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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3953_Библиотеки_им_академика_М_И_Перельмана
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2
Venous and Lymphatic Anatomy
Alberto Caggiati
Department of Anatomy, University “La Sapienza,” Rome, Italy
THE ROOTS OF THE DRAINING SYSTEMS:
THE MICROVASCULAR BED
The microvascular bed includes the terminal arterioles, the precapillary sphincters, the
capillaries and the small venules. The microvascular bed also includes the initial lymphatics,
the lymphatic capillaries and artero-venous anastomoses (AVA). The wall of the arterioles
contains smooth muscle cells and these are the major site of systemic vascular resistance.
The rhythmical contractile activity of the precapillary sphincter causes intermittent flow in
the capillaries (vasomotion) and allows a large number of capillaries to remain open or
closed for long periods. The walls of the capillaries are made up of flat endothelial cells lying
on a basal lamina (BL) and oriented with the vessel’s long axis. In some organs, capillaries
have pericapillary cells (pericytes) imbedded within the BL, which play a contractile role.
Endothelial cells secrete vasoconstrictor, vasodilator, mitotic agents, and their own BL.
Capillaries are drained by venules. Initially, the venular wall is strengthened by
pericytes, then by smooth muscle cells, increasing in number and layers. Initial lymphatics
are blindly ending tubes, 5–50 mm wide, making up a net of lymphatic capillaries. Their
wall is made up of flat endothelial cells, a discontinuous BL and fine anchoring fibrils.
The wall permits the capillary to drain water, solutes, cells or cellular remnants from the
tissue spaces. Then, the lymph passes into larger and richly valvulated lymphatic vessels
with a very thin wall composed of endothelium, basal lamina and collagen, with scattered
smooth muscle cells.
The microvascular bed of some tissues (e.g., skin) contains direct connections between
arterioles and venules. Such AVA allow blood to bypass the capillary bed. Accordingly,
the flow in these shunts does not participate in transfer of gases, nutrients or wastes. The
arrangement of these connections may be extremely simple(direct connections) or extremely
complex, like in the skin, where AVA play an important role in heat regulation.
THE SUPERFICIAL VENOUS SYSTEM OF THE LOWER LIMB
The capillaries of the subcutaneous tissue are drained by two main venular plexuses.
The more superficial is situated in the dermal papillae. The deeper venular plexus is placed
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at the boundary between the papillary and the reticular layers of the dermis. These
plexuses are drained by a tremendously complicated net of interconnected veins that lie
superficially with respect to all the fasciae of the limb: the epifascial veins (Fig. 1) These
are very thin-walled and run close to the dermis surrounded only by amorphous fat. For
these reasons, epifascial veins are more prone to varicose changes (dilatation, elongation,
and tortuosity). Epifascial veins are extremely variable in number, size, and path.
Nevertheless, there is some order in their variability, because a few of them are quite
constant in size, path, and connections. These have been designated in longitudinal and
oblique groups (Table 1).
Longitudinal epifascial veins are parallel to the saphenous veins (SVs) and richly
connected with them. For these reasons, they have been designated “accessories” of the
relative saphenae, and in order to allow their easy identification, they are discriminated
on the basis of their topography [for the great SV: anterior,
a
posterior, and superficial
accessories (Figs. 2 and 3); for the small SV: superficial accessory]. Besides the accessories
of the saphenae, longitudinal epifascial veins also include the lateral venous plexus, whose
veins course along the lateral leg and thigh.
Oblique epifascial veins connect main longitudinal veins, SVs, or their accessories
(Fig. 4). In the thigh, oblique veins are called “circumflex veins” due to their path. The
anterior thigh circumflex vein (ATCV) connects the lateral venous plexus with the GSV.
The posterior thigh circumflex vein (PTCV) originates from the SSV, from the lateral
plexus, or from reticular veins of the posterior thigh to drain into the GSV or its posterior
accessory. These veins are responsible for reflux transmission between the great and the
small SVs.
