Page 84 - Concise Pathology for Exam Preparation ( PDFDrive )

4 Haemodynamic Disorders, Thrombosis and Shock 69

Q. What are the pathophysiologic categories of oedema?

of
Ans. Important pathophysiologic categories oedema are enumerated below:
Increased hydrostatic pressure
1.
is
to

Hydrostatic pressure capillaries the force that tends drive fluid through

(a)
of
capillary wall into interstitial space.
a
in
at
A
a
to

rise hydrostatic pressure venular end capillary level more than

(b)
of
plasma oncotic pressure results oedema.
in
Increased hydrostatic pressure may due to
be
(c)
(i) Impaired venous return
- Congestive heart failure
- Constrictive pericarditis
- Ascites (liver cirrhosis)
- Venous obstruction
- Thrombosis
a
- External pressure due mass
to
(ii) Arteriolar dilatation
- Heat
- Neurohumoral dysregulation
Reduced plasma oncotic pressure
2.
Normally, plasma oncotic pressure exerted by plasma proteins and drives fluid
is
(a)
into the vessels.

(b)
Reduced oncotic pressure causes increased movement of fluid into interstitial

space.
be
Decreased plasma oncotic pressure may due to
(c)
(i) Protein-losing glomerulopathies (nephrotic syndrome)

(ii) Reduced synthesis proteins (liver cirrhosis)
of
(iii) Decreased intake proteins (malnutrition famine oedema)
of
as
in

(iv) Protein-losing gastroenteropathies and malabsorption
3.
Lymphatic obstruction

(a)

Normally, interstitial fluid escapes via lymphatic system. Lymphatic obstruction

of
in
causes accumulation fluid interstitial space.
(b)
Lymphatic obstruction may be

(i) Inflammatory

(ii) Neoplastic

(iii) Post-surgical

(iv) Post-irradiation

(v) Due congenital absence lymphatics
of
to

is

4.

Sodium retention: Increased sodium retention invariably associated with water
as

as
retention, which leads increased plasma volume well hydrostatic pressure.

to
to
Dilutional effect on albumin leads decreased plasma colloid oncotic pressure. Causes
of sodium retention include
Excessive salt intake with renal insufficiency
(a)
Increased tubular reabsorption sodium
(b)
of
Renal hypoperfusion
(c)
(d) renin–angiotensin–aldosterone secretion
Increased

5.
Inflammation: Endothelial lining may be injured by toxins and their products,

eg, histamine, anoxia, venoms, drugs and chemicals. Endothelial damage leads to

of
increased vascular permeability and leakage plasma proteins into the interstitial

in
tissue resulting oedema.
Q. Write briefly on normal regulatory mechanisms responsible for
maintaining sodium and water balance.
is
of
Ans. Eighty percent sodium reabsorbed by proximal convoluted tubule under the
of
influence intrinsic and extrinsic renal mechanisms (Flowchart 4.1).
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