Introduction

The anatomy of the left renal vein (LRV) is more complicated than that of the right because of its complex embryogenesis and the collocative relationship with the abdominal aorta and the superior mesenteric artery. The LRV is normally anterior, and travels to the right side in front of the aorta. Developmental venous anomalies of the LRV occur as circumaortic or retroaortic LRV [27]. Many reports have indicated the clinical significance of retroaortic LRV (RLRV) or circumaortic left renal vein (CLRV) (also called “circumaortic venous ring”, or “renal collar”), e.g., in postpartum renal vein thrombosis with RLRV [41], gross hematuria, or microscopic hematuria attributed to RLRV with renal vein hypertension [12, 23], associated with the posterior nutcracker phenomenon or syndrome [8, 23, 32]. Furthermore, the LRV is normally located in the retroperitoneal space, in front of the renal artery. A retropelvic tributary (RPT) of the renal vein, also called the posterior primary tributary [35, 36], the posterior renal vein [30] or the supernumerary renal vein [30] is a common variation of the LRV; knowledge of the incidence and imaging features of the venous tributary is very important to avoid malpractice or hazardous results.

Although the anatomical variations, CLRV, RLRV, and RPT, have been well reported, statistical findings and analysis of their incidences are conflicting or limited in the literature. In this paper, three cadaver cases with anatomical variations of the LRV are described with special reference to a detailed review of the literature and meta-analysis in terms of either clinical reports or cadaver dissections.

Materials and methods

During routine gross dissection in the laboratory of the Anatomy Department of Tokyo Medical University in 2006–2007, three cases of anatomic variations of the LRV, CLRV, RLRV, and RPT were encountered.

Results

CLRV occurred in a 96-year-old Japanese male. The LRV split into two limbs of unequal caliber, which passed either in front of or behind the abdominal aorta to drain into a single inferior vena cava (IVC). The upper ventral limb received the left suprarenal vein and opened into the IVC at a normal level. The tenuity below the dorsal limb passed obliquely and downwards in the posterior aspect of the aorta to join the IVC 4.5 cm below the upper trunk (Fig. 1a).

Fig. 1
figure 1

Photograph of the CLRV (arrows in a), RLRV (b) and RPT (asterisk in c). The arrows (in c) showed the communicating veins between the RPT and lumbar and ascending lumbar veins. alr accessory left renal a.; ao aorta; ct celiac trunk; ivc inferior vena cava; im inferior mesenteric a.; lk left kidney; lov left ovarian v.; lr left renal a.; lrv left renal v.; lsrg left suprarenal gland; lsrv left suprarenal v.; lu left ureter; rk right kidney; rov right ovarian v.; rr right renal a.; rrv right renal v.; sm superior mesenteric a.

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RLRV occurred in an 81-year-old Japanese female. The LRV, after receiving the suprarenal and ovarian veins, passed behind the aorta to join the IVC at the level between the second and third lumbar vertebrae (Fig. 1b).

RPT occurred in a 69-year-old Japanese female. The main trunk of the LRV received the ovarian and the suprarenal veins, and ran transversely in front of the aorta to empty into the IVC at the usual level. Besides the main trunk, an additional renal vein was located below the LRV and behind the renal pelvis and artery and joined the LRV via a thicker connecting trunk (Fig. 1c).

In all of the three cases, there were anastomosis between the CLRV/RLRV/RPT and the ascending lumbar veins and/or the second and third lumbar veins, in particular, the PRT presented complex anastomosis with the lumbar veins (Fig. 1a–c).

Discussion

In this study, three different anatomical variations of the LRV identified in cadaver dissection, the CLRV, RLRV, and RPT, were described.

The incidences of CLRV and RLRV in cadaver dissection and clinical observation (MDCT scan, MRI, angiography, surgical series) are shown in Tables 1 and 2, respectively. Case reports or studies with a small sample size (<100 subjects or samples) have not been included in Tables 1 and 2.

Table 1 The incidences of CLRV and RLRV in cadaver dissections
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Table 2 The incidences of CLRV and RLRV in clinical investigations
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According to our statistics, the incidences of CLRV ranged from 0.6 to 17.0 % in cadaver dissection, and from 0.1 to 10.0 % in clinical reports (Tables 1, 2). The median incidences of CLRV were 7.0 % (200/2,839) in cadavers examined (Table 1) and 1.8 % (287/16,221) in clinical subjects examined (Table 2). This shows that CLRV is one of the most common congenital venous variations. The median incidence of CLRV in clinical reports was markedly lower than that with cadaver dissection. This might indicate that the detection of CLRV in CT/MDCT or angiography was relatively difficult compared with that in cadaver dissection. Among these findings, the detection of CLRV in angiography (10 %, [25]) was relatively easy compared with that in CT/MDCT (0.1 %, [14]; 0.3 %, [36]).

On the other hand, the incidences of isolated RLRV ranged from 0.5 to 3.5 % in cadaver dissection, and from 0.4 to 9.3 % in clinical reports (Tables 1, 2). The median incidences of RLRV were 1.7 % (52/2,999) in cadavers examined (Table 1) and 2.2 % (354/16,046) in clinical subjects examined (Table 2). This shows that the incidence of RLRV was not significantly different in cadaver dissection and clinical reports, although it was a little higher in cadaver dissection. However, rate of detection of RLRV in operations was the lowest (0.4 %, [7]; 0.5 %, [36], but relatively easy by ultrasonography (9.3 %, [18]).

The incidence of RPT is shown in Table 3. It was previously identified in 30.0 % [28], 30.4 % [30], and 46.4 % [35] of cases in cadaver dissection. This is very frequent.

Table 3 The incidence of the retropelvic tributary of the renal vein
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Furthermore, the incidences of the communicating veins between the LRV and retroperitoneal veins, e.g., lumbar, ascending lumbar, capsular, and hemiazygos veins, are shown in Table 4. This was identified to range from 30.0 to 84.2 % in cadaver dissections (median of 68.7 %) and from 34.0 to 75.8 % in clinical reports (median of 57.5 %) (Table 4). Both had very high incidences of RPT, which were higher in cadaver dissection.

Table 4 The incidence of communicating veins between the LRV and retroperitoneal veins
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Moreover, most commonly, the location of the communicating vein was the second lumbar vein, but frequently the third lumbar vein, and, on occasion, both the second and the third lumbar veins [3, 4, 42]. As for our present cases, they usually involve communicating veins in the dorsal limb of the CLRV, or the RLRV, and/or the RPT, which receives easily drainage of the lumbar, vertebral, capsular, and hemiazygos systemic veins [4, 5, 24].

In summary, the veins in question, referred to as CLRV or RLRV, are not rare variations. In addition, the RPT showed high incidence and, thus, perhaps should not be called congenital variations (or aberrant veins, supernumerary veins), but rather usual features. The relatively high frequency of CLRV, RLRV, or the RPT and branches communicating with the retroperitoneal veins makes them one of the most common types of congenital variation. An understanding of this is essential in cases of renal transplantation, renal surgery, uroradiology, gonadal color Doppler imaging, surgery of aneurysm of abdominal aorta, and gonadal surgery.