Multidetector row CT angiography of living related renal donors: is there a need for venous phase imaging?

Anatomical Variants of the Renal Veins and Their Relationship with Morphofunctional Alterations of the Kidney: A Systematic Review and Meta-Analysis of Prevalence

Background: Variations in renal veins are quite common, and most people do not experience issues due to them. However, these variations are important for healthcare professionals, especially in surgical procedures and imaging studies, as precise knowledge of vascular anatomy is essential to avoid complications during medical interventions. The purpose of this study was to expose the frequency of anatomical variations in the renal vein (RV) and detail their relationship with the retroperitoneal and renal regions. Methods: A systematic search was conducted in the Medline, Scopus, Web of Science, Google Scholar, CINAHL, and LILACS databases from their inception until January 2024. Two authors independently carried out the search, study selection, and data extraction and assessed methodological quality using a quality assurance tool for anatomical studies (AQUA). Ultimately, consolidated prevalence was estimated using a random effects model. Results: In total, 91 studies meeting the eligibility criteria were identified. This study included 91 investigations with a total of 46,664 subjects; the meta-analysis encompassed 64 studies. The overall prevalence of multiple renal veins was 5%, with a confidence interval (CI) of 4% to 5%. The prevalence of the renal vein trajectory was 5%, with a CI of 4% to 5%. The prevalence of renal vein branching was 3%, with a CI of 0% to 6%. Lastly, the prevalence of unusual renal vein origin was 2%, with a CI of 1% to 4%. Conclusions: The analysis of these variants is crucial for both surgical clinical management and the treatment of patients with renal transplant and hemodialysis.

Anatomical variants of renal veins: A meta-analysis of prevalence

The main aim of this article is to establish the actual prevalence of renal vein variations (circumaortic renal vein, retroaortic renal vein, double renal vein), and to increase awareness about them. To this purpose, we have performed a meta-analysis of prevalence, using the MetaXL package, We included 105 articles in the final analysis of prevalence, of which 88 contained data about retroaortic renal vein, 84 - about circumaortic renal vein, and 51 - about multiple renal veins. The overall prevalence for retroaortic renal vein was 3% (CI:2.4-3.6%), for circumaortic renal vein - 3.5% (CI:2.8-4.4%), and for multiple renal veins - 16.7% (14.3-19.2%), much higher on the right 16.6 (14.2-19.1%) than on the left side 2.1 (1.3-3.2%). The results were relatively homogenous between studies, with only a minor publication bias overall.

Retrocaval ureter: a meta-analysis of prevalence

INTRODUCTION

Retrocaval ureter is a congenital abnormality of the right ureter, which has been shown, in rare cases to cause clinical symptoms, mainly due to the development of ureterohydronephrosis.

PURPOSE

The purpose of this article is to identify the prevalence of the retrocaval ureter, and to emphasize its clinical and surgical importance.

DESIGN

A meta-analysis of prevalence, on cases obtained from PubMed, Web of Science, and Scopus databases.

RESULTS

A total number of 13 studies contained data that allowed us to estimate the prevalence of the retrocaval ureter, which was identified overall in 9 cases, out of 18,493 subjects. The overall prevalence of retrocaval ureter was 0.13%, with a 95% confidence interval between 0.06 and 0.27%. There was no publication bias, all studies being under the funnel.

CONCLUSIONS

The overall prevalence of retrocaval ureter is 0.13%. Even if this is obviously a rare condition, its presence must be suspected by practitioners, especially in the presence of urological symptoms without a clear cause.

Laparoscopic donor nephrectomy in unusual venous anatomy - donor and recepient implications

OBJECTIVES

Laparoscopic donor nephrectomy is now a commonly performed procedure in most of renal transplantation centers. However, the suitability of laparoscopy for donors with abnormal venous anatomy is still a subject of debate.

