Contrast-enhanced ultrasound in renal cystic lesions: an update

This narrative review aims to describe the current status of contrast-enhanced ultrasound (CEUS) in characterizing renal cystic lesion. The imaging techniques usually performed for their evaluation are ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) with different criteria of application based on the individual case and the purpose of the examination. Generally, US, as a non-ionizing examination, is the first imaging modality performed and therefore the one that incidentally detects cystic lesions. CT is the most performed imaging modality for cystic lesion assessment before MRI evaluation. It provides better characterization and management and has been introduced into the Bosniak classification. In this context, CEUS is making its way for its characteristics and represents the emerging technique in this field. With these premises, the authors analyze the role of CEUS in the evaluation of renal cysts, starting with an explanation of the technique, describe its main advantages and limitations, and end with a discussion of its application in the Bosniak classification and management, following the current major guidelines.

Comparative analysis of ultrasound-guided percutaneous biopsy of native kidneys in children and adults using the free-flank supine antero-lateral decubitus positioning

PURPOSE

Ultrasound-guided percutaneous biopsy (USPB) of the native kidneys is the preferred diagnostic method for several nephrological conditions in both adult and pediatric populations. Conventionally, native kidney biopsies are conducted with patients in the prone position (PP). However, an alternative approach involving the supine oblique antero-lateral position (SALP) has been explored, particularly for individuals who are obese, elderly, or critically ill.

METHODS

This study aimed to assess the feasibility and outcomes of USPB performed in SALP with a Free-Flank setting (FF-SALP) in pediatric patients (Group A) compared to adults (Group B). Data from kidney biopsies conducted between 2008 and 2021 were gathered. The study focused on the safety and the prevalence of biopsy samples containing a minimum of 10 glomeruli, histopathological yield in both groups.

RESULTS

Complication rates were low in both groups (5.6% vs. 3.7%; p = 0.454), without major complications noted. The pediatric group achieved a significantly higher mean number of glomeruli per biopsy compared to the adult group (20.6 ± 12.3 vs. 15.7 ± 9.4; p < 0.001). However, when evaluating the minimum threshold of 10 glomeruli (76.3% vs. 68.5%; p = 0.072) and histopathologic yield (95.3% vs. 93.5%; p = 0.408), no differences were observed between groups.

CONCLUSION

USPB of native kidneys in the FF-SALP position is a safe and effective method for tissue sampling in patients with parenchymal disease. It demonstrated comparable diagnostic yields and complication rates in the pediatric and adult populations, providing advantages in terms of airway management, making it particularly useful for pediatric patients that require general anesthesia.

Based on functional and histopathological correlations: is diffusion kurtosis imaging valuable for noninvasive assessment of renal damage in early-stage of chronic kidney disease?

PURPOSE

To evaluate the potential of 3 T magnetic resonance diffusion kurtosis imaging (DKI) in assessing the renal damage in early-stage of chronic kidney disease (CKD) patients with normal or slightly changed functional index, using histopathology as reference standard.

METHODS

49 CKD patients and 18 healthy volunteers were recruited in this study. CKD patients were divided into two groups based on estimated glomerular filtration rate (eGFR): Study group I (eGFR ≥ 90 ml/min/1.73 m2 [n = 20]) and Study group II (eGFR < 90 ml/min/1.73 m2 [n = 29]). DKI was performed in all participants. The DKI parameters (mean kurtosis [MK], mean diffusivity [MD], fractional anisotropy [FA]) of renal cortex and medulla were measured. The differences of parenchymal MD, MK and FA values among the different groups were compared. The correlations between DKI parameters and clinicopathological characteristics were assessed. Diagnostic performance of DKI to assess renal damage in early-stage of CKD was analyzed.

RESULTS

The cortex MD and MK showed significant difference among three groups (P < 0.05): trend of cortex MD: Study group II < Study group I < control group; trend of cortex MK: control group < Study group I < Study group II. The cortex MD and MK and medulla FA were correlated with eGFR and Interstitial fibrosis/Tubular atrophy score (0.3 < r < 0.5). Cortex MD and MK yielded an AUC of 0.752 for differentiating healthy volunteers from CKD patients with eGFR ≥ 90 ml/min/1.73 m2.

CONCLUSION

DKI shows potential in non-invasive and multi-parameter quantitative assessment of renal damage in early-stage of CKD patients and provide additional information for changes in renal function and histopathology.

[Renal Biopsy]

The extent of renal biopsy indication is being widened because of the increasing incidence of incidental renal masses; the increasing treatment options for renal cell carcinoma, including ablation therapy and novel targeted treatment; and the increasing incidence of kidney transplantation. However, percutaneous renal biopsy is technically difficult, particularly for beginners, because the skin-to-organ distance is relatively longer than those associated with other organs. In the present review, we will discuss the indications, technical considerations, efficacy, and complications of renal biopsy. Furthermore, we share practical tips of renal biopsy through many examples to help radiologists perform renal biopsy safely and effectively in various situations.

