Presentation Authors: Christian Daniel Fankhauser, Sharon Waisbrod, Cindy Fierz, Benedikt Kranzbühler, Marian Severin Wettstein*, Daniel Eberli, Tullio Sulser, Zurich, Switzerland, Hugh Mostafid, Surrey, United Kingdom, Thomas Hermanns, Zurich, Switzerland
Introduction: The American Urological Association guideline for asymptomatic microscopic hematuria recommends that patients with asymptomatic microscopic hematuria (AMH) should undergo computerized tomography (CT) of the abdomen and pelvis for evaluation of the upper urinary tract. Although CT offers the highest diagnostic accuracy to detect upper urinary tract cancers (UTC), CT is also associated with high doses of ionizing radiation and contrast media induced allergies or nephropathy. Our aim was to evaluate the diagnostic accuracy of renal ultrasound (US) compared to CT and to assess the impact of CT findings in patients referred for initial evaluation of AMH.
Methods: All patients who underwent abdominal US and CT for AMH between 2011 and 2017 were included in this retrospective analysis. Age, gender, pack years, results of further diagnostic interventions including imaging, renal biopsy, ureterorenoscopy (URS), renal biopsy or surgery were extracted from medical charts. The ability of renal ultrasound to detect upper tract urinary cancers (UTUC) or renal cell cancers (RCC) was assessed and compared with the performance of abdominal CT as reference test.
Results: Mean age and number of pack years of all 432 included patients was 53.9 years (SD 13.7) and 25 pack years (IQR 12-40) respectively. Female patients represented 37% of the cohort. Only 3/432 ( < 1%) patients with AMH were finally diagnosed with RCC and no single patient with UTUC. Asymptomatic kidney stones were diagnosed in 60 (13.9%) patients. Renal US correctly identified 2 patients with RCC and missed to diagnose 1 patient with a RCC of 3.2cm diameter, which was detected on CT. The resulting specificity and negative predictive value (NPV) of US was 96% (95%CI 94%-98%) and 100% (95%CI 99%-100%). Follow-up imaging in 12 patients was necessary because of Bosniak IIF renal cysts of which 1 patient was upgraded to a Bosniak III cyst. False positive CT findings caused invasive interventions in 5 patients (1%). Three patients underwent diagnostic URS for suspected but not confirmed UTUC, one patient a partial nephrectomy and one patient a radical nephrectomy, of which both specimens showed benign histology.
Conclusions: The low prevalence of UTUC and RCC and the high specificity of US resulted in a high NPV to exclude UTUC and RCC in patients with AMH using US. As a consequence only a minority of patients with AMH will benefit from CT diagnostics. In contrast the vast majority of patients with AMH will be exposed to potentially harmful invasive procedures, ionizing radiation and harmful contrast media.