Pediatric ureteropelvic junction obstruction: can magnetic resonance urography identify crossing vessels?

Parikh, Kushal; Hammer, Matthew R.; Kraft, Kate H.; Ivančić, Vesna; Smith, Ethan A.; Dillman, Jonathan R.

doi:10.1007/s00247-015-3412-y

Cited by 19 publications

(16 citation statements)

References 20 publications

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Sir, Parikh et al [1] published the interesting article "Pediatric ureteropelvic junction obstruction: can magnetic resonance urography identify crossing vessels?" in the November 2015 issue of Pediatric Radiology.

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confidence: 99%

“…This was followed by a thoughtprovoking letter to the editor -"Direct visualization of crossing renal vessels on MRU achieved by splitting intravenous contrast dose" -that described a novel protocol for contrast administration during magnetic resonance urography (MRU) [2]. The study by Parikh et al [1] included 25 MRUs of patients diagnosed with ureteropelvic junction obstruction who underwent surgery. Crossing vessels were identified on 10 of the MRUs and 9 were confirmed surgically (ĸ = 0.92).…”

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confidence: 99%

“…The freeware "CHOPfMRU," available at www.chop-fmru.com, utilized in studies by Parikh et al [1] and Weiss et al [3], has built-in capabilities to do so [5]. The CHOP-fMRU software has a maximum intensity projection (MIP) time feature that allows the user to view any given slice of a dynamic sequence with maximum enhancement at every pixel.…”

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confidence: 99%

“…Previously, a crossing vessel was identified on the angiographical phase of the MRU, and then the vascular finding correlated with the excretory images [1,3]. The CHOPfMRU software can automatically generate, with just three additional clicks, combined angiographical and excretory images similar to that of the split-bolus technique but using a single bolus.…”

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Detection of renal crossing vessels in MR urography made simple

et al. 2016

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Sir, Parikh et al. [1] published the interesting article "Pediatric ureteropelvic junction obstruction: can magnetic resonance urography identify crossing vessels?" in the November 2015 issue of Pediatric Radiology. This was followed by a thoughtprovoking letter to the editor -"Direct visualization of crossing renal vessels on MRU achieved by splitting intravenous contrast dose" -that described a novel protocol for contrast administration during magnetic resonance urography (MRU) [2]. The study by Parikh et al. [1] included 25 MRUs of patients diagnosed with ureteropelvic junction obstruction who underwent surgery. Crossing vessels were identified on 10 of the MRUs and 9 were confirmed surgically (ĸ = 0.92). We published a similar study of 41 MRUs in patients with ureteropelvic junction obstruction [3]. Crossing vessels were identified on 17 MRUs and 15 were confirmed intraoperatively. Ureteral obstruction by the crossing vessel was visualized on the MRUs in only 9/17 cases. In our series, the sensitivity and specificity of MRU to detect renal crossing vessels in the setting of ureteropelvic obstruction was 88.2% and 91.7%, respectively. Thus, these two studies demonstrate the value of MR urography to diagnose crossing vessels with a single bolus post-contrast dynamic series.Proposed split-bolus MRU allows simultaneous visualization of the renal vessels and the collecting system [2]. In their pictorial essay, Battal et al. [4] presented the utility of splitbolus MRU in a number of vascular anomalies related to the urinary tract, including crossing vessels [4]. However, to date, there is no systematic evaluation of using this method to diagnose crossing vessels. Split-bolus MRU requires careful real-time monitoring in order to time the second contrast injection. The additional procedural step and monitoring increase unnecessarily the scan time and add complexity to the examination.We would like to point out a simple way to get concurrent images of the renal angiographical and excretory phases using the single-bolus contrast technique. The freeware "CHOPfMRU," available at www.chop-fmru.com, utilized in studies by Parikh et al. [1] and Weiss et al. [3], has built-in capabilities to do so [5]. The CHOP-fMRU software has a maximum intensity projection (MIP) time feature that allows the user to view any given slice of a dynamic sequence with maximum enhancement at every pixel. Accordingly, the user is not limited to specific timing of the injections for image acquisition as in the split-bolus technique. The maximally enhanced pixels can be selected simultaneously from the entire dynamic data set including the kidneys, ureters and vessels. The only limitation to MIP reconstruction is significant patient motion.Generating the combined angiographical and excretory images using the CHOP-fMRU software is simple. The step-bystep instructions had previously been described in the appendix part (Step 8) of the publication by Khrichenko et al. [5].

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confidence: 99%

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confidence: 99%

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Detection of renal crossing vessels in MR urography made simple

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“…by Dr. Parikh et al [1]. They aimed to show whether magnetic resonance urography (MRU) can accurately identify the crossing renal vessels in the suspicion of ureteropelvic junction (UPJ) obstruction.…”

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Direct visualization of crossing renal vessels on MRU achieved by splitting intravenous contrast dose

Kocaoğlu

2015

Pediatr Radiol

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Sir,We read with great interest the article published in the November 2015 issue of Pediatric Radiology titled "Pediatric Ureteropelvic Junction Obstruction: Can Magnetic Resonance Urography Identify Crossing Vessels?" by Dr. Parikh et al. [1]. They aimed to show whether magnetic resonance urography (MRU) can accurately identify the crossing renal vessels in the suspicion of ureteropelvic junction (UPJ) obstruction. They used a single-bolus MRU technique that involves a dynamic 3-D gradient recalled echo sequence in addition to 2-D/ 3-D T2-weighted and 2-D T1-weighted sequences. Based on the MRU study, there were 10 cases of crossing renal vessels at the site of the UPJ narrowing; however surgery confirmed 9 cases of crossing renal vessels, of which 7 were primarily responsible for the UPJ narrowing. In the remaining two cases, crossing renal vessels were not the cause of the UPJ obstruction. The authors could demonstrate the obstructing crossing renal vessels with a high degree of accuracy.We would like to share our split-bolus MRU protocol, which can illustrate aberrant vessels including crossing renal vessels, retroiliac ureter, retrocaval ureter, nutcracker syndrome and retroiliac ureters that can cause urinary tract obstruction [2]. Split-bolus CT has also been shown to illustrate the obstructing vessels previously [3]. In single-bolus MRU protocol, the renal vasculature and collecting system appear at different phases and cannot be visualized concurrently. In our MRU protocol we split the intravenous gadolinium dose (split-bolus MRU) in order to show the collecting system and the vessels simultaneously. For functional MRU, onethird of the total contrast dose is given and 3-D T1-weighted gradient recalled echo (GRE) sequence is carried out to measure differential renal function. After the completion of the dynamic series, two-thirds of the total contrast medium is administered and 3-D T1-weighted GRE sequence is repeated during the arterial and venous phases to generate MR angiographic images. The later scans allow us to demonstrate the renal vasculature and collecting system at the same time and help in diagnosing the aberrant vessels. Where dynamic renal function is concerned, some researchers suggest a low dose of gadolinium, which reduces the T2* effect and gives more accurate results [4]. Therefore, splitting the intravenous contrast dose is in fact an advantage for functional estimation.Preoperative detection of the aberrant vessels as a cause of urinary tract obstruction may change the surgical technique and prevent additional intervention. In order to easily detect the aberrant vessels, MRU protocol can be modified in cases with clinical and previous imaging findings suggestive of obstructing vessels. Compliance with ethical standards Conflicts of interest None References 1. Parikh KR, Hammer MR, Kraft KH et al (2015) Pediatric ureteropelvic junction obstruction: can magnetic resonance urography identify crossing vessels? Pediatr Radiol 45:1788-1795 2. Battal B, Kocaoğlu M, Akgun V et al (2015) Split...

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