Is an ultrasound reasonable to evaluate for tendinopathy in a patient with right lower leg pain on prednisone, azathioprine, and tacrolimus with a history of cystic fibrosis status post bilateral lung transplant?

Ultrasound Evaluation for Tendinopathy in Post-Lung Transplant Patient on Immunosuppression

Ultrasound is strongly recommended as the first-line imaging modality for evaluating tendinopathy in a patient with right lower leg pain who is on prednisone, azathioprine, and tacrolimus following lung transplantation for cystic fibrosis.

Rationale for Ultrasound Imaging

Ultrasound offers several advantages for evaluating tendinopathy in this immunosuppressed transplant patient:

• Non-invasive imaging: Avoids exposure to radiation or contrast agents that could further stress the renal system, which may already be compromised due to calcineurin inhibitor (tacrolimus) therapy 1

• High sensitivity: Provides excellent visualization of soft tissue structures including tendons, allowing detection of:

  • Tendon thickening
  • Hypoechoic areas within tendons
  • Peritendinous fluid
  • Neovascularization (with Doppler)

• Real-time assessment: Allows dynamic evaluation of tendon function during movement

• Cost-effective: Less expensive than MRI while maintaining good diagnostic accuracy for tendinopathy

Increased Risk of Tendinopathy in This Patient

This patient has multiple risk factors for tendinopathy:

1. Chronic corticosteroid use (prednisone): Associated with tendon weakening and increased risk of rupture 1

2. Calcineurin inhibitor therapy (tacrolimus): May cause musculoskeletal complications including tendinopathy 1

3. History of cystic fibrosis: CF patients often have underlying musculoskeletal issues that may be exacerbated post-transplant

4. Post-transplant status: Immunosuppressive regimens can contribute to musculoskeletal complications

Diagnostic Algorithm

1. Begin with ultrasound evaluation of the right lower leg, focusing on:

   • Achilles tendon
   • Posterior tibial tendon
   • Peroneal tendons
   • Anterior tibial tendon

2. If ultrasound is negative but clinical suspicion remains high:

   • Consider MRI for more detailed soft tissue evaluation
   • Evaluate for other causes of leg pain (vascular, neurological)

3. If ultrasound confirms tendinopathy:

   • Grade severity
   • Assess for partial or complete tears
   • Evaluate surrounding structures for associated pathology

Management Considerations

If tendinopathy is confirmed:

1. Conservative management:

   • Rest and activity modification
   • Physical therapy
   • Orthotic devices to unload affected tendons 1

2. Medication adjustments (in consultation with transplant team):

   • Consider tacrolimus dose adjustment if levels are high 1
   • Avoid fluoroquinolone antibiotics which may worsen tendinopathy

3. Monitor for progression:

   • Serial ultrasound examinations
   • Close clinical follow-up

Important Caveats and Pitfalls

• Do not discontinue immunosuppressive medications without transplant team consultation, as this could precipitate graft rejection

• Be vigilant for infection in this immunosuppressed patient, as infection can mimic tendinopathy symptoms

• Consider drug interactions when prescribing additional medications, particularly those affecting CYP3A4 metabolism which could alter tacrolimus levels 2

• Monitor renal function as tacrolimus nephrotoxicity is common and may require dose adjustment 1

• Be aware of increased rupture risk in tendons weakened by chronic steroid use, particularly with physical therapy or increased activity