Contrast-enhanced ultrasonography with microbubbles for successful screening of kidney tumours

Sir, A 70-year-old female had developed chronic kidney disease (CKD) stage 5 due to autosomal dominant polycystic kidney disease (ADPKD), for which she performed peritoneal dialysis for 1 year until her kidney transplantation. On clinical evaluation, the patient mentioned a weight loss of 2 kg in the last 6 months but with normal appetite and without asthenia. Medical examination revealed the absence of fever and no lymphadenopathies. The polycystic liver and both native polycystic kidneys were enlarged on abdominal palpation, but with no obvious change in volume versus previous check-ups. The chest X-ray, cardiac echography and dermatological and gynaecological examinations were normal. The abdominal ultrasonography revealed nodular lesions in both native polycystic kidneys, which had not been visualized before, of 1.4 cm diameter in the right and 2 cm diameter in the left kidney. Colour Doppler and power Doppler could not demonstrate arterial flow in these nodules. However, a contrast-enhanced ultrasonography (CEUS) with the use of Sono-Vue R © (BR1, Bracco, Milan, Italy), a contrast agent generating microbubbles by mixing with saline solution, showed vascularization in both lesions, suggesting solid vascularized tumours (Figure 1). Ultrasound-guided fine needle punctures of both lesions were performed. The cytology of the suspected mass in the right kidney was considered normal. The puncture of the left nodular lesion revealed papillary cells with nuclear atypia, suggesting a neoplasm. Shortly thereafter, a surgical resection of the left kidney was performed. Histopathology confirmed the diagnosis of polycystic kidney disease with the presence of a subcapsular nodule, revealing a renal cell carcinoma (RCC), Fuhrman grade 3. Further staging with head and chest CT scan, bone scintigraphy and contrast-enhanced abdominal CT scan did not demonstrate metastases. The RCC was staged as a pT1a/N0/M0, compatible with stage 1 disease. The post-operative follow-up was uneventful, and a 36-month post-operative check-up excluded tumour relapse. RCC is an infrequent complication of ADPKD. An increased incidence as compared to the general population has not clearly been demonstrated, but the disease seems to have different and more aggressive characteristics in ADPKD [1]. In general, diagnosing RCC in ADPKD is difficult and often delayed, partially because of the cystic nature of ADPKD itself. Moreover, typical symptoms for RCC such as fever, flank pain and haematuria are frequently observed in ADPKD due to other complications, like lithiasis, mass effect, cyst bleeding or cyst infection [1]. The patient in the presented case did not have any complaints or clinical aberrations, except for a moderate weight loss. The diagnosis was suspected on an ultrasound examination, confirmed by Fig. 1. Contrast-enhanced sonography after intravenous injection of 2.4 mL Sono-Vue R © in the arterial phase: the hyperechogenic spots correspond to Sono-Vue R © bubbles in vessels within the nodule and around the cyst (arrows).