Abstract:

Objective

To assess the clinical value of CT (or MRI) guided second-look ultrasound examination for renal tumors missed by initial conventional ultrasound and analyze the causes of missed diagnosis.

Methods

A total of 2354 patients with pathologically confirmed renal parenchymal tumors who underwent urological surgery at Shanxi Cancer Hospital from January 2013 to December 2022 were selected. Among them,30 cases (31 lesions) had renal tumors missed by initial ultrasound. The anatomical characteristics indicated by CT/MRI were used as the reference standard to analyze the causes of missed diagnosis by initial ultrasound descriptively. In the above cases, 24 patients (25 lesions) underwent a second ultrasound examination under the guidance of contrast-enhanced CT/MRI. Cross sectional images of the kidneys were obtained through transverse scans of the waist and back, coronal images were obtained through longitudinal scans of the waist, and sagittal images were obtained through longitudinal scans of the back in the prone position. The patients were divided into a negative group and a positive group according to whether the renal tumor was detected. Tumor size, side, polarity, deep or shallow location, growth pattern, and pathological type of lesions were compared by the Fisher’s exact test between the two groups, and the factors affecting secondary detection were analyzed.

Results

Thirty cases (31 lesions) were missed by initial ultrasound examination with a missed diagnosis rate of 1.3% (30/2354), among which 27 lesions (27/31, 87.1%) were ≤ 4 cm,5 (5/31, 16.1%) were ≤ 1 cm, 23 (23/31, 74.2%) were deep, and 14 (14/31, 45.2%) had an exophytic rate＜50%. Twenty-four cases (25 lesions) were examined by a second ultrasound examination, involving 7 lesions in the negative group (7/25, 28.0%) and 18 lesions in the positive group (18/25, 72.0%). All of the 4 lesions with a diameter ≤ 1 cm were missed, accounting for 57.1% (4/7) of the negative group. In 11 lesions with a diameter ＞1 but≤ 2 cm, there were 2 missed cases, accounting for 28.6% (2/7) of the negative group, and 9 detected cases, accounting for 50% (9/18) of the positive group. In 6 lesions with a diameter ＞2 but ≤ 3 cm, one lesion was missed, accounting for 14.3% (1/7) of the negative group, and 5 lesions were detected, accounting for 27.8% (5/18) of the positive group. All of 4 lesions with a diameter ＞3 cm were detected,accounting for 22.2% (4/18) of the positive group. There was a statistical difference in lesion size between the two groups (P＜0.05), but not in lesion side, polarity, deep or shallow location, growth pattern, or pathological type (P＞0.05).

Conclusion

Anatomical features of renal tumors, such as diameter ≤ 4 cm, deep position (medial or dorsal), and exophytic rate ＜ 50%, are the main reasons for the missed diagnosis of renal tumors by conventional ultrasound. During second-look ultrasound examination, sonographers should perform cognitive fusion of CT/MRIand ultrasound images, and construct a three-dimensional concept of kidney tumor in the mind. Then, real-time dynamic three-dimensional ultrasound should be performed from the cross-sectional, coronal, and sagittal aspects of the kidney to display the three-dimensional anatomical characteristics of the lesions, which can effectively improve the detection rate of renal tumors.

Key words: Renal tumors, Second-look ultrasound, Missed diagnosis, Anatomical characteristics