Role of Ultrasound In Renal Transplantation

1. Role of Ultrasound In Renal Transplantation Dr. Ahmed Refaey Consultant Radiologist Prince Sultan Military Medical City

2. Ultrasound is often the initial diagnostic modality as it is noninvasive, relatively inexpensive, does not require intravenous contrast, can be obtained at the bedside, and can often rapidly and accurately depict many of the common complications

3. Normal anatomy

4. Knowledge of the exact renal transplant procedure performed is essential for accurate interpretation of both normal and abnormal findings. Particularly important is knowledge of the vascular anatomy, so that all vessels and anastomoses can be evaluated for patency, stenosis or other complications.

5. * Vascular supply from end-to-sideanastomosis of donor artery and vein to external iliac artery and vein.   • If multiple arteries, usually joined with single anastomosis to EIA or can be anastomosed separately to the external iliac artery • Ureteranastomosed to superolateral wall of urinary bladder

6. The transplanted kidney is usually placed in an extraperitoneal location in the right or left iliac fossa • The superficial location makes it ideal for US evaluation.

8. Normal color doppler findings : - arteries : brisk upstroke, low resistance with normal RI of 0.6 – 0.75 - normal velocity of main renal artery < 200 cm/s - veins : may be monophasic with continous flow, or demonstrate some pulsatility with cardiac cycle.

10. Renal artery Doppler flow pattern

11. The transplanted kidney is a solitary functioning kidney, so there is usually a physiological hypertrophy, 15% in first 2weeks and may increase by 40% in first 6 months.

12. US Evaluation of Complications of Renal Transplantation • Classically, the complications affecting the transplanted kidney can be categorized as: - anatomic - functional - vascular.

13. Complications Anatomic Functional Rejection Drug toxicity Acute tubular necrosis - Perinephric fluid collections - hydronephrosis - parenchymal masses. Vascular - Renal artery thrombosis - Renal vein thrombosis - Renal artery stenosis - Renal vein stenosis - Arteriovenous fistulas - Pseudoaneurysms.

14. Anatomic Complications - Perinephric fluid collections - hydronephrosis - parenchymal masses.

15. Perinephric Fluid collections • Hematoma • Urinoma • Lymphocele • Abscess

16. found in ≤50% of renal transplants. • The clinical relevance of a fluid collection depends on its composition, size, location and whether or not it is exerting mass effect on the transplant kidney, ureter or other adjacent structures • Mass effect from perinephric fluid can result in: -hydronephrosis -kinking of the vascular pedicle -edema of the leg, abdominal wall, labia or scrotum.

17. Hematoma - often present in the immediate postoperative period ≤2 weeks after surgery - usually located either in the subcutaneous tissue , or around the transplant - the sonographic characteristics vary with age - acute and chronic hematoma : echogenic - intermediate hematoma: fluid filled, internal septations.

19. Urinoma - often present in the immediate postoperative period ≤2 weeks after surgery - serious complication, usually caused by a defect in the uretrovesicalanastmosis - appear as well-defined anechoic collections without septations, unless infected or mixed with blood

21. Lymphocele - a more delayed complication, occurring 4 to 8 weeks after surgery - usually located between the bladder and the kidney - cystic, but a majority tend to have septations - due to disruption of the adjacent lymphatic channels

24. Abscess • uncommon, but can occur in the early postoperative period due to pyelonephritis or bacterial seeding of a urinoma, hematoma or lymphocele • Suspected when the patients presents with fever and increased WBCs • Sonographically, can vary from an echo-free to complex echopattern.

26. Anatomic Complications - Perinephric fluid collections - hydronephrosis - parenchymal masses.

27. Hydronephrosis • Either due to extrinsic compression ( perinephric fluid collection ) • or due to renal calculi, clot, anastomotic edema and ureteralstenosis . • It should be noted that anastomotic edema often results in transient hydronephrosis of the transplanted kidney. • Also, apparent hydronephrosis may be the result of an increased hydrostatic pressure due to a full bladder; evaluation after voiding can avoid diagnostic error in this setting.

29. Parenchymal masses • Focal parenchymal lesions in the renal transplant, whether hypoechoic or hyperechoic, are non-specific findings • Differential considerations include: - focal pyelonephritis - hematoma - abscess - infarction - renal cell or transitional cell carcinoma - post-transplantation lymphoproliferative disorder (PTLD)

31. Anatomic Complications - Perinephric fluid collections - hydronephrosis - parenchymal masses.

32. Functional Complications • Rejection • Drug toxicity • Acute tubular necrosis

33. Ultrasound plays a more limited role in the evaluation of functional complications. • very difficult to distinguish from one another by imaging criteria alone.

34. Rejection • Hyperacute rejection • Acute rejection • Chronic rejection

35. Rejection • Hyperacute rejection : no role since the diagnosis is typically made immediately after transplant while still in the operating room

36. Acute rejection - Acute rejection takes several days to develop and peaks at 1 to 3 weeks after transplant - findings have been shown to be unreliable in its diagnosis. In cases of severe acute rejection, the transplanted kidney becomes edematous , globular, hypoechoic mass with poor differentiation of the central renal sinus fat with elevation of the resistive index

37. Acute transplant rejection Enlarged, globular, hypoechoic renal transplant with loss of the normal corticomedullary differentiation and ill definition of renal sinus fat due to severe edema

38. Acute rejection Spectral doppler image of a segmental artery reveals a mildly increased resistive index due to parenchymal edema

40. Chronic rejection - most common cause of late graft loss - begins 3 months after the transplantation. - US: cortical thinning , mild hydronephrosis , prominent sinus fat, dystrophic calcification, decreased color, normal or increased RI.

42. Acute tubular necrosis • More common than rejection • Little sonographic change in parenchyma pattern. • ATN occurs in the immediate post transplant period as a result of ischemia, thus more commonly seen in cadaveric transplants

43. Acute tubular necrosis

44. In summary, most cases of functional complications have non-specific imaging findings consisting of parenchymal edema and elevated resistive indices and require tissue analysis with renal biopsy for diagnosis.

45. Complications Anatomic Functional Rejection Drug toxicity Acute tubular necrosis - Perinephric fluid collections - hydronephrosis - parenchymal masses. Vascular - Renal artery thrombosis - Renal vein thrombosis - Renal artery stenosis - Renal vein stenosis - Arteriovenous fistulas - Pseudoaneurysms.

46. Vascular Complications - Renal artery thrombosis - Renal vein thrombosis - Renal artery stenosis - Renal vein stenosis - Arteriovenous fistulas - Pseudoaneurysms. Early complications Late complications post biopsy complications

47. Vascular complications occur in less than 10% of transplant recipients • Often correctable • Ultrasound plays a pivotal role in identifying and quantifying vascular complications of renal transplants.

48. Early complications • Renal artery thrombosis and renal vein thrombosis are both devastating complications seen in the early post operative period that can rapidly lead to graft loss.

49. Renal artery thrombosis • a rare early complication • can be caused by severe rejection, acute tubular necrosis or faulty surgical technique. • Doppler US shows absent intrarenal arterial and venous flow