MATERIALS AND METHODS

Between August 2007 and August 2014, 243 laparoscopic donor nephrectomies were performed in our institution. All donors were evaluated with preoperative three-dimensional spiral computed tomography (CT) angiography Thirteen (5.35%) donors had a left renal vein anomaly. A retrospective analysis was performed to collect donor and recipient demographics and perioperative data.

RESULTS

Four donors had a type I retroaortic vein, seven had type II retroaortic vein and a circumaortic vein was seen in three donors. The mean operative time was 114±11 minutes and mean warm ischemia time was 202±12 seconds. The mean blood loss was 52.7±18.4mL and no donor required blood transfusion. Mean recipient creatinine at the time of discharge was 1.15±0.18mg/dL, and creatinine at six months and one year follow-up was 1.12±0.13mg/dL and 1.2±0.14mg/dL, respectively. There were no significant differences in operative time, blood loss, warm ischemia time, donor hospital stay or recipient creatinine at 6 months follow-up, following laparoscopic donor nephrectomy in patients with or without left renal vein anomalies.

CONCLUSION

Preoperative delineation of venous anatomy using CT angiography is as important as arterial anatomy. Laparoscopic donor nephrectomy is safe and feasible in patients with retroaortic or circumaortic renal vein with good recipient outcome.

[Study of renal veins by multidetector-row computed tomography scans]

PURPOSE

To determine the prevalence of renal vein variants. To investigate the distribution of renal veins.

METHODS

We retrospectively reviewed spiral computed tomography (CT) scans of the abdomen performed during a two-month period. The same protocol was used for all CT scans: same multidetector-row CT scanner (Siemens(®)), 1 to 2-mm section thickness, injection of intravenous iomeprol. The study group included 121 patients, aged 21.7 to 93.4 years (mean age 60.9 ± 15.4 years). The sex ratio was 2/1, with 80 men and 41 women.

RESULTS

Seventy-three percent of the study group (88 patients) had no variants of the renal veins. Indeed almost 40% (48 patients) had one artery and one vein on each side, with typical course, and 33% (40 patients) had course and/or number variants of the renal arteries. Variants of the right renal vein consisted in multiple veins in 20.6% (25 cases). We detected no case of multiple left renal veins, but we described variations of its course in 9.1% (11 cases): 5 cases of retroaortic left renal vein (4.1%) and 6 cases of circumaortic left renal vein (5%). Three of these 11 patients had an associated double right renal vein. The probability to have a right renal vein variant was significantly higher than a left one (OR = 2.6, P = 0.01). And we found a significantly higher risk of having a venous variant in women (OR = 2.4, P = 0.04). We detected no case of inferior vena cava variant.

CONCLUSION

In our study, prevalence of a circum- or retroaortic left renal vein appeared higher than previously reported in the literature (9.1%). Knowledge of anatomical variants of renal vasculature is crucial and this study puts the emphasis on variations of course and number of renal vessels. Those variations are not so uncommon and should be known by radiologists and also by surgeons. Their knowledge has major clinical implications in practice and it contributes to the safety of renal and retroperitoneal surgery.

Three-phase, contrast-enhanced, multidetector CT in the evaluation of complicated renal cysts: comparison of the postcontrast phase combination

BACKGROUND

Multiphasic multidetector computed tomography (MDCT) is widely used for the assessment and diagnosis of complicated renal cysts.

PURPOSE

To determine the optimal combination of postcontrast phases of MDCT for the evaluation of complicated renal cysts.

MATERIAL AND METHODS

In 164 renal cysts with pathology confirmation or follow-up >2 years, the Bosniak category was recorded by two radiologists in consensus. They reviewed the MDCT images during three interpretation sessions. In the first session, the radiologists evaluated two phases of images (unenhanced and corticomedullary phases), while during the second session, they evaluated two phases of images (unenhanced and parenchymal phases), and in the third session, they evaluated all three phases of images (unenhanced, corticomedullary, and parenchymal phases). The diagnostic accuracy for evaluating renal cysts was compared in each session using receiver-operating characteristics (ROC) analysis.