Interfascial (saphenous) veins course in an intermediate plane between epifascial and
deep veins and are the great saphenous vein (GSV), the small saphenous vein (SSV), and
its thigh extension (not mentioned in the CEAP). They course deeply in the subcuta-
neous tissue, close to the deep fascia (DF). They are covered by a continuous
Figure 1 Planar anatomy of the veins of the lower limb. The saphenous compartment (*) is
delimited by the saphenous fascia (sf) and the muscular fascia (mf) and hosts only the great
saphenous vein. Epifascial veins course in the epifascial compartment (EC). The deep compartment
(DC) hosts intramuscular veins (imv) and axial veins (av).
a
The anterior accessory of the GSV at the upper thigh, courses deeply (just above the muscular
fascia, like the GSV) and below a hyperechoic fascia that resembles the GSV covering (Fig. 4).
However, the AAGSV can be easily identified because it courses more anteriorly with respect to the
GSV with a path corresponding to that of the underlying femoral artery and veins.
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connective membrane, the saphenous fascia (SF). DF and SF fuse at the sides of the SVs,
delimiting the saphenous compartment (SC) (Fig. 1). The superficial venous arcade of the
dorsum of the foot, which connect the saphenous veins (medial marginal vein, dorsal
arcuate vein, and lateral marginal vein), show the same topography and fascial
Table 1 Nomenclature of the Superficial Veins
Great saphenous vein:
Sapheno-femoral junction
Terminal valve
Pre-terminal valve
External pudendal vein
Superficial circumflexiliac vein
Superficial epigastric vein
Superficial dorsal vein of clitoris or penis
Anterior labial veins
Anterior scrotal veins
Anterior accessory of the great saphenous vein
Posterior accessory of the great saphenous vein
Superficial accessory of the great saphenous vein
Small saphenous vein:
Sapheno-popliteal junction
Terminal valve
Pre-terminal valve
Cranial extension of the small saphenous vein
Superficial accessory small saphenous vein
Anterior thigh circumflex vein
Posterior thigh circumflex vein
Intersaphenous veins
Lateral venous system
Dorsal venous network of the foot
Dorsal venous arch of the foot
Superficial metatarsal veins (dorsal and plantar)
Plantar venous subcutaneous network
Superficial digital veins (dorsal and plantar)
Lateral marginal vein
Medial marginal vein
Source: Modified from Ref. 1.
gsv
pa
sa
aa
Figure 2 The great saphenous vein (GSV) course with related nerve, artery, and lymphatics within
its compartment (white space). Its accessories course in a more superficial plane of the subcutaneous
tissue. Abbreviations: aa, anterior accessory; sa, superficial accessory; pa, posterior accessory.
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relationships. Varicose changes in refluxing SVs are relatively slow to develop and less
pronounced than those of nonsaphenous, being visible only by Duplex sonography in many
limbs. This is due to the deep position of the SVs, to their thicker wall, and to the fasciae of
the SC, which oppose their dilatation.
Sapheno-Femoral Junction
The GSV terminates at the groin in the common femoral vein (CFV). In about 70% of
limbs, a valve is placed just above its opening (supra-saphenic valve) to protect the lower
limb vasculature from the abdomino-pelvic hydrostatic column (Fig. 5). There is also
usually a valve at the GSV opening (terminal valve, TV), to prevent reflux from the CFV.
Oblique epifascial veins
Figure 4 Oblique epifascial veins connect longitudinal epifascial with the great saphenous vein or
with deep veins, via perforators.
Figure 3 Dotted lines indicate the path of the posterior (left) and anterior (right) accessories of the
great saphenous vein.
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A few centimeters below the terminal valve is the pre-terminal valve (PTV), which
prevents reflux from tributaries of the SFJ into the GSV trunk. The TV is present in 100%
of limbs and the PTV in about 70%. SFJ tributaries reach the GSV between the PTV and
the TV. All SFJ tributaries may be the source of reflux, especially those connected to
pelvic veins (external pudendal vein, genital veins). Full Duplex evaluation of the SFJ
should assess PFV, TV, PTV competence and flow patterns in SFJ tributaries.
