Configuration of the extra-renal venous system in relation to the left renal vein: A cadaveric study and new proposed classification.

The advent of laparoscopic live-donor nephrectomy for renal transplantation has prompted the need to define the precise anatomical relations of the left renal vein (LRV) and its tributaries. The left kidney is preferred as the greater length of the LRV facilitates implantation in the recipient. While previous studies have described variations in the LRV system, the connections between the left ascending lumbar vein (LALV) and LRV tributaries have been less well-defined. This study aims to further characterise the LALV and proposes a novel classification for its relation to other veins. Dissection of the LRV system, including the left suprarenal vein (LSV), left gonadal vein (LGV) and LALV, was performed in 38 cadavers. Their drainage points into the LRV were recorded, and measurements taken of the distances from these points to the junction of the LRV and inferior vena cava (IVC). The position of the LRV in relation to the aorta was anterior in 35 cases (92%), entirely posterior in 1 case (3%), and circumaortic in 2 cases (5%). Duplication of the LSV and LGV occurred in 6 (16%) and 10 (27%) cases respectively. A direct posterior connection between the LALV and LRV was identified in 32 (86%) cases. The drainage point of the LALV into the LRV lay between the IVC and LGV in 8 (25%) cases. In 20 cases (63%), the drainage points of the LALV and LGV were equidistant from the IVC; and in 5 cases (16%), those of the LALV and posterior branch of the LRV were equidistant from the IVC. In these two groups, the vessels shared a confluent trunk in 10 and 4 cases respectively. In 3 cases, connections were observed between all three vessels (LALV, LGV and posterior branch of LRV). No confluence trunk was shared by the LALV and LSV. These results confirm the high incidence of communicating LALVs, which represent a potentially troublesome source of operative bleeding if unrecognised. Confluent venous trunks may also present difficulties during vessel ligation prior to nephrectomy. It is suggested that a novel classification of the relation of the LALV based on these findings may assist in surgical planning and reduce complications.

Development of the renal vasculature.

The kidney vasculature has a unique and complex architecture that is central for the kidney to exert its multiple and essential physiological functions with the ultimate goal of maintaining homeostasis. An appropriate development and coordinated assembly of the different vascular cell types and their association with the corresponding nephrons is crucial for the generation of a functioning kidney. In this review we provide an overview of the renal vascular anatomy, histology, and current knowledge of the embryological origin and molecular pathways involved in its development. Understanding the cellular and molecular mechanisms involved in renal vascular development is the first step to advance the field of regenerative medicine.

The clinical anatomy of the inferior vena cava: a review of common congenital anomalies and considerations for clinicians.

Anomalies in the course and drainage of the Inferior Vena Cava (IVC) may complicate normal functioning, correct diagnosis, and therapeutic interventions within the abdomen. Development of the IVC occurs during the 4th to 8th week of gestation, and due to its developmental complexity, there are many opportunities for malformations to occur. Although most IVC anomalies are clinically silent and are usually discovered incidentally on abdominal imaging, aberrations may be responsible for formation of thrombosis, back pain, and anomalous circulation of blood to the heart. In this review, we will discuss the most common variations and abnormalities of the IVC, which include the posterior cardinal veins, the subcardinal veins, the supracardinal veins, persistent left IVC, IVC duplication, situs inversus, left retroaortic renal vein, left circumaortic renal collar, scimitar syndrome, and IVC agenesis. For each abnormality outlined above, we aim to discuss relevant embryology and potential clinical significance with regards to presentation, diagnosis, and treatment as is important for radiologists, surgeons, and clinicians in current clinical practice.

Renal failure due to renal vein thrombosis in a fetus with growth restriction and thrombophilia.

We report a case of renal vein thrombosis diagnosed at 27 weeks of gestation in a dichorionic twin pregnancy. The left kidney of one fetus was hyperechoic and enlarged with echoic streaks following the direction of interlobular veins and the loss of corticomedullary differentiation. In the following weeks, left kidney became smaller and echoic, and Doppler examination showed no flow in both artery and vein. The right kidney had totally normal appearance in the beginning, but it became enlarged and hyperechoic, and progressed into a small echoic kidney with no flow in artery and vein. In the postnatal ultrasound examination, both kidneys appeared hyperechoic with no vascularization in the hilum region. There was thrombosis in arteries and veins of both kidneys, as well as in the inferior vena cava. The investigation for thrombophilia resulted with the combined presence of heterozygote mutation in factor V Leiden and prothrombin 20210 genes.

Bilateral renal venous thrombosis and adrenal hemorrhage: sequential prenatal US with postnatal recovery.

