Electrical impedance spectroscopy and the diagnosis of bladder pathology

Bladder pathology is usually investigated visually by cystoscopy. At present, definitive diagnosis of the bladder can be made by biopsy only, usually under general anaesthesia. This is a relatively high-cost procedure in terms of both time and money and is associated with discomfort for the patient and morbidity. Thus, we used an electrical impedance spectroscopy technique for differentiating pathological changes in the urothelium and improving cystoscopic detection. For ex vivo study, a whole or part of the patient's urinary bladder was used to take the readings less than half an hour after excision at room temperature, about 27 degrees C, using the Mk3.5 Sheffield System (2-384 kHz in 24 frequencies). In this study, 145 points (from 16 freshly excised bladders from patients) were studied in terms of their biopsy reports matching to the electrical impedance measurements. For in vivo study, a total of 106 points from 38 patients were studied to take electrical impedance and biopsy samples. The impedance data were evaluated in both malignant and benign groups, and revealed a significant difference between these two groups. The impedivity of the malignant bladder tissue was significantly higher than the impedivity of the benign tissue, especially at lower frequencies (p < 0.001). In addition, the receiver operating characteristic (ROC) curve for impedance measurements indicated that this technique could provide diagnostic information (individual classification is possible). Thus, the authors have investigated the application of bio-impedance measurements to the bladder tissue as a novel and minimally invasive technique to characterize human bladder urothelium. Therefore, this technique, especially at lower frequencies, can be a complementary method for cystoscopy, biopsy and histopathological evaluation of the bladder abnormalities.