Classic descriptions of the SFJ tributaries include the following vessels: external
pudendal, superficial dorsal vein of clitoris or penis, anterior labial or scrotal veins
(from the external genitalia), superficial circumflex iliac vein (from the lateral abdominal
and pelvic wall), and the superficial epigastric vein (from the anterior abdominal wall).
The accessories of the GSV must also be included in the group of SFJ tributaries. The
termination of the SFJ tributaries varies greatly. In fact, they usually end into the GSV, but,
less frequently, they can join directly the common femoral vein. Further, saphenous
tributaries can join themselves before ending, forming large trunks that can be confused
with the GSV (Fig. 6).
In about one-third of limbs with an incompetent GSV, the reflux does not originate
from the CFV, but it comes from one of the GSV inguinal tributaries. This occurs more
frequently from the external pudendal or from veins draining the external genitalia. In
most cases, junctional reflux descend along the GSV. It is not rare to observe a junctional
reflux passing from the GSV in one of its inguinal tributaries at the groin or at the upper
thigh. This occurs more frequently into the anterior accessory.
SSV Termination and SPJ
The morphology of the SSV termination varies greatly. This is because in the embryo, the
SSV extends along the posterior face of the thigh (the so-called “post-axial vein”) to end
into the inferior gluteal vein. In most limbs, the thigh portion of the embryonic SSV
disappears when the deep system develops and the SSV ends in the popliteal vein. In about
one-third of limbs, the thigh portion of the SSV persists in part (Fig. 7). It is of particular
clinical relevance when the termination of the SSV is into the GSV via the posterior thigh
circumflex vein (Giacomini’s anastomosis).
SSV
TV
ISV
PTV
Figure 5 Valves of the sapheno-femoral junctions. Abbreviations: SSV, suprasaphenic valve;
ISV, infrasaphenic valve; TV, terminal valve; PTV, preterminal valve.
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DEEP VEINS OF THE LOWER LIMB
The term deep veins designates indiscriminately all veins that course below the deep
(muscular) fascia. In turn, this group of veins is quite heterogeneous from both anatomic
and functional points of view (Table 2).
Intramuscular veins are arranged as a plexus around bundles of myocites. They are
particularly developed in the muscles of the foot sole, of the calf, and of the buttock,
where they actively contribute to the propulsion of blood (muscle pumps). Isolated
thrombosis of muscular sinusoids may simulate muscular disease but are easy to be
evidenced by Duplex.
Figure 6 Variability of the veins draining into the terminal portion of the great saphenous vein.
Abbreviations: I, superficial circumflex iliac vein; E, superficial epigastric vein; P, pudendal vein;
LF, lateral superficial femoral vein; MF, medial and superficial femoral vein; AS, accessory
saphenous vein; SS, double saphenous vein; S, vena saphena magna; F, femoral vein. Source:
Modified from Ref. 5.
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Axial veins, whose role is to conduct blood toward pelvic collectors, aresatellite ofthe
corresponding arteries. They are constantly double at the leg. Anterior tibial, posterior tibial,
and peroneal veins join to form the popliteal at different levels of the popliteal fossa. For
this reason, in many limbs the popliteal may appear double. The popliteal passes into the
femoral vein, which receives the deep femoral vein at the upper thigh to form the common
femoral vein. Thecommon femoral vein, after receiving thegreat saphenous, continues into
the external iliac. Duplex investigation of limbs with clinical evidence of DVT must take
into account that occlusion may occur in only one branch of a duplicated femoral
or popliteal.
