Detection And Characterisation Of Renal Masses By Multidetector Computed Tomography

Abstract

PURPOSE To study the role of triphasic (unenhanced, corticomedullary and nephrographic phases) multidetector computed tomography in the detection and characterization of renal masses and to study the enhancement pattern of renal parenchyma. MATERIAL AND METHODS This was a cross sectional prospective study which included 30 consecutive cases of renal masses detected on MDCT. The post biopsy or surgical data were used as a reference standard. The patient’s age, gender and tumour size and CT features including septations, calcification, density, margins, wall irregularity were analysed. In addition enhancement pattern and enhancement in corticomedullary and nephrographic phases were analysed. Chi square test was used to assess the association between subtype of renal masses (benign or malignant) and gender, morphological features, and type of contrast enhancement. To assess the association between benign and malignant masses with respect to age, size of lesion, contrast enhancement in corticomedullary and nephrographic phases student T test was used. The diagnostic efficacy and cut off values of enhancement and degree of enhancement in various phases was determined by reciever operating characteristic (ROC) curve. The curves were analysed for cut off values to differentiate RCC from other masses. In all our analysis p value < 0.05 was significant. RESULTS The mean age of patients was 53 ± 12 years (range 26 to 82 years) which include 19 males and 11 females. 7 out of 13 (53.8 %) cases of RCC were seen in the age group of 50 to 60 years with a mean age of 60.77 years. The male to female sex XI ratio in patients with RCC was 2.2 : 1 which included 9 males and 4 females. The most common presentation of renal masses in our setting was loin pain which was seen in 25 out of 30 cases (83 %). The renal cortex demonstrated a mean attenuation of 32 ± 3 HU on unenhanced CT images. Cortical mean enhancement was 122± 15 HU during corticomeduallary phase and 137 ± 9 HU during nephrographic phase. Out of 30 cases, 14 cases were benign and 15 were malignant masses. The mean attenuation value of malignant masses in unenhanced CT images was 34.8 HU where as in benign masses was 9.2 HU. In corticomedullary phase the malignant masses showed rapid enhancement with a mean HU value of 96.53 ± 12.977 and a rapid decrease of in enhancement in following nephrographic phase with mean HU value of 72.93 ± 10.194. The ROC curve analysis showed that the cut off values with highest sensitivity and specificity for characterization of RCC from other masses was 71.5 HU in corticomedullary phase (sensitivity 100%, specificity 99.9% ), 41.5 HU in nephrographic phase (sensitivity 100% , specificity 99.8 %). CONCLUSION For characterization of renal masses the enhancement pattern and enhancement in corticomedullary and nephrographic phases are useful parameters in differentiating benign from malignant masses. The malignant masses demonstrated greater enhancement in corticomedullary phase than in nephrographic phase. The normal renal cortex demonstrated greater enhancement in nephrographic phase than in corticomedullary phase. MDCT protocol for evaluation of renal masses should include unenhanced, corticomedullary and nephrographic phases for better detection and characterization of renal massses.