Yonsei Med J.  2018 May;59(3):389-396. 10.3349/ymj.2018.59.3.389.

Low-Dose Unenhanced Computed Tomography with Iterative Reconstruction for Diagnosis of Ureter Stones

• Chi BH
• Chang IH
• Lee DH
• Park SB
• Kim KD
• Moon YT
• Huh TK

• KMID: 2407862
• DOI: http://doi.org/10.3349/ymj.2018.59.3.389

Abstract

PURPOSE
To study the clinical application of low-dose unenhanced computed tomography with iterative reconstruction technique (LDCT-IR) on renal colic in the emergency department.
MATERIALS AND METHODS
We conducted a prospective, single-blinded, randomized, and non-inferiority study. From March 2014 to August 2015, 112 patients with renal colic were included, and were randomized to either LDCT-IR (n=46) or standard-dose unenhanced CT (SDCT) (n=66) groups. The accuracy of urolithiasis diagnosis was the primary endpoint of this study. Radiation dose, size and location of the stone, hydronephrosis, other diseases except urolithiasis, and results of treatment were analyzed between the two groups.
RESULTS
The average effective dose radiation of SDCT was approximately four times higher than that of LDCT-IR (6.52 mSv vs. 1.63 mSv, p < 0.001). There was no significant difference in the accuracy of ureteral stone diagnosis between the two groups (LDCT-IR group: 96.97% vs. SDCT group: 98.96%, p=0.392). No significant difference was observed regarding the size and location of a stone, hydronephrosis, and diagnosis of other diseases, except urolithiasis. False negative results were found in two LDCT-IR patients and in one SDCT patient. In these patients, stones were misread as vascular calcification, and were difficult to diagnose because evidence of hydronephrosis and ureteral dilatation was not found.
CONCLUSION
LDCT-IR, as a first-line imaging test, was non-inferior to SDCT with respect to diagnosis of ureter stones, and was clinically available for the evaluation of renal colic.

Keyword

Low-dose; computed tomography; urolithiasis; renal colic

MeSH Terms

Diagnosis*
Dilatation
Emergency Service, Hospital
Humans
Hydronephrosis
Prospective Studies
Renal Colic
Ureter*
Urolithiasis
Vascular Calcification

Figure

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  Fig. 1 Flow chart of the patient inclusion and review protocol. ED, emergency department; LDCT-IR, low-dose unenhanced computed tomography with iterative reconstruction technique; SDCT, standard-dose unenhanced computed tomography.

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  Fig. 2 A comparison between LDCT-IR and SDCT for a ureter stone. (A) LDCT-IR sets (axial, coronal, and sagittal images) of a 35-year-old man with a right lower ureteral stone (white arrows). The body mass index of the patient was 34.3 kg/m2, and the effective radiation dose was 3.384 mSv. (B) SDCT sets (axial, coronal, and sagittal images) of a 50-year-old woman with a left upper ureteral stone (white arrows). The body mase index of the patient was 20.8 kg/m2, and the effective radiation dose was 4.416 mSv. LDCT-IR, low-dose computed tomography with iterative reconstruction technique; SDCT, standard-dose unenhanced computed tomography.

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  Fig. 3 LDCT-IR and SDCT for false negative findings for ureter stone and causes other than ureter stone. (A) LDCT-IR sets (axial, coronal, and sagittal images) of a 21-year-old man with a right mid ureteral stone (white arrows). The radiologist did not discriminate between a ureter stone and vascular calcification. (B) LDCT-IR sets (axial, coronal, and sagittal images) of a 40-year-old man with a left mid ureteral stone (white arrows). The radiologist discriminated it as a vascular calcification rather than as a ureter stone. (C) SDCT sets (axial, coronal, and sagittal images) of a 33-year-old woman with a left lower ureteral stone (white arrows). The radiologist discriminated the calcification because there was no ureteral dilatation and no ureteral course tracking. (D) SDCT sets (axial, coronal, and sagittal images) of a 40-year-old man who complained of left flank pain. The radiologist discriminated the several diverticula in D-colon with pericolic infiltration (white arrows) and no urinary stone. The final diagnosis of left flank pain was acute diverticulitis. LDCT-IR, low-dose computed tomography with iterative reconstruction technique; SDCT, standard-dose unenhanced computed tomography.

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