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Chapter 20 Inferior Vena Cava: Embryology and Anomalies 293
to 3.3% based on autopsy series.
6,
17,
23,
25–
28
(see Table 1 ). Despite the increase
in preoperative imaging, studies have demonstrated that these anomalies are
often missed during preoperative workup by both the surgeon and the radiolo-
gist. These undiagnosed anomalies can lead to vascular injury and potentially
life-threatening hemorrhage during aortic and retroperitoneal surgery. In a
series from the Mayo Clinic, of eight patients with venous anomalies under-
going aortic reconstruction which was complicated by significant (>500 cc)
blood loss, seven were undiagnosed preoperatively.
24
Retroaortic and Circumaortic Left Renal Vein
During the sixth through the eighth week of development, the subcardinal and
supracardinal veins form a central anastomotic web around the aorta, as earlier
discussed. The anterior segment of the web becomes the left renal vein, while
the posterior portion regresses. Failure of regression of the posterior portion
leads to circumaortic left renal vein (Fig. 2 ), while persistence of the posterior
segment and regression of the anterior segment lead to a retroaortic left renal
vein (Fig. 3 ).
8
There are four classifications of retroaortic left renal vein. In
type I, the left renal vein passes directly behind the aorta and inserts at the nor-
mal location on the IVC. Type II descends from its takeoff at the renal hilum
and intersects the IVC at approximately L4/5. Types I and II tend to occur
with similar frequency in the literature.
10,
17
Type III is the circumaortic left
renal vein, which occurs more frequently than type I or II, as discussed below.
Type IV descends from the renal pelvis to insert on the left common iliac vein.
There are very few case reports of this type of anomaly in the literature.
10,
29
The presence of a retroaortic left renal vein is a very dangerous clini-
cal situation, associated with a significant risk of damage, hemorrhage, and
interoperative death if the vessel is not identified and protected during aortic
surgery.
29
In radiographic series, the incidence of retroaortic left renal vein
Fig. 2 CT scan of patient with circumaortic left renal vein. The preaortic branch
(arrow 1) and the retroaortic branch (arrow 2) of left renal vein are seen
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294 B. Knipp et al.
ranges from 0.1% to 3.2%.
4,
10–
14,
16–
19
Surgical series cite rates from 0.9% to
2.8%,
17,
20–
21,
23–
24
and autopsy series cite from 1.1% to 3.5%.
17,
23,
25–
28
In a study
by Brener et al., 9 of 20 (45%) retroaortic left renal veins were injured dur-
ing dissection, leading to two nephrectomies and two deaths. They concluded
that the most dangerous maneuver with respect to venous injury during aortic
dissection is circumferential dissection of the proximal aorta.
30
In the Mayo
series, 5 of 26 cases of retroaortic left renal vein were injured (19%); only
one was identified preoperatively. In this series, the diagnostic accuracy of
preoperative imaging was only 19% for retroaortic left renal vein and 25%
for circumaortic left renal vein. All diagnoses were made by CT scanning;
ultrasound was uniformly unable to diagnose this condition. Limiting analysis
to CT scanning only, the preoperative diagnostic accuracy was still only 45%
for retroaortic left renal vein and 33% for circumaortic left renal vein.
24
Bartle
et al. recommend a superior approach to obtain proximal control once a retro-
aortic left renal vein has been identified.
21
The circumaortic left renal vein is arguably more dangerous than the ret-
roaortic renal vein, as the presence of the preaortic branch can lead to a false
sense of security if preoperative diagnosis of the anomaly is not made.
22
This
anomaly is likely underreported due to the fact that surgeons do not generally
look for a retroaortic left renal vein branch once the preaortic vein has been
found. Nonetheless, the rate is reported to range from 0% to 9% in the radio-
graphic literature,
4,
10–
14,
16–
19
0.2% to 9.4% in surgical series,
17,
20–
22,
24
and 0.6%
to 16.8% in autopsy series.
