Adult Ureteropelvic Junction Obstruction: Insights with Three-dimensional Multi–Detector Row CT

Vascular compression syndromes in the abdomen and pelvis: a concise pictorial review

Vascular compression syndromes are a diverse group of pathologies that can manifest asymptomatically and incidentally in otherwise healthy individuals or symptomatically with a spectrum of presentations. Due to their relative rarity, these syndromes are often poorly understood and overlooked. Early identification of these syndromes can have a significant impact on subsequent clinical management. This pictorial review provides a concise summary of seven vascular compression syndromes within the abdomen and pelvis including median arcuate ligament (MAL) syndrome, superior mesenteric artery (SMA) syndrome, nutcracker syndrome (NCS), May-Thurner syndrome (MTS), ureteropelvic junction obstruction (UPJO), vascular compression of the ureter, and portal biliopathy. The demographics, pathophysiology, predisposing factors, and expected treatment for each compression syndrome are reviewed. Salient imaging features of each entity are illustrated through imaging examples using multiple modalities including ultrasound, fluoroscopy, CT, and MRI.

Evaluating pediatric ureteropelvic junction obstruction: Dynamic magnetic resonance urography vs renal scintigraphy 99m-technetium mercaptoacetyltriglycine

BACKGROUND

Ureteropelvic junction obstruction (UPJO) is a common congenital urinary tract disorder in children. It can be diagnosed as early as in utero due to the presence of hydronephrosis or later in life due to symptomatic occurrence.

AIM

To evaluate the discrepancy between dynamic contrast-enhanced magnetic resonance urography (dMRU) and scintigraphy 99m-technetium mercaptoacetyltriglycine (MAG-3) for the functional evaluation of UPJO.

METHODS

Between 2016 and 2020, 126 patients with UPJO underwent surgery at Robert Debré Hospital. Of these, 83 received a prenatal diagnosis, and 43 were diagnosed during childhood. Four of the 126 patients underwent surgery based on the clinical situation and postnatal ultrasound findings without undergoing functional imaging evaluation. Split renal function was evaluated preoperatively using scintigraphy MAG-3 (n = 28), dMRU (n = 53), or both (n = 40). In this study, we included patients who underwent surgery for UPJO and scintigraphy MAG-3 + dMRU but excluded those who underwent only scintigraphy MAG-3 or dMRU. The patients were divided into groups A (< 10% discrepancy) and B (> 10% discrepancy). We examined the discrepancy in split renal function between the two modalities and investigated the possible risk factors.

RESULTS

The split renal function between the two kidneys was compared in 40 patients (28 boys and 12 girls) using scintigraphy MAG-3 and dMRU. Differential renal function, as determined using both modalities, showed a difference of < 10% in 31 children and > 10% in 9 children. Calculation of the relative renal function using dMRU revealed an excellent correlation coefficient with renal scintigraphy MAG-3 for both kidneys.

CONCLUSION

Our findings demonstrated that dMRU is equivalent to scintigraphy MAG-3 for evaluating split renal function in patients with UPJO.

Pelviureteric junction obstruction in adults: A systematic review of the literature

Background

Pelviureteric junction obstruction (PUJO) is a common urological disorder that can present at any stage of life. The underlying etiology in children has been well studied; however, a gap exists in the literature for the adult population. Herein, we performed a systematic review of the literature to evaluate the current evidence on the underlying etiologies of adult patients presenting with PUJO.

Materials and methods

Four electronic databases were searched for relevant studies assessing the underlying etiologies of pelviureteric junction obstruction in adults. Studies were assessed for eligibility based on predefined inclusion and exclusion criteria, and a critical appraisal of methodological quality and risk of bias was performed. Finally, qualitative and quantitative data analyses were performed.

Results

Twelve studies comprising a total of 513 patients with radiologically confirmed PUJO met the inclusion criteria and were included in our analysis. The most common finding was crossing vessels, which were observed in 50.5% of patients, followed by intrinsic ureteral stenosis (27.1%), adhesions (15.3%), and high insertion of the ureter (10.1%).

