Teaching Case

A 67-year-old man was referred to the emergency department with gross hematuria and subacute right flank pain irradiating to the groin area. His medical history included nephrolithiasis, hypertension and smoking.

At ultrasound examination, a solid mass was detected in the right kidney (Fig. 1). CT showed a 9cm-large, exophytic mass involving the mid-lower pole of the right kidney. There was heterogeneous enhancement after intravenous contrast administration with peripheral nodular hypervascular areas and central areas of necrosis (Fig. 2a-c). During the cortico-medullary phase markedly dilated ipsilateral patent renal veins, and a tortuous network of collateral venous circulation and early and rapid filling of the main renal vein and inferior vena cava. These findings are consistent with arteriovenous fistula (AVF) (Fig. 3a-c). There was no opacification of the collecting system and tumour extension into the perirenal space. Metastatic lung nodules were also present.

´Renal cell carcinoma (RCC) is the most common renal neoplasm and accounts for about 2% of adult malignancies [1]. The classic presentation of RCC is haematuria (55%), abdominal pain (40%), and palpable abdominal mass (35%). This classic triad occurs in less than 10% of patients and at present more than 50% of RCC are diagnosed incidentally during cross-sectional imaging studies [2]. Nevertheless, occasionally there are some unusual presentations that can be misleading, including rare metastatic sites, paraneoplastic syndrome, and haemorrhage or vascular malformation like AVFs [1, 2, 3]. AVFs are an aberrant vascular shunt between the arterial and venous system due to absence of a capillary bed. The prevalence of AVFs is 0.04% in the general population and there are two types: congenital or acquired (after biopsy, trauma, and malignancy). RCC can promote some angiogenic factors that could explain the hypervascularity and the prevalence AVFs [2]. On cross-sectional imaging, differentiation between AVFs (and arteriovenous malformations) and RCC can be challenging [1]. Contrast-enhanced CT and MRI findings of AVFs are enlarged and tortuous vessels, hypertrophic draining veins during the early arterial and early enhancement of the inferior vena cava; numerous collateral circulations can be expected [2]. AVFs-related symptoms include congestive heart failure, abdominal bruit and renal hypertension [3].

The case was discussed at the multidisciplinary committee, and taking the good general condition of the patient into consideration, a total nephrectomy was performed. Pathologic evaluation of the specimen revealed a clear cell renal cell carcinoma, Fuhrman 4/4 with invasion of renal vein and perirenal fat (pT3aNxMx).