Semins et al [31], in a prospective study of 22 patients with renal colic, concluded that noncontrast half-Fourier acquisition single-shot turbo spin-echo MRU can reliably detect presence of upper tract obstruction using visualization of a stone and secondary signs of obstruction; using CT as the reference standard, the combination of stone or perinephric fluid and ureteral dilation gave MRU a sensitivity of 84 %, specificity of 100 %, and accuracy of 86 % (95 % CI 0.72-1.0). Radiography Abdomen and Pelvis There is relatively limited evidence to support the use of radiography of the abdomen and pelvis for initial imaging of patients with symptomatic hydronephrosis with unknown cause. CT is more sensitive for obstructive urolithiasis. Innes et al [32] performed a retrospective multicenter observational cohort study of 1,026 patients with renal colic, finding that adding radiography to screening for hydronephrosis (in this study, by CT) increased sensitivity in all stone categories, specifically from 39% to 68% for large stones and from 60% to 82% for interventional stones. They conclude that this level of sensitivity may be sufficient to reassure physicians about a renal colic diagnosis in the setting of known hydronephrosis without CT imaging for many patients. In a retrospective study of 939 patients with renal colic, Abdel-Gawad et al [33] reported that KUB had limited sensitivity of 53% to 62% and specificity of 67% to 69% for the detection of ureteral calculi. Notably, 90% of stones are radio-opaque, consisting of calcium oxalate, calcium phosphate, and struvite. Although KUB may be comparatively insensitive for stones <4 mm and those in the mid and distal ureters, its use may improve stone detection rates at the margins where obstruction is not readily demonstrated with US [34]. Some studies of patients with renal colic have investigated the combination of radiography and US.
Hydronephrosis on Prior Imaging Unknown Cause. Semins et al [31], in a prospective study of 22 patients with renal colic, concluded that noncontrast half-Fourier acquisition single-shot turbo spin-echo MRU can reliably detect presence of upper tract obstruction using visualization of a stone and secondary signs of obstruction; using CT as the reference standard, the combination of stone or perinephric fluid and ureteral dilation gave MRU a sensitivity of 84 %, specificity of 100 %, and accuracy of 86 % (95 % CI 0.72-1.0). Radiography Abdomen and Pelvis There is relatively limited evidence to support the use of radiography of the abdomen and pelvis for initial imaging of patients with symptomatic hydronephrosis with unknown cause. CT is more sensitive for obstructive urolithiasis. Innes et al [32] performed a retrospective multicenter observational cohort study of 1,026 patients with renal colic, finding that adding radiography to screening for hydronephrosis (in this study, by CT) increased sensitivity in all stone categories, specifically from 39% to 68% for large stones and from 60% to 82% for interventional stones. They conclude that this level of sensitivity may be sufficient to reassure physicians about a renal colic diagnosis in the setting of known hydronephrosis without CT imaging for many patients. In a retrospective study of 939 patients with renal colic, Abdel-Gawad et al [33] reported that KUB had limited sensitivity of 53% to 62% and specificity of 67% to 69% for the detection of ureteral calculi. Notably, 90% of stones are radio-opaque, consisting of calcium oxalate, calcium phosphate, and struvite. Although KUB may be comparatively insensitive for stones <4 mm and those in the mid and distal ureters, its use may improve stone detection rates at the margins where obstruction is not readily demonstrated with US [34]. Some studies of patients with renal colic have investigated the combination of radiography and US.