Extrarenal azotemia may be defined as a pronounced retention of nitrogenous metabolites not caused by disease of the kidneys. The term azotemia seems preferable to uremia, since the clinical signs of uremia are not always present. This form of azotemia is not a circumscribed entity but a condition which may result from a number of unrelated causes. The essential features are oliguria or anuria, azotemia, and no anatomic lesion in the kidneys sufficient to explain renal insufficiency.
In hospitals in which routine determinations of blood urea are made during the last few days of life a surprisingly large number of patients will be found to have an elevation of blood urea to uremic levels. This report is based on a study of 84 cases of this type in which the blood urea nitrogen concentration of the patient attained a level of 50 mg. per hundred cubic centimeters or higher before
BELL ET, KNUTSON RC. EXTRARENAL AZOTEMIA AND TUBULAR DISEASE. JAMA. 1947;134(5):441-446. doi:10.1001/jama.1947.02880220025005