A neonate presented with bilateral renal venous thrombosis (RVT) and adrenal hemorrhage. Serial fetal ultrasonography showed progressive development of severe atrophy of one kidney and mild atrophy of the other. At sequential postnatal imaging, both kidneys showed progressive growth. Bilateral fetal RVT is quite uncommon, and postnatal recovery of a kidney severely affected by RVT is very rare.

Inferior vena cava in urology: importance of developmental abnormalities in clinical practice.

Anomalies of the inferior vena cava (IVC) have been known since 1793, when Abernethy first described a congenital, mesocaval shunt and azygous continuation of the IVC in a 10-month-old infant with polysplenia and dextrocardia. The IVC is formed by a complex process of embryogenesis during the sixth to tenth week of gestation. It forms from continuous appearance and regression of the three paired veins: posterior cardinal, subcardinal, and supracardinal. Improper completion of the developmental process may result in at least 14 anatomic anomalies, out of which the following four are usually encountered in clinical practice: duplication of the IVC, transposition or left-sided IVC, retroaortic left renal vein, and circumaortic left renal vein. It is suggested that the preoperative diagnosis of the vascular anomalies reduces the complication rate of abdominal vascular procedures. Our vast experience with approximately 400 kidney donors who were evaluated preoperatively with spiral CT scan with three-dimensional reconstruction (3D) reconfirmed this view. Thereafter, it became easier to choose the side and decide between laparoscopic vs. open approach. This prompted us to write the present article focusing on those developmental anomalies of the IVC that may be encountered by the urologist and their implication on the clinical practice.

Pivotal role of the sub-supracardinal anastomosis in the development and course of the left renal vein.

A retroaortic left renal vein is encountered frequently in the dissecting room and in radiological investigations. A number of recent reports of this variation led us to review the development of the renal veins and the inferior vena cava to understand its etiology. For further insight, we also examined our collection of serial sections of cat embryos. In human embryos of about 15 mm the "renal collar," a venous ring around the aorta, is formed by anastomoses between subcardinal and supracardinal veins. The ventral part of the "renal collar" is formed from the intersubcardinal anastomosis, the dorsal part from the intersupracardinal anastomosis and the lateral parts from the sub-supracardinal anastomoses. The primitive renal veins drain venous blood from the metanephros into the sub-supracardinal anastomoses. A retroaortic left renal vein would form if the dorsal part of the sub-supracardinal anastomosis and the intersupracardinal anastomosis persist whereas the ventral part of the sub-supracardinal anastomosis and the intersubcardinal anastomosis regress.

Clinical implications of left ovarian vein incomplete duplicity with embryonic intersubcardinal anastomosis-derived branches.

During the dissection of a female human cadaver a case of a duplex ovarian vein was observed. It was unique in its upper course where it anastomosed with an inferior polar renal vein, which in turn was linked to an upper polar renal vein by means of a joining branch. It is hypothesised that this represent a persistent link between the left subcardinal vein and the left sacrocardinal vein, together with some branches of a venous net, which represent the embryological intersubcardinal anastomosis. The gonadal vein arises from the distal (or postrenal) left subcardinal vein portion; the left renal vein develops from the intersubcardinal anastomosis. The venous net derived from the intersubcardinal anastomosis may represent a bypass system in cases of left renal vein occlusion. Left gonadal vein duplicity may also play an important role in the anatomical basis of idiopathic left ovarian vein syndrome or left varicocele, and can lead to mistakes being made during venous sclerotherapy.

Vasculogenesis and angiogenesis in the subcardinal venous plexus of quail mesonephros: spatial and temporal morphological analysis.

Vasculogenesis and angiogenesis are involved in a coordinated program for the development of the mesonephric subcardinal venous plexus of quail embryo. Vasculogenesis occurs between days 3 and 4 of incubation, while angiogenesis takes place from day 5 to day 7. Examination of vascular corrosion casts and whole mounts, and tissue sections labelled with specific markers to hemangioblast lineage (QH1, LEP100 and AcPase activity), allowed us to distinguish six phases in the formation of subcardinal plexus. (1) Appearance of isolated angioblast-like cells where the subcardinal plexus will form. (2) Alignment of angioblast-like cells into cellular strands. (3) Formation of compact vascular cords by association of angioblast-like strands. (4) Polygonal interconnection of vascular cords to constitute the primary subcardinal plexus. In this stage, isolated angioblast-like cells were present inside inter-vascular spaces. (5) The splitting of primary inter-vascular spaces by angiogenic sprouts to form secondary subcardinal plexus (outward angiogenesis). Isolated angioblast-like cells were not present in this stage. (6) Expansion of the secondary subcardinal plexus by insertion of slender transcapillary tissue pillars (inward angiogenesis) and angiogenic sprouts. We also describe three morphogenetic gradients during the development of the subcardinal plexus: ventral-to-dorsal, cranial-to-caudal and lateral-to-medial.

