Acute Miliary Diseases of the Lung

Abstract

The presence OF disseminated miliary lesions in the lungs, demonstrable on the chest roentgenogram, is of frequent occurrence and is seen in a wide variety of diseases. More than 80 conditions capable of producing this appearance have been recorded (1–3). Such a long list of possibilities makes it extremely difficult to establish a clinical diagnosis in a given case, and any lead obtainable from the roentgenogram is of considerable help. For instance, roentgen evidence of associated enlargement of the hilar and mediastinal nodes, pleural involvement, or cardiac abnormality may suggest one or another etiology. Some writers have considered differences in sharpness, configuration, size, number, and distribution of the individual miliary nodules helpful in differential diagnosis. An approach which has proved particularly useful in this institution, but which has not been emphasized in the literature, is the observation of change in the roentgen findings—specifically, the rate of progression or regression of the miliary appearance. The purpose of the present contribution is to evaluate the importance of observing and recording this rate of change, and to illustrate some of the conditions which can cause rapidly changing diffuse miliary lesions. In a discussion of this sort it is important that the terms used be clearly understood. In the literature numerous descriptive expressions, many of which are vague, have been applied to the appearance under discussion: stippling, beading, mottling, diffuse infiltration, fibrosis, reticulation, honeycomb pattern, etc. Since miliary tuberculosis gives a rather consistent roentgen picture, which is well known, an attempt has been made to avoid confusion by describing the present material in terms of this disease. Our use of the word miliary, then, denotes a similarity to the roentgen appearance of miliary tuberculosis as regards size, number, and distribution of the lesions, and is not merely an indication of the millet-seed size of the individual nodules. A completely uniform roentgen distribution of the nodules in the lungs is not stipulated, since a greater concentration in the central and basal portions is not uncommonly seen in miliary tuberculosis. This does not reflect the even distribution found at autopsy, the discrepancy being probably attributable to the greater thickness of lung traversed by the roentgen beam in these areas. Localized pulmonary emphysema may further modify the distribution as seen on the roentgenogram. The numerous disseminated diseases of the lung which fail to show a distinct miliary character are not included in this study. Classification of miliary diseases into acute, subacute, and chronic categories offers certain advantages in differential diagnosis. We have used a grouping based on serial roentgenograms and not on the clinical course, which usually, but not invariably, coincides with it.