Ultrasound Versus Computed Tomography-Guided Native Parenchymal Kidney Biopsies for Hospitalized Patients: Comparison of Clinical Outcomes and Complications

ABSTRACT

Percutaneous native kidney biopsies performed with ultrasound (US) or computed tomography (CT) guidance are important in the workup of medical renal disease, with modality choice often dependent on the performing institution, with various complication rates reported. We compared the complication rates and types of complication of US- versus CT-guided native parenchymal renal biopsy among hospitalized patients. One hundred five consecutive inpatient US- and CT-guided native parenchymal renal biopsies performed by radiologists at a tertiary care academic center between 2006 and 2020 were reviewed retrospectively. Complication rates of biopsy were calculated and compared between the 2 modalities. Comparisons with regard to types of complications were made using the Society of Interventional Radiology grading scale, American Society of Anesthesiologists score, and other clinical data. One hundred five hospitalized adult patients (58 women and 47 men; average age, 53 years) underwent native parenchymal kidney biopsy during the study period. Sixty-three (60%) were CT-guided and 42 (40%) were US-guided. Complication rates between CT- versus US-guided biopsies were 40% versus 19% ( P = 0.03), respectively. There were 7 major and 18 minor complications for CT-guided biopsies and 3 major and 5 minor complications for US-guided biopsies. No statistically significant difference was found in preprocedural American Society of Anesthesiologists Classification score, international normalized ratio, platelet count, or body mass index. Computed tomography-guided native parenchymal kidney biopsy was associated with a higher overall complication rate compared with US-guided biopsy for hospitalized patients. Most complications were minor, which required no treatment or additional follow-up.

Targeted Renal Biopsy: Predictors on Imaging

Objectives The renal nephrometry score uses imaging characteristics such as lesion diameter, location, and proximity to hilar vessels to categorize renal masses by complexity for preoperative planning. These characteristics may also be used to determine the best approach to targeted renal biopsy. This study was conducted to investigate the impact of renal lesion characteristics as measured by the renal nephrometry score on the choice of modality used for performing a targeted renal lesion biopsy and increasing the chance of yielding a diagnostic biopsy.

Materials and Methods All targeted computed tomography (CT)/ultrasound-guided renal biopsies performed by our radiology department from January 2017 to February 2020 were reviewed. Radiological characteristics and pathological outcomes were recorded with data on lesion size/ side, location in craniocaudal/anterior–posterior planes, endophytic/exophytic/mixed nature, and skin-lesion distance.

Statistical Analysis Chi-squared tests, multivariate analysis, and t-tests were used in this study.

Results Of the 145 consecutive patients included in the study, 86.2% (125/145) biopsies were diagnostic. About 54.5% (79/145) biopsies were ultrasound-guided, while 45.5% (66/145) were CT-guided. About 62.1% (90/145) biopsies revealed renal cell carcinoma. The highest rate of diagnostic biopsy was in the exophytic, laterally positioned mass either entirely below lower polar or above upper polar line. Ultrasound was preferred for lesions under 4cm and 4 to 7cm (p = 0.06). CT was used for anterior lesions and ultrasound for posterior and lateral lesions (p < 0.001). Of the 20 nondiagnostic biopsies, 7/20 had a repeat biopsy, 7/20 underwent surveillance, 5/20 underwent partial or total nephrectomy, and 1/20 underwent a pathological lymph node biopsy.

Conclusions Our study highlights some factors radiologists should consider when predicting whether CT or ultrasound guidance is more appropriate and the probability of achieving a diagnostic biopsy based on lesion characteristics. At our institution, both modalities achieved high accuracy, although we favored ultrasound in lateral, posterior, and small lesions. These factors should be weighed against local experience and preference.

Percutaneous ultrasound-guided renal biopsies in a paediatric population: comparison of coaxial and non-coaxial techniques using 18-gauge core biopsy needles

BACKGROUND

Percutaneous ultrasound-guided biopsy is performed in paediatric patients for evaluation of diffuse renal parenchymal disease. When compared with the non-coaxial technique, the coaxial technique has the advantages of obtaining multiple tissue cores via a single capsular puncture and post-biopsy tract embolisation.

OBJECTIVES

To compare the coaxial and non-coaxial techniques of percutaneous ultrasound (US)-guided biopsy of native kidney parenchyma in children and adolescents with renal disease.

MATERIALS AND METHODS

We retrospectively identified consecutive patients who underwent percutaneous US-guided renal biopsy using an 18-gauge core biopsy needle from July 2019 to July 2021 in a single tertiary paediatric nephrology centre. Focal renal tumour biopsy and transplant kidney biopsy were excluded. The total glomerular yield, specimen adequacy, complication rate and procedural time between the coaxial and non-coaxial groups were compared.

RESULTS

There were 34 percutaneous US-guided renal biopsies: 22 using a coaxial technique and 12 using a non-coaxial technique. The total median glomerular yield obtained was higher in the coaxial group (coaxial=37.9; non-coaxial=22.2; P=0.02). No statistically significant difference was noted between specimen adequacy (coaxial=100%; non-coaxial=91.7%; P=0.35). While no statistically significant difference was detected for overall complication rates (coaxial=13.6%; non-coaxial=41.7%; P=0.09), the coaxial group had a lower rate of haemorrhagic complications (coaxial=4.5%; non-coaxial=41.7%; P=0.01). One patient in the non-coaxial group had post-biopsy haemorrhage requiring embolisation. The procedural time was shorter in the coaxial group (coaxial=26.3 ± 7.0 min; non-coaxial=51.3 ± 11.5 min; P&lt;0.001).

CONCLUSION

Percutaneous US-guided renal biopsy in children using the coaxial technique has significantly higher total glomerular yield, shorter procedural time and fewer haemorrhagic complications, compared to biopsies using the non-coaxial technique.

Multimodality imaging of renal lymphoma and its mimics

Lymphomatous involvement of the genitourinary system, particularly the kidneys, is commonly detected on autopsies; yet on conventional diagnostic imaging renal lymphoma is significantly underestimated and underreported, in part due to its variable imaging appearance and overlapping features with other conditions. We present a spectrum of typical and atypical appearances of renal lymphoma using multimodality imaging, while reviewing the roles of imaging in the detection, diagnosis, staging, and surveillance of patients with lymphoma. We also illustrate a breadth of benign and malignant entities with similar imaging features confounding the diagnosis of renal lymphoma, emphasizing the role of percutaneous image-guided biopsy. Understanding the spectrum of appearances of renal lymphoma and recognizing the overlapping entities will help radiologists improve diagnostic confidence and accuracy.