Embryological consideration of drainage of the left testicular vein into the ipsilateral renal vein: analysis of cases of a double inferior vena cava.

The right gonadal vein (GV=testicular vein in men, ovarian vein in women) usually drains into the inferior vena cava (IVC) while the left gonadal vein drains into the left renal vein (RV). This anatomical difference induces relatively weak haemodynamics in the left testicular vein (TV) and is considered to be a cause of a left varicocele. In textbooks on embryology, it has been documented that bilateral supracardinal veins (=origin of right and left IVC) and the subcardinal sinus (=origin of RVs and GVs) symmetrically develop during early embryogenesis. However, persistence and regression of the right and left supracardinal veins, respectively, results in drainage of the left GV into the ipsilateral RV. A double IVC (DIVC) commonly originates from a failure of disappearance of the left supracardinal vein. Although there have been a considerable number of case reports on DIVC, little attention has been paid to the anatomy of the left GV in such cases. We report here an autopsy case, a 72-year-old Japanese man, with a DIVC. This case belongs to type BC of McClure and Butler's classification. In this case, it was observed that the right TV drained into the confluence of the right IVC with the ipsilateral RV, while the left TV drained into the left RV in spite of the presence of the left IVC. This case indicates that the embryonic anastomosis point between the subcardinal sinus and the supracardinal vein on the left side is different from that on the right side. Statistical analysis of many case reports of DIVC also suggests that the bilateral supracardinal veins tend to asymmetrically anastomose with the subcardinal sinus during embryogenesis. These data imply that drainage of the left GV into the ipsilateral RV leads to regression of the left supracardinal vein but also to asymmetrical anastomosis between the supracardinal veins and the subcardinal sinus.

Double left renal vein associated with abdominal aortic aneurysm.

Double left renal vein is a rare venous anomaly. We operated on 72-year-old man of abdominal aortic aneurysm (AAA) with double left renal vein. Massive hemorrhage was encountered during encircling the tape around the abdominal aorta. One vein passing posterior to the aorta was injured. Further dissection revealed the presence of double left renal vein forming a ring around the aorta. The patient underwent an abdominal aortic replacement following prompt repair of the injured vein. He had an uneventful postoperative course without renal complication. We missed that preoperative computed tomographic (CT) scan had demonstrated double left renal vein. Preoperative contrast-enhanced CT scan is useful and essential not only for evaluation of AAA, but also for establishing the presence of venous anomalies. Venous anomalies should be taken into consideration on the AAA operation.

[Role of embryogenesis of the left renal vein and spermatic veins in etiopathogenesis of idiopathic varicocele]. / Ruolo della embriogenesi della vena renale sinistra e delle vene spermatiche nella etiopatogenesi del varicocele idiopatico.

The aim of this work was to clearly illustrate that the haemodynamic pathogenesis of the varicocele can be a consequence of a retrograde flux along the internal spermatic vein. The reflux is due to the use of a different path of drainage along the internal spermatic vein, which uses some collateral routes of the vessel, and mainly the nephrogenital branch. The diminishing pressure in the final segment of the internal spermatic vein is the focal points of the pathogenesis of the disease. The ontogenetic processes that lead to the formation of the left renal vein help in explaining the almost general one-sidedness of the disorder, its frequency and the fact that it is mostly the young who are affected by it. In fact, the variability of the timing and of the extension of the involution of the primitive venous system and of the processes of evolution which lead to the morphological definition of the tracts of the genital flow down, lead to the various manifestations of the idiopathic varicocele. This theory which also takes into account the physiological mechanisms of the venous drainage to the testicle in an anti-gravitation sense is part of the patterns that, under the diaphragm, rule the entire venous return of the blood toward to the heart.

Angiopoietin-2 is a site-specific factor in differentiation of mouse renal vasculature.

