This month, we examine some of the common pathologies of the
abdominal aorta and lower extremity arteries, along with the
diagnostic and therapeutic procedures associated with them.
As always, conscientious coders should communicate regularly
with physicians to keep up with the latest changes in the diagnosis
and treatment of vascular diseases.
Oxygen-enriched blood flows through the body’s tissues
via arteries. The aorta is the main artery from which
all the arteries of the systemic circuit branch. As it enters
the abdominopelvic cavity, it gives off a pair of inferior
phrenic arteries that supply the undersurface of the diaphragm.
Branching off the aorta just below the inferior phrenic arteries
is a single short trunk called the celiac artery, from
which the hepatic, left gastric, and splenic
arteries arise. Immediately below the celiac artery is
the single superior mesenteric artery. This artery
and its branches travel through the mesentery of the intestines
carrying blood to much of the intestinal tract.
Branching laterally from the aorta at the level of the superior
mesenteric arteries are two suprarenal arteries that
supply the adrenal glands. The paired renal arteries,
which supply the kidneys, arise from the lateral margins of
the aorta just inferior to the superior mesenteric artery.
The arteries that supply the ovaries and testes arise from
the ventral surface of the aorta a short distance below the
renal arteries. In the female, the ovarian arteries
pass down and laterally into the pelvic cavity to supply the
ovaries and also give off branches to the ureters and fallopian
tubes. The testicular (or internal spermatic)
arteries of the male are longer than the ovarian arteries
since they pass through the inguinal canal and enter the scrotum.
The aorta then travels down the ventral surface of the vertebral
column, carrying blood to the posterior abdominal wall via
four pairs of lumbar arteries. The abdominal aorta
ends in front of the fourth lumbar vertebra by splitting into
the right and left common iliac arteries and
a small middle sacral artery. Each of the common iliac
arteries divides into the internal and external
iliac arteries. The internal iliac arteries enter the
pelvic cavity and divide into branches that supply the pelvic
organs and pelvic musculature.
The external iliac artery is actually a continuation of the
common iliac artery. It travels downward and enters the thigh
as it passes beneath the inguinal ligament. Upon entering
the thigh, the external iliac artery becomes the femoral
artery. The femoral artery passes along the anterior medial
region of the thigh. In the lower thigh, it passes to the
posterior surface of the knee through an opening in the tendon
of the adductor magnus muscle, and from that point on its
name is the popliteal artery. The popliteal artery
is the continuation of the femoral artery. It passes behind
the knee through the popliteal fossa, supplying the muscles
and skin of that area, and then divides into an anterior
tibial and posterior tibial artery.
The posterior tibial artery continues downward behind the
tibia, carrying blood to the muscles of the posterior compartment
of the leg. Behind the ankle, it divides into the medial
and lateral plantar arteries, which supply the sole
of the foot and form the plantar arch. Digital arteries
arise from the plantar arch. Near its origin, the posterior
tibial artery gives rise to the peroneal artery,
which supplies the peroneal muscles in the lateral compartment
of the leg.
The anterior tibial artery passes through the interosseous
membrane that connects the fibula to the tibia. It travels
down the ventral surface of the membrane, supplying the muscles
of the anterior compartment of the leg. The anterior tibial
artery passes in front of the ankle and ends on the dorsum
of the foot as the dorsalis pedis artery. The dorsalis
pedis artery supplies the dorsum of the foot and connects
with the plantar arch on the sole of the foot.
Aortic and Peripheral
Arterial Aneurysms
An aneurysm is a localized dilation of the aorta of a peripheral
artery. Aortic aneurysms can develop anywhere along
the length of the aorta, but ¾ are located in the abdominal
aorta. Saccular aneurysms represent localized outpocketings
of the aortic wall, whereas fusiform aneurysms are
characterized by a circumferential widening of the aorta.
Most aortic aneurysms are fusiform. The most common cause
of aortic aneurysms is arteriosclerosis, which may weaken
the aortic wall, causing it to expand. Hypertension and cigarette
smoking contribute to the process, and there is a familial
occurrence of abdominal aortic aneurysms. Trauma, arteritis
syndromes, syphilis, and congenital connective tissue disorders
can also lead to aneurysm formation.
Abdominal aortic aneurysms: Ninety percent of abdominal
aortic aneurysms begin below the renal arteries, often extending
distally into one or both iliac arteries. A dissecting aneurysm
is characterized by blood entering through a split or tear
in the intimal lining of the artery wall or by interstitial
hemorrhage. Dissecting aortic aneurysms may rupture, creating
a medical emergency.
Several laboratory procedures are used to determine the presence
of an aortic aneurysm. A plain abdominal x-ray may reveal
calcification of the aneurysm wall. Cross-sectional ultrasonography
usually gives a clear picture of the size of an aneurysm.
CT scanning with contrast and MRI scanning may also be done
for diagnostic purposes. Abdominal aortography indicates the
size and extent of the aneurysm and the origin of the major
blood vessels arising from the aorta. Contrast aortography
helps determine extension of the aneurysm above the renal
arteries.
Rupture of abdominal aortic aneurysms is uncommon when they
are less than 5 cm wide, but is dramatically more common in
aneurysms over 6 cm. Surgical repair consists of excision
of the aneurysm and replacement with a synthetic conduit (graft).
Graft material is usually Dacron. The graft may have to be
carried into either or both iliac arteries if the aneurysm
involves them. Extension of the aneurysm above the renal arteries
necessitates their reimplantation onto the synthetic graft.
Peripheral arterial aneurysms: Aneurysms can arise
in any of the aortic branches and are usually also the result
of arteriosclerosis. The most common peripheral arterial aneurysms
are those of the popliteal arteries, of which 70% are bilateral.
