Doppler normals: Arterial RI 0.5–0.7 (up to 0.85 acceptable early post-transplant). RI >0.9 = graft dysfunction — differential includes ATN, rejection, obstruction, and renal vein thrombosis. Assess anastomotic vessel velocities and evaluate for peritransplant fluid collections.
Renal Normal Measurements
| Structure | Normal Value |
|---|---|
| Renal cortex | Less echogenic than liver; cortical thickness >6 mm |
| Medullary pyramids | Less echogenic than cortex |
| Renal sinus | More echogenic than cortex |
| Parenchymal thickness | 15–20 mm |
| Renal size (male) | 10–14 cm long |
| Renal size (female) | 9–13 cm long |
Post-Transplant Complications Timeline
| Timeframe | Complication | US / Doppler Findings |
|---|---|---|
| Hours–days | Renal artery thrombosis | Absent arterial and venous flow; enlarged tender graft; surgical emergency |
| Hours–days | Renal vein thrombosis (RVT) | Absent venous flow; reversed diastolic arterial flow (RI approaching 1.0); acutely enlarged graft |
| Days 0–30 | ATN / acute rejection | Elevated RI >0.9; mild cortical echogenicity; indistinguishable on US — biopsy required; ATN usually reversible |
| Days 0–5 | Hematoma | Echogenic peritransplant fluid; may compress collecting system or ureter |
| Days 0–10 | Urinoma | Anechoic peritransplant fluid near ureterovesical anastomosis; calyceal leak |
| Weeks 2–6 | Lymphocele | Anechoic fluid with internal septations along medial border; most common late fluid collection; drainage if obstructing |
| Weeks–months | Renal artery stenosis | PSV >250 cm/s at anastomosis; RI <0.5 distal (tardus-parvus); RAR >3.5; responds to angioplasty |
| Months–years | Hydronephrosis / ureteral stricture | Calyceal dilatation; obstruction at anastomosis; confirm with nuclear medicine or antegrade pyelogram |
| Months–years | Chronic rejection | Cortical thinning; echogenic cortex; progressive RI elevation; graft volume loss |
Reversed diastolic flow (RI approaching 1.0) in the transplant renal artery = renal vein thrombosis until proven otherwise. This is a surgical emergency.
TIPS Evaluation
Transjugular intrahepatic portosystemic shunt (TIPS) patency is assessed with Doppler ultrasound. The most common site of stenosis is the cephalic (hepatic venous) end of the stent.
| Category | Sign | Criteria |
|---|---|---|
| Direct — shunt velocity | Malfunction | <90 cm/s OR ≥190 cm/s; OR change >50 cm/s from prior baseline |
| Indirect | Malfunction | MPV velocity >30 cm/s; new or increased collateral vessels; new or increased ascites; reversal of portal flow |
| Location | Most common stenosis site | Cephalic (hepatic venous) end of stent |
Reference
Sugi MD et al. Renal Transplant Complications. RadioGraphics. 2019;39(5):1327–1355.