Complications of renal transplantation: ultrasonographic evaluation

Abdominal lymphocele following multi-level anterior lumbar interbody fusion (ALIF) managed with a laparoscopic peritoneal window: case report and review of the literature

PURPOSE

Lymphocele formation following anterior lumbar interbody fusion (ALIF) is not common, but it can pose diagnostic and treatment challenges. The purpose of this case is to report for the first time the treatment of a postoperative lymphocele following a multi-level ALIF using a peritoneal window made through a minimally invasive laparoscopic approach.

METHODS

Case report.

RESULTS

A 74-year-old male with a history of prostatectomy and pelvic radiation underwent a staged L3-S1 ALIF (left paramedian approach) and T10-pelvis posterior instrumented with L1-5 decompression/posterior column osteotomies for degenerative scoliosis and neurogenic claudication. Three weeks after surgery, swelling of the left abdomen and entire left leg was reported. Computed tomography of the abdomen/pelvis demonstrated a large (19.2 × 12.0 × 15.4 cm) retroperitoneal fluid collection with compression of the left ureter and left common iliac vein. Fluid analysis (80% lymphocytes) was consistent with a lymphocele. Percutaneous drainage for 4 days was ineffective at clearing the lymphocele. For more definitive management, the patient underwent an uncomplicated laparoscopic creation of a peritoneal window to allow passive drainage of lymphatic fluid into the abdomen. Three years after surgery, he had no back or leg pain, had achieved spinal union, and had no abdominal swelling or left leg swelling. Advanced imaging also confirmed resolution of the lymphocele.

CONCLUSIONS

In this case report, creation of a peritoneal window minimally invasively via a laparoscope allowing passive drainage of lymphatic fluid into the abdomen was safe and effective for management of an abdominal lymphocele following a multi-level ALIF.

The aging of the immune system and its implications for transplantation

By the last third of life, most mammals, including humans, exhibit a decline in immune cell numbers, immune organ structure, and immune defense of the organism, commonly known as immunosenescence. This decline leads to clinical manifestations of increased susceptibility to infections, particularly those caused by emerging and reemerging microorganisms, which can reach staggering levels-infection with SARS-CoV-2 has been 270-fold more lethal to older adults over 80 years of age, compared to their 18-39-year-old counterparts. However, while this would be expected to be beneficial to situations where hyporeactivity of the immune system may be desirable, this is not always the case. Here, we discuss the cellular and molecular underpinnings of immunosenescence as they pertain to outcomes of solid organ and hematopoietic transplantation.

Page kidney following spontaneous subcapsular hematoma immediately after kidney transplantation: a case report

BACKGROUND

Page kidney (PK) is the occurrence of kidney hypoperfusion and ischemia due to pressure on the kidney by a subcapsular hematoma (SH), a mass, or fluid collection. SH after renal transplantation may result in kidney ischemia and graft loss.

CASE PRESENTATION

We present a rare case of early spontaneous SH in an allograft kidney that led to a decrease in renal function. A 56-year-old male patient underwent deceased donor kidney transplantation. After declamping, appropriate renal perfusion and immediate diuresis were observed, with no evidence of SH. However, his urinary output abruptly decreased 6 h postoperatively. Abdominal ultrasonography showed 28 mm deep SH on transplant and the resistive index (RI) increased to 0.98-1 and diastolic flow reversal was observed. Surgical interventions were performed 2 days after transplantation, following a further decrease in urinary output. Serum creatinine decreased to 2.2 mg/dL, urinary output increased to an average of 200 cc per hour and the RI value was decreased to 0.7 on POD 7.

CONCLUSION

In patients with abrupt decreased renal function after transplantation, SH should be suspected and the presence of PK should be determined using Doppler USG. In these cases, surgical intervention may avoid allograft dysfunction.

Sonographic Assessment of Renal Transplant Anastomotic Pseudoaneurysm: A Case Study

Renal transplant anastomotic pseudoaneurysms (RTAPs) are a rare vascular postoperative complication. The etiology of these pseudoaneurysms is attributed to infection or surgical vessel damage. RTAPs can lead to allograft dysfunction, allograft loss, or patient mortality due to rupture or sepsis. Because of these serious complications, expedient diagnosis is imperative for initiating surgical intervention and medical management. Sonography is a useful imaging modality for diagnosing and characterizing RTAPs. The sonographic findings, although not often described in detail in the literature, are definitive and unique. This case report describes the sonographic findings of a patient 22 days post renal autotransplant, who presented with excruciating abdominal pain. Sonographic examination identified multiple classic pseudoaneurysm findings and demonstrated intrarenal and extrarenal vascular abnormalities.