Conclusions

The underlying etiologies of PUJO in adults remain unclear. This study indicated that obstruction secondary to crossing vessels is the most common cause of obstruction in adults and occurs more frequently than in the pediatric population.

Imaging of ureter: a primer for the emergency radiologist

In this review article, we will discuss the gamut of abnormalities involving the ureters. In the emergency department, ureterolithiasis is the most common indication for imaging abdomen and pelvis. However, spectrum of ureteral abnormalities including congenital, infectious and inflammatory, primary and secondary ureteral malignancies, retroperitoneal fibrosis rare described in this article may be encountered. Thus, we will describe acute subacute as well as chronic conditions that may affect ureter. Knowledge of common, as well as rare entities and their imaging features, is of utmost importance to enable appropriate management.

Congenital Anomalies of the Upper Urinary Tract: A Comprehensive Review

The upper urinary tract is the most common human system affected by congenital anomalies. Congenital anomalies of the kidneys and ureters comprise a wide spectrum of disorders ranging from simple variants with no clinical significance to complex anomalies that may lead to severe complications and end-stage renal disease. They may be classified as anomalies of renal form, which are subclassified as structural anomalies (eg, persistent fetal lobulation, hypertrophied column of Bertin, and dromedary hump) and fusion anomalies (eg, horseshoe kidney and pancake kidney); anomalies of renal position (eg, renal malrotation, simple renal ectopia, and crossed renal ectopia) and renal number (eg, renal agenesis and supernumerary kidney); and abnormalities in development of the urinary collecting system (eg, pyelocaliceal diverticulum, megacalycosis, ureteropelvic junction obstruction, duplex collecting system, megaureter, ectopic ureter, and ureterocele). US is usually the first imaging modality used because of its low cost, wide availability, and absence of ionizing radiation. Intravenous urography and voiding cystourethrography are also useful, mainly for characterization of the collecting system and vesicoureteral reflux. However, intravenous urography has been replaced by CT urography and MR urography. These imaging methods not only allow direct visualization of the collecting system but also demonstrate the function of the kidneys, the vascular anatomy, adjacent structures, and complications. Comprehension of congenital anomalies of the upper urinary tract is crucial for an accurate diagnosis and correct management. The authors discuss the spectrum of these anomalies, with emphasis on embryologic development, imaging findings, clinical manifestations, and complications. Online supplemental material is available for this article. ^©RSNA, 2021.

CT imaging findings of abdominopelvic vascular compression syndromes: what the radiologist needs to know

Abdominopelvic vascular compression syndromes include a variety of uncommon conditions characterized by either extrinsic compression of blood vessels by adjacent anatomical structures (i.e., median arcuate ligament syndrome, nutcracker syndrome, May-Thurner syndrome) or compression of hollow viscera by adjacent vessels (i.e., superior mesenteric artery syndrome, ureteropelvic junction obstruction, ureteral vascular compression syndromes, portal biliopathy). These syndromes can be unexpectedly diagnosed even in asymptomatic patients and the predisposing anatomic conditions can be incidentally discovered on imaging examinations performed for other indications, or they can manifest with atypical abdominal symptoms and acute complications, which may lead to significant morbidity if unrecognized. Although computed tomography (CT) is an accurate noninvasive technique for their detection, the diagnosis remains challenging due to the uncommon clinical presentation and often overlooked imaging features. Dynamic imaging may be performed in order to evaluate patients with inconstant symptoms manifesting in a specific position. The purposes of this paper are to review the CT imaging findings of abdominopelvic vascular compression syndromes, correlating with anatomical variants and to provide key features for the noninvasive imaging diagnosis.

Dynamic MRI and isotope renogram in the functional evaluation of pelviureteric junction obstruction: A comparative study

OBJECTIVE

The aim of this study was to evaluate and compare the diagnostic accuracy of dynamic contrast- enhanced magnetic resonance imaging (dMRI) and isotope renogram in the functional evaluation of pelviureteric junction obstruction (PUJO).

