 Hello everyone, I am Dr. Alka Singhal, Associate Director of Radiology at Medanta Medicity Hospital, Delhi, India. My area of focus is ultrasound. Anything to do with ultrasound, a work with great zeal and passion to achieve the best diagnostic results in a given scenario. Today, here we discuss evaluation of a post-renal transplant doctor recipient, where we will discuss the grayscale imaging, color-empowered imaging, spectral doctor imaging. By all these, we aim to evaluate the immediate complications and the delayed complications, the perinepric elections and the sinister vascular complications. Hope you enjoyed the video. History of renal transplant. As we all know, renal transplant has come a long way. From the first transplant between two monozygotic twins to that between brother to sister and then to between father and son and now between two friends like in case of ectosilina, comase and ectrofrancia. Now, why do we need renal transplant? For the treatment for end-stage renal disease is chronic dialysis or to go for a transplant. Advantages of going for transplant is there is better survival and better quality of life. And this is owing to better surgical techniques and better immunosuppression and better donor recipient matching. Of course, imaging is a crucial component in the evaluation of renal transplant. What is preemptive renal transplant? When we do a renal transplant before the point of deterioration of the kidney function to the point of dialysis. So, especially this is valuable in cases of children and adolescents. So, this advantages are the lower risk of rejection of the donor kidney, improved survival rates and improved quality of life and it avoids dialysis and its complications. The surgical technique. All must make a note of the surgical procedures followed and the CT if you have any variation in the renal anatomy and the renal vasculature anatomy. Typically at an open surgery the renal graft is placed extraperitonally in the right ailekosa. For robotic renal transplants there is often a flap construction and they are partly intraperitoneal. Now the transplant has three main anastomosis. Between the artery to artery the vein to vein and the ureter. So, the renal artery anastomosis is end to side anastomosis between the donor renal artery to the external ailek artery or we can have to the internal ailek artery and different factors such as diabetic and age of the patient are taken into consideration before finalizing the plan. In case of a child as a recipient and donor as a mother, common ailek artery is chosen for the human size compatibility. The renal vein anastomosis is an end to side anastomosis between the donor renal vein and the recipient external ailek vein and the donor ureter is implanted in the superior aspect of the bladder dome. Now, how does kidney look on gray scale? Similar to as a native kidney as we have all been scanning we will assess the size, the orientation, the ecogenicity, ecortico-mattery differentiation, any hydronefroses, any calculi, any mass lesion, any perinephric collection, any vasculature disturbances and we will use the help of color and power and spectral Doppler for further assessment. Our transducer frequency can be increased to a higher frequency transducer as and when it is permitted to get better image resolution. Common abnormalities, hydronefroses as we all see, clinically it presents with Ryzen 3M creatinine and the differential diagnosis is often chronic rejection where you can also have mild hydronefroses. But in cases of transplant kidney as a kidney is a denerve kidney it is very important to reassess after emptying the bladder to exclude any false positives. Look for any stains as well. The incidence of renal calculi in post transplant kidneys is higher owing to hypercalcemia and secondary and tertiary hyperparathyroidism and patients do not feel the typical colic as these cases are denervated kidneys. The perinephric fluid collections are very common indication for a renal graft Doppler ultrasound. What is the role of ultrasound? One, to see if there is any collection. If yes, measure the size, give a volume estimate, characterize it whether it is a seruma, hematoma, urinoma, lymphocytes or an abscess. How? We will come to that. Given anatomical relationship of the collection with the important vascular structures and other structures in the abdomen. Serumas are usually composed of clear serous fluid and they appear clear and echoic on ultrasound. Urinomas again are a urine collection. They will appear as clear and echoic areas and on sampling they will show elevated creatinine levels as compared to serum creatinine levels. Hematoma fluid will classically show the appearances of blood and depending upon the age of the blood. Lymphocytes again they are clear and echoic collections and their fluid creatinine here is equal to the serum creatinine. Of course differential cell count and WVCs would be elevated in case of lymphocytes. Abscess will show typical appearances of pus and there would be associated clinical history of piratesia. Perinephric collections are significant based on their size and location. If they are small and they are inserting no mass effects they can usually be left alone and followed up with serial ultrasound. Larger collections and we may cause obstructive effects may be obstruct the ureter, cause hydronephrosis or obstruct on a vascular pedicle and compromise the perfusion of the kidney. These may need decompression either by any form of drainage or surgical management. Commonest that we see is a seroma which is a clear and echoic collection along the margin of the kidney and the differential diagnosis is urinoma. Perinephric hematoma are common mostly post biopsy cases where there is a small subcapsular collection or there may be large subcapsular