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Diagnostic tests and imaging

- The diagnosis of acute renal failure is based on the history, physical examination, laboratory tests, and imaging studies.

- The following tests and imaging may be used to diagnose acute renal failure:

  • Serum creatinine and BUN: These are blood tests that measure the levels of creatinine and urea in the blood. Creatinine is a waste product of muscle metabolism that is normally filtered by the kidneys. Urea is a waste product of protein metabolism that is normally excreted by the kidneys. A rise in serum creatinine and BUN indicates a decrease in kidney function. The ratio of BUN to creatinine can help differentiate prerenal from intrinsic causes of acute renal failure. A ratio greater than 20:1 suggests prerenal causes, whereas a ratio less than 10:1 suggests intrinsic causes
  • Urine output: This is a measure of how much urine is produced in 24 hours. A normal urine output is about 1.5 liters per day for adults. A urine output less than 0.5 ml/kg/hour for more than 6 hours indicates oliguria, which is a sign of acute renal failure.
  • Urine tests: These include urinalysis, urine electrolytes, urine osmolality, urine specific gravity, and urine sediment examination. Urinalysis can reveal abnormalities such as proteinuria, hematuria, pyuria, or casts that suggest kidney damage or infection. Urine electrolytes can help assess tubular function and differentiate prerenal from intrinsic causes of acute renal failure. Urine osmolality and specific gravity can help assess the concentration ability of the kidneys and differentiate prerenal from intrinsic causes of acute renal failure. Urine sediment examination can help identify cellular or crystalline components that indicate glomerular or tubular injury.
  • Blood tests: These include serum electrolytes, blood gas analysis, complete blood count (CBC), and other tests depending on the suspected cause of acute renal failure. Serum electrolytes can reveal imbalances such as hyperkalemia, hyponatremia, hyperphosphatemia, hypocalcemia, or hypermagnesemia that result from impaired kidney function. Blood gas analysis can reveal metabolic acidosis due to accumulation of acids or loss of bicarbonate by the kidneys. CBC can reveal anemia due to decreased erythropoietin production by the kidneys or blood loss.
    • Other tests may include liver function tests, coagulation studies, lactate dehydrogenase (LDH), haptoglobin, antinuclear antibody (ANA), antineutrophil cytoplasmic antibody (ANCA), complement levels, serum protein electrophoresis, blood cultures, or drug levels.
  • Imaging tests: These include renal ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), or renal scintigraphy.
    • Renal ultrasound is the preferred imaging modality for renal assessment, as it can provide valuable information such as kidney size, shape, echogenicity, blood flow, and presence of obstruction, cysts, masses, or stones.
    • CT or MRI can provide more detailed information on the renal parenchyma, vessels, and collecting system, and can help identify causes such as renal artery stenosis or thrombosis, renal vein thrombosis, pyelonephritis, abscess, infarction, or tumor.
    • Renal scintigraphy can help evaluate renal perfusion and function using radioactive tracers that are filtered by the kidneys.
    • Biopsy: This is a procedure that involves removing a small sample of kidney tissue for microscopic examination. A biopsy can help confirm the diagnosis and determine the cause and extent of kidney damage in cases of acute renal failure that are unexplained or refractory to treatment. A biopsy can also help differentiate acute from chronic kidney injury by assessing the degree of fibrosis and scarring in the kidney tissue.

Questions on Diagnostic tests and imaging

Correct Answer is D

Explanation

Correct. Loop diuretics are prescribed in acute renal failure to increase urine output and promote fluid excretion. This helps reduce fluid overload and decrease edema.

Correct Answer is B

Explanation

Incorrect. Increasing the dwell time would not address the issue of cloudy dialysis fluid and potential infection.

Correct Answer is B

Explanation

Incorrect. Preventing infection and complications is important, but it is not the priority over assessing kidney function in acute renal failure.QUESTIONS

Correct Answer is A

Explanation

Incorrect. While anemia can be associated with chronic kidney disease, it is not a specific risk factor for acute renal failure.

Correct Answer is B

Explanation

Incorrect. Increased respiratory rate and shallow breathing are not typical respiratory manifestations of acute renal failure.QUESTIONS

Correct Answer is A

Explanation

Incorrect. Chicken and fish are sources of protein and do not have high potassium content that would require restriction in most cases.

Correct Answer is D

Explanation

Correct. The nurse's best response is to encourage the client to follow their healthcare provider's instructions and avoid medications that may harm the kidneys. Compliance with prescribed treatment plans and avoiding nephrotoxic medications are essential to support kidney function and prevent further damage.

Correct Answer is C

Explanation

Incorrect. The cost of CRRT and intermittent hemodialysis can vary based on the healthcare setting and the client's needs. The cost-effectiveness depends on individual factors and resource availability.

Correct Answer is A

Explanation

Incorrect. Antihypertensive agents are prescribed to manage hypertension and do not treat anemia in clients with renal failure.QUESTIONS

Correct Answer is C

Explanation

Incorrect. Excessive thirst and dry mucous membranes are not specific to hyperkalemia and are not the most critical indicators of severe hyperkalemia.

