The enhancement of the renal cortex and medulla and the renal function: a correlative study of conventional CT scan with glomerular filtration rate / 中华放射学杂志

ABSTRACT

Objective To study the relationship between the enhancement of renal cortex and medulla during the conventional CT scans with and without contrast enhancement and the renal glornerular filtration rate (GFR). Methods Thirty five cases with unilateral posternal obstructive hydronephrosis According to GFR, the 70 kidneys were divided into 4 groups normal, slightly impaired, moderately impaired and severely impaired. In the cortical phase of enhanced CT scan, the enhancing intensity of the renal cortex and medullar was measured and following measures were calculated CTce - CTcp, CTmc -CTmp,ratio of enhancement of affected and unaffected renal cortex and medullar, and the ratio of those of each case CTac/CTnc, CTam/CTum, CTac/CTam, CTnc/CTnm, (CTac/CTam) / (CTuc/CTum). The differences of these measures in different groups were analyzed with one-way ANOVA and their correlation with GFR was studied with Pearson test. The best indicator to reflect enhancement of renal cortex was selected from these measures, and all the kidneys were divided into 4 groups accordingly strong, less strong, medium and weak. Then its consistency with GFR groups were calculated. Result (1) The differences of CTce - CTcp ( 154. 98 ± 28. 70 ), ( 122.67 ± 39. 32 ), ( 81.30 ± 32.94 ) and ( 57.60 ±23.49) HU respectively, CTac/CTuc 0. 97 ±0. 09, 0. 79 ±0. 18, 0. 64 ±0. 24 and 0. 51 ±0. 13 respectively,CTam/CTum 0. 98 ±0. 26, 0. 89 ±0. 18, 0. 86 ±0. 31 and 0. 75 ±0. 28 respectively, CTam/CTum 2. 76 ±0. 35,2. 35 ± 0. 79, 1. 83 ± 0. 68 and 1.73 ± 0. 28 respectively, CTac/CTam and ( CTac/CTam)/( CTuc/CTum) 1.00 ±0. 28,0. 89 ±0. 34, 0. 75 ±0. 17 and 0. 69 ±0. 14 respectively of different GFR groups were evident( P < 0. 05 ) . ( 2 ) Positive correlation was found between GFR and CTce-CTcp ( r = 0. 887, P <0. 01 ), CTac/CTuc ( r = 0. 872, P < 0. 01 ), CTam/CTum ( r = 0. 504, P < 0. 01 ), CTac/CTam ( r =0. 772, P < 0. 01 ), (CTac/CTam) / (CTuc/CTum) ( r = 0. 663, P < 0. 01 ). ( 3 ) Selecting CTac/CTam to reflect enhancement of renal cortex, the diseased kidneys can be divided into groups of strong ( CTac/CTam ≥2. 60); less strong (2. 20 ≤CTac/CTam <2. 60); medium ( 1.80 ≤CTac/CTam <2. 20); and weak ( CTac/CTam < 1. 80). The consistency with GFR grouping was 80. 0%. Conclusions There is significant correlation between renal cortex-related indicators and GFR, especially CTac/CTam, which can be used as the indicator of renal function in patients with unilateral or bilateral postrenal obstructive hydronephrosis. The conventional contrast enhanced CT scan can be taken as a semi-quantitative method of GFR measuring with relative low X-ray dosage compared with CT perfusion.