Polyoma BK Virus in Kidney Transplant Recipients: Screening, Monitoring, and Management

Polyomavirus BK virus (BKPyV) infection is an important complication of kidney transplantation and allograft failure. The prevalence of viremia is 10%-15%, compared with BK-associated nephropathy (BKPyVAN) at 3%-5%. Given that there are no effective antiviral prophylaxis or treatment strategies for BKPyVAN, active screening to detect BKPyV viremia is recommended, particularly during the early posttransplant period. Immunosuppression reduction to allow viral clearance may avoid progression to severe and irreversible allograft damage. The frequency and duration of screening are highly variable between transplant centers because the evidence is reliant largely on observational data. While the primary treatment goals center on achieving viral clearance through immunosuppression reduction, prevention of subsequent acute rejection, premature graft loss, and return to dialysis remain as major challenges. Treatment strategies for BKPyV infection should be individualized to the recipient's underlying immunological risk and severity of the allograft infection. Efficacy data for adjuvant therapies including intravenous immunoglobulin and cidofovir are sparse. Future well-powered and high-quality randomized controlled trials are needed to inform evidence-based clinical practice for the management of BKPy infection.

Computed Tomography-guided Core Needle Biopsy for Renal Tumors: A Review

Small renal tumors are sometimes challenging to diagnose accurately through imaging alone, and image-guided biopsies are performed when histological diagnoses are needed. Although ultrasound guidance is usually chosen for renal tumor biopsies, computed tomography guidance is preferred for selected cases; e.g., obese patients or when the target is undetectable by ultrasound (as those in the upper pole). In the 14 recently published studies covering ≥50 procedures, computed tomography-guided renal tumor biopsies had a wide range diagnostic yield (67.4%-97.4%). Complications often occurred; however, most were minor and asymptomatic. No biopsy-related deaths and tumor seeding occurred. This study aimed to review the advantages and disadvantages, procedure techniques, diagnostic yields, and complications of core needle biopsies for renal tumors under computed tomography guidance.

Diffusion-Weighted Imaging and Mapping of T1 and T2 Relaxation Time for Evaluation of Chronic Renal Allograft Rejection in a Translational Mouse Model

We hypothesized that multiparametric MRI is able to non-invasively assess, characterize and monitor renal allograft pathology in a translational mouse model of chronic allograft rejection. Chronic rejection was induced by allogenic kidney transplantation (ktx) of BALB/c-kidneys into C57BL/6-mice (n = 23). Animals after isogenic ktx (n = 18) and non-transplanted healthy animals (n = 22) served as controls. MRI sequences (7T) were acquired 3 and 6 weeks after ktx and quantitative T1, T2 and apparent diffusion coefficient (ADC) maps were calculated. In addition, in a subset of animals, histological changes after ktx were evaluated. Chronic rejection was associated with a significant prolongation of T1 time compared to isogenic ktx 3 (1965 ± 53 vs. 1457 ± 52 ms, p < 0.001) and 6 weeks after surgery (1899 ± 79 vs. 1393 ± 51 ms, p < 0.001). While mean T2 times and ADC were not significantly different between allogenic and isogenic kidney grafts, histogram-based analysis of ADC revealed significantly increased tissue heterogeneity in allografts at both time points (standard derivation/entropy/interquartile range, p < 0.05). Correspondingly, histological analysis showed severe inflammation, graft fibrosis and tissue heterogeneity in allogenic but not in isogenic kidney grafts. In conclusion, renal diffusion weighted imaging and mapping of T2 and T1 relaxation times enable detection of chronic renal allograft rejection in mice. The combined quantitative assessment of mean values and histograms provides non-invasive information of chronic changes in renal grafts and allows longitudinal monitoring.

Quantitative image features from radiomic biopsy differentiate oncocytoma from chromophobe renal cell carcinoma

Purpose: To differentiate oncocytoma and chromophobe renal cell carcinoma (RCC) using radiomics features computed from spherical samples of image regions of interest, "radiomic biopsies" (RBs). Approach: In a retrospective cohort study of 102 CT cases [68 males (67%), 34 females (33%); mean age ± SD, 63 ± 12    years ], we pathology-confirmed 42 oncocytomas (41%) and 60 chromophobes (59%). A board-certified radiologist performed two RB rounds. From each RB round, we computed radiomics features and compared the performance of a random forest and AdaBoost binary classifier trained from the features. To control for overfitting, we performed 10 rounds of 70% to 30% train-test splits with feature-selection, cross-validation, and hyperparameter-optimization on each split. We evaluated the performance with test ROC AUC. We tested models on data from the other RB round and compared with the same round testing with the DeLong test. We clustered important features for each round and measured a bootstrapped adjusted Rand index agreement. Results: Our best classifiers achieved an average AUC of 0.71 ± 0.024 . We found no evidence of an effect for RB round ( p = 1 ). We also found no evidence for a decrease in model performance when tested on the other RB round ( p = 0.85 ). Feature clustering produced seven clusters in each RB round with high agreement ( Rand index = 0.981 ± 0.002 , p < 0.00001 ). Conclusions: A consistent radiomic signature can be derived from RBs and could help distinguish oncocytoma and chromophobe RCC.