RESULTS

There were 106 benign renal cysts and 58 malignant renal cysts. The areas under the ROC curves (AUCs) of the second and third sessions were greater than that of the first session (P < 0.05). The sensitivity, specificity, positive predictive value, and negative predictive value of the first session were 74%, 88%, 77%, and 86%, respectively, and those of the second session were 90%, 85%, 77%, and 94%, respectively. The values of the third session were identical to those of the second session.

CONCLUSION

Unenhanced and parenchymal phase CT scans are sufficient for differentiating malignant from benign renal cysts and there was no additional value by adding the corticomedullary phase to the combination of unenhanced and parenchymal phase CT.

Diagnostic accuracy of 64-MDCT angiography in the preoperative evaluation of renal vessels and compared with laparotomy findings in living donor kidney

INTRODUCTION

Multidetector-row computed tomography (MDCT) angiography is a reliable technique in preoperative renal anatomy evaluation in live renal donors.

OBJECTIVES

To investigate the accuracy of early arterial phase findings and compares them with intraoperative findings.

METHODS

In this prospective study, 100 potential live donors undergoing preoperative MDCT and nephrectomy during 2010-2013 were included. The examination was performed with a 64-detector scanner including early arterial and venous phase. MDCT angiography started by bolus tracking and venous phase was acquired 9 s after arterial phase. Anatomical findings and vein and artery attenuation values were recorded and arterial phase findings were compared with intraoperative findings.

RESULTS

All anatomical findings reported by MDCT in early arterial phase were confirmed by intraoperative findings with sensitivity of 100%. Right renal vein was supernumerary in 17 cases and left renal vein was circumaortic in 3 and retroaortic in 5 cases. Renal arteries had early branching in 13, two arteries in 12 and accessory in 8 cases. Vein and artery attenuation values had significant difference between early arterial and venous phase (p < 0.001).

CONCLUSION

Early arterial phase has similar results to venous phase in preoperative evaluation and intraoperative findings and could be used alone to reduce radiation dose.

Current status of low dose multi-detector CT in the urinary tract

Over the past several years, advances in the technical domain of computed tomography (CT) have influenced the trend of imaging modalities used in the clinical evaluation of the urinary system. Renal collecting systems can be illustrated more precisely with the advent of multi-detector row CT through thinner slices, high speed acquisitions, and enhanced longitudinal spatial resolution resulting in improved reformatted coronal images. On the other hand, a significant increase in exposure to ionizing radiation, especially in the radiosensitive organs, such as the gonads, is a concern with the increased utilization of urinary tract CT. In this article, we discuss the strategies and techniques available for reducing radiation dose for a variety of urinary tract CT protocols with metabolic clinical examples. We also reviewed CT for hematuria evaluation and related scan parameter optimization such as, reducing the number of acquisition phases, CT angiography of renal donors and lowering tube potential, when possible.

Low-radiation-dose dual-phase MDCT protocol with split contrast media dose and time optimization: protocol design for renal donors evaluation

BACKGROUND

A routine, multiphase, computed tomography (CT) protocol is associated with high radiation exposure to potential kidney donors. To reduce radiation exposure, several authors have suggested a reduction in the number of phases.

PURPOSE

To evaluate a low-radiation-dose, dual-phase protocol (i.e. a protocol with an unenhanced phase and combined vascular and excretory phase) for the preoperative evaluation of potential renal donors.

MATERIAL AND METHODS

Sixty-five potential renal donors were divided into two groups. The first group was scanned with a routine quadric-phase protocol (non-contrast, arterial, venous, and delayed), and the second group was scanned with a triple-phase protocol (dual phase protocol + venous phase). In the second group, we replaced CT angiography with a routine abdominal CT technique. In addition to the evaluation of renal arteries, veins, and excretory systems, the radiation dose of the suggested protocol was compared to that of the routine quadric-phase protocol.