Angiopoietin-1 (Ang-1) stimulates endothelial and vascular network differentiation through the Tie-2 receptor tyrosine kinase, while Ang-2 modulates this activation in embryo and tumor growth. The nephrogenic pattern of Ang-2 was documented in a mouse strain that expresses the LacZ reporter gene driven by the Ang-2 promoter. Heterozygous animals were healthy with morphologically normal kidneys, and they were examined after X-gal staining. At embryonic days 10.5 (E10.5) and E12.0, transgene expression was absent in the mesonephros and metanephros. At E14.0, expression was noted in the metanephric artery and its major branches. At E19.0 and in neonatal kidneys, expression was maintained in larger renal artery branches, extending to arcuate and smaller cortical vessels. Histologically, transgene expression was located in multiple layers of vessel wall cells, extending further from the endothelium than alpha-smooth muscle actin. The mesangium of immature glomeruli also expressed LacZ. In the first 3 postnatal weeks, a new pattern became evident, with intense X-gal staining in the inner stripe of the outer medulla, where a subset of thin descending limbs of loops of Henle expressed the transgene. This dynamic and developmentally regulated pattern indicates that Ang-2 is an early marker of the renal pericyte and vascular smooth muscle lineage and is also an epithelial-derived growth factor. Because Tie-2 is widely expressed by differentiating renal endothelia, this study is consistent with the hypothesis that Ang-2 has roles in kidney vascular maturation.

Anomalies of the inferior vena cava and renal veins: embryologic and surgical considerations.

Anomalies of the inferior vena cava and renal veins occur infrequently but if unidentified can lead to significant morbidity during surgical exploration. An understanding of the embryologic development of the vena cava and its tributaries is necessary to understand the genesis of these sometimes complex anomalies and their accompanying anatomic variants. Newer radiologic modalities in the form of spiral computed tomography (CT) and three-dimensional reconstruction of spiral CT allow clear definition of the anatomy of these anomalies. Variations in the embryologic evolution of the vena cava dictate the different venous anomalies that may be encountered in the retroperitoneum. Additionally, the utility of newer radiologic modalities in the identification of these anomalies is discussed.

Absence of renal vein valves in humans and baboons.

There is disagreement on the presence of renal vein valves. Cadaveric anatomical and radiological studies were undertaken on renal veins to determine their presence. No valves were demonstrated in the samples studied (56 adult human, 11 fetal and 11 Chacma baboon kidney pairs). The significance and reasons for this disagreement are discussed.

The renal veins in the human cadaveric fetus: their importance as contributors to collateral flow.

The venous collateral flow emanating from and around the renal veins was investigated in the human cadaveric fetus. Experimental venous occlusion was performed along several venous pathways under the sphere of influence of the renal veins in 11 fetuses. Radiological techniques were used to investigate renal venous collateral flow. Extensive venous collaterals centered on the left renal vein were observed. It is concluded that the left renal vein is a major venous collateral pathway in the fetus whereas the right renal vein contributes little. This potential for collateralisation may be operative in the adult and may play a dominant role in disease states.

Congenital anomalies of the inferior vena cava: embryogenesis and MR features.

This article describes the MR appearances of the six most common congenital anomalies of the inferior vena cava. As a basis for understanding those anomalies, it describes the embryology of the inferior vena cava, based on an actual study of embryos and fetuses. The article takes a fresh look at the original research in this area, discusses the possible embryogenesis of the relevant anomalies, and describes different opinions on that subject, where different opinions exist.

Regional variation of postjunctional alpha-adrenoceptor responses in the developing renal vascular bed of sheep.

Postjunctional alpha 1- and alpha 2-adrenoceptor vasoconstrictor responses were evaluated in isolated segments of main renal artery, segmental renal artery, and renal vein from fetal (130-138 d of gestation; term 145 d), newborn (3-15 d age), and nonpregnant adult sheep. Vascular rings were mounted at their optimal resting tension and responses to phenylephrine (alpha 1-adrenoceptor agonist) and guanabenz and UK14304 (both alpha 2-adrenoceptor agonists) were determined. Optimal resting tension increases with development in the main renal artery, segmental renal artery, and renal vein of sheep. Arterial vessels develop more isometric tension to alpha 1-adrenoceptor stimulation than to alpha 2-adrenoceptor stimulation, whereas venous segments develop similar isometric tension to alpha 1- and alpha 2-adrenoceptor stimulation. The segmental renal artery develops more isometric tension to alpha 2-adrenoceptor stimulation than the main renal artery. No large developmental differences exist among vessels in the sensitivity (concentration required for half maximal response, ED50) to alpha-adrenoceptor stimulation except for the renal vein with alpha 2-adrenoceptor stimulation. Maximum isometric tension corrected for vessel cross-sectional area decreases with age for all vessels with both alpha 1- and alpha 2-adrenoceptor stimulation. These findings may reflect developmental differences in receptor number and affinity or differences in vascular smooth muscle function. In addition, these data suggest that whereas both alpha 1- and alpha 2-adrenoceptors mediate vasoconstriction in the renal circulation, they may do so at different sites.