Light Chain Deposition Disease Diagnosed Using Computed Tomography-Guided Kidney Biopsy

Light chain deposition disease (LCDD) is characterized by the deposition of monoclonal immunoglobulin light chains in the kidney, which can cause end-stage kidney disease if not treated. While kidney biopsy is required for definitive diagnosis, choosing an appropriate biopsy method may be problematic when examining patients with atrophic kidneys. A 66-year-old Japanese man was referred to our institution with a three-month history of leg edema. Clinical investigations revealed proteinuria levels of 7.5 g/day. CT-guided percutaneous kidney biopsy was selected as the biopsy method because atrophic kidneys were poorly visualized on ultrasonography. Kidney biopsy revealed nodular glomerulosclerosis, exclusive deposition of the κ chain, and powdery electron-dense deposits, all of which were indicative of LCDD. Bence-Jones protein was detected in the urine. The patient also had an abnormal serum-free light chain ratio. Bone marrow biopsy revealed multiple myeloma; therefore, the patient was diagnosed to have LCDD with multiple myeloma. The patient was treated with daratumumab, bortezomib, cyclophosphamide, and dexamethasone. After a one-year follow-up, the patient had hematological and renal responses without any treatment-related adverse effects. Our case demonstrates the effectiveness of daratumumab as a treatment for LCDD with nephrotic-range proteinuria. Additionally, we suggest that CT-guided kidney biopsy should be considered as a diagnostic test in patients with kidney atrophy when making a definitive diagnosis.

Active bleeding after kidney biopsy: Successful ultrasound-guided direct thrombin embolization into the cortical fistula

A 27-year-old man, previously diagnosed with IgA nephropathy, was referred for native kidney biopsy. After the procedure, the patient presented active bleeding revealed by Doppler and contrast-enhanced ultrasonography at the biopsy site. Successful embolization of the cortical fistula, the focus of bleeding, was achieved using ultrasound-guided thrombin injection and confirmed by Doppler ultrasonography, contrast-enhanced ultrasonography, and CT angiography. This case report shows that contrast-enhanced ultrasonography is useful for detecting active bleeding after a solid organ biopsy. Moreover, ultrasound-guided thrombin embolization is a safe and minimally invasive treatment and an alternative to angiography-guided embolization.

Diagnostic renal mass biopsy is associated with individual categories of PADUA and RENAL nephrometry scores: Analysis of diagnostic and concordance rates with surgical resection

BACKGROUND

Renal mass biopsy (RMB) is a safe and accurate method for diagnosis and clinical management of renal masses. However, the non-diagnostic rate is a limiting factor. We tested the hypothesis that imaging characteristics and anatomic complexity of the mass may impact RMB diagnostic outcome using the preoperative aspects and dimensions used for an anatomical (PADUA) classification and radius-exophytic/endophytic-nearness-anterior/posterior-location (RENAL) score.

MATERIAL AND METHODS

Single institution, retrospective study of 490 renal masses from 443 patients collected from 2001 to 2018. Outcome measurements include (1) diagnostic and concordance rates amongst RMB types and RMB with surgical resection specimens; (2) association between diagnostic RMB and anatomical complexity of renal masses. The analysis was conducted in unselected masses and small renal masses (SRMs).

RESULTS

RMB was performed by fine needle aspiration (FNA), core needle biopsy (CNB), or both (FNA+CNB). Non-diagnostic rate was significantly higher for FNA compared to CNB and FNA+CNB in both unselected and SRMs. Subset analysis in the FNA+CNB group showed similar diagnostic rates for FNA and CNB. In unselected masses, specificity for FNA, CNB, and FNA+CNB was 100%. Sensitivity was higher for CNB (90.1%, P = 0.002) and FNA+CNB (96.3%, P = 0.004) compared to FNA (66.7%). For unselected masses, endophytic growth predicted a non-diagnostic CNB. R.E.N.A.L location entirely between the polar lines (central) and entirely above the upper polar line predicted a diagnostic CNB. Sonography-guidance predicted a diagnostic FNA. For SRMs, non-diagnostic CNB was associated with endophytic growth, while diagnostic CNB was associated with renal sinus invasion and operator experience. More cystic masses were sampled by FNA, but diagnostic results were similar for FNA and CNB.

CONCLUSIONS

Endophytic growth consistently predicted a non-diagnostic CNB in unselected and SRMs, whereas sonography-guidance predicted a diagnostic FNA. Cystic masses could be adequately sampled by FNA.

Image-guided core biopsy of 2-cm or smaller renal tumors

PURPOSE

The purpose of this study was to retrospectively evaluate diagnostic yield, risk factors for diagnostic failure, and safety of image-guided core biopsy of renal tumors≤2cm.

MATERIALS AND METHODS

Eighty-four biopsies of 84 renal tumors (mean size, 1.5±0.4[SD] cm; range, 0.6-2.0cm) from 84 patients (53 men, 31 women; mean age, 61.7±12.7 [SD] years; age range, 34-87 years) were included. All adverse events (AEs) were evaluated based on the CIRSE classification. The 84 procedures were classified as diagnostic or nondiagnostic. Multiple variables related to the patients, tumors, and procedures were assessed to identify variables associated with diagnostic failure.

RESULTS

All 84 biopsies (100%) were technically successful, defined as penetration of the target and acquisition of some specimens. Eighty (80/84; 95.2%) biopsy procedures were diagnostic and four (4/84; 4.8%) procedures were nondiagnostic. Among 80 diagnosed renal tumors, 71/80 (88.8%) tumors were malignant (49 clear cell renal cell carcinomas [RCCs], 14 papillary RCCs, 3 chromophobe RCCs, 3 metastatic renal cancers, 1 lymphoma, and 1 unclassified RCC) and 9/80 (11.2%) lesions were benign (5 angiomyolipomas, 3 oncocytomas, and 1 inflammatory lesion). No significant differences existed in any variables between the two groups. A total of 57 (57/84; 67.9%) procedures resulted in 56 Grade 1, 2 Grade 2, and 1 Grade 3 AEs.

CONCLUSION

Image-guided biopsy of renal tumors≤2cm is safe and has a high diagnostic yield.