Correct Answer is A

Explanation

Incorrect. While ciprofloxacin and other antibiotics may have renal-related side effects, they are not a common cause of intrinsic acute renal failure.

Correct Answer is A

Explanation

Incorrect. Promoting shallow breathing to retain carbon dioxide is not a recommended intervention for correcting metabolic acidosis. Respiratory acidosis and metabolic acidosis are different types of acid-base imbalances with distinct causes and treatments.

Correct Answer is C

Explanation

Incorrect. Decreased respiratory rate and shallow breathing are not directly associated with uremia.

Correct Answer is B

Explanation

Incorrect. Fluid restriction is not typically recommended in acute renal failure, especially if the client is experiencing fluid depletion and dehydration.

Correct Answer is A

Explanation

Incorrect. While a renal ultrasound can visualize the blood vessels in the kidneys, its primary purpose is to assess kidney structure, not blood flow.

Correct Answer is A

Explanation

Incorrect. Seasonal allergies are not associated with an increased risk of acute renal failure.

Correct Answer is C

Explanation

Incorrect. Chronic kidney disease (CKD. is a risk factor for intrinsic acute renal failure, not postrenal.

Correct Answer is A

Explanation

Incorrect. The timing of loop diuretic administration is determined by the healthcare provider's order and the client's specific needs. Taking diuretics at bedtime may result in increased nighttime urination and sleep disruption.QUESTIONS

Correct Answer is B

Explanation

Incorrect. Deep breathing exercises are not specific interventions for correcting metabolic acidosis.

Correct Answer is B

Explanation

Incorrect. Removing jewelry and metallic objects is a standard precaution for all imaging procedures, but it is not specific to a CT scan with contrast dye.

Correct Answer is B

Explanation

Incorrect. High blood sugar levels and frequent urination are not directly related to acute renal failure. These symptoms are more characteristic of diabetes mellitus.

Correct Answer is A

Explanation

Incorrect. Thiazide diuretics may cause electrolyte imbalances and metabolic disturbances, but they are not a common cause of prerenal acute renal failure.QUESTIONS

Incorrect. Hypoactive bowel sounds and constipation are not directly related to fluid overload in acute renal failure.

Incorrect. While the statement is partially true, it does not capture the acute and sudden nature of acute renal failure. The inability of the kidneys to filter waste products from the blood is one of the manifestations of AKI.

Incorrect. Administering pain medication before passive range-of-motion exercises is not a standard practice and does not directly prevent complications of immobility.

Incorrect. Excessive fluid intake and fluid overload may contribute to fluid retention and edema in prerenal acute renal failure, but they are not the primary pathophysiological process in acute renal failure.

Incorrect. While UTIs and kidney stones can cause kidney injury, they are not the exclusive causes of acute renal failure, which can have various underlying etiologies.

Correct. A renal nuclear scan, also known as a renal scintigraphy, involves injecting a small amount of radioactive material intravenously. The radioactive material is taken up by the kidneys, and the scan creates images that assess kidney function and blood flow.QUESTIONS

Incorrect. Increased respiratory rate and depth are not typically associated with acute renal failure or its fluid and electrolyte imbalances.

Incorrect. Gentle stretching exercises may not be appropriate for a client experiencing muscle cramps, as stretching could exacerbate the discomfort.

Incorrect. Encouraging the client to drink water freely would exacerbate fluid overload and impair the body's ability to eliminate excess fluids.

Incorrect. While a renal biopsy can provide information about the kidney's structure, its primary purpose is to obtain a tissue sample for histological examination, not to assess blood flow.

Correct. Fresh fruits and vegetables are generally low in phosphate and are suitable for a low-phosphate diet. These foods can help meet the client's nutritional needs while adhering to the dietary restriction.

Incorrect. Increasing the client'sfluid intake is not appropriate during a hypotensive episode, as it may not rapidly improve blood pressure and could lead to fluid overload.

Incorrect. Diabetes mellitus is a risk factor for chronic kidney disease, but it is not a specific risk factor for prerenal acute renal failure.

Incorrect. Elevated creatinine levels can be seen in both acute and chronic kidney diseases, but they are not exclusively seen in chronic kidney disease.

Incorrect. Adhesive tape can cause skin irritation and damage when removed, especially in clients at risk for impaired skin integrity.

Incorrect. Excessive fluid intake may contribute to fluid overload and decreased urine output in prerenal acute renal failure, but it is not the primary pathophysiological process that leads to decreased urine output.

Incorrect. Urinary tract obstruction is also associated with postrenal acute renal failure, not intrinsic causes.

Incorrect. Warm, flushed skin and headache are not directly related to metabolic acidosis.

Incorrect. The description provided refers to the insertion of a urinary catheter for bladder drainage, not hemodialysis.

Incorrect. Renal ultrasound is an imaging test that provides information about the structure of the kidneys but does not directly measure GFR.

Correct. Before an MRI scan, clients need to remove all metal objects and devices, including jewelry, piercings, hearing aids, and certain medical implants. Metal can interfere with the MRI's magnetic field and cause safety concerns during the procedure.
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