RESULTS

The suggested protocol was efficient in the evaluation of renal arteries, veins, and excretory systems in all studied potential renal donors. Renal arteries were well visualized in the combined vascular excretory phase using the routine abdominal CT technique; no significant difference was noted when these results were compared to those obtained from the CT angiography used in the quadric-phase protocol. The mean effective radiation dose of our suggested dual-phase protocol was only 34% of the dose resulting from the routine quadric-phase protocol.

CONCLUSION

Use of a low-radiation, dual-phase, CT protocol, which relied on both an unenhanced phase and a combined vascular and excretory phase, significantly reduced radiation dose. Furthermore, the proposed protocol provides adequate visualization of renal arteries and veins, and affords sufficient opacification of the urinary tract using improved acquisition triggering.

Multidetector computed tomography with triple-bolus contrast medium administration protocol for preoperative anatomical and functional assessment of potential living renal donors

OBJECTIVE

To evaluate multidetector computed tomography (MDCT) with a triple-bolus contrast administration protocol for preoperative anatomical and functional assessment of living renal donors.

METHODS

Fifty-five potential living renal donors underwent MDCT of which 27 proceeded to donor nephrectomy. A triple-bolus contrast administration protocol was used for simultaneous acquisition of arterial, nephrographic, and excretory phases. MDCT images were independently reviewed in random order by two radiologists blinded to surgical anatomy findings. Diagnostic accuracy for anatomical variants was quantified by sensitivity and specificity. Differential renal function (DRF) was derived from MDCT for 54 patients and compared with technetium-99 m dimercaptosuccinic acid renography (Tc-99 m DMSA).

RESULTS

All triple-bolus MDCT examinations were technically adequate. Accessory renal arteries and veins were identified at surgery in 33% (n = 9/27) and 22% (n = 6/27) of donor kidneys. The mean difference between MDCT-derived DRF and DMSA was 0.8% (95% CI 0.1-1.6) with 95% limits of agreement of -4.6% (95% CI -3.3 to -5.9) to 6.3% (95% CI 5.0-7.6). MDCT delivered a mean (SD, range) radiation dose of 9.5 (3.6, 3.6-17.3) mSv.

CONCLUSION

MDCT with a triple-bolus contrast administration provides accurate anatomical and functional evaluation of living renal donors.

Assessment of the kidney tumor vascular supply by two-phase MDCT-angiography

PURPOSE

Current kidney surgery uses less invasive laparoscopic and nephron-sparring procedures. Thus, perfect imaging of the renal vasculature is essential for surgery planning. The aim of our retrospective study was to evaluate the accuracy of 16-detector-row CT-angiography in assessing the vascular anatomy of the kidney with a tumor.

SUBJECTS AND METHODS

Referred for computed tomography (CT) because of a suspected renal tumor, 50 consecutive patients (mean age 58.6 years; range 43-82) were enrolled into our retrospective study. All examinations were performed with 16x0.75 mm collimation after the intravenous application of 80 ml of a non-ionic contrast material. The imaging protocol contained two-phase scanning in the arterial and then in the venous phase. The vascular anatomy of the kidney with tumor was evaluated using volume rendered (VRT) and maximum intensity images (MIP). Findings were compared with the anatomy found during surgery.

RESULTS

Forty-seven patients underwent nephrectomy, with an advanced clinical stage (IV) found in the three remaining ones. Correct topography of the renal hilus, including a number of arteries and veins, and the anatomy of their branching, was described in 46 patients. A very small upper polar artery was overlooked in one patient. The accuracy for the only-arterial was 97.9% and only-venous anatomy was 100%. The parasitic vasculature of the tumor was discovered in 10 cases and all of them were confirmed by surgery (100% accuracy). Macroscopic intravenous spread of the tumor was discovered in two cases, but microscopic intravenous invasion was confirmed during histology of the kidney specimens in another two cases, the overall tumor staging accuracy reaching 95.7%.

CONCLUSION

Two-phase multidetector CT is a valuable tool for assessing vascular supply of the kidney before surgery due to the tumor and can fully replace catheter-based angiography.