The “Black Pattern”, a Simplified Ultrasound Approach to Non-Traumatic Abdominal Emergencies

Background: A key issue in abdominal US is the assessment of fluid, which is usually anechoic, thus appearing “black”. Our approach focuses on searching for fluid in non-traumatic patients, providing a new, simplified method for point-of-care US (POCUS). Objective: Fluid assessment is based on a three-step analysis that we can thus summarize. 1. Look for black where it should not be. This means searching for effusions or collections. 2. Check if black is too much. This means evaluating anatomical landmarks where fluid should normally be present but may be abnormally abundant. 3. Look for black that is not clearly black. This means evaluating fluid aspects, whether wholly anechoic or not (suggesting heterogeneous or corpusculated fluid). Discussion: Using this simple method focused on US fluid presence and appearance should help clinicians to make a timely diagnosis. Although our simplified, systematic algorithm of POCUS may identify abnormalities; this usually entails a second-level imaging. An accurate knowledge of the physio–pathological and anatomical ultrasound bases remains essential in applying this algorithm. Conclusion: The black pattern approach in non -traumatic emergencies may be applied to a broad spectrum of abnormalities. It may represent a valuable aid for emergency physicians, especially if inexperienced, involved in a variety of non-traumatic scenarios. It may also be a simple and effective teaching aid for US beginners.

Evaluation of the Graft Kidney in the Early Postoperative Period: Performance of Contrast-Enhanced Ultrasound and Additional Ultrasound Parameters

OBJECTIVES

To evaluate the various quantitative parameters of Doppler ultrasound, contrast-enhanced ultrasound (CEUS), and shear wave elastography (SWE) of graft kidneys in the early postoperative period and to explore their utility in the diagnosis of parenchymal causes of graft dysfunction.

METHODS

In this ethically approved study, consecutive patients who underwent renal transplantation from March 2017 to August 2018 were recruited, and those with urologic or vascular complications and those who denied consent were excluded. All patients underwent ultrasound with Doppler, SWE, CEUS (using sulfur hexafluoride), and renal scintigraphic examinations 3 to 10 days after transplantation. A composite reference standard was used, including the clinical course, renal function test results, urine output, and histopathologic results for graft dysfunction. Cortical SWE values, quantitative CEUS parameters (generated from a time-intensity curve), and their ratios were analyzed to identify graft dysfunction and differentiate acute tubular necrosis (ATN) from acute rejection (AR).

RESULTS

Of the 105 patients included, 19 developed graft dysfunction (18.1%; 12 ATN, 5 AR, and 2 drug toxicity) in the early postoperative period. The peak systolic velocity in the interpolar artery showed a significant difference between control and graft dysfunction groups (P < .001) as well as between ATN and AR (P = .019). Resistive indices and SWE did not show significant differences. Ratios of the time to peak showed a significant difference between control and graft dysfunction groups (P < .05). The rise time and fall time of the large subcapsular region of interest and the rise time ratio were significantly different between ATN and AR (P = .03).

CONCLUSIONS

Contrast-enhanced ultrasound can be used to diagnose parenchymal causes of early graft dysfunction with reasonable diagnostic accuracy.

Efficacy of Lymphatic Sealing Using the LigaSure in Kidney Transplantation: A Pilot Study

BACKGROUND

Iliac vessel lymphatic ligation is critical in kidney transplantation, because it is associated with the occurrence of lymphocele. Lymphocele can also affect the renal graft. This study aimed to evaluate the efficacy of lymphatic sealing using LigaSure (an electrothermal bipolar sealing device) in kidney transplantation as compared with conventional silk-tie ligation.

METHODS

This retrospective study included 100 consecutive patients from a prospectively registered database who underwent kidney transplantation at Seoul St. Mary's Hospital, South Korea, between December 1, 2019 and November 12, 2020. Comorbidities, primary renal disease, transplantation variables, surgical variables, and posttransplantation outcomes were compared between conventional and LigaSure lymphatic ligations. Subgroup analyses were performed by anastomosis pattern.