MATERIAL AND METHODS

Forty-two patients included in the study were investigated with isotope renogram and subsequently, subjected to dMRI. Time-activity curves were generated for both isotope renogram and dMRI. Out of the 42 cases, 9 cases were conservatively managed. Thirty-three cases were taken up for surgical intervention.

RESULTS

Of 33 patients taken up for surgical intervention, 12 underwent laparoscopic nephrectomy and 21 of them pyeloplasty. The mean glomerular filtration rates (GFRs) as measured by isotope renogram and dMRI were 22.5+4.2 mL/min and 23.8+3.1 mL/min respectively. The calculation of GFR by isotope renogram, showed good correlation with that of dMRI with correlation coefficient of 0.93. The dMRI was able to reveal the functional status of the renal unit accurately. dMRI did not yield false positive results with 20 of 21 patients scheduled for pyeloplasty and 11 of 12 patients scheduled for nephrectomy. Isotope renogram had a false positive result in 3 cases compared with surgical diagnosis.

CONCLUSION

Analysis of renal function using dMRI yielded results comparable to those of renal scintigraphy, with superior spatial and contrast resolution. It was also better in prompting management decisions with respect to the obstructed systems. dMRI can be used as a "one stop imaging examination" that can replace different imaging methods used for morphological, etiological and functional evaluation of PUJO.

CT Imaging of Emergent Renal Conditions

The kidneys are paired intra-abdominal organs which provide essential functions and maintain homeostasis throughout the human body. Numerous disease processes affect the kidneys and cause acute renal dysfunction or other potentially catastrophic complications. These conditions can be broadly categorized into obstructive, infectious, hemorrhagic, traumatic, and vascular diseases. Imaging plays a vital role in the work-up and diagnosis of acute and emergent renal conditions. Evaluation of emergent renal conditions with a focus on CT imaging is discussed.

Ectopic insertion of a duplicated ureter into prostatic urethra: Demonstration by 3D multi-detector computed tomography urography

Ectopic insertion of the ureter in the genitourinary tract is a rare congenital disorder, usually associated with ureteral duplication. Identification of the insertion open is critical for ureteric re-implantation. However, the challenge in the diagnosis of ectopic insertion of the ureter usually is to identify its insertion, particularly when the affected ureter is not dilated. Multi-detector computed tomography (MDCT) urography with nonionic iodinated contrast media delineates the ureteric course in the normal functioning kidney in the excretory phase [1]. This report presented a young male patient with ectopic insertion of a duplicated ureter diagnosed by MDCT urography. Three-dimensional (3D) analysis technology, such as volume rendering (with a color display improving the visualization of complex anatomy and 3D relationships) and maximum intensity projection (similar in principle to projection angiography), is useful for the illustration of urinary tract anatomy [1]. Rotated volume rendering reconstruction images and continual thinner maximum intensity projection reformatted images can be viewed as videos, which provides detail delineation of the ectopic ureteral insertion and its associated ureteral duplication.In this study, we reported MDCT urography and 3D analysis technology as an appropriate diagnostic method for the ectopic ureteral insertion and its associated complications.

Agreement between static magnetic resonance urography and diuretic renal scintigraphy in patients with ureteropelvic junction obstruction after pyeloplasty

BACKGROUND

Ureteropelvic junction obstruction (UPJO) is the most common cause of hydronephrosis within childhood that usually treat by surgery. According to anatomical variations in different individuals, scheduling similar procedures for all patients is not suitable, and thus the best decision for an appropriate surgical technique should be considered separately for each patient. Regardless of the type of applied technique, creating a funnel-shape UPJ with a suitable size is a successful treatment. In this context, the assessment of a successful surgical treatment in a short-term follow-up means repairing revealed anatomical defects. The present study aimed to compare the diagnostic value of static magnetic resonance urography (MRU) and diuretic-based renalscintigraphy (DRS) in patients with UPJO after pyeloplasty.

MATERIALS AND METHODS

A total of 30 consecutive patients with UPJO, who underwent unilateral pyeloplasty between 2012 and 2013 were assessed. All subjects underwent DRS and also MRU about 1-month after the former procedure.

