinine levels increase at the same rate, the ratio of the BUN to creatinine remains constant; elevated serum creatinine and BUN levels suggest renal dysfunction.

Urinalysis

Description:

  • A urine test for evaluation of the renal system and renal disease

Interventions

  • Wash perineal area and use a clean container for collection.
  • Obtain 10 to 15 mL of the first morning voiding if possible.
  • Refrigerated samples may alter the specific gravity.
  • If the client is menstruating, note this on the laboratory requisition form.

Specific gravity determination

Description:

  • A urine test that measures the ability of the kidneys to concentrate urine

Interventions

  • Specific gravity can be measured by a multipletest dipstick method (most common method), refractometer (an instrument used in the laboratory setting), or urinometer (least accurate method).
  • Factors that interfere with an accurate reading include radiopaque contrast agents, glucose, and proteins.
  • Cold specimensmay produce a false high reading.
  • Normal value is 1.016 to 1.022 (may vary depending on the laboratory).
  • An increase in specific gravity (more concentrated urine) occurs with insufficient fluid intake, decreased renal perfusion, or increased ADH.
  • A decrease in specific gravity (less concentrated urine) occurs with increased fluid intake or diabetes insipidus; it may also indicate renal disease or the kidneys inability to concentrate urine.

Urine culture and sensitivity testing

Description:

  • A urine test that identifies the presence of microorganisms (culture) and determines the specific antibiotics to treat the existing microorganism (sensitivity) appropriately

Interventions

  • Clean the perineal area and urinary meatus with a bacteriostatic solution.
  • Collect the midstream sample in a sterile container.
  • Send the collected specimen to the laboratory immediately.
  • Identify any sources of potential contaminants during the collection of the specimen, such as the hands, skin, clothing, hair, or vaginal or rectal secretions.
  • Urine from the client who drank a very large amount of fluids may be too dilute to provide a positive culture.

Creatinine clearance test

 Description

  • The creatinine clearance test evaluates howwell the kidneys remove creatinine from the blood.
  • The test includes obtaining a blood sample and timed urine specimens.
  • Blood is drawn when the urine specimen collection is complete.
  • The urine specimen for the creatinine clearance is usually collected for 24 hours, but shorter periods such as 8 or 12 hours could be prescribed. The creatinine clearance test provides the best estimate of the glomerular filtration rate (GFR) and the normal GFR is 125 mL/min.

Interventions

  • Encourage fluids before and during the test.
  • Instruct the client to avoid caffeinated beverages during testing.
  • Check with the physician regarding the administration of any prescribed medications during testing.
  • Instruct the client about the urine collection.
  • At the start time, ask the client to void (or empty the tubing and drainage bag if the client has a Foley catheter) and discard the first sample.
  • Collect all urine for the prescribed time.
  • Keep the urine specimen on ice or refrigerated and check with the laboratory regarding adding a preservative to the specimen during collection.
  • At the end of the prescribed time, ask the client to empty the bladder (or empty the tubing and drainage bag if the client has a Foley catheter) and add that final urine to the collection container.
  • Send the labeled urine specimen to the laboratory in a biohazard bag along with the requisition.
  • Document specimen collection, time started and completed, and pertinent assessments.

Uric acid test

Description:

  • A 24-hour urine collection sample is tested to diagnose gout and kidney disease.

Interventions

  • Encourage fluid intake and a regular diet during testing.
  • Follow the same procedure for urine collection as with the creatinine clearance test.

Vanillylmandelic acid (VMA) test

Description

  • The test is a 24-hour urine collection to diagnose pheochromocytoma, a tumor of the adrenal gland.
  • The test determines catecholamine levels in the urine.

Interventions

  • Check with the laboratory regarding medication restrictions.
  • Instruct the client to avoid foods such as caffeine, cocoa, vanilla, cheese, gelatin, licorice, and fruits for at least 2 days before and during urine collection and to check with the physician regarding the administration of any prescribed medications before or during testing.
  • Instruct the client to avoid stress; encourage adequate food and fluid intake during the test.
  • Follow the same procedure for urine collection as for the creatinine clearance test.

KUB (kidneys, ureters, and bladder) radiography

Description:

  • An x-ray of the urinary system and adjacent structures to detect urinary calculi.
  • Interventions:Nospecific preparation is necessary.

Bladder ultrasonography (bladder scanning)

  • Bladder ultrasonography is a noninvasive method for measuring the volume of urine in the bladder.
  • Bladder ultrasonography may be performed for evaluating urinary frequency, inability to urinate, or amount of residual urine (the amount of urine remaining in the bladder after voiding).

Computed tomography (CT) and magnetic resonance imaging (MRI)

  • Description: These imaging methods provide cross-sectional views of the kidney and urinary tract.
  • Interventions: See Chapter 66.