RESULTS

The mean age of patients was 47.4 ± 12.40 (range, 24-73) years. The LigaSure and conventional groups comprised 50 (50%) patients. Hypertension history, number of anastomosed renal arteries, and anastomosis patterns differed significantly between groups (P < .05). No significant difference was found in postoperative outcomes. In the subgroup analysis, greater drain volume was found at postoperative day 1 in the end-to-end internal iliac artery-renal artery anastomosis group (P = .001) because the internal iliac artery dissection results in longer lymphatic ligation. Nevertheless, no differences in drain removal time (P = .528) or lymphocele incidence were found between subgroups.

CONCLUSION

LigaSure is expected to benefit from surgery time and will be identified in subsequent studies. LigaSure can be safely and comfortably used for iliac lymphatic ligation in kidney transplantation. In conclusion, LigaSure lymphatic ligation is superior to conventional lymphatic ligation in kidney transplantation.

Intraperitoneal Ultrasound-Guided Safe Laparoscopic Fenestration of Lymphocele After Kidney Transplantation

Background: Lymphocele is a common complication after kidney transplantation, which does not require treatment unless it is symptomatic. In this study, we aimed to evaluate the incidence, clinical symptoms, treatment choices, and success of different treatment methods of symptomatic lymphocele. Materials and Methods: We evaluated 168 patients who had kidney transplantation between January 2012 and January 2020. Patients with decreased kidney functions due to lymphocele formation during the clinical follow-up were included in the study. External drainage catheter was placed in all patients, except one. In case of treatment failure with external drainage, laparoscopic fenestration guided by intraperitoneal ultrasonography was performed. Clinical symptoms and success rates of treatments were evaluated. Results: Symptomatic lymphocele requiring interventional treatment was detected in 15 (8.9%) of 168 renal transplant patients. All of the symptomatic lymphocele cases had increased serum creatinine levels, whereas 10 had decreased urine volume, 4 had abdominal discomfort, and 2 had ipsilateral lower extremity edema. External drainage catheter was placed as the first-line treatment in 13 patients. In 6 cases, due to treatment failure with external drainage and in 2 patients as a first-choice treatment, laparoscopic fenestration was performed. No lymphocele recurrence was observed during follow-up. Conclusion: Among various methods defined in the treatment of lymphocele, use of laparoscopic fenestration is increasing because of its high success rate and advantages over other methods. Intraperitoneal ultrasound-guided laparoscopic fenestration is a useful and safe method that can be performed as a first-choice treatment since it eliminates the risk of organ injury or bleeding.

Multimodality imaging of pancreas-kidney transplants

Simultaneous pancreas-kidney transplant remains a treatment option for patients with insulin-dependent diabetes mellitus type 1, aimed at restoring normoglycemia, alleviating insulin dependency, avoiding diabetic nephropathy, and thereby improving the quality of life. Imaging remains critical in the assessment of these transplant grafts. Ultrasound with Doppler remains the primary imaging modality for establishing baseline assessment of the graft as well as for evaluating vascular, parenchymal, and perigraft complications. Noncontrast MR imaging is preferred over non-contrast CT for evaluation of parenchymal or perigraft complications in patients with decreased renal function, although contrast-enhanced CT/MR imaging may be obtained following multidisciplinary consultation in cases with high clinical and laboratory suspicion for graft dysfunction. Catheter angiography is reserved primarily for therapeutic intervention in suspected or confirmed vascular complications. An understanding of the surgical techniques and imaging appearance of a normal graft is crucial to identify potential complications and direct timely management. This article provides an overview of surgical techniques, normal imaging appearance, as well as the spectrum of imaging findings and potential complications in pancreas-kidney transplants.

Imaging of Renal Transplant Complications throughout the Life of the Allograft: Comprehensive Multimodality Review