In case of thrombosis of the popliteal-femoral axis, the drainage of the limb can be
allowed by other veins, which, in normal conditions, are small sized and hemodynamically
irrelevant. Main collateral path are:
1. A double femoral vein
2. The deep femoral venous axis. In fact, the popliteal vein is connected with the
roots of the deep femoral by anonymous muscular veins, which can enlarge
when the femoral vein is occluded
3. The obturator vein, which normally drains only a small portion of the medial
thigh to confluence into the internal iliac
4. The sciatic vein, which normally drains only the sciatic nerve and drains into the
inferior gluteal veins. It may be connected with the deep and superficial veins
of the posterior leg. The sciatic vein can be the source of a reflux responsible for
leg varicose veins.
5. Perforating veins (PVs) (Table 3 and Fig. 8).
Figure 7 The path of the thigh extension of the small saphenous vein (dotted line).
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PERFORATING VEINS
PVs are the vessels that connect superficial collectors with subfascial veins. Most of them
are valvulated and permit only flow toward the subfascial compartment. Most of them are
microscopically sized and hemodynamically irrelevant. PVs have been designated in
“direct PVs” (those connecting a superficial vein with an axial deep vein) and “indirect
PVs” (those connecting a superficial vein with a intramuscular vein).
More than 100 PVs are in the lower limbs. In fact, one or two veins accompany
all the perforating arteries that supply the subcutaneous layer. Theoretically, each of
these PVs can dilate and assume clinical relevance in varicose syndromes or in DVT.
However, PVs, which more frequently assume clinical relevance, are quite constant and
have been grouped and designated according with their topography. CEAP designates
only thigh (AP17) and leg (AP18) PVs. PVs may represent the starting point of a reflux
or its point of re-entry. In both conditions, they play a pivotal role in the hemodynamics
of varicose limbs and need specific treatment for their selective interruption. PVs have
been designated on the basis of their topography (Fig. 8).
The Veins of the Pelvis
Pelvic veins are of great clinical importance due to their role in venous thrombo embolism
(VTE), pelvic congestive syndromes, and varicose veins of the lower trunk and limbs.
Table 2 Nomenclature of the Deep Veins
Thigh Common femoral vein
Femoral vein
Deep femoral vein
Deep femoral communicating veins (accompanying veins of perforating
arteries)
Medial circumflex femoral vein
Lateral circumflex femoral vein
Sciatic vein
Knee Popliteal vein
Genicular venous plexus
Leg Sural veins
Soleal veins
Gastrocnemius veins
Medial gastrocnemius veins
Lateral gastrocnemius veins
Intergemellar vein
Anterior tibial veins
Posterior tibial veins
Fibular or peroneal veins
Foot Medial plantar veins
Lateral plantar veins
Deep plantar venous arch
Deep metatarsal veins (plantar and dorsal)
Deep digital veins (plantar and dorsal)
Pedal vein
Source: Modified from Ref. 1.
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Table 3 Nomenclature of the Perforating Veins (PVs)
Foot perforators Dorsal foot PV or intercapitular veins 1
Medial foot PV 2
Lateral foot PV 3
Plantar foot PV 4
Ankle perforators Medial ankle PV 5
Anterior ankle PV 6
Lateral ankle PV 7
Leg perforators Medial leg PV
Paratibial PV 8
Posterior tibial PV (cockett PV) 9
Anterior leg PV 10
Lateral leg PV 11
Posterior leg PV
Medial gastrocnemius PV 12
Lateral gastrocnemius PV 13
Intergemellar PV 14
Para-achillean PV 15
Knee perforators Medial knee PV 16
Suprapatellar PV 17
Lateral knee PV 18
Infrapatellar PV 19
Popliteal fossa PV 20
Medial thigh PV
PV of the femoral canal 21
Inguinal PV 22
Anterior thigh PV 23
Lateral thigh PV 24
Thigh perforators Posterior thigh PV
Postero-medial 25
Sciatic PV 26
Posterolateral 27
Pudendal PV 28
Gluteal perforators Superior gluteal PV 29
Mid gluteal PV 30
Lower gluteal PV 31
Source: Modified from Ref. 1.
Figure 8 Topography of main groups of perforating veins.
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