Page 425 - Textbook of Pathology, 6th Edition

FIBROMUSCULAR DYSPLASIA ii) Increased intraluminal pressure due to prolonged upright 409
posture e.g. in nurses, policemen, surgeons etc.
Fibromuscular dysplasia first described in 1976, is a non-
atherosclerotic and non-inflammatory disease affecting iii) Compression of iliac veins e.g. during pregnancy,
arterial wall, most often renal artery. Though the process may intravascular thrombosis, growing tumour etc.
involve intima, media or adventitia, medial fibroplasia is the iv) Hormonal effects on smooth muscle.
most common. v) Obesity.
vi) Chronic constipation.
MORPHOLOGIC FEATURES. Grossly, the involvement
is characteristically segmental—affecting vessel in a bead- MORPHOLOGIC FEATURES. The affected veins, espe-
like pattern with intervening uninvolved areas. cially of the lower extremities, are dilated, tortuous,
Microscopically, the beaded areas show collections of elongated and nodular. Intraluminal thrombosis and
smooth muscle cells and connective tissue. There is often valvular deformities are often found.
rupture and retraction of internal elastic lamina.
Histologically, there is variable fibromuscular thickening
The main effects of renal fibromuscular dysplasia, of the wall of the veins due to alternate dilatation and
depending upon the region of involvement, are renovascular hypertrophy. Degeneration of the medial elastic tissue
hypertension and changes of renal atrophy. may occur which may be followed by calcific foci. Mural
thrombosis is commonly present which may get organised
and hyalinised leading to irregular intimal thickening.
VEINS
EFFECTS. Varicose veins of the legs result in venous stasis
NORMAL STRUCTURE which is followed by congestion, oedema, thrombosis, stasis,
dermatitis, cellulitis and ulceration. Secondary infection
The structure of normal veins is basically similar to that of results in chronic varicose ulcers.
arteries. The walls of the veins are thinner, the three tunicae
(intima, media and adventitia) are less clearly demarcated, PHLEBOTHROMBOSIS AND THROMBOPHLEBITIS
elastic tissue is scanty and not clearly organised into internal CHAPTER 15
and external elastic laminae. The media contains very small The terms ‘phlebothrombosis’ or thrombus formation in veins,
amount of smooth muscle cells with abundant collagen. All and ‘thrombophlebitis’ or inflammatory changes within the
veins, except vena cavae and common iliac veins, have valves vein wall, are currently used synonymously.
best developed in veins of the lower limbs. The valves are
delicate folds of intima, located every 1-6 cm, often next to ETIOPATHOGENESIS. Venous thrombosis that precedes
the point of entry of a tributary vein. They prevent any thrombophlebitis is initiated by triad of changes: endothelial
significant retrograde venous blood flow. damage, alteration in the composition of blood and venous
stasis. The factors that predispose to these changes are cardiac
failure, malignancy, use of oestrogen-containing compounds,
VARICOSITIES
postoperative state and immobility due to various reasons.
Varicosities are abnormally dilated and tortuous veins. The
veins of lower extremities are involved most frequently, MORPHOLOGIC FEATURES. The most common
called varicose veins. The veins of other parts of the body locations for phlebothrombosis and thrombophlebitis are The Blood Vessels and Lymphatics
which are affected are the lower oesophagus (oesophageal the deep veins of legs accounting for 90% of cases; it is
varices, Chapter 19), the anal region (haemorrhoids, Chapter commonly termed as deep vein thrombosis (DVT). Other
20) and the spermatic cord (varicocele, Chapter 23). locations are periprostatic venous plexus in males, pelvic
veins in the females, and near the foci of infection in the
abdominal cavity such as acute appendicitis, peritonitis,
VARICOSE VEINS
acute salpingitis and pelvic abscesses.
Varicose veins are permanently dilated and tortuous Grossly, the affected veins may appear normal or may be
superficial veins of the lower extremities, especially the long distended and firm. Often, a mural or occlusive thrombus
saphenous vein and its tributaries. About 10-12% of the is present.
general population develops varicose veins of lower legs, Histologically, the thrombus that is attached to the vein
with the peak incidence in 4th and 5th decades of life. Adult wall induces inflammatory-reparative response beginning
females are affected more commonly than the males, from the intima and infiltrating into the thrombi. The
especially during pregnancy. This is attributed to venous response consists of mononuclear inflammatory cells and
stasis in the lower legs because of compression on the iliac fibroblastic proliferation. In late stage, thrombus is either
veins by pregnant uterus. organised or resolved leading to a thick-walled fibrous
vein.
ETIOPATHOGENESIS. A number of etiologic and
pathogenetic factors are involved in causing varicose veins. EFFECTS. The clinical effects due to phlebothrombosis and
These are as follows: thrombophlebitis may be local or systemic.
i) Familial weakness of vein walls and valves is the most Local effects are oedema distal to occlusion, heat, swelling,
common cause. tenderness, redness and pain.