Anatomical variations of the renal arteries: Cadaveric and radiologic study, review of the literature, and proposal of a new classification of clinical interest

Renal Artery Triplication: An Unusual Morphological Variant

Renal vasculature depicts great morphological variability and clinical significance due to the great number of procedures performed on kidneys. The current imaging report presents a right-sided renal artery (RA) triplication and origin from the abdominal aorta (AA), which was incidentally identified during computed tomography angiography (CTA). The typical RA corresponded to the main hilar artery (MHA), the second RA corresponded to the superior polar artery (SPA), and the third RA corresponded to the inferior polar artery (IPA). RA triplication occurs in 0.9%-4.5% and depicts wide morphological variability. The current report corresponds to one superior polar, one inferior polar, and a main hilar renal artery, which represents a rare morphological type of RA triplication. Kidney transplantation surgery, endoscopic surgery, and renal angiography require adequate knowledge of RAs and their variants to avoid pitfalls and iatrogenic lesions from clinicians.

Anatomical variability of kidney arterial vasculature based on zonal and segmental topography

Introduction

To date, there is no unified approach to the lobar, zonal, and segmental structure of the kidney vasculature. There is no recognizable approach to define basic characteristics in regard to the lobes and segments identifying of the kidney. The branching of the renal artery has often been the subject of scientific research. This study aimed to analyze the arterial anatomy on the basis of zonal and segmental topography.

Materials and methods

This study is a prospective cadaver study on autopsy material using corrosion casting and CT imaging techniques. The arterial vasculature was visualized using corrosive casting. In this study, 116 vascular casts were included. We identified the number of arteries in the kidney hilum, their topography, branching variations of the renal artery, and local blood supply zones of renal masses considering second- and third-order renal artery branches. We used a micro-CT BRUKER SkyScan 1178, digital camera, Mimics-8.1, and R.

Results

This study has shown that RA divides into two or three zonal arteries, forming a two- or three-zonal vascular supply system. In the case of the two-zonal system, 54.3% of cases accounted for RA branching into ventral and dorsal arteries, whereas 15.5% of cases referred to superior polar and inferior polar zonal arteries. The three-zonal system implies 4 types of RA branching: 1) superior polar, ventral, and dorsal zonal branches (12.9%); 2) ventral, dorsal, and inferior polar zonal branches (9.5%); 3) two ventral and one dorsal zonal branches (5.2%), and 4) superior polar, central, and inferior polar zonal branches (2.5%).

Conclusions

The results of this research make us reconsider Grave's classification theory.

Image-guided study of swine anatomy as a tool for urologic surgery research and training

PURPOSE

To describe the anatomy of the swine urinary system using computed tomography and to discuss the role of this animal as an experimental model for urological procedures.

METHODS

Three male Landrace pigs underwent computed tomography and the anatomy of the urinary system and renal circulation was analyzed and described.

RESULTS

In all animals, 2 kidneys, 2 ureters and one bladder were identified. Each kidney presented a single renal artery vascularization, with a mean diameter on the right of 4.45 and 5.31 mm on the left (p < 0.0001) and single renal vein drainage, with a mean diameter on the right of 5.78 and 5.82 mm on the left (p = 0.0336). The average renal length was 9.85 cm on the right and 10.30 cm on the left (p < 0.0001). The average renal volume was 113.70 cm3 on the right and 109.70 cm3 on the left (p < 0.0001). The average length of the ureter was 19.78 cm on the right and 22.08 cm on the left (p < 0.0001). The average bladder volume was 423.70 cm3.

CONCLUSIONS

The data obtained show similarities with human anatomy, suggesting the viability of the swine model for planning preclinical trials, basic research, refinement in experimental surgery and surgical training for urological procedures.

Renal-aortic ratio as an objective measure of renal artery diameter a computed tomography angiography study

Background

Considering vital role of renal arteries in many surgical procedures, diameter of renal arteries seems to be an important measure of kidney perfusion. In this study, we analyzed a new parameter, renal-aortic ratio (R-Ar) as an objective measure of the renal artery diameter.

Method

The study included CT angiographic images from 254 patients (129 women and 125 men). R-Ar was calculated by dividing the diameter of the main renal artery for each kidney by the aortic diameter.

Results

R-Ar values for the whole study group ranged between 0.0863 and 0.5083; the ranges of R-Ar values for women and men patients were 0.1150–0.5083 and 0.0863–0.4449, respectively. In 412 cases (81.10%), the kidney was supplied by a single renal artery (RA variant) and in 96 (18.90%) by more than one artery (sRA variant). A significant difference was found in R-Ar values for RA and sRA variants (p = 0.0008). When the anatomical variant of renal perfusion was not considered on statistical analysis, a significant difference was found between the R-Ar values for women and men (p = 0.0259). No statistically significant difference was observed in R-Ar values for the right and left kidneys (p = 0.3123). Spearman’s coefficient of rank correlation between patient age and renal-aortic ratio values for the whole study group equaled − 0.36.

