Computed tomography value of differentiating small renal massesJustina Miksaite1, Kristina Zviniene1, Algidas Basevicius1, Daimantas Milonas2

Lithuanian University of Health Sciences, Kaunas Clinics, Department of Radiology1

Lithuanian University of Health Sciences, Kaunas Clinics, Department of Urology2

Key wordsSmall renal masses, renal cell carcinoma, angiomyolipoma, oncocytoma.

Conclusions1. Evaluating all small solid renal masses, the most

valuable sign – size; malignant masses – size, enhancement characteristics and central scar; benign – egzophytic/endophytic growth.

2. Contrast enhanced CT showed high sensitivityand specificity for evaluating malignant renalmasses enhancement and specific evaluatingmass size.

3. Both reviewers ~ 70 % of cases submited thesame diagnosis.

Aims and objectiveTo determine CT value diagnosing small (less than 4 cm) solid renal masses.

1. To determine the most valuable signs of computed tomography (CT) differentiating small renal masses;

2. To investigate the diagnostic accuracy of contrast-enhanced CT of small renal masses;

3. To evaluate and compare accuracy of renal massses diagnoses by two independent radiologists.

Methods

Results

The most often found solid renal masses CT signs.

Table 1.Patient demographic and clinical data.

Renal massesContrast enhancement

Calcification Central scar Contains fatHomogenous Heterogenous Hypovascular

Clear cell RCC - + - + - +/-

Papillary cellRCC - - + + - -

ChromopfobeRCC - - + +/- + -

AML - - +

Oncocytoma + - - - + -

Parameters Malignant masses Benign masses P-valueNo. of patients (%) 63 (64.3%) 35 (35.7%)Male/Female No. (%) 26 (41.3%)/37 (58.7%) 15 (42.9%)/20 (57.1%) 0.88Laterality (right/left) No. (%) 28 (44.4%)/35 (55.6%) 13 (57.1%)/22 (42.9%) 0.53Size (cm), medina (quartiles) 3.1 (2.6-3.8) 2.5 (2.0-3.2) 0.006Age (years), mediana (quartiles) 66 (57-72) 66 (59-80) 0.16Contact with collecting system (%), Y/N 31 (49.2%)/32 (50.8%) 11 (31.4%)/24 (68.6%) 0.13Contour, No. (%)

ExophyticEndophytic

20 (31.7%)43 (68.3%)

13 (37.1%)22 (62.9%)

0.65

Location, No.(%)Upper poleMid poleLower pole

14 (22.2%)24 (38.1%)25 (39.7%)

8 (22.9%)15 (42.9%)12 (34.3%)

0.90.670.66

Parameters Malignant massesN=63

Benign massesN+35

P-value

Enhancement, No. (%)HypovascularHomogenousHeterogenous

12 (19.0)13 (20.6)38 (60.3)

7 (20.0)11 (31.4)17 (48.6)

0.90.330.29

Calcification, No. (%)+-

57 (90.5)6 (9.5)

33 (94.3)2 (5.7)

0.7

Central fibrous scar, No. (%)+-

55 (87.3)8 (12.7)

25 (71.4)10 (28.6)

0.06

Table 2.CT signs distribution of small renal solid masses.

Parameters Total accuracy (%) 1 researcher (%)

2 researcher (%)

Total accuracy of correct diagnosis:malignant/benign 70.4 69.4 71.4Total accuracy of malignant masses diagnosis 73.0 73.0 73.0Total accuracy of benign masses diagnosis 65.7 62.9 68.6Total accuracy of correct histology (malignant/benign) 56.1 53.1 59.2Total accuracy of correct histology (between malignant masses)

57.9 54.0 61.9

Total accuracy of correct histology (between benign masses)

52.9 51.4 54.3

Table 3.Two reviewers determination of correct diagnosis results.

Ninety-eight patients who had undergone CT (CT with unenhanced, arterial, corticomedullary and excretory phase scanning) in Lithuanian University of Health Sciences, Kaunas Clinics, Department of Radiology were evaluated. Two independent reviewers who were unaware of the diagnosis retrospectively recorded tumor attenuation on CT scans, enhancement characteristics (homogenous, heterogenous or hypovascular), location of tumor center(upper, middle or inferior poles, central or peripheral part), intratumoral calcification/fat, central scar, and patient age and sex. The predictive value of each CT finding were determined by using univariate and multivariate logistic regression analysis.

The mean patients age was 66 years (range, 58 to 74 years). Fifty-seven patients were female (58.2 %) and forty-one were male (41.8 %). All of 98 patients had solid renal masses: 63 malignant, 35 benign renal masses. Other parameters are submited in Table 1. Malignant renal masses more often had central fibrous scar and were enhancing heterogenously than benign renal masses, but these CT signs were not statistically significant (Table 2). The predictive value of each CT findings (in different groups: all renal masses, malignant and benign) were determined by using univariate and multivariate logistic regression analysis.

Tumor size and central fibrous scar were valuable predictors for differentiating malignant masses fat from benign at multivariate analysis (P < .003 and P < .001 ). Mass growth (egzophytic or endophytic) was valuable predictor for differentiating benign masses (P < .032).

The mass enhancement sensitivity for detection of malignancy, specificity were high, positive predictive value 69,9 %, negative predictive value 43,4 %.

Comparison of correct renal masses diagnoses provided by two independent radiologists presented in Table 3.