MDCT urography: retrospective determination of optimal delay time after intravenous contrast administration

Abstract

The optimal delay time after intravenous (i.v.) administration of contrast medium (CM) for opacification of the upper urinary tract (UUT) for multidetector computed tomography urography (MDCTU) was investigated. UUT opacification was retrospectively evaluated in 36 four-row MDCTU examinations. Single- (n=10) or dual-phase (n=26) MDCTU was performed with at least 5-min delay after i.v. CM. UUT was divided into four sections: intrarenal collecting system (IRCS), proximal, middle and distal ureter. Two independent readers rated UUT opacification: 1, none; 2, partial; 3, complete. Numbers and percentages of scores, and the 5%, 25%, 50%, 75% and 95% percentiles of delay time were calculated for each UUT section. After removing diseased segments, 344 segments were analysed. IRCS, proximal and middle ureter were completely opacified in 94% (81/86), 93% (80/86) and 77% (66/86) of cases, respectively. Median delay time was 15 min for complete opacification. The distal ureter was completely opacified in 37% (32/86) of cases and not opacified in 26% (22/86). Median delay time for complete opacification was 11 min with 25% and 75% percentiles of 10 and 16 min, respectively. At MDCTU, opacification of the IRCS, proximal and middle ureter was hardly sensitive to delay time. Delay times between 10 and 16 min were favourable in the distal ureter.

CT urography: definition, indications and techniques. A guideline for clinical practice

“…If a corticomedullary phase is employed, data acquisition is usually started 25-35 s after start of CM injection [9,22]. The nephrographic phase starts after a delay of 90-110 s after start of the CM injection [9,23,28,30,32,33,37], while for the final excretory phase a fixed delay of 240-480 s after the start of CM injection has been used [9,[28][29][30]32]. In more recent times, excretory phase data acquisition has been further delayed to 720 s for improved depiction of the lower ureter [38].…”

“…Single-bolus CM injections use 100-150 ml of nonionic CM (300-370 mgI/ml) injected at a rate of 2-3 ml/s [9,22,23,[28][29][30][31][32][33][34][35][36][37]. If a corticomedullary phase is employed, data acquisition is usually started 25-35 s after start of CM injection [9,22].…”

Delineation of upper urinary tract segments at MDCT urography in patients with extra-urinary mass lesions: retrospective comparison of standard and low-dose protocols for the excretory phase of imaging

“…It has previously been shown that delay time for CTU in the excretory phase after i.v.administration of contrast media is crucial for the proportion of urinary tract segments completely delineated, particularly for the distal ureter [5][6][7]. Delay time for the excretory phase exceeded 10 min in most patients, which is usually associated with increased success at delineating the ureter [3,[5][6][7]. Ancillary manoeurvres were restricted to the i.v.…”

“…hydration of the patient, i.v. administration of low doses of frusemide prior to CTU [6][7][8], and obtaining additional CT images in the excretory phase [9]. However, one major concern in CTU is additional radiation exposure due to (repetitive) CT data acquisitions in the excretory phase [3,10].…”

“…It has been demonstrated that the quality of depiction and delineation of the upper urinary tract at CTU in the excretory phase can be improved by means of optimizing delay times for imaging after i.v. administration of contrast media [5][6][7], i.v. hydration of the patient, i.v.…”