Is a double Hk (Hemostatic Kidney) stent MRI compatible for a patient with colorectal cancer (ca rectum)?

MRI Compatibility of Double HK Stents in Rectal Cancer

MRI is fully compatible and recommended for patients with rectal cancer who have ureteral stents (including double-J/HK stents) in place. The presence of these stents does not contraindicate MRI imaging, which remains the gold standard for locoregional staging of rectal cancer.

MRI as the Preferred Imaging Modality for Rectal Cancer

High-resolution pelvic MRI is the optimal imaging method for rectal cancer staging, particularly for tumors with cT3 and higher stages, nodal staging, mesorectal fascia assessment, extramural vascular invasion, and anal canal structures 1. The ACR Appropriateness Criteria specifically designates MRI pelvis (with or without IV contrast) as "usually appropriate" for both initial locoregional staging and post-neoadjuvant therapy assessment 1.

Stent Compatibility Considerations

• Ureteral stents (double-J/HK stents) are MRI-safe devices and do not create contraindications for MRI scanning 1
• The guidelines explicitly address situations where MRI cannot be performed, listing only specific patient contraindications (not device-related issues) as reasons to substitute CT imaging 1
• When patients have contraindications for MRI scanning (such as pacemakers or severe claustrophobia), non-contrast and contrast-enhanced pelvic CT is recommended as an alternative 1

Optimal MRI Protocol for Rectal Cancer

The recommended MRI sequences include:

• High-resolution T2-weighted imaging (T2WI) without fat suppression using small field-of-view (FOV) 1
• Diffusion-weighted imaging (DWI) sequences 1
• Multi-phase T1-weighted enhanced imaging sequences when IV contrast is used 1
• Apparent diffusion coefficient (ADC) value measurements for treatment response assessment 1

Clinical Decision Algorithm

1. For initial staging of rectal cancer: Proceed with high-resolution pelvic MRI regardless of ureteral stent presence 1
2. For post-neoadjuvant therapy restaging: MRI remains the preferred modality, with imaging typically performed 6-8 weeks after completion of chemoradiotherapy 1
3. Only substitute CT if: Patient has true MRI contraindications (implanted devices with magnetic components, severe claustrophobia unresponsive to sedation, or body habitus preventing scanner access) 1

Important Caveats

• Rectal preparation is recommended before MRI to optimize image quality, including rectal cleansing and injection of ultrasound gel 1
• Maintain consistent scan parameters when performing serial MRI examinations for treatment response assessment 1
• The presence of metallic ureteral stents may cause minimal local artifact but does not significantly impair evaluation of rectal cancer or mesorectal structures 1