Complications of Renal Transplantation: Evaluation with US and Radionuclide Imaging

Abstract

Following renal transplantation, patients are often evaluated with ultrasonography (US) or radionuclide imaging to assess renal function and the presence of possible complications. Both modalities are inexpensive, noninvasive, and nonnephrotoxic. A basic understanding of the surgical techniques commonly used for renal transplantation is useful when imaging these patients in order to recognize complications and to direct further imaging or intervention. The most frequent complications of renal transplantation include perinephric fluid collections; decreased renal function; and abnormalities of the vasculature, collecting system, and renal parenchyma. Perinephric fluid collections are common following transplantation, and their clinical significance depends on the type, location, size, and growth of the fluid collection, features that are well-evaluated with US. Causes of diminished renal function include acute tubular necrosis, rejection, and toxicity from medications. Radionuclide imaging is the most useful modality for assessing renal function. Vascular complications of transplantation include occlusion or stenosis of the arterial or venous supply, arteriovenous fistulas, and pseudoaneurysms. Although the standard for evaluating these vascular complications is angiography, US is an excellent noninvasive method for screening. Other transplant complications such as abnormalities of the collecting system and renal parenchyma are well-evaluated with both radionuclide imaging and US.

Renal transplant vascular complications: the role of Doppler ultrasound

“…A limited number of studies have attempted to identify the presence of TRAS using contrast-enhanced ultrasound, but the role of this technique is still unclear [18]. In contrast to the diagnosis of native renal artery stenosis, indirect signs are of little use in the diagnosis of TRAS because the transplanted artery can be directly visualized in most cases, its tardus-parvus waveform cannot be compared with that of the contralateral kidney, and because the resistance to flow is influenced by numerous variables [19] except in particular cases (Fig. 1).…”

“…1). Acceleration time is the only indirect index that displays high sensitivity in the diagnosis of TRAS, but only when the degree of stenosis exceeds 80 % [19] (Table 3). Secondary effects, such as turbulence, reverse flow, and spectral dispersion, can be evaluated in the segment immediately downstream from the stenosis.…”

“…Narrowing of arterial vessels within the graft has been reported, but it is difficult to visualize with CDUS or with angiography. CDUS is also particularly useful during follow-up and in the diagnosis of recurrence of TRAS after treatment [19].…”

Renal transplantation parenchymal complications: what Doppler ultrasound can and cannot do

“…In B-mode, the US pattern of acute tubular necrosis is extremely variable. The kidney can often present normal features, while an increase in the size and a reduction in the echogenicity with a loss of the corticomedullary differentiation may be signs of an oedematous graft [11]. Cortical thickness and echogenicity with prominent pyramids have been also described, as in the case of ATN involving the native kidneys [12].…”

“…According to the recent literature, the incidence of AGP has been reported to be around 19-23 % [11]. Important risk factors for this complication include immunosuppressive therapy, invasive urological procedures such as bladder catheterism or urethral stenting and post-transplantion urethral bladder reflux (Fig.…”