The kidney is the most commonly transplanted solid organ. Advances in surgical techniques, immunosuppression regimens, surveillance imaging, and histopathologic diagnosis of rejection have allowed prolonged graft survival times. However, the demand for kidneys continues to outgrow the available supply, and there are efforts to increase use of donor kidneys with moderate- or high-risk profiles. This highlights the importance of evaluating the renal transplant patient in the context of both donor and recipient risk factors. Radiologists play an integral role within the multidisciplinary team in care of the transplant patient at every stage of the transplant process. In the immediate postoperative period, duplex US is the modality of choice for evaluating the renal allograft. It is useful for establishing a baseline examination for comparison at future surveillance imaging. In the setting of allograft dysfunction, advanced imaging techniques including MRI or contrast-enhanced US may be useful for providing a more specific diagnosis and excluding nonrejection causes of renal dysfunction. When a pathologic diagnosis is deemed necessary to guide therapy, US-guided biopsy is a relatively low-risk, safe procedure. The range of complications of renal transplantation can be organized temporally in relation to the time since surgery and/or according to disease categories, including immunologic (rejection), surgical or iatrogenic, vascular, urinary, infectious, and neoplastic complications. The unique heterotopic location of the renal allograft in the iliac fossa predisposes it to a specific set of complications. As imaging features of infection or malignancy may be nonspecific, awareness of the patient's risk profile and time since transplantation can be used to assign the probability of a certain diagnosis and thus guide more specific diagnostic workup. It is critical to understand variations in vascular anatomy, surgical technique, and independent donor and recipient risk factors to make an accurate diagnosis and initiate appropriate treatment.^©RSNA, 2019.

Current status of imaging diagnosis in the transplanted kidney. A review of the literature with a special focus on contrast-enhanced ultrasonography

Objectives

Ultrasonographic scanning is currently the most widespread imaging diagnostic procedure. The method provides real-time morphological, vascular and elastographic information in a non-invasive manner. In recent years, harmonic vascular examination has become accessible using intravenous contrast agents. In urological pathology, this procedure is used in the detection and evaluation of vascular and ischemic complications, in the classification of complex cysts according to the Bosniak system, also in the renal lesions with uncertain etiology and in acute pyelonephritis for the detection of abscesses. The contrast agent (SonoVue) is angiospecific and can be used in patients transplanted immediately after surgery without adverse effects or impaired renal function. Thus, it is desirable to be used in the nephrological pathology of the renal graft and to develop diagnostic models based on the evaluation of renal microvascularization, as well as the quantitative data resulting from the graphical representation of the specific parameters. The purpose of this review is to evaluate the current state of the literature regarding the place and role of contrast substance ultrasound in the early diagnosis of acute renal graft dysfunction and to make a differential diagnosis of this pathological entity.

Method

This review quantifies the role of contrast ultrasound in the diagnosis of acute complications of the renal graft. The research was conducted based on the databases PubMed, MedScape, Cochrane, according to the search criteria such as contrast-enhanced ultrasound + kidney transplant, “time intensity curves” + “kidney transplant”, filtered for the period 2004–2018.

Results

In the nephrological pathology of the renal graft, contrast-enhanced ultrasound is a valuable tool, superior to Doppler ultrasound in predicting the evolution of the renal graft, identifying very small early defects in renal microvascularization. A number of studies succeeded in identifying acute graft dysfunction, some of which establish its etiology - humoral rejection versus acute tubular necrosis. On the other hand, the contrast-enhanced ultrasound parameters do not have the ability to distinguish between cellular and humoral rejection.

Conclusions

If, at present, the histopathological examination is the only one that can differentiate with certainty the cause of acute renal graft dysfunction, we consider that contrast-enhanced ultrasound, as a non-invasive imaging technique, opens a favorable perspective for increasing the survival of the renal graft and decreasing the complications in the renal transplant. The combination of other ultrasound techniques, together with contrast-enhanced ultrasound, could lead to the development of new diagnostic models.

Imaging findings of infectious and inflammatory diseases of the urinary system mimicking neoplastic diseases

Neoplastic diseases affecting the urinary organs are common, and diagnosis by imaging is usually straightforward. However, infectious/inflammatory processes also commonly affect these organs and can be mistaken for a neoplasm. Familiarity with these potential mimickers and awareness of their imaging presentations are key for correct diagnosis. We present the imaging findings of non-neoplastic infectious/inflammatory diseases that can mimic a neoplastic process.

Oliguria due to extensive subcapsular hematoma in renal graft: does surgical intervention ensure better outcomes?

A 58-year-old male patient, with end-stage renal disease secondary to hypertension, underwent living-related kidney transplant at our transplant unit. The transplant surgery went uneventful and brisk urine output was recorded. Four hours after the transplant, the output suddenly dropped despite normal central venous pressure. Doppler scan revealed an extensive peri-allograft hematoma and high renal arterial resistive indices (RI). The patient was taken to the operating room where capsulotomy of the subcapsular hematoma was done. Postoperatively, the urine output restored to normal and the patient was sent home on the 5th post-operative day with adequately functioning renal graft. Surgical capsulotomy seems to be a valid approach in the management of such cases.