collection or it may track down to dependent areas and away from the kidney itself as well and depending upon the age it will have varied appearances and it can be quantified and followed up with ultrasound. Urinoma seen between the transplant kidney and the bladder again as an anechoic collection and the collection increases in size over a short period of time. Percutaneous tapping will show elevated creatinine consistent with the urinoma unlike in case of a seroma or a lymphocytes. Urinomas are secondary to urinary fistula or leaks and they occur in the postoperative phase usually within the first two weeks and clinical signs obviously include decreased urine output and fullness and tenderness in the operative bed. Treatment they need prompt treatment and decompression first we can try with four least catheter. It may sometimes heal that small leak or percutaneous drainage or percutaneous nephrostomy or if that fails then surgical treatment may need to be instituted. Rare complications of urinoma include due to rupture urinary acitis or ascending into the thoracic leading to urinary thoracic. Lymphocytes are usually seen in the later part of the transplant about one to two months or more and they are caused by leakage from injured lymphocytes at surgery and these are adequate they may contain sceptations and if there is any ecogenicity within the collection it suggests secondary infection and needs to be evaluated further and treated accordingly. Peritransplant abscess is rare but can be seen and they are usually a sequelae to pylonephritis or secondary infection of any pre-existing perinephric collection such as urinoma, hematoma or seroma or lymphocytes. Fever was often seen along with signs of mass effect and needs to be investigated. Any patient who is fibrill and any pre-retransplant collection should be assumed to be an abscess unless proved otherwise. The infection may ascend into the kidney and may develop into intrarenal abscesses and when more permanent emphysemitis pylonephritis may ensue where gas shadows are seen within the renal signs. Coming to the applied anatomy the vascular anatomy the main part that we want to assist here and understand. So, as we all know the main renal artery when it reaches a renal hyalum it divides into the dorsal and the ventral remi which further divide into segmental arteries and they are usually five to six in number apical, anterior superior, interior inferior or middle inferior and posterior segmental arteries. We identify these and we sample the segmental arteries at least at the three samples at the three poles of the kidney and sample the renal artery at the hyalum in the origin. The renal artery has to be traced from the anastomotid side to an area before the anastomotid side because we also have to sample the external ilic artery and part of it. So, the renal artery has to be sampled all in complete total. Also include assessment of renal vein and external ilic vein and we record the PSV, EDV, RI, SAT and acceleration index at all the samples. At depiction of the color Doppler it is easy to identify origin of the renal artery from the internal ilic artery with appropriate color Doppler settings which can be very nicely demonstrated. Here is another demonstration showing the main renal artery as it's arising from the external ilic artery. So, which ones are the segmental artery? I hope it's all clear. Again, there's another schematic diagram on comparative anatomical and an ultrasound correlation to show the segmental arteries. Identification of these is very important because these are the ones we aim to sample during our renal graft Doppler evaluation. So, here we have sampled right kidney upper pole segmental arteries and as we all know the typical renal arterial flow signature is a rapid systolic upstroke and a diastolic flow and the RI's are normally between 0.5 to 0.7. We sample the middle segmental arteries, the lower pole segmental arteries, renal artery at the hyalum and the renal artery at the origin and we sample the renal vein the normal waveform is continuous and monophasic. We sample the external ilic artery which shows resistive flow how to optimize our Doppler settings. We can use a higher frequency transducer whichever gives us the required depth of resolution and renal transplants are mostly superficial. So, we can go for a higher frequency transducer easily. We can use how many can compound imaging as well. The most important thing is not to apply any probe pressure because this will compress the vasculature of the transplant and will impede the diastolic flow and increase the resistive index and optimize the Doppler settings of PRA velocity range wall filter to maximize the performance. Just a table illustrating the various factors that need to be reset every time because each patient's body habits changes. So, even though your machine has been optimized by the application specialist you still may need to adjust the factors for appropriate results. So, using the transducer frequency we discussed transducer pressure should be minimal Doppler gain highest possible avoiding the noise Doppler filter is the lowest possible to detect this low flow and PRF suit the velocity range of the required area. Complications of the renal graph as per the ultrasound findings. So, based on an ultrasound findings what are the differential diagnosis of the complications that could be happening to the patient. So, increase in size of renal transplant you could be looking at rejection infection or thrombosis venous thrombosis a decrease in size of renal transplant you could be looking at chronic ischemia or chronic rejection a high RI values could be seen in acute tibial necrosis obstruction infections severe rejection or its strength of compression low RI could be seen in arterial stenosis