Diagnostic Ultrasound - Abdomen and Pelvis

Renal Transplant Rejection
IMAGING
General Features
• Best diagnostic clue
○ No specific imaging characteristics
Ultrasonographic Findings
• Grayscale ultrasound
○ Acute rejection (AR): Nonspecific allograft edema,
urothelial thickening
○ Chronic rejection (CR): Cortical atrophy, increased
echogenicity, calcification
• Pulsed Doppler
○ Resistive index (RI) measured in segmental, interlobar
and arcuate arteries
○ AR: Elevated RI may be present but is not specific
○ Elevated RI > 0.80 associated with increased risk of
failure or death with functioning graft chronic allograft
nephropathy (CAN), may be related to recipient factors
• Color Doppler
○ May be decreased in AR or CR
Nuclear Medicine Findings
• Tc-99m MAG3 renogram may show decreased perfusion
and uptake but is nonspecific
Imaging Recommendations
• Best imaging tool
○ Ultrasound-guided renal biopsy is gold standard
• Acute humoral antibody-mediated rejection: transmural
arteritis and fibrinoid necrosis
• Chronic rejection: Vascular sclerosis, fibrosis, and tubular
atrophy
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Elevation of creatinine
○ Oliguria or anuria
○ Fever, graft tenderness or swelling
Demographics
• Epidemiology
○ Reduced problem with modern therapy
○ 14% in first 3-6 months
○ Acute cellular rejection most common, after 1st
postoperative week
Natural History & Prognosis
• Varying severity
• Acute rejection
Treatment
• Depends on type of rejection
Risk Factors
• Immune sensitization, ABO incompatible transplants, prior
transplantation
Diagnoses: Kidney Transplant
DIFFERENTIAL DIAGNOSIS
Acute Tubular Necrosis/Delayed Graft Function
• Clinical diagnosis
• May have decreased diastolic flow
Infection
• Clinical diagnosis, positive urine cultures
• Thickened urothelium, mild dilatation of ureter and pelvis
Calcineurin Inhibitor Toxicity
• Clinical diagnosis
PATHOLOGY
General Features
• Acute cellular rejection: T-cell-mediated reaction
Staging, Grading, & Classification
• Acute cellular rejection: T-cell-mediated reaction
• Acute antibody-mediated rejection: Immediate
"hyperacute" or delayed "accelerated acute" due to
preformed antibodies
○ Caused by donor-specific antibody to graft microvascular
antigens complement activation
• Chronic allograft nephropathy: Final common pathway of
different insults to transplant resulting in progressive
failure, including chronic rejection
Gross Pathologic & Surgical Features
• Adequate biopsy sample requires at least 10 glomeruli and
2 arteries with 2 separate cores through cortex
• Acute cellular rejection: T lymphocyte interstitial infiltration,
tubulitis, and arteritis
DIAGNOSTIC CHECKLIST
Consider
• Failed renal transplant as cause of a solid pelvic mass (±
calcifications)
SELECTED REFERENCES
1. Naesens M et al: Intrarenal resistive index after renal transplantation. N Engl
J Med. 370(7):677-8, 2014
2. Rodgers SK et al: Ultrasonographic evaluation of the renal transplant. Radiol
Clin North Am. 52(6):1307-24, 2014
3. McArthur C et al: Early measurement of pulsatility and resistive indexes:
correlation with long-term renal transplant function. Radiology. 259(1):278-
85, 2011
4. Radermacher J et al: The renal arterial resistance index and renal allograft
survival. N Engl J Med. 349(2):115-24, 2003
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