Sonography in Benign and Malignant Renal Masses

Contrast-enhanced ultrasound (CEUS) reliably rules out neoplasm in developmental renal pseudotumor

BACKGROUND

Renal pseudotumors appear as benign cortical hypertrophies and are typically assessed by contrast-enhanced computed tomography or magnetic resonance imaging to rule out malignancy.

PURPOSE

To investigate whether contrast-enhanced ultrasound (CEUS) can rule out renal neoplasm and thus potentially reduce cross-sectional imaging and further follow-up in these patients.

MATERIAL AND METHODS

Thirty-two patients with presumption of developmental renal pseudotumor on CEUS between June 2011 and July 2019 were retrospectively analyzed. All patients were examined with a standardized renal US protocol including B-mode, color-coded duplex sonography (CCDS), and CEUS by an experienced radiologist (EFSUMB level 3). Images were retrospectively interpreted in consensus by two highly experienced radiologists. Histopathological reports, cross-sectional imaging findings, and clinical course (treatment response, long-term imaging follow-up) were defined as standard of reference.

RESULTS

CEUS correctly identified 8/9 neoplastic lesions and missed one oncocytoma within the 32 included patients. Irregular vessel structure (88.9% vs. 13.0%, P = 0.007) and hyperenhancement (66.6% vs. 17.4%, P = 0.031) on CEUS were more common in neoplasm compared to developmental pseudotumors reaching statistical significance. Compared with the standard of reference, CEUS had 89% sensitivity (95% confidence interval [CI] 57-98), 96% specificity (95% CI 80-99), a positive predictive value of 89% (95% CI 57-98), and a negative predictive value of 96% (95% CI 79-99) for ruling out renal malignancy in developmental pseudotumors.

CONCLUSION

CEUS is a safe and fast method to rule out neoplasm in the diagnostic work-up of renal pseudotumors. In conjunction with B-mode and CCDS, CEUS has the potential to reduce further (invasive) diagnostic procedures.

Prospective Comparison of Contrast-Enhanced Ultrasound and Magnetic Resonance Imaging to Computer Tomography for the Evaluation of Complex Cystic Renal Lesions

OBJECTIVE

To prospectively evaluate the diagnostic accuracy of contrast enhanced ultrasound (CEUS) and MRI compared to computed tomography (CT) as the current gold standard for the characterization of cystic renal lesions using the Bosniak classification.

METHODS

Between July 2014 and October 2017 we prospectively enrolled patients with cystic renal lesions. Based on the Bosniak classification of complex renal lesions (≥BII-F) we evaluated the accuracy of observed agreement by Cohen's Kappa coefficient and calculated sensitivity, specificity, positive and negative predictive values (PPV/NPV) between the three imaging modalities CT, MRI and CEUS.

RESULTS

We evaluated 65 cystic renal lesions in 48 patients (median age 63 years, range 36-91 years; 18 females, 30 males). According to CT 29 (47%) of the cystic renal lesions were classified as complex. The agreement between CEUS and CT in the classification of complex cystic lesions was fair (agreement 50.8%, Kappa 0.31), and was excellent between MRI and CT (agreement 93.9%, Kappa 0.88). Compared to CT, CEUS and MRI had a sensitivity of 100% and 96.6%, a specificity of 33.3% and 91.7%, a PPV of 54.7% and 90.3%, and a NPV of 100% and 97.1% with an accuracy of 63.1% and 93.8% respectively.

CONCLUSION

CEUS has an excellent sensitivity and NPV and represents a promising non-invasive screening tool for renal cystic lesions. The classification of complex renal cysts based on MRI and CT scans correlated closely.

Congenital Anomalies of the Upper Urinary Tract: A Comprehensive Review

The upper urinary tract is the most common human system affected by congenital anomalies. Congenital anomalies of the kidneys and ureters comprise a wide spectrum of disorders ranging from simple variants with no clinical significance to complex anomalies that may lead to severe complications and end-stage renal disease. They may be classified as anomalies of renal form, which are subclassified as structural anomalies (eg, persistent fetal lobulation, hypertrophied column of Bertin, and dromedary hump) and fusion anomalies (eg, horseshoe kidney and pancake kidney); anomalies of renal position (eg, renal malrotation, simple renal ectopia, and crossed renal ectopia) and renal number (eg, renal agenesis and supernumerary kidney); and abnormalities in development of the urinary collecting system (eg, pyelocaliceal diverticulum, megacalycosis, ureteropelvic junction obstruction, duplex collecting system, megaureter, ectopic ureter, and ureterocele). US is usually the first imaging modality used because of its low cost, wide availability, and absence of ionizing radiation. Intravenous urography and voiding cystourethrography are also useful, mainly for characterization of the collecting system and vesicoureteral reflux. However, intravenous urography has been replaced by CT urography and MR urography. These imaging methods not only allow direct visualization of the collecting system but also demonstrate the function of the kidneys, the vascular anatomy, adjacent structures, and complications. Comprehension of congenital anomalies of the upper urinary tract is crucial for an accurate diagnosis and correct management. The authors discuss the spectrum of these anomalies, with emphasis on embryologic development, imaging findings, clinical manifestations, and complications. Online supplemental material is available for this article. ^©RSNA, 2021.