Relation of Color Doppler Twinkling Artifact and Scale or Pulse Repetition Frequency

OBJECTIVE

The aim of this study is to determine the effect of scale/pulse repetition frequency (PRF) on the appearance of color Doppler twinkling artifact.

MATERIALS AND METHODS

We commenced this cross-sectional study for 20 months from November 2014 to July 2016. During routine ultrasound examination, we observed multiple case of twinkling artifact produced by renal stones, calcifications in the thyroid nodules, bony fragments and intestinal gases, etc., We observed twinkling artifact with low- and high-PRF settings in 500 different structures. A total of 500 other structures were included wherein there was no Doppler twinkling artifact produced by them, with usual optimum PRF settings. These structures were also evaluated with low- and high-PRF to determine the effect of PRF on twinkling artifact effectively. All the patients were examined according to the AIUM guideline for appropriate examination protocol. Data were collected from the observation of twinkling artifact with low- and high-PRF/scale and evaluated with the help of IBM SPSS 24 package, the results were summarized as follow.

RESULTS

Change in scale/PRF could not affect the twinkling artifact. The twinkling artifact observed with low-PRF was the same as seen with high-PRF. There was a significant agreement between low- and high-PRF in the production of color twinkling artifact. The kappa value of agreement was estimated as 0.96, whereas the Pearson's correlation was significant with the value of 0.001. Same twinkling artifact was created with low- and high-PRF, with no significant variation.

CONCLUSION

Twinkling artifact is independent of PRF/Scale.

Early urological complications after kidney transplantation: An overview

Urological complications, especially urine leaks, remain the most common type of surgical complication in the early post-transplant period. Despite major advances in the field of transplantation, a small minority of kidney transplants are still being lost due to urological problems. Many of these complications can be traced back to the time of retrieval and implantation. Serial ultrasound examination of the transplanted graft in the early post-operative period is of key importance for early detection. The prognosis is generally excellent if recognized and managed in a timely fashion. The purpose of this narrative review is to discuss the different presentations, compare various ureterovesical anastomosis techniques and provide a basic overview for the management of post-transplant urological complications.

Quantitative evaluation of renal parenchymal perfusion using contrast-enhanced ultrasonography in renal ischemia-reperfusion injury in dogs

This study evaluated whether renal perfusion changes can be noninvasively estimated by using contrast-enhanced ultrasonography (CEUS) in renal ischemia-reperfusion injury and investigated the correlation between renal perfusion measured by CEUS and necrosis and apoptosis of renal tubular epithelial cells. In six dogs with experimentally induced renal ischemia-reperfusion injury, changes in time to peak intensity, peak intensity, and area under the curve were measured on CEUS. Peak intensity and area under the curve of the renal cortex began to decrease on day 1 (about 20% lower than baseline) and reached the lowest levels (about 50% of baseline) on day 4. They then gradually increased until day 10, at which time peak intensity was about 87% and area under the curve was about 95% of baseline; neither fully recovered. Both parameters were strongly correlated with the necrosis scores on histopathologic examination on day 4 (r = −0.810 of peak intensity and r = −0.886 of area under the curve). CEUS allowed quantitative evaluation of perfusion changes in acute renal ischemia-reperfusion injury, and CEUS results were correlated with renal tubular damage on histopathologic examination. Thus, CEUS could be a noninvasive, quantitative diagnostic method for determining progress of renal ischemia-reperfusion injury.

Sonographic Appearance of Chromic 2-0 Catgut Sutures in the Parenchyma of a Renal Allograft

A renal transplant recipient had a urinary fistula repaired and a double-pigtail ureteral stent left and later surgically removed. At this same time, an open biopsy was performed and closed with chromic 2-0 catgut sutures. A sonogram revealed an artifactual image that was interpreted as a fragmented piece of the stent that was left in the patient. An exploratory surgery performed, however, was unremarkable, and the renal incision was again closed with chromic 2-0 catgut sutures. A repeated sonogram demonstrated the previous artifact, which raised the suspicion that this appearance should be attributed to the chromic 2-0 catgut sutures. An experiment using a model of coupling gel and chromic 2-0 catgut sutures demonstrated artifacts that matched those seen during sonography of this particular renal allograft. This sonographic artifactual appearance may be seen in hypostenic patients with a high-frequency transducer centered over chromic 2-0 catgut sutures.