RESULTS

The Kendall's tau correlation showed a very strong correlation between results of MRU and diuretic renal scintigraphy (r = 0.932, P < 0.001). This strong correlation was also shown by Somers'd test (r = 0.932, P < 0.001) similarly.

CONCLUSIONS

Our study shows a strong agreement between DRS and MRU to assess UPJO. MRU static fluid has a high accuracy for assessment of renal system anatomy. Due to the lack of dangerous consequences of contrast materials, MRU can be the best option instead of DRS.

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

BACKGROUND

MR Urography (MRU) is an increasingly used imaging modality for the evaluation of pediatric genitourinary obstruction.

OBJECTIVE

To determine whether pediatric MR urography (MRU) reliably detects crossing vessels in the setting of suspected ureteropelvic junction (UPJ) obstruction. The clinical significance of these vessels was also evaluated.

MATERIALS AND METHODS

We identified pediatric patients diagnosed with UPJ obstruction by MRU between May 2009 and June 2014. MRU studies were evaluated by two pediatric radiologists for the presence or absence of crossing vessels. Ancillary imaging findings such as laterality, parenchymal thinning/scarring, trapped fluid in the proximal ureter, and presence of renal parenchymal edema were also evaluated. Imaging findings were compared to surgical findings. We used the Mann-Whitney U test to compare continuous data and the Fisher exact test to compare proportions.

RESULTS

Twenty-four of 25 (96%) UPJ obstructions identified by MRU were surgically confirmed. MRU identified crossing vessels in 10 of these cases, with 9 cases confirmed intraoperatively (κ = 0.92 [95% CI: 0.75, 1.0]). Crossing vessels were determined to be the primary cause of UPJ obstruction in 7/9 children intraoperatively, while in two children the vessels were deemed incidental and noncontributory to the urinary tract obstruction. There was no significant difference in age or the proportions of ancillary findings when comparing children without and with obstructing vessels.

CONCLUSION

MRU allows detection of crossing vessels in pediatric UPJ obstruction. Although these vessels are the primary cause of obstruction in some children, they are incidental and non-contributory in others. Our study failed to convincingly identify any significant predictors (e.g., age or presence of renal parenchymal edema) that indicate when a crossing vessel is the primary cause of obstruction.

CT Urography for Evaluation of the Ureter

Over the past decade, computed tomographic (CT) urography has emerged as the primary imaging modality for evaluating the urinary tract in various clinical settings, including the initial workup of hematuria. With the widespread implementation of CT urography, it is critical for radiologists to understand normal ureteral anatomy and the varied appearance of pathologic ureteral conditions at CT urography. Pathologic findings at CT urography include congenital abnormalities, filling defects, dilatation, narrowing, and deviations in course. These abnormalities are reviewed, along with the indications for CT urography, current imaging protocols with specific techniques for optimal evaluation of the ureter, and dose reduction strategies.

Left nutcracker syndrome and right ureteropelvic junction obstruction

We report a rare case of left nutcracker syndrome and right ureteropelvic junction obstruction in a young woman who suffered flank pain and hematuria. The diagnosis was confirmed with the help of Doppler ultrasonography, retrograde pyelography, magnetic resonance angiography, and magnetic resonance urography. A surgery that involves left renal vein decompression and dismembered Anderson-Hynes pelvioplasty was performed. The patient was followed up for 23 months, and her symptoms were relieved.

Usefulness of computed tomography performed immediately after excretory urography in patients with delayed opacification or dilated upper urinary tract of unknown cause

PURPOSE

To evaluate the diagnostic value of computed tomography (CT) performed immediately after excretory urography (EU) in patients with delayed renal opacification or dilated upper urinary system with nonconclusive diagnosis after EU.

MATERIALS AND METHODS

CT was performed immediately after EU in 39 patients with delayed opacification or dilated upper urinary system of unknown cause, without additional intravenous contrast administration for the CT study. We classified EU + CT findings as benign or malignant causes and we compared our results with the final diagnosis.

