Medical Surgical Renal Lab values & Urine analysis #1

Question

A client comes to the hospital for a cat (CT) scan with IV contrast. Which of these labs are most important to check before proceeding with the IV contrast? Select all that apply.

Answers

  1. BUN
    • Rationale:

      This answer is correct because BUN stands for Blood Urea Nitrogen and is a waste product of protein. BUN is an important test to perform to see how the kidneys are functioning.

  2. Creatinine
    • Rationale:

      This answer is correct because creatinine is a blood test that indicates how the kidneys are functioning. Creatinine > 1.3 indicates a bad kidney.

  3. Glucose
    • Rationale:

      This answer is not correct because glucose is not tested when performing a CT scan with IV contrast. Because IV contrast causes decreased renal blood flow plus the contrast is excreted by the kidneys, it is important to check the client’s BUN and creatinine before proceeding with the test.

  4. Potassium
    • Rationale:

      This answer is not correct because potassium is not normally checked when performing a CT scan with IV contrast. Because IV contrast causes decreased renal blood flow plus the contrast is excreted by the kidneys, it is important to check the client’s BUN and creatinine before proceeding with the test.

  5. Sodium
    • Rationale:

      This answer is not correct because sodium is not usually checked when performing a CT scan with IV contrast. Because IV contrast causes decreased renal blood flow plus the contrast is excreted by the kidneys, it is important to check the client’s BUN and creatinine before proceeding with the test.

Overview

Because IV contrast causes decreased renal blood flow plus the contrast is excreted by the kidneys, it is important to check the client’s BUN and creatinine before proceeding with the test. The intravenous injection of contrast dye for a CT scan causes fast renal vasodilation followed by prolonged vasoconstriction and results in a decrease in the renal blood flow and a drop in the filtration fraction.

Explanation

Learning Outcomes

The intravenous injection of contrast dye for a CT scan causes fast renal vasodilation followed by prolonged vasoconstriction and results in a decrease in the renal blood flow and a drop in the filtration fraction. Recommendations post-IV contrast are to drink 8-10 glasses of water to help flush the contrast from the kidneys. The normal blood urea nitrogen (BUN) level is 8 to 20 mg/dL. The normal creatinine is 0.8 to 1.2 mg/dL. These should be monitored carefully.

Test Taking Tip

The most accurate tests to perform for kidney function are the BUN and creatinine blood tests. Increased blood levels of BUN and creatinine can show that the kidneys may not be functioning correctly.

Video Rationale