Intravenous pyelography

  • Description: An x-ray procedure in which an intravenous injection of a radiopaque dye is used to visualize and identify abnormalities in the renal system.

Preprocedure interventions

  • Obtain an informed consent.
  • Assess the client for allergies to iodine, seafood, and radiopaque dyes.
  • Withhold food and fluids after midnight on the night before the test.
  • Administer laxatives if prescribed.
  • Inform the client about possible throat irritation, flushing of the face, warmth, or a salty or metallic taste during the test.

Postprocedure interventions

  • Monitor vital signs.
  • Instruct the client to drink at least 1 L of fluid unless contraindicated.
  • Assess the venipuncture site for bleeding.
  • Monitor urinary output.
  • Monitor for signs of a possible allergic reaction to the dye used during the test and instruct the client to notify the physician if any signs of an allergic reaction occur.

Renal angiography

Description:

  • An injection of a radiopaque dye through a catheter inserted into the femoral artery to examine the renal blood vessels and renal arterial supply

Preprocedure interventions

  • Obtain an informed consent.
  • Assess the client for allergies to iodine, seafood, and radiopaque dyes.
  • Inform the client about a possible feeling of burning or heat along the vessel when the dye is injected.
  • Withhold food and fluids after midnight on the night before the test.
  • Instruct the client to void immediately before the procedure.
  • Administer enemas if prescribed.
  • Shave injection sites as prescribed.
  • Assess and mark the peripheral pulses.

Postprocedure interventions

  • Assess vital signs and peripheral pulses frequently as prescribed
  • Maintain bed rest and apply a sandbag or other device that will provide pressure to prevent bleeding, if prescribed, at the insertion site for 4 to 8 hours.

Renal scanning

Description:

  • An intravenous (IV) injection of a radioisotope for visual imaging of renal blood flow, glomerular filtration, tubular function, and excretion

Preprocedure interventions

  • Obtain an informed consent.
  • Assess for allergies.
  • Inform the client that the test requires no dietary or activity restrictions.
  • Assist with administering the radioisotope as necessary.
  • Instruct the client to remain motionless during the test.
  • Instruct the client that imaging may be repeated at various intervals before the test is complete.

Postprocedure interventions

  • Encourage fluid intake unless contraindicated.
  • Assess the client for signs of delayed allergic reaction such as itching and hives.
  • The radioisotope is eliminated in 24 hours; wear gloves for excretion precautions.
  • Follow standard precautions when caring for incontinent clients and double-bag client linens per agency policy.

Cystoscopy and biopsy of the bladder

Description:

  • The bladder mucosa is examined for inflammation, calculi, or tumors by means of a cystoscope; a sample for biopsy may be obtained.

Preprocedure interventions

  • Obtain an informed consent.
  • If a biopsy is planned, withhold food and fluids after midnight the night before the test.
  • If a cystoscopy alone is planned, no special preparation is necessary, and the procedure may be performed in the physician’s office; postprocedure interventions include increasing fluid intake.

Postprocedure interventions following biopsy

  • Monitor vital signs.
  • Increase fluid intake as prescribed.
  • Monitor intake and output.
  • Encourage deep-breathing exercises to relieve bladder spasms.
  • Administer analgesics as prescribed.
  • Administer sitz or tub 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.
  • Inform the client that burning on urination, pink-tinged or tea-colored urine, and urinary frequency are common after cystoscopy and resolve in a few days.
  • Monitor for bright red urine or clots, and notify the physician if this occurs.

Renal biopsy

Description:

  • Insertion of a needle into the kidney to obtain a sample of tissue for examination; usually done percutaneously

Preprocedure interventions

  • Assess vital signs.
  • Assess baseline coagulation studies; notify the physician if abnormal results are noted.
  • Obtain an informed consent.
  • Withhold food and fluids after midnight the night before the test.

Interventions during the procedure:

  • Position the client prone with a pillow under the abdomen and shoulders.

Postprocedure interventions

  • Monitor vital signs, especially for hypotension and tachycardia,which could indicate bleeding.
  • Provide pressure to the biopsy site for 30 minutes.
  • Monitor the hemoglobin and hematocrit levels for decreases, which could indicate bleeding.
  • Place the client in the supine position and on bed rest for 8 hours as prescribed.
  • Check the biopsy site and under the client for bleeding.
  • Encourage fluid intake of 1500 to 2000 mL as prescribed.
  • Observe the urine for gross and microscopic bleeding.
  • Instruct the client to avoid heavy lifting and strenuous activity for 2 weeks.
  • Instruct the client to notify the physician if either a temperature greater than 100 F or hematuria occurs after the first 24 hours postprocedure.

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