17,
25–
28
In 15% of cases, multiple preaortic or retro-
aortic left renal vein branches exist. The retroaortic branch of the circumaortic
left renal vein tends to run obliquely to the aorta, putting it at increased risk
from clamp injury. Once the diagnosis of circumaortic left renal vein has been
made, however, one branch (ideally the more diminutive) can be ligated safely.
Bartle et al. recommend securing proximal control of the aorta below the level
of the circumaortic left renal vein, as opposed to approaching it superiorly as
recommended for the purely retroaortic left renal vein.
21
Fig. 3 CT scan of patient with retroaortic left renal vein ( arrow )
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Chapter 20 Inferior Vena Cava: Embryology and Anomalies 295
While a retroaortic left renal vein is generally asymptomatic, they
occasionally present with symptoms of venous outflow obstruction from the
renal, pelvic, or gonadal vessels (Table 2 ). One study has documented an
association between retroaortic left renal vein and varicocele. In a case control
study of 277 patients, the rate of retroaortic left renal vein was 9.3% in patients
with a left or bilateral varicocele compared with 2.2% of control patients.
31
The authors conclude that the retroaortic left renal vein may be part of the
etiology of varicocele, and conversely the presence of varicocele in a patient
undergoing aortic surgery should suggest the potential presence of a retroaor-
tic left renal vein. Koc et al. presented case reports of two female patients with
pelvic congestion syndrome and double retroaortic left renal veins, suggesting
a correlation.
32
Gibo et al. documented a case of gross hematuria secondary to
retroaortic left renal vein in a 13-year-old female; left renal venous hyperten-
sion was verified with pullback pressures.
33
One rare but potential complication of a retroaortic left renal vein in a
patient with an abdominal aortic aneurysm is rupture of the aneurysm into the
left renal vein secondary to compression of the vein by the expanding aneu-
rysm against the vertebral bodies leading to pressure necrosis. These patients
generally do not present with high output cardiac failure or massive lower
extremity edema, as do patients with aortocaval fistulae. Instead they gener-
ally present with one or more of the following: left flank pain due to stretch
of Gerota’s fascia from venous congestion of the kidney, hematuria, and acute
renal failure which tends to resolve with prompt repair of the fistula. A physi-
cal finding of this condition is a new left flank bruit. A palpable thrill in the
left renal vein noted during surgical dissection can be a diagnostic clue to the
presence of this complication.
Table 2 Most common presenting symptoms of caval anomalies.
Most common symptoms
Retroaortic or circumaortic left renal vein
Asymptomatic
Varicocele
Pelvic congestion syndrome
Unexplained hematuria
Left-sided or duplicated vena cava
Asymptomatic
Lower extremity swelling
Recurrent deep venous thrombosis
Venous stasis ulceration
Absent retrohepatic vena cava with azygos continuation, absent pararenal
or infrarenal vena cava
Asymptomatic
Lower extremity swelling
Recurrent deep venous thrombosis
Venous stasis ulceration
Hemoptysis
Marsupial cava
Asymptomatic
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296 B. Knipp et al.
Left-Sided Vena Cava
During normal development, the infrarenal vena cava develops from the right
supracardinal vein during the seventh to eighth week of gestation. The poste-
rior cardinal veins, which develop earlier during the fourth week, provide the
outflow from the lower extremities by developing into the iliac veins. These
veins form ventral and dorsal anastomoses in the midline, and then divide again
as they run caudally. Once the right supracardinal vein develops, it descends
and joins the iliac confluence in the dorsal location. The anterior anastomosis
regresses; persistence of this anastomosis and joining of the right supracardinal
vein at this point lead to preaortic iliac vein confluence, which will be discussed
separately. The left supracardinal vein generally regresses, as do the posterior
cardinal veins above the iliac confluence.
If the left supracardinal vein persists and the right vein regresses, this leads to a
left-sided vena cava. This is generally a mirror image transposition below the renal
veins; the left gonadal vein inserts on the vena cava and the right inserts on the right
renal vein (Figs. 4 and 5 ). The vena cava crosses to the right side at approximately
the level of the renal arteries, generally crossing in front of the aorta. Prevalence of
this anomaly ranges from 0.04% to 1.5% in radiographic series,
4,
11–
12,
14–
17
0.1% to
0.3% in surgical series,
21,
24
and 0.1% to 0.6% in autopsy series.
