Roentgen Size of Normal Kidneys

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Size of the kidneys is an important consideration in the diagnosis, prognosis, course, and treatment of renal disease. One of the simplest and most direct methods of estimating renal size is from measurements made on an anteroposterior roentgenogram of the abdomen. Practical application of this information requires knowledge of the range in size of normal kidneys as determined by the same method. The purpose of this paper is to report the kidney size in 1,286 patients from a general hospital population without recognizable renal disease. The kidney size was measured on abdominal roentgenograms obtained during intravenous urography, expressed as a function of the patient's body surface area, and correlated with the age, sex, and race. From these data, idealized normal (gaussian) distribution curves were constructed which indicate the range in size of normal kidneys in the population studied and the difference in size between each kidney in an individual subject. Material Included in this study were 1,286 in- and out-patients (322 children, 363 male adults, and 601 female adults) from the general population of a large hospital. The size of the kidneys was measured on anteroposterior abdominal roentgenograms exposed at a 40-inch target-film distance during intravenous urography. Only those patients were accepted whose history, physical examination, and routine laboratory findings disclosed no evidence of renal disease. Reasons for performing the examinations included fever of unknown origin, enuresis, congenital heart disease, abdominal pain of unknown etiology, and routine survey examination as part of a general medical evaluation. Special attention was given to excluding patients with hypertension, elevated blood urea nitrogen, abnormal urinalysis, or a history compatible with pyelonephritis or glomerulonephritis. Cases were included in the study only if both renal outlines were visualized sufficiently well to ensure accurate measurement. No patient was excluded merely on the basis of an unusual discrepancy in size of the 2 kidneys, but they were excluded if intravenous urography was otherwise abnormal. Table I indicates the number of patients included in the study, according to age, sex, and race. Methods The length of each kidney was determined by measuring the maximum distance from the cephalad to the caudad margin (Fig. 1). In the occasional case, in which the adrenal gland could not be separated from the kidney, the gland was included in the measurement of renal length. The medial margin of the kidney was determined by drawing a line between the most medial aspects of the upper and lower poles. The width of the kidney was then ascertained by measuring the maximum distance from the lateral to the medial margin along a line perpendicular to the length line. The body surface area of each patient was obtained from his height and weight, by use of the DuBois nomograph (3). The following data were punched on tabulation cards: identification number of each patient, age, sex, race, body surface area, and length and width of each kidney. This information then was compatible input for an IBM 7072 computer. A postulated “;renal index” was calculated for each kidney.