Joint Program in Nuclear Medicine

Renal Transplant Scintigraphy

Richard Kuno, MD
Kevin J. Donohoe, MD

December 17, 1996

Presentation

Imaging Technique

Imaging Findings

There is prompt blood flow to the renal transplant with counts appearing in the graft within 3 seconds of flow within the iliac artery. On the dynamic images, there is severely delayed excretion of the radiotracer.

Discussion

• Early complications usually occur within 1-2 weeks and can include
  • acute preservational injury,
  • operative complications, and
  • hyperacute or acute rejection.
• Later complications occur after 1-2 weeks and can include
  • chronic rejection,
  • cyclosporin toxicity,
  • recurrent disease,
  • renal artery stenosis (RAS),
  • obstruction, and
  • lymphoceles.

Early Complications

Acute preservational injury is a type of acute tubular necrosis and is a common occurrence. Factors increasing the risks for acute preservational injury include: cadaveric transplants, long cold ischemia time, and advanced donor age. Scintigraphically, acute preservational injury shows normal or slightly decreased perfusion but significant parenchymal dysfunction.

Hyperacute rejection occurs immediately post-operatively and is secondary to preformed antibodies. This type of rejection is irreversible but is rare in the modern era due to close allogenic matching between donor and host. Acute rejection is much more common and usually occurs 5 days to years following transplant. Acute rejection is an important cause of early deterioration and is predominantly cell mediated (T cell). Scintigraphy usually shows reduced perfusion while function is relatively maintained. Biopsy may be required for diagnosis. Acute rejection often responds to anti-rejection therapy.

Immediate post-operative complications can include the “surgical" complications of urine leak, vascular or ureteral obstruction/stenosis, and hematoma. For urine leaks, early scintigraphic images can show cold areas. Delayed views are the key to diagnosis and often show gradual fill-in of these cold regions. Urine leaks need immediate treatment. Hematomas can present as non-specific cold areas and are difficult to diagnose with scintigraphy. Ureteral obstruction can be particularly difficult to diagnose and often require a multi-modality approach. For obstruction, scintigraphy usually shows a rising renogram curve, prominent renal pelvis, and normal perfusion (early in obstruction). Poorly functioning grafts may not show a dilated pelvis. Ultrasound (US) can play a crucial role in diagnosing post-operative complications, often directly visualizing fluid collections, dilated collecting systems, and vascular stenosis.

Delayed complications

Delayed complications can include lymphoceles, chronic rejection, cyclosporin toxicity, recurrent disease, renal artery stenosis, and ureteral stenosis. Lymphoceles usually develop several weeks to months post-operatively and often appear as simple fluid collections on US. Lymphoceles can exert significant pressure effects and cause vascular and ureteral compromise. They may require drainage and/or sclerosis. Although cold regions on scintigrams can represent lymphoceles, scintigrams should not be used for the primary diagnosis of this complication. Chronic rejection is a slow, irreversible process, and is inadequately understood. Antirejection drugs are not very effective for this condition. Renal scintigraphy shows decreased perfusion and function, but biopsy is often required for definitive diagnosis. Chronic rejection can often not be differentiated by scintigraphy from cyclosporin toxicity, renal artery stenosis, or ureteral stenosis. Ultrasound, biopsy, and lab work (cyclosporin levels) may be helpful in evaluating chronic post-transplant complications.

Conclusion

Scintigraphy can play a vital role in the diagnosis of complications following renal transplantation. Unfortunately, scintigrams are often non-specific. The amount of time elapsed post-transplantation can provide a clue as to the most common complications expected; however, other studies such as ultrasound, renal biopsy, and lab work often play a crucial function in making the correct final diagnosis.

References

2. Thomsen HS, et al. Prospective evaluation of radionuclide monitoring in renal transplantation. Contrib Nephrolog 1990. 79:108-112.

3. Letourneau JG, Day DL, et al. Imaging of renal transplants AJR 1988; 150:833-838.

4. Surratt JT, Siegel MJ, et al. Sonography of complications in pediatric renal allografts. Radiographics 1990; 10:687-699.

5. Becker JA. The role of radiology in evaluation of the failing renal transplantation. Radiol Clin N Am 1991; 29:511-526.

Click here to go to Joint Program in Nuclear Medicine home page and Copyright notice.