Sonographic Evaluation of Clinically Significant Perigraft Hematomas in Kidney Transplant Recipients

OBJECTIVE

The purpose of this study was to assess the sensitivity of ultrasound in evaluating peritransplant hematomas that require surgical evacuation in recipients of kidney transplants.

MATERIALS AND METHODS

Thirty-four patients who underwent 37 hematoma evacuations underwent ultrasound examinations in the 24 hours before surgical evacuation. The operative reports were evaluated for presence and size of collection, presence of active bleeding at operation, and composition of the hematoma. The clinical findings leading to the ultrasound examination were recorded. Ultrasound examinations were evaluated in consensus by two board-certified and fellowship-trained abdominal radiologists for the presence, size, and echogenicity of the collection; subjective perfusion visualized with color and power Doppler ultrasound; velocities of the renal arteries; and arcuate artery resistive indexes.

RESULTS

Ten of the 37 imaged hematomas (27%) had either no or small (< 50 mL) fluid collections on ultrasound examination. With sonographic volumetry, the reported intraoperative volumes were underestimated by 46%. The mean arcuate artery resistive index was 0.82 in the superior pole, 0.81 in the mid pole, and 0.78 in the inferior pole of the kidney. A decrease in hemoglobin level was the most sensitive clinical finding for determining the presence of perigraft hematomas.

CONCLUSION

Our results suggest that gray-scale sonography alone appears to have limited sensitivity in detecting clinically significant peritransplant hematomas and that its use may result in overall underestimates of hematomas.

Correlation of Doppler parameters with renal pathology: A study of 992 patients

Ultrasound examination is a non-invasive diagnostic technique that is used on patients with suspected or established renal disease. The purpose of this study was to determine the role of intrarenal Doppler ultrasonography in the assessment of the renal pathology of patients with chronic kidney disease (CKD), as shown by kidney biopsy. This retrospective analysis enrolled 992 consecutive patients with CKD who underwent intrarenal Doppler ultrasonography and a kidney biopsy at the Departments of Nephrology of three hospitals between January 2006 and December 2010. Doppler parameters, including the peak systolic velocity (PSV), end-diastolic velocity and resistive index (RI) of the interlobar arteries, were compared with the renal biopsy findings. The RI of the interlobar arteries was correlated with the estimated glomerular filtration rate and the histological damage scores, demonstrating the most evident correlation with the tubulointerstitial damage (TI) score among the three histological components. The PSV of the interlobar arteries increased as the CKD stage progressed and correlated with a number of the renal histological changes, including the glomerulosclerosis and TI scores. The RI and PSV of the interlobar artery are correlated with the histopathological pattern in CKD. Thus, the RI and PSV of the interlobar artery may be potential indicators for monitoring the progression of renal damage.

Corticomedullary strain ratio: a quantitative marker for assessment of renal allograft cortical fibrosis

OBJECTIVES

To quantitatively assess the correlation between the corticomedullary strain ratio and cortical fibrosis in renal transplants.

METHODS

Using quasistatic ultrasound elasticity imaging, we prospectively assessed the corticomedullary strain ratio in renal allografts of 33 patients who underwent renal transplant sonography and biopsy. Based on Banff score criteria for renal cortical fibrosis, 33 allografts were divided into 2 groups: group 1 (n = 19), with mild (<25%) fibrosis; and group 2 (n = 14), with moderate (>26%) fibrosis. We used 2-dimensional speckle-tracking software to perform offline analysis of cortical and medullary strain induced by external compression by the ultrasound transducer. We then calculated the corticomedullary strain ratio (cortical normalized strain/medullary normalized strain; normalized strain = developed strain/applied strain [deformation from the abdominal wall to the pelvic muscles]). An unpaired 2-tailed t test was used to determine differences in normalized strain and the strain ratio between the groups. Receiver operating characteristic curve analysis was performed to determine the best strain ratio cutoff value for identifying moderate fibrosis.

RESULTS

Normalized strain differed between the cortex and medulla (mean ± SD: group 1, 4.58 ± 2.02 versus 2.58 ± 1.38; P = .002; group 2, 1.71 ± 0.42 versus 2.60 ± 0.87; P = .0011). The strain ratio in group 1 was higher than in group 2 (2.06 ± 1.33 versus 0.70 ± 0.20; P = .0007). The area under the receiver operating characteristic curve was 0.964. The sensitivity and specificity of a strain ratio cutoff value of 0.975 for determining moderate fibrosis were 92.9% and 94.7%, respectively.

