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Use of ultrasonography, computed tomography, 67galliumscintiscanning, and 111indium seintiscanning of labeled autologous leukocytes in the detection of intra-abdominal in. The clinician is frequently presented with a febrile patient in whom the fever source is unknown. Correct diagnosis and prompt surgical treatment is particularly important in intra-abdominal infection where, untreated, the abscess has an associated mortality rate that ranges from 2% (appendicial abscess)to greater than 40% (pancreatic abscess) [1]. The associated morbidity, reflected in increased hospital stay and cost, is significant [1]. Classical signs and symptoms of occult infection are frequently absent, present only in retrospect, or misleading. Among 60 patients with subphrenic abscess reported by De Cosse et al. [2], 11 were first discovered at postmortem examination. In a recent study of 93 patients with documented subphrenic abscess [3], abdominal pain was absent in 62%, fever was absent in 18%, and wound drainage was absent in 82%; there was a mean delay in diagnoses of 5.5 weeks. At the present time no diagnostic modality is consistently successful in diagnosing and localizing these lesions. Abnormal findings utilizing conventional x-ray techniques have been disappointingly infrequent; 18-61% of patients have had an abnormal chest x-ray and 14-80% of patients have had positive findings on abdominal x-rays in the face of subphrenic abscess [4]. Recently, newer techniques have been developed and perfected to facilitate early diagnosis of septic foci. The purpose of this paper is to review the methodology and accuracy of several of these techniques and to relate our own experience with the use of l~lindium radioactive labeling of polymorphonuclear leukocytes in the detection of a septic source. UltrasonographyMechanical vibrations at high frequencies ranging between 1 and 5 MHz form the basis of ultrasonography. A transducer is used to contact the skin surface and to transmit the mechanical energy of the high frequency sound waves. Sound energy is reflected back toward the transducer after contact with successive tissue interfaces. Reception by the transducer generates an electrical signal that is transmitted to an oscilloscope where the reflections are imaged. The factors affecting echo formation have been reviewed by Ferruci [5]. Internal echos on gray-scale ultrasonography are the result of collagen, the presence of which enhances the sound velocity in tissue. The varying elastic properties of the intra-abdominal organs distinguish one from another via their sound wave reflections. Various pathologic processes alter the sound waves in recognizable ways; in addition, localized collections of

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