Contrast-enhanced ultrasound (CEUS) in nephrology: Has the time come for its widespread use?

Grey-scale ultrasound has an important diagnostic role in nephrology. The absence of ionizing radiations and nephrotoxicity, rapidity of execution, excellent repeatability, the possibility to perform the test at the patient's bed and the low cost represent important advantages of this technique. Paired with real-time sonography and colour-power-Doppler contrast-enhanced ultrasound (CEUS) reduces the diagnostic gap with computed tomography (CT) and magnetic resonance (MR) and represents a major step in the evolution of clinical ultrasound. Although there are several situations in which contrast-enhanced CT and MR are indicated (i.e. evaluation of cystic or ischemic lesions, traumatisms and ablative therapies of the native and transplanted kidney), the use of CT contrast media presents a high risk of contrast-induced nephropathy (i.e. in elderly people, subjects with comorbidities and those with renal dysfunction), while gadolinium-based RM contrast agents are contraindicated for the risk of nephrogenic systemic fibrosis (i.e. in patients with severe renal dysfunction). In these situations, CEUS may be a viable alternative, however, as any technique associated with the infusion of pharmacological substances, the potential advantages and risks of CEUS should be critically evaluated. In this regard, the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) has published the guidelines for the use of CEUS for the kidney imaging and the International Contrast Ultrasound Society (ICUS) has been recently founded. The aim of this review is to offer an updated overview of the potential applications of CEUS in nephrology, reporting some indications and possible risks associated to its use.

[Contrast enhanced ultrasound in renal diseases]. / L'imaging ecocontrastografico nella patologia renale.

Contrast-enhanced ultrasound (CEUS) is one of the most interesting and promising clinical applications of imaging and ultrasound. Thanks to the absence of ionizing radiation, the lack of nephrotoxicity and low cost it has the potential to become a reference in imaging of the kidney. This review, besides providing a brief description of the proper methodology, presents possible applications of CEUS in nephrology and urology, including renal ischemia, the differential diagnosis of cystic and solid lesions, follow-up of ablative therapies, kidney trauma, kidney transplant, inflammatory diseases, ischemic nephropathy and vesicoureteral reflux.

[Ultrasound assessment in renal infections]. / L'ecografia nelle infezioni del rene.

Urinary tract infections (UTIs) are a common clinical problem, especially among women. Ultrasound assessment is indicated in case of complicated UTIs, in particular in children, pregnant women and patients with chronic kidney disease. Even though B-mode imaging alone is rarely diagnostic in case of particular kidney infections such as focal and multifocal acute pyelonephritis, Doppler and power-Doppler (PD) techniques are able to increase its sensitivity. Contrast-enhanced ultrasound (CEUS) further improves the signal-to-noise ratio, thus increasing the diagnostic accuracy of ultrasound in case of renal infectious disease. Recent studies performed on kidney transplant recipients have indeed demonstrated the high sensitivity and specificity of CEUS in diagnosing acute pyelonephritis. Moreover, ultrasonography is a useful diagnostic tool in case of kidney abscesses, emphysematous pyelonephritis, early phases of pyonephrosis, and in the evaluation and monitoring of echinococcal cysts. Ultrasound imaging is less specific in diagnosing xanthogranulomatous pyelonephritis, malacoplakia and renal tuberculosis. Finally, several authors recommend routine ultrasound assessment in HIV patients, given the high incidence of renal complications in this population of patients.

Indication to renal biopsy in DM2 patients: potential role of intrarenal resistive index.

Diagnosis of diabetic nephropathy is generally based, rather than on histological confirmation, on clinical criteria (long history of diabetes, presence of proteinuria, diabetic retinopathy or peripheral neuropathy). This clinical approach has perhaps limited utility in DM2 patients, because only 50% of them show microvascular complications in presence of nephropathy. Eco-colour-Doppler sampling of interlobular renal arteries and determination of their resistance indices (RI), was proposed in the differential diagnosis of numerous nephropathies. Aim of this study was to evaluate whether RI can be useful in discerning non-diabetic renal disease (NDRD), in order to better define indications to perform renal biopsy among proteinuric DM2 patients. All patients were submitted to: echo-colour-Doppler study of renal vessels; systematic screening for diabetic retinopathy; needle renal biopsy. RI resulted to be significantly higher in diabetic glomerulosclerosis (GSD) group as compared with NDRD group, while no significant difference was found with respect to NDRDs overlapping GSD (overlapping group). The last one showed however median RI significantly higher than isolated NDRD group. Normalized chi square Pearson for the hypothesis that RI can predict GSD resulted 0.73, while it resulted 0.43 for the hypothesis that diabetic retinopathy can predict GSD. Echo-colour-Doppler can significantly contribute, more than the other parameters proposed (nephritic or nephrotic syndrome, hematuria, diabetic retinopathy), to the identification of underlying nephropathy in DM2 subjects. In the light of our experience, it seems that the detection of RI values > 0.72 suggests the diagnosis of GSD or mixed forms, reducing the indications to renal biopsy only in presence of values < 0.72.

[Kidney transplantation and lymphomas]. / Linfomi nel trapianto renale.

Post-transplant lymphoproliferative disease (PTLD) accounts for 30% of nonskin cancers after kidney transplants. Diffuse large B-cell lymphoma is the most frequent form of PTLD. The incidence of PTLD increases over time: from 1.2% at 5 years to 6.8% at 20 years. Its late occurrence is therefore not unusual. Moreover, not only is it more frequent but also more serious than the early type because of the lower responsiveness to therapy. Epstein-Barr virus (EVB) infection is one of the most important risk factors for this disease, along with the use of antilymphocyte agents, which should be avoided in EVB-negative patients. During the first year after transplant, EBV-PCR monitoring can be helpful for the early diagnosis of EBV-associated PTLD, especially in children. No effective strategy has yet been reported for the prevention of late PTLD. Interruption of immunosuppression is the first step of therapy, but it is rarely effective by itself. Rituximab (4-8 doses) is widely used and is successful in about 50% of cases. Chemotherapy becomes essential in relapsed or refractory disease, but it significantly increases the risk of life-threatening infections. The mortality rate is around 50% 12 months after diagnosis, often due to the side effects of chemotherapy.