A simple kinetic assay for plasma ammonia, suitable for small laboratories.

To the Editor: With scanning auger microscopy (SAM), a relatively new technique, one can obtain information on the chemical composition and bonding within the first few atomc layers of the surface in a solid material; and one can analyze for trace elements without damaging the specimen, a rare capability among measurement techniques. So far, the usefulness of the method has been demonstrated in fields such as plastics and metallurgy. Here, a clinical diagnostic problem suitable for SAM analysis is briefly illustrated in a study of a bone-biopsy specimen. A 62-year-old woman was admitted for evaluation of pain and swelling of the left thigh and calf. The left lower limb was cyanotic and edematous, and Homans’ sign was elicited. Except for a high erythrocyte sedimentation rate, results of routine laboratory tests were negative or within the normal range. Intravenous therapy with heparmn was started. After disappearance of the edema, a hard mass, 12 cm in its largest diameter, was palpated in the inguinal region. A plain radiograph revealed an irregular, high-density opacity; phlebography exhibited complete obstruction of the femoral vein with formation of a rich collateral venous system. THORIUM