Imaging guided percutaneous renal biopsy: do it or not?

Since its first reported application, renal biopsy became an important part of the diagnostic algorithm, considered advantages and risks, to better manage therapeutic options. The biopsy can be performed with different techniques (open, laparoscopic, transjugular, transurethral and percutaneous). Currently, the percutaneous approach is the modality of choice. Percutaneous biopsy can be performed under CT or US guidance, but critical benefits and disadvantages have to be considered. Core needle biopsy is usually preferred to fine-needle aspiration because of the sample quality, usually obtaining multiple cores, especially in heterogeneous tumors. Principal complications are hematuria (1-10%), perinephric hematoma (10-90%), pneumothorax (0,6%), clinically significant pain (1,2%).

Renal biopsy under augmented reality guidance

Kidney biopsies are currently performed using preoperative imaging to identify the lesion of interest and intraoperative imaging used to guide the biopsy needle to the tissue of interest. Often, these are not the same modalities forcing the physician to perform a mental cross-modality fusion of the preoperative and intraoperative scans. This limits the accuracy and reproducibility of the biopsy procedure. In this study, we developed an augmented reality system to display holographic representations of lesions superimposed on a phantom. This system allows the integration of preoperative CT scans with intraoperative ultrasound scans to better determine the lesion's real-time location. An automated deformable registration algorithm was used to increase the accuracy of the holographic lesion locations, and a magnetic tracking system was developed to provide guidance for the biopsy procedure. Our method achieved a targeting accuracy of 2.9 ± 1.5 mm in a renal phantom study.

Computed Tomography-Guided Kidney Transplant Biopsy Outcomes: A Single-Center Experience

OBJECTIVES

Percutaneous kidney transplant biopsy is typically performed using ultrasonographic guidance; computed tomography is an alternative modality used to obtain kidney allografttissuewhen ultrasonographyguided percutaneous kidney transplant biopsy is technically challenging. Studies examining postbiopsy outcomes in kidney transplant patients using a computed tomography-guided approach are scarce. Our goal was to reportthe incidence of nonsevere and severe complications in computed tomographyguided percutaneous kidney transplant biopsies and the potential risk factors.

MATERIALS AND METHODS

We retrospectively reviewed computed tomography-guided percutaneous kidney transplant biopsies in patients undergoing work-up for kidney allograft rejection between 2013 and 2017. Demographics, comorbidities, laboratory data, history of antiplatelet and/or anticoagulant use, and complications were assessed.

RESULTS

: During the study period, 28 patients underwent computed tomography-guided percutaneous kidney transplant biopsies; mean age was 57.5 ± 15.5 years, and 12 (43%)werewomen.Twenty-three patients (82%) were obese, with a body mass index greater than 30 kg/m². Our cohort of kidney transplant recipients included 21 (75%) from deceased donors and 7 (25%) from living-related donors. At the time of biopsy, 6 patients (21%) had elevated blood pressure (defined as > 160/90 mm Hg). One patient had severe complications, which included a significant decrease in hemoglobin requiring transfusion and a perinephric hematoma with worsening renal function. This was a morbidly obese patient whose blood pressure was elevated at the time of biopsy with a platelet count of 93 × 10³/mm³ and international normalized ratio of 1.21.

CONCLUSIONS

A computed tomography-guided percutaneous kidney transplant biopsy is a safe and effective alternative to obtain kidney tissue in the obese population and is associated with low rates of complications. In this study, we highlighted the need to achieve adequate blood pressure control and assess bleeding risk factors, such as platelet count and international normalized ratio, prior to biopsy.

Towards an Advanced Virtual Ultrasound-guided Renal Biopsy Trainer

Ultrasound (US)-guided renal biopsy is a critically important tool in the evaluation and management of non-malignant renal pathologies with diagnostic and prognostic significance. It requires a good biopsy technique and skill to safely and consistently obtain high yield biopsy samples for tissue analysis. This project aims to develop a virtual trainer to help clinicians to improve procedural skill competence in real-time ultrasound-guided renal biopsy. This paper presents a cost-effective, high-fidelity trainer built using low-cost hardware components and open source visualization and interactive simulation libraries: interactive medical simulation toolkit (iMSTK) and 3D Slicer. We used a physical mannequin to simulate the tactile feedback that trainees experience while scanning a real patient and to provide trainees with spatial awareness of the US scanning plane with respect to the patient's anatomy. The ultrasound probe and biopsy needle were modeled using commonly used clinical tools and were instrumented to communicate with the simulator. 3D Slicer was used to visualize an image sliced from a pre-acquired 3-D ultrasound volume based on the location of the probe, with a realistic needle rendering. The simulation engine in iMSTK modeled the interaction between the needle and the virtual tissue to generate visual deformations on the tissue and tactile forces on the needle which are transmitted to the needle that the user holds. Initial testing has shown promising results with respect to quality of simulated images and system responsiveness. Further evaluation by clinicians is planned for the next stage.

Basic Interventional Procedures: Practice Essentials

There has been an increasing demand in image-guided minimally invasive procedures and these have become an integral part of present-day clinical practice. Basic interventional radiology (IR) procedures have greatly reduced the need for invasive procedures for sampling as well as treating conditions like abscess and fluid collections. Owing to their minimally invasive nature, most of these procedures may be performed on the outpatient patients as daycare procedures. Some of these procedures in critically ill patients may be lifesaving. Basic interventional radiology (IR) procedures consist of image-guided fine-needle aspiration cytology and biopsy, tru-cut (core) biopsy, needle aspiration/drainage and percutaneous catheter drainage. This review aims to provide practice requisites for basic IR procedures.