CONCLUSIONS

Strain values vary in different compartments of the kidney. The corticomedullary strain ratio on ultrasound elasticity imaging decreases with increasing renal cortical fibrosis, which makes it potentially useful as a noninvasive quantitative marker for monitoring the progression of fibrosis in renal transplants.

Ultrasound tissue characterization of the normal kidney

AIM

Ultrasound tissue characterization (USTC) is a precursor of ultrasound virtual histology (USVH), already applied to B-mode images of coronary, carotid, and peripheral arteries, as well as venous thrombosis. Elevated echogenicity has been described for a rejected transplanted kidney. We analyzed data from healthy young adults as reference for further renal USTC.

METHODS

Ultrasound kidney images of 10 volunteers were analyzed. Pixel brightness in the 0-to-255 range was rescaled to zero for black and 200 for fascia brightness before automatic classification into 14 ranges, including "blood-like" (0-4), "fat-like" (8-26), "hypoechoic muscle-like" (41-60), "hyperechoic muscle-like" (61-76), 4 ranges of "fiber-like" (112-196), "calcium-like" (211-255) and intermediary intervals. Nomenclature was readapted using nonechoic, hypoechoic I to IV, echoic I to IV, hyperechoic I to IV, and saturated echoes to avoid inference to actual kidney tissue. Descriptive and comparative statistics were based on percentages of pixels in specific brightness ranges.

SAMPLE POPULATION

Eight women and 2 men, 26 ± 4 years (range, 22-34 years) old, were studied. Kidney length was 10.5 ± 0.9 cm (9.0-12.0 cm). Doppler US resistivity index was 0.67 ± 0.03 (0.62-0.71).

RESULTS

Original fascia brightness converted to 200 value had a mean ± SD of 206 ± 16 (range, 181-236). Kidney grayscale median averaged 37 ± 6 (27-48). Most pixels were hypoechoic II to IV (8-60), averaging 78% ± 6% (66%-87%). Percentages for fat-like, intermediary fat/muscle-like, and hypoechoic muscle-like intervals averaged 25%, 28%, and 25%, respectively.

CONCLUSIONS

A reference database for USTC/USVH of normal young kidneys was created for future comparisons with transplanted and abnormal kidneys. Normal renal echoes have low brightness. Hyperechoic pixels may represent abnormalities.

Ultrasonographic features of kidney transplants and their complications: an imaging review

Renal transplantation is the treatment of choice for managing patients with end-stage kidney disease. Being submitted to a very serious surgical procedure, renal transplant recipients can only benefit from follow-up imaging and monitoring strategies. Ultrasound is considered as the principal imaging test in the evaluation of renal transplants. It is an easily applied bedside examination that can detect possible complications and guide further imaging or intervention. In this imaging review, we present essential information regarding the sonographic features of healthy renal transplants, detailing the surgical technique and how it affects the sonoanatomy. We focus on various complications that occur following renal transplantation and their sonographic features by reviewing pertinent literature sources and our own extensive imaging archives.

Using microdialysis for early detection of vascular thrombosis after kidney transplantation in an experimental porcine model

BACKGROUND

In kidney transplantation (KTx), vascular thrombosis has a major impact on morbidity and graft survival. The ischaemia, caused by thrombosis, can lead to interstitial metabolite changes. The aim of this experimental study was to create conditions in which the graft would be prone to vascular thrombosis following KTx and then to evaluate the role of microdialysis (MD) for its early detection.

METHODS

Sixteen randomized pigs in the control group received heparin and immunosuppressive drugs, while the case group received none. Based on histopathological evidence of vascular thrombosis, the case group was subdivided into mildly and severely congested subgroups. Using MD, we evaluated the interstitial concentrations of glucose, lactate to pyruvate ratio, glutamate and glycerol in the transplanted grafts during different phases of KTx.

RESULTS

Following reperfusion, we noted considerable changes. The severely congested subgroup showed a low and decreasing level of glucose. Only in this group did the lactate to pyruvate ratio continue to increase until the end of monitoring. The glycerol level increased continuously in the entire case group and this increase was most significant in the severely congested subgroup. In all of the study groups, glutamate concentration remained in a low steady state until the end of monitoring.