advanced arterial sclerosis or AVF and hydronephosis could be seen in cases of obstruction stone clot or any anastomotix stenosity malnurogenic bladder or bladder outlet obstruction. So, coming to specific cases now acute rejection what do we see one the kidneys enlarged edematos meso globular outline like edematos and roundness. It may be hyperequic or may show increased renal parenchymal ecogenicity the thickened renal cortex and their loss of corticometallary differentiation can be seen and the central sinus egos are ill-defined due to extensive edema due to rejection. Of course, biopsy will confirm the diagnosis on spectral Doppler the findings are non-specific elevation of RI over 0.8 chronic rejection kidney small in size goes on progressively reducing shrinking and there is diffuse thinning of the renal cortex again biopsy is needed to confirm the diagnosis on spectral Doppler non-specific elevation of RI is seen over 0.8. So, coming to post transplant acute tibial necrosis this accounts for majority of cases of renal failure occurring within the first few weeks of transplant again the clinically present with decreased urinary output and elevated creatinine levels. What do we see on ultrasound there is graft enlargement swelling and the kidneys edematous there is obscured corticometallary differentiation usually hyperequic kidney power scattered areas of increased patchy ecogenicity may also be seen at times the kidney may appear completely normal. On spectral Doppler again what the finding is non-specific elevation of RI. Coming to the next the renal artery stenosis now we have a short transitory from the anastomotid site to the time the renal artery enters the kidney. So, renal artery stenosis can be at the site of anastomosis before the site of anastomosis or after the site of anastomosis. Majority or 50% of the cases are seen at the site of anastomosis and usually the end-to-end anastomosis have three times greater risk of renal arterial stenosis. The spectral Doppler ultrasound shows focal elevation of the velocities at the site and power stardust waveform in the distal part beyond that. This is a sample case of renal artery stenosis showing peak systolic velocities of about 400 centimeters per second and in the renal parenchyma the segmental arteries show power stardust waveform. Coming to the renal arterial thrombosis, renal arterial thrombosis could be global when the main renal artery is occluded or could be focal depending upon the segmental arteries that are composed. Accordingly if we could have a wedge-shaped parenchyma in part or total loss of the kidney which could be appreciated on color or power Doppler as area of no flow and further imaging is needed and urgent intervention is needed to rescue the kidney. So this is a case where there's hardly any flow seen in the renal artery thrombosis case and post-surgery the kidney has been re-perfused and showing normal systolic flow. Adjust the differentiation between the three things acute rejection acute tubular necrosis and vascular complications. All are present clinically similarly but they are all managed in different manner. Diagnosis is really really important because there are timelines for that. Acute rejection is managed by immunosuppressants acute tubular necrosis requires supportive care. Vascular complications often require urgent surgical intervention. Coming to renal main thrombosis again this can present as slowly going renal failure or acutely going renal failure with decreased urinary function swelling and tenderness. Ultrasonic findings usually include enlarged kidney reduced or absent venous flow and increased resistance on the arterial side. Reverse diastolic flow on Doppler. So initially there may be elevated ri loss of diastolic flow and later diastolic flow reversal. So this is critical to recognize depending on the time that you recognize and you put in corrective factors you may be able to salvage the kidney. Otherwise the renal function deteriorates eventually the patient is back to dialysis as in the case that I'm just about to discuss. So here there's a sampling done at the renal hyalum and the spectral Doppler wave from shows characteristic diastolic reversal and this was proven this patient is currently under dialysis. So a little bit of differentiation point if the renal vein is patent then we think more of ATM versus rejection. If renal vein is occluded we think of renal venous thrombosis. Other rare complications that you may come across is AV fistula and studio aneurysms which are often posed biopsy and show typical aliasing and the vascular flow patterns. RACS renal allograft compartment syndrome rare but needs surgical intervention to rescue the kidney. PTLD post transplant lympho proliferative disorder due to immunosuppressions less often seen these days. I have yet to see one. Neoplasm is a very important topic because these patients are undergoing immunosuppression. With immunosuppressions there's 100 times increased risk for melanin Cs and commonly skin cancers and melanomas. So that needs to be evaluated but beyond that for the kidneys there is a tenfold increased risk of renal cell carcinoma more so in the native kidneys. So an evaluation of the native kidneys is also a part of renal transplant Doppler evaluation. Please remember evaluate them as well do a complete thorough evaluation. Thanks for watching till the end and I hope you like the video and find it useful in your day to day practice of evaluation for renal transplant recipient. Remember these patients may often have teenage renal function where contrast CT acting or CT renal angiography may be contraindicated. Hence reliance on your color Doppler evaluation and spectra Doppler evaluation is all the more important for the physician to make timely important management decisions.