Retroperitoneal Tumor: A Silent Trespasser - Role of Image-Guided Fine-Needle Aspiration Cytology with Histopathological Correlation in Early Diagnosis

OBJECTIVE

Retroperitoneal lesions present a great diagnostic challenge. Here we analyze the spectrum of retroperitoneal lesions and the utility of cytohistopathological correlation in early diagnosis.

STUDY DESIGN

This 7-year study was undertaken in 338 patients with a retroperitoneal mass (kidney/adrenal/ pancreas/retroperitoneal lymph node, or soft tissue origin). In a prospective analysis, 81 patients underwent image-guided fine-needle aspiration cytology (FNAC) and 70 of the 81 underwent Tru-cut biopsy/histopathological evaluation. Clinical, radiological, and pathological details of 257 patients were retrieved from institutional records for retrospective analysis. A total of 119 patients, i.e., 70 in the prospective analysis and 49 in the retrospective analysis, had cytohistopathological correlation.

RESULTS

Of the 338 cases, 88.4% were malignant (n = 274), 2.6% were benign (n = 8), 9% were nonneoplastic (n = 28), and 9% were inadequate (n = 28). Most were renal in origin (n = 106; 34.2%), followed by retroperitoneal soft tissue (n = 96; 31%). The most common nonneoplastic lesion was tubercular lymphadenitis (42.85%) and the most common benign lesion was paraganglioma (42.85%). The most common malignancy was renal cell carcinoma (21.16%), followed by Wilms' tumor (13.86%). In infancy and early childhood, Wilms' tumor, neuroblastoma, and germ cell tumor were the most common malignancies, while in middle age it was renal cell carcinoma, followed by pancreatic adenocarcinoma, and in the elderly age group it was metastatic carcinoma. Most malignancies were noted in the 5th to 6th decades. The overall sensitivity, specificity, and diagnostic accuracy of image-guided FNAC was 98.02, 72.22, and 94.12%, respectively.

CONCLUSION

Image-guided FNAC is highly sensitive and specific for early diagnosis of an otherwise silent retroperitoneal mass. It saves patient from meticulous surgical procedures for diagnostic reasons and allows more rational planning of management. Knowledge of the distribution of tumors by age group helps to narrow down differential diagnoses.

Comparing laparoscopic and percutaneous renal biopsy for diagnosing native kidney disease: A matched pair analysis

BACKGROUND

Percutaneous renal biopsy is a well-established diagnostic procedure in patients with underlying medical renal disease. Aim of this study is to compare the adequacy of the biopsy material, the diagnostic yield, and the complication rates of the trans-peritoneal laparoscopic approach and the image-guided percutaneous approach to renal biopsy in the diagnosis of native kidney disease.

METHODS

We performed a matched-pair analysis matching 1:3 40 patients who underwent trans-peritoneal laparoscopic renal biopsy to 120 patients who underwent percutaneous renal biopsy in the same years. Patients were retrospectively analyzed. Differences in adequacy of biopsy material (i.e. number of glomeruli, continuous), diagnostic yield (categorical) and postoperative complications across the two groups were assessed using Wilcoxon Rank sum or χ² test.

RESULTS

Laparoscopic biopsy was associated with a higher number of harbored glomeruli (median 50, IQR 20-77) compared to the percutaneous approach (median 10, IQR 7-15), P<0.001. Adequate biopsies containing at least ten glomeruli were obtained in a significantly higher percentage of patients in the laparoscopic group versus the percutaneous group (92.5% vs. 57.1%, P<0.001). The laparoscopic approach was also associated with a significantly higher diagnostic yield than the percutaneous approach (82.5% vs. 63.5%, P=0.027). Patients who underwent laparoscopic biopsy had no perioperative or postoperative complications, resulting in a significantly lower complication rate than percutaneous biopsy (0% vs. 4%, P<0.001), particularly in the need for transfusion for post-procedure bleeding (0% vs. 1.8%, P<0.001).

CONCLUSIONS

In this retrospective matched-pair analysis comparing patients undergoing renal biopsy for medical kidney disease, trans-peritoneal laparoscopic renal biopsy was safer and more effective for the diagnosis of medical renal diseases compared to percutaneous renal biopsy. Prospective trials with a good follow-up are needed to define the best candidate for each approach.

LEVEL OF EVIDENCE

4.

Angiographic management of percutaneous renal procedure-related bleeding: A single-center experience

OBJECTIVES

To present the radiological and clinical results of transcatheter arterial embolization in patients with active bleeding after percutaneous renal procedures.

METHODS

A total of 79 consecutive patients who underwent angiography for percutaneous renal procedure-related bleeding were included in the present retrospective analysis. Patient characteristics, angiographic management and clinical outcomes were analyzed.

RESULTS

On angiography, bleeding foci were observed in 81.0% of the patients (64/79), all of whom underwent transcatheter arterial embolization. Among the 15 patients (19.0%) with negative angiographic findings, empirical transcatheter arterial embolization was carried out in six patients (40.0%). The technical success rate in 64 patients with positive angiographic findings was 100%, and the clinical success rate in 70 patients who underwent transcatheter arterial embolization was 85.7% (60/70). A total of 14.3% (10/70) of patients with clinical failure underwent repeat transcatheter arterial embolization and all achieved clinical recovery. There were no major complications. There was no statistical difference in estimated glomerular filtration rate values before the percutaneous renal procedure and those measured 7 days after transcatheter arterial embolization (43.4 ± 24.4 to 44.6 ± 25.1 mL/min/1.73 m² ; P = 0.189). Clinical failure was not associated with age, sex, type of renal procedures, bleeding tendency, presence of active bleeding on angiography, latency time and embolic agents used (P > 0.05).

CONCLUSIONS

Transcatheter arterial embolization is a safe and effective method of treating percutaneous renal procedure-related bleeding without renal function deterioration.