Conclusion

The analysis of the renal-aortic ratio values demonstrated that the diameter of renal arteries depended primarily on their number, and the relative diameter of renal arteries in women was larger than in men.

Accessory polar renal artery not pre-operatively visualized at extra-peritoneal para-aortic lymphadenectomy

The objective of this video is to describe the technique of extra-peritoneal para-aortic laparoscopic lymphadenectomy and emphasize potential vascular risks that should be taken into account during the procedure.The procedure was performed at Donostia University Hospital, a tertiary referral and educational center in San Sebastián, Spain.A 58-year-old woman, body mass index 25.4 kg/m², G2P2, with a diagnosis of intermediate-risk endometrial adenocarcinoma, International Federation of Gynecology and Obstetrics (FIGO) IBG2 based on pre-operative endometrial histology and pre-operative magnetic resonance imaging (MRI), but upstaged to high-risk endometrial adenocarcinoma on final report (IBG3). In our hospital, risk stratification is based on pelvic MRI (myometrial invasion, cervical invasion) and biopsy (histology and grade) to tailor surgery. Computed tomography (CT) scan pre-operatively is only performed for type 2 endometrial carcinoma and grade 3 histologies.The local institutional review board was consulted, which confirmed that the study was exempt from requiring approval.The patient underwent an extra-peritoneal para-aortic laparoscopic lymphadenectomy, trans-peritoneal bilateral pelvic lymphadenectomy, and a total hysterectomy and bilateral salpingo-oophorectomy.It is mandatory to check pre-operative imaging studies in order to identify vascular anomalies that are not uncommon and may increase the risk of vascular complications.1 Frequently these vascular anomalies, such as a retro-aortic left renal vein, or a double vena cava or left vena cava, may be a casual finding in the pre-operative study, and often such findings are not reported by the radiologist. It is vitally important that the surgeon checks for and identifies any such anomolies, as the risk of complications may be decreased if anomalies of this type are detected pre-operatively.In addition, in the case of existing polar renal arteries, these are frequently not identified in the pre-operative study,2 leading to a risk of injury and partial renal necrosis. There are several anatomical variations of the renal arteries, with an aortic lower polar artery found in 3% of cadavers and 1% of patients on CT, more frequently on the right side.3 Renovascular hypertension4 secondary to an injury of an accessory polar renal artery (APRA) has also been described.Although vascular anomalies, especially venous ones, are more frequently found at the infra-renal left level, in this video we show access to the right side of the dissection and the care that needs to be taken in order not to damage a vascular structure at this level. Special caution is required with the right side of the dissection so as not to injure any perforating veins, including Fellow's vein, when pushing all the nodes to the roof of the dissection.The dissection maneuvers are fine and blunt, establishing bridges of tissue to be sectioned, and thus identifying vascular structures, such as a right APRA that is to be identified and preserved.The surgeon must have a good knowledge of retro-peritoneal vascular anatomy, they should examine pre-operative imaging studies to check for vascular anomalies, and they need to possess an accurate surgical technique to avoid potential vascular injury during laparoscopic para-aortic lymphadenectomy.

A Case Study of Malrotated Kidneys with Asymmetric Multiple Renal Arteries, Variant Venous Drainage, and Unilateral Ureteral Duplication

Variations in the arterial, venous, and ureteral patterning of the right (r) and left (l) kidneys are common; however, concomitant involvement with all three systems is rare. Specimens that demonstrate anatomic variation across multiple systems provide an opportunity to illustrate links between anatomic concepts, embryologic development, clinical practice, and education. During anatomic study of the abdominal cavity, a total of five major arteries (3l and 2r) emerged from the aortic and common iliac axes in a cadaveric donor. Through continued study, multiple contributing veins, of different caliber, coalesced into four major renal veins (2l and 2r) that returned blood from the kidneys to the inferior vena cava (IVC) at different locations. In addition, unilateral duplication of the kidney with concomitant ureters was evident on the right side. Both ureters continued inferiorly and independently entered the bladder, each with an observable orifice adjacent to the bladder trigone. Most evident in the specimen was the anteriorly directed hilum for both kidneys. Reported measures for each of the observed anatomic variations suggest that the current specimen has an estimated incidence of less than 0.3%. This comparatively rare specimen provides an example of important anatomic concepts that are relevant to educational and clinical practices.

