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Question 362
Pathology → General
Classification
Question
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A tissue is exposed to an acute injurious stimulus. After a brief initial vascular response, progressive vasodilatation and fluid movement into the extravascular compartment occur. The resulting inflammatory fluid is protein-rich rather than a simple transudate. Which change most directly accounts for this distinction?
Question Stem
Select the single best answer.
Options
A
A sustained increase in arteriolar hydrostatic pressure without alteration of the vessel wall
B
A reduction in plasma oncotic pressure caused by acute loss of circulating albumin
C
Increased permeability of the vessel wall to plasma proteins
D
Obstruction of lymphatic drainage before any vascular permeability change
E
Persistent constriction of small vessels throughout the inflammatory response
Explanation
Acute inflammation produces haemodynamic changes followed by increased vascular permeability. Although vasodilatation raises hydrostatic pressure and initially promotes fluid movement, the defining mechanism producing a protein-rich inflammatory exudate is increased vessel-wall permeability to plasma proteins.
Option Validity
A) Increased hydrostatic pressure contributes to early fluid movement but does not by itself explain the protein-rich inflammatory exudate.
B) Reduced plasma oncotic pressure is a mechanism of transudation rather than the characteristic inflammatory exudate.
D) Impaired lymphatic drainage can cause oedema but is not the principal vascular mechanism producing the acute inflammatory exudate.
E) Small-vessel constriction is brief and is followed by vasodilatation; persistent constriction does not produce the characteristic exudate.
Further Reading
Saxena R. Textbook for MRCOG-1. Chapter 5: Pathology. General Pathology, pp.161–175.