Laparoscopic Approach in Management of Renal Cell Carcinoma During Pregnancy: State of the Art

Renal cell carcinoma (RCC) is extremely rare in pregnant women. However, this is one of the most reported urologic tumors during pregnancy. The aim of this review was to evaluate RCC during pregnancy in terms of epidemiology, risk factors, diagnosis, natural history of disease, and the safety of laparoscopic approach in the management of this tumor. RCC presentation is frequently made incidentally during an ultrasonography performed for other reasons, such as hydronephrosis owing to non-neoplastic causes. The optimal time for surgery during pregnancy and the consequences of surgery on the maternal and fetal well-being are major considerations. Risks for adverse pregnancy outcomes should be explained, and the patient's decision about pregnancy termination should be considered. Ultrasound is good in diagnosing renal masses, with a sensitivity comparable to that of computed tomography only for exophytic masses larger than 3 cm. Magnetic resonance imaging is reproducible and a good, though expensive, alternative to computed tomography scans for the evaluation of renal lesions in pregnant women. Radical nephrectomy or nephron-sparing surgery are essential treatments for management of RCC. Laparoscopic surgery has historically been considered dangerous during pregnancy and avoided whenever possible, because of concerns regarding surgery-related risks, such as uterine injury, miscarriage, teratogenesis, preterm birth, and hypercapnia. The laparoscopic treatment during pregnancy is becoming increasingly accepted where feasible with low morbidity. However, the combination of a multidisciplinary approach, multi-specialty communication, and skilled surgeons can give the best possible outcomes for mother and fetus.

Contrast-enhanced ultrasound (CEUS) of cystic and solid renal lesions: a review

Incidentally detected renal lesions have traditionally undergone imaging characterization by contrast-enhanced computer tomography (CECT) or magnetic resonance imaging. Contrast-enhanced ultrasound (CEUS) of renal lesions is a relatively novel, but increasingly utilized, diagnostic modality. CEUS has advantages over CECT and MRI including unmatched temporal resolution due to continuous real-time imaging, lack of nephrotoxicity, and potential cost savings. CEUS has been most thoroughly evaluated in workup of complex cystic renal lesions, where it has been proposed as a replacement for CECT. Using CEUS to differentiate benign from malignant solid renal lesions has also been studied, but has proven difficult due to overlapping imaging features. Monitoring minimally invasive treatments of renal masses is an emerging application of CEUS. An additional promising area is quantitative analysis of renal masses using CEUS. This review discusses the scientific literature on renal CEUS, with an emphasis on imaging features differentiating various cystic and solid renal lesions.

Prospective comparison of use of contrast-enhanced ultrasound and contrast-enhanced computed tomography in the Bosniak classification of complex renal cysts

AIM

To compare contrast-enhanced ultrasound and contrast-enhanced computed tomography in the evaluation of complex renal cysts using the Bosniak classification.

METHODS

Forty-six patients with 51 complex renal cysts were prospectively examined using contrast-enhanced ultrasound and contrast-enhanced computed tomography and images analysed by two observers using the Bosniak classification. Adverse effects and patients' preference were assessed for both modalities.

RESULTS

There was complete agreement in Bosniak classification between both modalities and both observers in six cysts (11.8%). There was agreement of Bosniak classification on both modalities in 21 of 51 cysts (41.2%) for observer 1 and in 17 of 51 cysts (33.3%) for observer 2. Contrast-enhanced ultrasound gave a higher Bosniak classification than corresponding contrast-enhanced computed tomography in 31 % of cysts by both observers. Histological correlation was available in three lesions, all of which were malignant and classified as such simultaneously on both modalities by at least one observer, with remaining patients followed up with US or CT for 6-24 months. No adverse or side effects were reported following the use of US contrast, whilst 63.6% of patients suffered minor side effects following the use of CT contrast. 81.8% of the surveyed patients preferred contrast-enhanced ultrasound to contrast-enhanced computed tomography.

CONCLUSION

Contrast-enhanced ultrasound is a feasible tool in the evaluation of complex renal cysts in a non-specialist setting. Increased contrast-enhanced ultrasound sensitivity to enhancement compared to contrast-enhanced computed tomography, resulting in upgrading the Bosniak classification on contrast-enhanced ultrasound, has played a role in at best moderate agreement recorded by the observers with limited experience, but this would be overcome as the experience grows. To this end, we propose a standardised proforma for the contrast-enhanced ultrasound report. The benefits of contrast-enhanced ultrasound over contrast-enhanced computed tomography include patients' preference and avoidance of ionising radiation or nephrotoxicity, as well as lower cost.

Usefulness of diffusion tensor imaging for the differentiation between low-fat angiomyolipoma and clear cell carcinoma of the kidney

To investigate the value of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in differentiating clear-cell renal cell carcinoma (CCRCC) from low-fat renal angiomyolipomas (RAML), and to obtain the optimal b value. Fifty patients, including 30 cases of CCRCC and 20 cases of low-fat RAML, were retrospectively recruited to participate in this study. Before renal nephrectomy, all subjects underwent functional magnetic resonance imaging. For diffusion tensor imaging (DTI), a respiratory-triggered coronal echo planar imaging sequence was performed with three groups of different b values (0 and 400, 600, and 800). The ADC and FA of kidneys were analyzed and compared between different b values using analysis of variance. Receiver operation characteristic analysis was computed to assess the diagnostic performance of ADC and FA in differentiating low-fat RAML from CCRCC and to determine the optimal b values. With either CCRCC or low-fat RAML, the ADC values decreased with increased b values and significant differences were observed (F = 11.34, 23.15, P < 0.05), while the FA values were not significantly different (F = 0.28, 2.80, P > 0.05). The statistical differences in ADC, and the FA values for CCRCC and low-fat RAML were significantly different (P < 0.05). When the b value was 0.800 s/mm², the cutoff FA value for differentiating CCRCC from low-fat RAML was 0.254 × 10.3 mm²/s, and had a sensitivity of 100 %, and a specificity of 73.3 %. MR-DTI can be used to differentiate CCRCC from low-fat RAML.