[Biopsies of kidney lesions: when and how?]

The demand for image-guided renal biopsy has increased due to the better detection of renal lesions; however, despite modern imaging techniques many small renal tumors cannot be classified as benign because they cannot be differentiated from renal cell carcinoma. Ultrasound and computed tomography (CT)-guided kidney biopsy is a safe and accurate method in the diagnostics of renal lesions and can be helpful in the selection of new ablative and pharmaceutical forms of treatment and avoid unnecessary operations. This article describes the clinical indications for an image-guided biopsy and discusses factors which should be considered when performing a biopsy.

Image-Guided Renal Interventions

Image-guided renal biopsies have an increasing role in clinical practice. Renal mass and renal parenchymal biopsy indications, techniques, and other clinical considerations are reviewed in this article. Image-guided renal mass ablation shows significant promise and increasing clinical usefulness as more studies demonstrate its safety and efficacy. Renal mass ablation indications, techniques, and other considerations are also reviewed.

Contrast-enhanced ultrasound (CEUS) in abdominal intervention

The introduction of ultrasound contrast agents has rendered contrast-enhanced ultrasound (CEUS) a valuable complementary technique to address clinically significant problems. This pictorial review describes the use of CEUS guidance in abdominal intervention and illustrates such application for a range of clinical indications. Clinical application of CEUS discussed include commonly performed abdominal interventional procedures, such as biopsy, drainage, nephrostomy, biliary intervention, abdominal tumor ablation and its subsequent monitoring, and imaging of vascular complications following abdominal intervention. The purpose of this article is to further familiarize readers with the application of CEUS, particularly its specific strength over alternative imaging modalities, in abdominal intervention.

Diffuse Renal Cortical Hemorrhage in the Setting of Subcapsular Hematoma: Diagnosis and Treatment with Embolization

PURPOSE

To describe radiologic findings, embolization technique, and clinical outcomes in patients with renal subcapsular hematoma and diffuse cortical hemorrhage.

MATERIALS AND METHODS

Ten patients with renal subcapsular hematoma and diffuse cortical hemorrhage were reviewed. Nine of the 10 had undergone procedures (nephrostomy, n = 4; biopsy, n = 4; embolization of a cerebral aneurysm, n = 1) and 1 patient was receiving oral anticoagulation. Computed tomography (CT), angiography, and embolization of bleeding sites were performed in all patients.

RESULTS

CT and angiography revealed subcapsular hematoma with diffuse cortical hemorrhage at the level of the interlobar and/or arcuate branches. Total embolization of intrarenal arterial branches was required in 3 patients. Partial embolization, which also resulted in permanent functional loss, was required in 4. The functional loss was likely caused by the embolization procedure and the underlying renal disease. In these 4 patients, renal failure was demonstrated by scintigraphy in 3 cases and based on the need to start chronic hemodialysis in 1 case. In the remaining three patients, embolization did not compromise renal function.

CONCLUSIONS

Diffuse cortical hemorrhage unrelated to the site of puncture may be seen in some cases of subcapsular hematoma. The cause is likely the laceration of transcortical capsular arteries secondary to enlargement of the subcapsular hematoma. In the present case series, embolization achieved hemorrhage control, but loss of renal function was observed in patients with underlying renal disease.

Future of the Renal Biopsy: Time to Change the Conventional Modality Using Nanotechnology

At the present time, imaging guided renal biopsy is used to provide diagnoses in most types of primary and secondary renal diseases. It has been claimed that renal biopsy can provide a link between diagnosis of renal disease and its pathological conditions. However, sometimes there is a considerable mismatch between patient renal outcome and pathological findings in renal biopsy. This is the time to address some new diagnostic methods to resolve the insufficiency of conventional percutaneous guided renal biopsy. Nanotechnology is still in its infancy in renal imaging; however, it seems that it is the next step in renal biopsy, providing solutions to the limitations of conventional modalities.

Renal Tumor Biopsy Technique

Objective:

To review hot issues and future direction of renal tumor biopsy (RTB) technique.

Data Sources:

The literature concerning or including RTB technique in English was collected from PubMed published from 1990 to 2015.

Study Selection:

We included all the relevant articles on RTB technique in English, with no limitation of study design.

Results:

Computed tomography and ultrasound were usually used for guiding RTB with respective advantages. Core biopsy is more preferred over fine needle aspiration because of superior accuracy. A minimum of two good-quality cores for a single renal tumor is generally accepted. The use of coaxial guide is recommended. For biopsy location, sampling different regions including central and peripheral biopsies are recommended.

Conclusion:

In spite of some limitations, RTB technique is relatively mature to help optimize the treatment of renal tumors.

Ultrasound-Guided Percutaneous Core Needle Biopsy of Abdominal Viscera: Tips to Ensure Safe and Effective Biopsy

Ultrasound-guided percutaneous core needle biopsy (USPCB) is used extensively in daily clinical practice for the pathologic confirmation of both focal and diffuse diseases of the abdominal viscera. As a guidance tool, US has a number of clear advantages over computerized tomography or magnetic resonance imaging: fewer false-negative biopsies, lack of ionizing radiation, portability, relatively short procedure time, real-time intra-procedural visualization of the biopsy needle, ability to guide the procedure in almost any anatomic plane, and relatively lower cost. Notably, USPCB is widely used to retrieve tissue specimens in cases of hepatic lesions. However, general radiologists, particularly beginners, find USPCB difficult to perform in abdominal organs other than the liver; indeed, a full understanding of the entire USPCB process and specific considerations for specific abdominal organs is necessary to safely obtain adequate specimens. In this review, we discuss some points and techniques that need to be borne in mind to increase the chances of successful USPCB. We believe that the tips and considerations presented in this review will help radiologists perform USPCB to successfully retrieve target tissue from different organs with minimal complications.