CONCLUSION

MD can be an appropriate method for early detection of vascular complications after KTx. Decreasing glucose levels, increased lactate to pyruvate ratio and increased glycerol levels are appropriate indicators for early detection of vascular thromboses following KTx. Particularly, the glycerol level could predict the necessity and urgency of intervention needed to ultimately save the transplanted kidney.

Doppler parameters in renal transplant dysfunction: correlations with histopathologic changes

OBJECTIVES

The aim of this study was to assess the relationship between intrarenal Doppler parameters and histopathologic changes shown on kidney biopsy in renal transplant dysfunction.

METHODS

We retrospectively reviewed the records of 113 patients (61 men and 52 women; age range, 22-76 years; mean age ± SD, 50.9 ± 12.7 years) who underwent both transplanted kidney sonography and biopsy from May 1, 2007, to May 31, 2009. Doppler parameters of the interlobar arteries, including the peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI), were compared with kidney biopsy findings. According to histopathologic findings, the 113 patients were divided into two groups: 1, interstitial fibrosis/tubular atrophy and vascular/glomerular sclerosis (n = 79); and 2, edematous changes in glomeruli without fibrosis (n = 34). The correlations between Doppler parameters and histopathologic findings were statistically analyzed.

RESULTS

There were statistically significant differences in the PSV and EDV of the interlobar arteries between groups 1 and 2. Both the PSV and EDV in group 1 were significantly lower than those in group 2 (P < .001). There was no significant difference in the RI of the interlobar arteries between the two groups (P > .05). There were no significant differences in the PSV, EDV, and RI of the main renal artery between the two groups (all P > .05).

CONCLUSIONS

The PSV and EDV of the interlobar artery have statistical correlations with histopathologic types in renal transplant dysfunction. Both the PSV and EDV in interstitial fibrosis/tubular atrophy and vascular/glomerular sclerosis seem lower than those in glomerulopathy without fibrosis. Hence, the PSV and EDV of the interlobar artery may potentially be used as hemodynamic indicators for monitoring the progress of renal transplants.

Extraperitoneal urine leak after renal transplantation: the role of radionuclide imaging and the value of accompanying SPECT/CT - a case report

BACKGROUND

The differentiation of the nature of a fluid collection as a complication of kidney transplantation is important for management and treatment planning. Early and delayed radionuclide renography can play an important role in the evaluation of a urine leak. However, it is sometimes limited in the evaluation of the exact location and extent of a urine leak.

CASE PRESENTATION

A 71-year-old male who had sudden anuria, scrotal swelling and elevated creatinine level after cadaveric renal transplantation performed Tc-99 m MAG3 renography to evaluate the renal function, followed by an ultrasound which was unremarkable. An extensive urine leak was evident on the planar images. However, an exact location of the urine leak was unknown. Accompanying SPECT/CT images confirmed a urine leak extending from the lower aspect of the transplant kidney to the floor of the pelvic cavity, presacral region and the scrotum via right inguinal canal as well as to the right abdominal wall.

CONCLUSIONS

Renal scintigraphy is very useful to detect a urine leak after renal transplantation. However, planar imaging is sometimes limited in evaluating the anatomical location and extent of a urine leak accurately. In that case accompanying SPECT/CT images are very helpful and valuable to evaluate the anatomical relationships exactly.

Kidney transplantation: structural and functional evaluation using MR Nephro-Urography

End-stage-renal disease (ESRD) is a major health issue in the United States, and the Medicare costs of ESRD totaled nearly USD 21 billion in 2005. Renal transplantation has emerged as the treatment of choice in this patient population, providing improved quality of life and lower healthcare costs compared with other treatment options. Imaging evaluation of a graft kidney plays a critical role in the postoperative care of the renal transplant patient. In the past, diagnostic evaluation of the transplant kidney has depended upon a combination of ultrasonography, computed tomography, MRI, and biopsy, used in conjunction with the patient's clinical presentation. However, new and developing advances in MR technology has lead to the development of MR Nephro-Urography (MRNU), which provides both anatomic and functional evaluation of the kidney in a single examination. It is expected that the increasing use of MRNU will have a significant impact on the management of renal transplant patients. This review describes MRNU methodology, examines known posttransplant complications, and highlights the utility of MRNU as a comprehensive imaging examination to diagnose both surgical and medical complications of the transplant kidney.