Article

Renal transplant Doppler ultrasound

Renal transplant Doppler: technique, resistive indices, peritransplant collections, vascular and urological complications, normal report and limitations.

What it is and when to indicate it

Renal transplant Doppler ultrasound assesses the graft in the iliac fossa: perfusion, urinary tract and peritransplant collections. It is indicated in the immediate postoperative period, in graft dysfunction (rising creatinine, oliguria) and in follow-up.

This page organizes the protocol in clear language and does not replace the original guidelines (AIUM, ACR, CBR), supervised training or clinical correlation.

Preparation and technique

• No special preparation is required; the graft is superficial in the iliac fossa
• Low-frequency curved transducer and linear for superficial detail
• Assess in B-mode: dimensions, echotexture, corticomedullary differentiation and urinary tract
• Color and spectral Doppler: main artery and vein, anastomoses and intraparenchymal vessels
• Correct the angle; sample interlobar/segmental arteries for the indices

Indices and what is normal

• Parenchymal resistive index (RI) typically between 0.60 and 0.80
• Very elevated RI (above 0.80) is nonspecific: rejection, acute tubular necrosis, compression, obstruction
• Absent or reversed diastolic flow indicates high resistance and is a warning sign
• Patent graft artery and vein, without focal aliasing suggesting anastomotic stenosis
• Good cortical perfusion to the periphery on color Doppler

Complications to recognize

• Peritransplant collections: hematoma, lymphocele, urinoma, abscess — measure and localize
• Hydronephrosis from ureteral obstruction (edema, stone, stricture)
• Graft artery stenosis: focal velocity increase and distal tardus-parvus
• Arterial thrombosis (absent flow) or venous thrombosis (reversed diastolic arterial flow) — emergencies
• Arteriovenous fistula or pseudoaneurysm after biopsy

Normal report template

• Graft of preserved dimensions and echotexture, with good corticomedullary differentiation
• No pelvicalyceal dilation and no significant peritransplant collections
• Patent graft artery and vein, with anastomoses without signs of stenosis
• Parenchymal resistive indices within normal range, with antegrade diastolic flow
• Homogeneous cortical perfusion to the periphery

Limitations and pitfalls

• Isolated RI is nonspecific: interpret with the clinical picture and the course
• Deep or tortuous anastomoses hampering velocity measurement
• Aliasing from inadequate PRF simulating stenosis
• Small collection versus loop: use planes and reassessment
• Report technical limitations and suggest further workup when indicated

Do not overdiagnose

Doppler alone does not distinguish the causes of elevated RI; correlate with the clinical picture, the course and, when needed, biopsy. Describe the findings well and avoid attributing a single cause to an isolated index.

Sources

Educational content; it does not replace original guidelines, medical evaluation or supervised training. Main references:

• AIUM. Practice Parameter for the Performance of an Ultrasound Examination of Solid-Organ Transplants.
• ACR-AIUM-SPR-SRU. Practice Parameter for the Performance of an Ultrasound Examination of the Abdomen and/or Retroperitoneum.
• Brazilian College of Radiology (CBR). Standardization and technical guidelines for ultrasound.
• Rumack CM, Levine D. Diagnostic Ultrasound (renal transplant).
• Radiopaedia. Renal transplant ultrasound (didactic support, not copied).

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