CT-guided Native Medical Renal Biopsy: Cortical Tangential versus Non-Tangential Approaches-A Comparison of Efficacy and Safety

Purpose To review a single-center experience with the cortical tangential approach during computed tomography (CT)-guided native medical renal biopsy and to evaluate its efficacy and safety compared with those of a non-cortical tangential approach. Materials and Methods This retrospective study received institutional review board approval, with a waiver of the HIPAA requirement for informed consent. The number of cores, glomeruli, and complications were reviewed in 431 CT-guided medical renal biopsies performed between July 2007 and September 2015. A biopsy followed a cortical tangential approach if the needle path was parallel to the renal cortical surface, at a depth closer to the renal capsule than the renal pelvic fat. A sample was considered adequate if the biopsy yielded at least 10 glomeruli at light microscopy, one glomerulus at immunofluorescence microscopy, and one glomerulus at electron microscopy. The χ² test, the t test, the Mann-Whitney test, and logistic regression modeling of sample adequacy were performed. Results One hundred fifty-six (36%) of 431 biopsies were performed with the cortical tangential approach. More cores were obtained for the cortical tangential group (2.6 vs 2.4, P = .001); biopsy needle gauge was not significantly different (P = .076). More adequate samples were obtained in the cortical tangential group (66.7% vs 49.8%, P = .001), with more glomeruli (23 vs 16, P = .014). Results were significant after controlling for needle gauge and number of cores (P = .008). The cortical tangential group had fewer complications (1.9% vs 7.3%, P = .018). Conclusion The cortical tangential approach, when applied to CT-guided native medical renal biopsies, results in higher rates of sample adequacy and lower rates of postprocedural complications. ^© RSNA, 2016.

Diagnostic modalities

The incidental detection of small renal masses on imaging undertaken to evaluate unrelated symptoms or conditions is an increasingly common occurrence. Accurate imaging characterisation is fundamental to determining optimum patient management. The goals of imaging small renal masses include determining whether a lesion is solid or cystic, if there are signs of biological aggressiveness and whether the lesion is likely benign or malignant. The current imaging practices and the evidence supporting the use of different imaging modalities for the characterisation of small renal masses are discussed. CT remains the primary imaging modality and is able to classify most masses into surgical or non-surgical lesions. MRI and contrast enhanced ultrasound are most often employed to problem solve in lesions deemed indeterminate on contrast enhanced CT or for patients in which CECT is contraindicated. Percutaneous biopsy should be considered in lesions that remain indeterminate after initial imaging investigations. Given the central role of imaging in the management of small renal masses, all multidisciplinary team members involved in renal cancer care should have an understanding of the performance of the different imaging modalities.

Kidney, Ureter, and Bladder Biopsy

Percutaneous urologic biopsy is a safe and effective technique and can comprise a significant proportion of the daily workload of the interventional radiologist. This article discusses the indications and rationale for the performance of renal, ureter, and bladder biopsy as well as the approach to performing such biopsies, pitfalls, and potential complications.

Single-port retroperitoneal renal biopsy using standard urological instruments

OBJECTIVE

To describe the surgical technique and initial experience with a single-port retroperitoneal renal biopsy (SPRRB).

MATERIALS AND METHODS

Between January and April 2013, five children underwent SPRRB in our hospital. A single 1.5 cm incision was performed under the 12th rib at mid-axillary line, and an 11 mm trocar was inserted. A nephroscope was used to identify the kidney and dissect the perirenal fat. After lower pole exposure, a laparoscopic biopsy forceps was introduced through the nephroscope working channel to collect a renal tissue sample.

RESULTS

SPRRB was successfully performed in five children. The mean operative time was 32 minutes, and mean estimated blood loss was less than 10 mL. The hospital stay of all patients was two days because they were discharged in the second postoperative day, after remaining at strict bed rest for 24 hours after the procedure. The average number of glomeruli present in the specimen was 31.

CONCLUSION

SPRRB is a simple, safe and reliable alternative to open and videolaparoscopic approaches to surgical renal biopsy.

Factors that can minimize bleeding complications after renal biopsy

Renal biopsy is a very important diagnostic tool in the evaluation of renal diseases. However, bleeding remains to be one of the most serious complications in this procedure. Many new techniques have been improved to make it safer. The risk factors and predictors of bleeding after percutaneous renal biopsy have been extensively reported in many literatures, and generally speaking, the common risk factors for renal biopsy complications focus on hypertension, high serum creatinine, bleeding diatheses, amyloidosis, advanced age, gender and so on. Our primary purpose of this review is to summarize current measures in recent years literature aiming at minimizing the bleeding complication after the renal biopsy, including the drug application before and after renal biopsy, operation details in percutaneous renal biopsies, nursing and close monitoring after the biopsy and other kinds of biopsy methods.

A modified technique for real time ultrasound guided pediatric percutaneous renal biopsy: the angled tangential approach

AIM

Pediatric renal biopsy may result in serious hemorrhagic complications, requiring additional diagnostic procedures, blood transfusion, vascular interventions, and prolongation of hospitalization. The aim of the present study was to propose the angled tangential approach technique for real-time ultrasound-guided pediatric percutaneous renal biopsy.

METHODS

A retrospective analysis of 166 percutaneous biopsies from June 2004 to May 2009 was performed. Patients' medical records, pathology results, and complications were reviewed.

RESULTS

No major complications were seen in the study group. The most frequently occurring minor complication was macroscopic hematuria, which occurred at the rate of 9.6%. Hematoma was detected in three cases and regressed spontaneously in all cases.

CONCLUSIONS

The angled tangential approach is a safe technique and an alternative option in pediatric percutaneous renal biopsies.