6,
26,
28
Fig. 4 Diagrammatic representation of a left-sided vena cava. Note that the caudal segment
of the right supracardinal vein has regressed inappropriately and the left side has persisted
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Chapter 20 Inferior Vena Cava: Embryology and Anomalies 297
Fig. 5
CT images of a patient with left-sided inferior vena cava. ( a )
Intrahepatic vena cava ( arrow ) in orthotopic position. ( b ) Vena cava cross-
ing the midline ( arrow ). ( c ) Left-sided vena cava ( arrow ). ( d ) Volume ren-
dered image of a inferior vena cava. Note the transition from a right-sided
structure superiorly to a left-sided structure inferiorly (See Color Plates)
In general, a left-sided inferior vena cava is asymptomatic, as the caliber of
the vessel is equivalent to that of the cava in the orthotopic position. However,
there is one case report in the literature of a left-sided IVC presenting as a
right-sided May-Thurner syndrome (compression of the right iliac venous
outflow tract by the overlying right iliac artery).
34
Preoperatively, a cavagram should be obtained through a left femoral vein
puncture to accurately roadmap the caval anomaly, the renal veins, and the
level of crossing of the IVC to the right. Exposure options for the aorta in this
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298 B. Knipp et al.
case include dissection and mobilization of the IVC, division of the right renal
vein, and division of the IVC.
21
However, caval division and reanastomosis are
frequently associated with thrombosis. Clamping of the cava is also frequently
associated with hemodynamic instability, which is generally poorly tolerated in
elderly patients. Alternatively, a retroperitoneal approach to the aorta, suprace-
liac proximal control, or intra-aortic control with a balloon are potential strate-
gies for managing a left-sided vena cava during aortic dissection.
24
Duplicated Vena Cava
During embryologic development, persistence of both the right and left supracardi-
nal veins leads to a duplicated vena cava. There are a variety of patterns to the dupli-
cated IVC, based on the embryologic development of multiple venous channels and
anastomoses between the left and right supracardinal veins (Figs. 6 and 7 ).
35
The duplicated vena cava has been reported as early as 1909.
36
The prevalence
of duplication of the vena cava depends on the modality used to diagnose it.
Fig. 6 Diagrammatic representation of a duplicated vena cava. In this case, there is no
regression of the caudal segment of either supracardinal vein
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Chapter 20 Inferior Vena Cava: Embryology and Anomalies 299
Radiological series report rates from 0.02% to 1.1%,
4,
11,
14–
17
surgical series
from 0.1% to 1.2%,
21–
22,
24
and autopsy series from 0.2% to 2.8%.
6,
26,
28
There
is a suggestion in the literature that this anomaly may be more prevalent in
females.
35
The left-sided IVC may be diminutive and easily mistaken for a
gonadal vein, in which case it is easily missed on CT scanning. Interoperatively,
it can be distinguished from the gonadal vessel by tracing its caudal extent to
the iliac vein which identifies it as a vena cava. Larger caliber left vena cavae
can be identified preoperatively, and may cause more interoperative difficulty.
Fig. 7 CT images from a patient with a dupli-
cated vena cava. ( a ) Coronal multiplanar recon-
struction demonstrating crossover ( arrow ) of the
left-sided caval structure with continuation of the
right-sided cava. Right-sided cava ( arrow 1 ) and
left-sided cava ( arrow 2 ) in coronal multiplanar
reconstruction ( b ) and axial section ( c )
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300 B. Knipp et al.
One preoperative clue that there may be a potential duplicated vena cava
may be the position of the left kidney. Some authors have suggested that the
left kidney being either at the level of the right kidney or lower is suggestive
of duplicated vena cava, as the left IVC is thought to exert caudal traction on
the developing left kidney.
35
In addition, because of the duplicate nature of
the anomaly, there is often size discrepancy between the two cavae, which can
lead to thrombosis of one or both vessels.