Aneurysms at
this site, particularly when bilateral, are frequently associated
with abdominal aortic aneurysms. Although popliteal aneurysms
rarely rupture, they may serve as a focus for abrupt thrombotic
occlusion of the involved popliteal artery, jeopardizing the
foot on the affected side. Thrombus within the aneurysms may
lead to distal embolism.
Popliteal aneurysms are confirmed by ultrasound studies or
CT scans. Arteriography is used to assess the circulation
distal to the aneurysm. Aneurysms of the iliac and femoral
arteries occur less frequently than popliteal aneurysms; however,
all aneurysms are treated with the same type of excision and
graft replacement surgery.
Occlusive
Arterial Diseases
Arteriosclerosis obliterans is the occlusion of blood
supply to the extremities by atherosclerotic plaques (atheromas).
Patients with arteriosclerosis obliterans have symptoms related
to chronic tissue ischemia. The first symptom is muscle pain
called intermittent claudication, which occurs only
while walking or otherwise exercising the muscles in the legs.
More advanced peripheral ischemia causes pain even at rest.
Rest pain begins in the most distal parts of the extremity
and is often unrelenting. A severely ischemic foot is painful,
cold, and often numb. As ischemia worsens, ulcerations may
appear, especially after local injury, typically on the toes
or heel or occasionally on the leg. Extensive obliterative
disease may result in necrosis or gangrene of affected tissues.
Acute ischemia is caused by sudden arterial occlusion
by embolization from the heart, arteriosclerotic plaque, or
an aneurysm, or by an acute thrombosis on preexisting atherosclerotic
disease. The extremity is cold, either pale or cyanotic, and
pulses are absent distal to the obstruction. In acute occlusion
of the aorta (saddle embolus), all pulses in the lower
extremities are absent.
Arteriography provides details of the location and
extent of occlusion. Complete angiography includes aortography
and bilateral femoral arteriography, visualizing the arteries
as far distally as the feet. Digital subtraction angiography
allows visualization of the vascular system while "subtracting"
other soft tissues.
Doppler ultrasonography is the most widely used noninvasive
diagnostic test to determine the presence of peripheral vascular
occlusive disease. Arterial stenosis and occlusion are easily
detected by listening with a velocity detector (Doppler probe).
Color-flow Doppler units visualize vessels without the need
for arteriography, the signal being encoded in color to show
direction of blood flow.
More accurate information with regard to the extent and location
of arterial lesions is obtained from segmental blood pressures
taken at the thigh, calf, and ankle, and segmental plethysmograph
recordings of pulse waveforms before and after exercise.
By noting pressure gradients and abnormal waveforms, isolated
aortoiliac disease can be distinguished from femoropopliteal
disease, below-knee disease, or any combination of these.
Bypass Grafting
Bypass grafting around an arterial obstruction is done with
either a section of an autologous vein or by suturing a synthetic
(PTFE) patch around the site of blockage, thereby effectively
bypassing the obstruction and creating an open channel for
blood flow to distal tissue. The saphenous vein is the most
commonly harvested vessel for peripheral bypass procedures.
Percutaneous
Transluminal Balloon Angioplasty
This minimally invasive procedure is performed to widen a
narrowed portion of an artery. The physician guides a catheter
to the narrowed artery. A smaller balloon-tipped catheter
is inserted by passing it through the guiding catheter to
the obstructed area. The balloon is inflated to exert pressure
on the narrowed area, thereby relieving the obstruction. Antithrombolytic
agents such as streptokinase may be used to dissolve an atherosclerotic
obstruction. Obstructions in the renal, iliac, vertebral,
and femoropopliteal arteries may be successfully treated in
this way.
Angioscopic-Assisted
In-Situ Bypass
The greater saphenous vein is the most commonly used arterial
substitute for bypasses below the groin. Older bypass techniques
involve removal of the entire vein through a long incision
inside the leg. Newer techniques leave the vein in place ("in-situ")
and disrupt the valves and side-branches through a series
of short incisions that heal more easily than a single long
one.
Stenting
Intravascular stents are tubular implants that resemble wire
cages. They are designed to restore normal blood flow in a
vessel by maintaining an open lumen after angioplasty has
been performed. The stent is first attached to the end of
a catheter and then guided to the site of the narrowed vessel
via an introducer through a peripheral vessel, such as the
femoral artery. Stenting is usually performed in a catheterization
lab by interventional radiologists.
Endovascular
Stent/Grafting
This technique, now undergoing clinical trials, involves
actually doing a bypass from within the blocked vessel. The
area of largest investigation is for abdominal aortic aneurysm
(AAA) repair in patients too ill to survive a traditional
open repair.
Minimally
Invasive In-Situ Bypass
The in-situ saphenous vein bypass has been the standard surgical
treatment of lower extremity arterial occlusive disease for
three decades. In this most recent procedural advancement,
only two small leg incisions are used, one at the groin and
one in the lower leg. Under angioscopic visualization, the
saphenous vein is dissected and divided at the level of the
proximal and distal anastomotic sites. A retrograde valvulotome
is inserted distally, and an introducer catheter is inserted
proximally. Working down the vein, first the valves are visualized
and lysed with the valvulotome, then occlusion coils are advanced
into the side branches. The proximal and distal anastomoses
are constructed, and the results are confirmed with an intraoperative
angiogram. Branches that cannot be occluded by coils are ligated
through very small extra incisions, if needed.
Now that we have reviewed the aorta and peripheral vascular
structures, their pathologies and various treatment methods,
try coding the surgical procedure on our Procedure
Practice page. Assign the ICD-9-CM diagnosis
code and both the ICD-9-CM and CPT-4 procedure codes, then
compare your answers to our suggested codes on the Coding
Recommendations page.
Good luck!
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