RESULTS

The combination of EU + CT correctly diagnosed 38 out of the 39 cases with a sensitivity of 97%. Correct diagnosis was established in all malignant cases (n = 17) but one benign case consistent with blood clots in the upper urinary tract was incorrectly diagnosed as a multicentric urothelial carcinoma. Sensitivity, specificity, and accuracy for the diagnosis of the underlying cause with EU + CT was 100%, 95%, and 97%, respectively. The final diagnoses were: urothelial carcinoma (n = 10), stone disease (n = 10), bladder tumor (n = 4), benign post-treatment ureteral stenosis (n = 4), ureteral invasion (n = 3), benign bladder disease (n = 2), urinary tract infections (n = 2), crossing vessels (n = 1), ureteropelvic junction obstruction (n = 1), retrocaval ureter (n = 1), and blood clots in the upper urinary tract due to bleeding renal metastasis from lung cancer (n = 1).

CONCLUSION

Combined EU and CT study allowed correct diagnosis of the underlying cause of delayed excretion or upper urinary tract dilatation in 97% of cases. The combination of EU and CT provides diagnosis reducing time and radiation.

[The ureters: findings at multidetector computed tomography]

Multidetector computed tomography (MDCT) and advances in CT urography techniques have enabled vast improvements in the depiction of the ureter. Studies of the ureter can find a wide variety of conditions including congenital defects and anatomic variants (anomalies in the origin, distribution, and distal insertion of the ureter) as well as all benign and malignant causes of focal and diffuse wall thickening (inflammatory and infectious processes, and neoplasms, as well as iatrogenic thickening and postsurgical changes). Other benign processes like ureteral kinking and stenosis due to extrinsic compression of the iliac vessels are also well characterized by MDCT. The aim of this article is to show the spectrum of ureteral variants and disease apart from common entities related to stones.

[Functional MR urography in children]

MR Urography (MRU) provides both morphologic and functional information without radiation exposure. It enables the assessment of split renal function, excretion, and quantification of obstruction. MRU is thus complementary to ultrasonography in the assessment of pre- and post-natal obstructive uropathies in children. If available, MRU should be definitely preferred to intravenous urography.

Vascular renal anatomy and the ureteropelvic junction: preoperative multidetector CT scanning with split-bolus injection as a predictor of laparoscopic findings

PURPOSE

To compare multidetector CT scan (MDCT) results with intraoperative findings in the detection of an inferior-pole pedicle crossing the ureteropelvic junction.

PATIENTS AND METHODS

Over the 2-year study period, 35 patients receiving laparoscopic pyeloplasty underwent preoperative investigation with a novel MDCT protocol in order to detect crossing vessels. Postprocessing, including maximum intensity projection, volume-rendering technique, and multiplanar reconstruction, was used in addition to standard axial views.

RESULTS

All the arteries found during laparoscopic surgery were detected by MDCT, but one radiologic false-positive was noted at the beginning of the series. Seven veins were not detected with MDCT. In the only case featuring an isolated inferior-pole vein, the aberrant vessel was identified by MDCT.

CONCLUSION

Multidetector CT scanning is a highly accurate way of providing all the information necessary preoperatively concerning renal parenchymal anomalies, urinary stones, and collecting system and vessel anatomy. It helps physicians make appropriate therapeutic decisions and gives surgeons information about what they can expect during laparoscopic procedures.

Maximizing clinical information obtained by CT

CT scanning is an integral part of the urologist's practice today. It is the most commonly used imaging modality and the one with which urologists are most familiar. CT urography, CT angiography, and 3D reconstruction enable the urologist to perform comprehensive evaluations of patients who have different urologic diseases, using a single imaging modality. It is thus prudent that urologists become familiar with CT applications, to maximize the clinical information available from them.

Renal Multidector Row CT

Multidetector row CT is the most recent advance in CT technology. An increased number of detector rows and more powerful x-ray tubes result in faster scanning time, increased volume coverage, and improved spatial and temporal resolution. MDCT technology allows superior image quality, decreased examination time, and the ability to perform complex multiphase vascular and three-dimensional examinations.