34
For exposure, the left IVC can often be ligated as there is usually com-
munication with the right IVC at the level of the iliacs.
1
In fact, there may be
numerous retroaortic communicating branches between the two vena cavae, a
situation which led to large volume blood loss and inability to perform an in
situ aortobifemoral graft in a patient reported by Bartle et al.
13
Again, a preop-
erative cavagram should be obtained via left femoral vein puncture to assess
the size of the left vena cava, its anastomoses (if any) with the right venous
system, and its relation to the renal vein.
Vena Caval Interruption with Azygos Continuation
In a 1961 report, Anderson et al. documented anomalous inferior vena
cava with azygos continuation (AIVC-AC) in 15 of 2500 patients with
congenital heart defects, for a rate of 0.6%; these were primarily diag-
nosed with angiocardiography in children with cyanotic heart lesions
such as cor biloculare, atrioventricular canal, anomalous connections
of the pulmonary veins, double outflow right ventricle, large atrial sep-
tal defects, pulmonary stenosis or atresia, or a combination of these.
Abdominal organ abnormalities such as heterotaxia, polysplenia, or
asplenia are also associated with this anomaly. In patients without cardiac
anomalies, this anomaly is very rare; in a series of 1055 autopsies, no
cases were found.
7
The mechanism of AIVC-AC is failure of union of the hepatic and subcar-
dinal segments to form the prerenal IVC. Drainage therefore persists through
the right supracardinal vein into the azygos system (AIVC-AC) or through the
left supracardinal vein into the hemiazygos system (AIVC-HC); both routes
may persist (Figs. 8 and 9 ).
AIVC-AC can present with hemoptysis secondary to azygos and bron-
chial hypertension, although it is usually asymptomatic. Lower extremity
swelling, deep venous thrombosis,
37
ulceration, and other signs of venous
obstructive disease have been reported. Cho et al. reported a case of an
otherwise healthy 32-year-old male with no other prothrombotic risk factors
who presented with a right popliteal deep venous thrombosis and extensive
embolism to bilateral segmental pulmonary arteries.
38
CT scanning revealed
that the patient had AIVC-AC. The patient was placed on lifelong coumadin
anticoagulation.
Radiographically, AIVC is suggested by a paraspinous shadow adjoining
the right hemidiaphragm on chest x-ray representing the hypertrophic azygos
vein draining into the superior vena cava (Fig. 10 ). This can be misdiagnosed
as a right paratracheal mass.
In cases of AIVC, current management recommendations for sympto-
matic patients include lifetime anticoagulant therapy, compression therapy,
and leg elevation, as well as avoiding prolonged immobility and oral con-
traceptive use.
39
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Chapter 20 Inferior Vena Cava: Embryology and Anomalies 301
Fig. 8 Diagrammatic representation of absence of the vena cava with azygos continua-
tion. This anomaly is due to the failure of union of the vena revehens with the prerenal
segment of the cava
Marsupial Cava
If the dorsal segment of the posterior cardinal ring at the iliac venous bifurcation
regresses and the anterior segment persists, this leads to a condition known as
preaortic IVC/iliac confluence, also known as marsupial cava . This anomaly is
very rare; one case (0.04%) was reported in the Mayo series.
24
It can be potentially
deadly if unrecognized during dissection of the iliac arterial segments. Venous
congestive symptoms are unusual in this anomaly. The critical maneuver is iso-
lation of the right iliac artery without dissecting the preaortic confluence of the
veins. If possible, either intra-arterial balloon occlusion or use of an aortic tube
graft should be considered to minimize manipulation of the caval confluence.
24
Absence of the Infrarenal Cava
Absence of the vena cava either in the prerenal segment or in its entirety with
consequent collateral flow through the lumbar and azygos systems is thought
to be not a true congenital condition but secondary to intrauterine thrombosis
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Fig. 9 CT images from a patient with absent inferior vena cava with azygos continu-
ation. ( a ) Demonstrates orthotopic vena cava ( arrow ) below renal veins. ( b ) The vena
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