Can a 24-year-old female with a past medical history (PMHx) of Phenylketonuria (PKU) safely undergo a Computed Tomography scan with contrast (CT scan with contrast)?

CT Scan with Contrast in a Patient with Phenylketonuria (PKU)

Yes, a 24-year-old female with phenylketonuria (PKU) can safely undergo a CT scan with contrast. PKU does not present any contraindication to iodinated contrast media used in CT imaging 1.

Understanding PKU and Contrast Media Compatibility

PKU is an autosomal recessive metabolic disorder characterized by deficiency or absence of phenylalanine hydroxylase enzyme activity, which leads to elevated phenylalanine levels in the blood and tissues 1, 2. The primary management of PKU involves:

• Phenylalanine-restricted diet
• Supplementation with phenylalanine-free formula containing tyrosine
• Regular monitoring of plasma phenylalanine levels
• Potential medication therapy (sapropterin, pegvaliase)

Why Contrast is Safe in PKU Patients:

1. No metabolic interaction: Iodinated contrast agents used in CT scans do not contain phenylalanine or aspartame and do not interfere with phenylalanine metabolism 1

2. No contraindication: Current guidelines on contrast administration do not list PKU as a contraindication for receiving iodinated contrast media 3

3. Standard precautions apply: The same general contraindications for contrast that apply to all patients would apply to PKU patients, including:

   • History of previous contrast reactions
   • Renal impairment
   • Pregnancy considerations (though not absolute contraindication)

Important Considerations Before the Procedure

While PKU itself doesn't contraindicate contrast use, the radiologist should be aware of:

1. Medication review: Ensure any medications the patient is taking for PKU (such as sapropterin) don't interact with contrast media 1

2. Metabolic status: Consider checking recent phenylalanine levels if the patient has poor metabolic control 1

3. Hydration status: Adequate hydration is important for all patients receiving contrast, particularly if using IV contrast, to minimize risk of contrast-induced nephropathy 3

4. Standard contrast precautions: The usual screening for renal function, contrast allergies, and other standard contraindications should be performed as with any patient 4

Post-Procedure Considerations

After the CT scan with contrast:

• Resume the patient's normal phenylalanine-restricted diet as soon as possible 1
• Encourage adequate hydration to help eliminate contrast from the system 3
• Monitor for standard post-contrast reactions (which are the same as in non-PKU patients)

Conclusion

The presence of PKU in a 24-year-old female does not contraindicate the use of CT contrast media. The standard protocols for contrast administration should be followed, with attention to the patient's overall metabolic status and medication regimen.