Integration of anatomical and radiological analysis suggests more segments in the human kidney

An increasing number of observations have called the general scheme of five renal segments into question: anatomists, radiologists, and surgeons have reported discrepancies between Graves's scheme and morphological observations. The aims of the present study are: (1) to assess the correspondence between a virtual and a real vascular cast of the kidney; (2) to analyze the arterial anatomy with reference to the renal segments. Fifteen kidneys were injected with acrylic resins to obtain vascular casts, which were also analyzed by computed tomography. A mean of 6.3 (range 4-8) avascular fissures was found, indicating a mean of 7.3 segments (range 5-9). In the superior and middle territories there was a single segment in 4 (26.7%) and 8 (53.3%) cases, respectively, and there were two segments in 11 (73.3%) and in 7 (46.7%) cases, respectively. In the inferior territory there was a single segment in two cases (13.3%), two segments in nine (60%), and three segments in four (26.7%). A mean segmental volume of 550.5 mm³ was calculated; the posterior (1,030.1 mm³ , 28.9%) and inferior (450.3 mm³ , 24.2%) segments were the largest. More third order branches were identified in the inferior segments than in the other segments (three branches of the inferior segmental artery in 26.6%). According to these data the inferior segment occupies the inferior pole, extending both anteriorly and posteriorly. In conclusion, the high correspondence between a virtual and a real vascular cast permits more segments to be identified than those described by Graves, and the volume of each segment can be calculated. Clin. Anat., 2018. © 2018 Wiley Periodicals, Inc.

The level of origin of renal arteries in horseshoe kidney vs. in separated kidneys: CT-based study

Purpose

Horseshoe kidney is a rare congenital anomaly with potential clinical implications. The aim of this study was to determine the number of renal arteries and veins and the level at which the arteries branched off their parental vessels in individuals with horseshoe kidney (HSK) and in persons with separated kidneys (SK).

Materials and methods

The analysis included computed tomography angiography studies of 331 patients (83 HSK and 248 SK). The number of renal vessels and diameters of renal arteries were determined, along with the level at which they branched in relation to other ramifications (four groups of origin were proposed) and their entrance of the vessels to the kidney.

Results

Number of renal arteries in HSK group was 4.57 ± 1.39 per patient and 2.4 ± 0.43 in SK group (p < 0.0001). The distribution of branching level of renal arteries in HSK group was: I group ~ 57%, II group ~ 27%, III group ~ 15% and IV group < 1%, whereas in SK group the distribution was respectively: I group ~ 99%, II group < 1%, III and IV group − 0% (p = 0.0001). In HSK group, diameter of renal arteries branching above the IMA was 4.61 ± 1.58 mm, as compared with 3.96 ± 1.34 mm for the arteries branching below (p = 0.0004). Number of veins was 566 in SK group (87.70% of kidneys were supplied by single vein) and 323 in HSK group (9.64% kidneys were supplied by two veins) (p < 0.0001).

Conclusion

In HSK group, renal arteries significantly more often branch off their parental vessels below the origin of IMA and such vessels are usually smaller.

The size of the renal artery orifice contributes to laterality of acute renal infarction

BACKGROUND

Acute renal infarction (ARI) is a rare disease with atrial fibrillation being its main cause. The possible laterality of ARI is controversial. This study aimed to evaluate the association between anatomical features of the renal arteries and ARI.

METHODS

This was a single-center cross-sectional study that evaluated the anatomical and clinical features of renal arteries. The anatomical features of the renal arteries were assessed using computed tomography.

RESULTS

A total of 46 patients (mean age 71.3 ± 14.0 years; men, 59%) were enrolled. ARI involved the left kidney in 63%, right kidney in 28%, and both kidneys in 9% of patients. The right renal artery orifice was often higher than that of the left renal artery (71%). The angle of divergence from the abdominal aorta was similar on both sides. The left renal artery orifice was larger than that of the right (83 ± 24, 72 ± 24 mm²; p = 0.03, respectively). A larger left orifice was present in 72% of all cases. ARI involved the side with the larger orifice in 64% of patients.

CONCLUSION

The size of the renal artery orifice may be a factor that contributes to the laterality of ARI. Assessment of anatomical features is important when considering the laterality of the disease.

Does the type of renal artery anatomic variant determine the diameter of the main vessel supplying a kidney? A study based on CT data with a particular focus on the presence of multiple renal arteries

Background

An in-depth knowledge of renal vascular anatomy is essential when planning many surgical procedures; however, a few data exists regarding renal artery diameter. The aim of this study was to assess this morphological feature and to investigate whether a correlation exists between renal artery diameter and the type of arterial supply, with a particular emphasis on variant anatomy and the presence of multiple renal arteries.

Materials and methods

Computed tomography angiography (CTA) studies of 248 patients, i.e., a total of 496 kidneys, were evaluated. The mean age of the patients was 66.4 ± 15.01 years. Renal artery diameter was measured based on the type of arterial blood supply.

Results

The frequency of occurrence of three anatomic variants of renal arterial supply was established: single renal artery (RA) 43.35%, single artery with prehilar branching (pRA) 37.30%, and multiple renal artery (mRA) 19.35%. The diameter of single renal arteries, with either prehilar or hilar branching, was significantly larger than when multiple arteries were present. A detailed analysis of just the mRA variant demonstrated that the diameter of the renal arteries in men was larger (p = 0.012) than those in women and that there was no difference in diameter with regard to the side of the body (p = 0.219).

Conclusions

The classification described in our study containing a detailed description of renal artery diameter. It may be helpful in clinical practice, especially for transplantologists, surgeons, and vascular surgeons.