To facilitate the noninvasive preoperative localization of islet cell tumors less than 15 mm in diameter, the authors examined the use of calcium as an insulin secretagogue in an arterial stimulation venous sampling (ASVS) technique. In four patients with episodic hypoglycemia, calcium gluconate (0.01-0.025 mEq Ca2+/kg) was injected directly into branches of the celiac plexus (gastroduodenal, splenic, and hepatic arteries) and the superior mesenteric artery. In all patients, serum levels of insulin rose abruptly in blood samples taken from the right hepatic vein 30 and 60 seconds after the infusion of calcium into the artery supplying the tumor; injection into an artery not supplying the tumor did not result in a similar rise. Accurate localization of the insulinomas was verified at surgery in three patients. In the fourth patient, who did not undergo surgery, arteriographic results were positive for insulinoma at the predicted site. On the basis of these results, the authors believe noninvasive ASVS may replace invasive portal venous sampling as the most effective method for the localization of occult insulinomas.

Intra-arterial calcium stimulation with right hepatic vein sampling for insulin gradients is the most sensitive preoperative test for localizing insulinomas.

Purpose-Thermal tissue ablation with radio frequency energy is an experimental treatment of renal tumor. We report early results of an ongoing trial of percutaneous radio frequency ablation for small renal tumors.Materials and Methods-Patients with percutaneously accessible renal tumors were evaluated for radio frequency ablation. Tumors were solid on computerized tomography (CT), 3 cm. or less in diameter and enlarging during at least 1 year. Ablation was performed at the Interventional Radiology suite under ultrasound and/or CT guidance. A 50 W., 460 kHz. electrosurgical generator delivered radio frequency energy via a percutaneously placed 15 gauge coaxial probe. At least 2, 10 to 12-minute ablation cycles were applied to each lesion. Patients were observed overnight before discharge from hospital and reevaluated 2 months later. Conclusions-Percutaneous radio frequency ablation of small renal tumor is well tolerated and minimally invasive. It will remain experimental until procedural and imaging parameters that correlate with tumor destruction are validated. ResultsKeywords kidney neoplasms; carcinoma; renal cell; surgical procedures; minimally invasive Renal tumors are being detected at increasing rates and smaller sizes with modern imaging techniques. Traditional treatment includes partial or radical nephrectomy but non-surgical ablative modalities are an option for patients with contraindications to surgery. The natural history of renal tumor is variable but those less than 3 cm. rarely metasta-size. [1][2][3][4][5] Management options for small renal masses include observation, experimental ablation and surgical removal. NIH Public Access

The CaStim has remained vastly superior to abdominal US, CT, or MRI over time as a preoperative localizing tool for insulinomas. The utility of the CaStim for this purpose and in this setting is thus validated.