جامعة بابل | University of Babylon



General pathology

Hemodynamic disorders:

Introduction:

Approximately 60% of body weight is water.

Body fluid divided into two parts:

intracellular fluid which represent 2 / 3 of body fluid.

Extracellular fluid which represent 1 / 3 of the body fluid, this further subdivided into intravascular compartment and the extravascular compartment (interstitial fluid).

Definition:

• Edema defined as signifies accumulation of excess fluid in the tissue spaces.

Following terms represent edema at specific body sites:

Hydrothorax (Pleural effusion), collection of fluid in the pleural cavity.

Hydropericardium, collection of fluid within pericardium.

Hydroperitoneum collection of fluid within peritoneal cavity (it commonly called Ascites).

Anasarca is a severe and generalized edema with profound subcutaneous tissue swelling.

Pitting edema: dermal and subcutaneous connective tissue swelling.

Mechanism and causes of Oedema formation:

In general, the opposing effects of vascular hydrostatic pressure and plasma colloid osmotic pressure are the major factors that govern movement of fluid between vascular and interstitial spaces, Normally, any outflow of fluid into the interstitium from the arteriolar end of the microcirculation is nearly balanced by inflow at the venular end; a small leftover amount of interstitial fluid is usually removed by the lymphatics. increased hydrostatic pressure or diminished plasma osmotic pressure leads to a net accumulation of extravascular fluid ( edema). As the interstitial fluid pressure increases, tissue lymphatics remove much of the excess volume, eventually returning it to the circulation via the thoracic duct. If the ability of the lymphatics to drain tissue is exceeded, persistent tissue edema results, so the following are the main causes of edema.

1- Increase hydrostatic pressure:

• Congestive heart failure.

• Constrictive pericarditis.

• Venous obstruction or compression, ( thrombosis, external pressure due to mass effect, and prolonged dependent lower extremities, and varicose veins).

2- Reduced plasma Osmotic pressure:

• Nephrotic syndrome (protein loss from kidney).

• Liver cirrhosis(decrease synthesis of plasma proteins by hepatocytes).

• Malnutrition (Kwashiorkor).

• Protein losing enteropathy.

3 – Lymphatic obstruction:(non-pitting edema).

Post surgical removal of LNs.

Post radiotherapy.

Neoplastic growth.

Parasitic infection, like in chronic infection with wuchereria bancrofti, that block the lymphatic drainage, lead to massive edema of legs (elephantiasis).

Congenital absence of lymphatic

3 – others:

sodium retentions due to renal pathology.

Inflammation (both acute and chronic).

Morphology of Oedema:

Oedema is more easily recognized grossly, Although any organ or tissue in the body may be involved, edema is most commonly encountered in subcutaneous tissues, the lungs, and the brain.

Subcutaneous edema may have different distributions depending on the cause, Edema of the dependent parts of the body (e.g., the legs when standing, the sacrum when recumbent) is a prominent feature of congestive heart failure Edema as a result of renal dysfunction or nephrotic syndrome is generally more severe than cardiac edema and affects all parts of the body equally. It may, however, be initially manifest in tissues with a loose connective tissue matrix, such as the eyelids, causing periorbital edema, Finger pressure over substantially edematous subcutaneous tissue displaces the interstitial fluid and leaves a finger-shaped depression, so-called pitting edema.

Pulmonary edema is a common clinical concern most typically in the setting of left ventricular failure but also occurring in renal failure The lungs are two to three times their normal weight, and sectioning reveals frothy, blood-tinged fluid representing a mixture of air, edema fluid, and extravasated red blood cells.

Edema of the brain may be localized to sites of injury (e.g., abscess or neoplasm) or may be generalized, as in encephalitis, hypertensive crises, or obstruction to the brain's venous outflow. Trauma may result in local or generalized edema depending on the nature and extent of the injury. With generalized edema, the brain is grossly swollen with narrowed sulci and distended gyri showing signs of flattening against the unyielding skull .

Congestion:

Increase in the volume of blood in an affected tissue or organ, it can further subdivided into active congestion &passive congestion.

Active (arterial) congestion: it results from arterial dilation, that leads to increase flow of blood into capillaries. It’s the type of congestion which responsible for redness at site of inflammation, exercise, and febrile state, it mediated by either sympathetic by vasoactive chemical mediators.

Passive (venous) congestion: its result from impairment of venous drainage, and it further subdivided into:

1- systemic venous congestion:

associated with right sided heart failure, due to greater proportion of blood accumulated in the venous compartment.

Common causes of right sided heart failure are:

• Chronic obstructive lung disease (COAD), like chronic bronchitis and emphysema.

• Pulmonary valve disease.

• Left sided heart failure.

2- localized venous congestion: (pulmonary, hepatic, ..).

Pulmonary venous congestion :

Causes:

1- left sided heart failure, (coronary artery disease& hypertension).

2- Mitral valve stenosis.

Mechanism;

Both of the above lead to rise pressure in the left atrium, and that lead to increase of pressure within pulmonary vein, resulting in congetion an d lung edema.

Morphology:

Gross: lung heavy dark red in color firm in consistency.

Microscopical: dilated alveolar venules and capillaries , that packed by RBCs., the alveolar spaces filled by pale homogenous transudate (lung edema), with numerous alveolar macrophages the packed with hemosidiren, since these cells seen in cases of heart failure so they called heart failure cells.

Complication:

Chronic pulmonary hypertension complicated by development of pulmonary hypertension which well further complicated by development of left sided heart failure, and systemic venous edema.

Hepatic venous congestion:

Its usually seen in association with liver cirrhosis, since the fibrosis of cirrhotic liver leads to distortion and obliteration of intra-hepatic portal circulation.

Morphological changes of chronic liver congestion , (CVC):

Gross: firm enlarged liver (hepatomegaly), cut section shows dark areas (congested centrilobular zone), alternated with pale areas (periportal areas), this give liver appearance resemble cut surface of nutmeg, hence the congested liver called "nutmeg liver".

Microscopical :the central vein and central ends of the sinusoids are distended and packed with RBCs, and appear dark in color, the hepatocytes undergo necrosis due to anoxia. The hepatocytes at the periphery of the hepatic lobule suffer mild anoxia so the develop fatty changes and appear pale in color.

Complication of liver cirrhosis:

1- congested splenomegaly.

2- Ascites.

3- Hemorrhoid and esophageal varices.

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Dr. Ali Zeki

Lec – 9 -

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