EXPERIENCE WITH THE BIOSTATOR FOR DIAGNOSIS AND ASSISTED SURGERY OF 21 INSULINOMAS

Surgical removal is the treatment of choice for insulinomas. Definitiv e biochemical diagnosis of organic hyperinsulinism has to be establish ed before surgery These tumors are sometimes undetected by preoperativ e imaging investigations and, in addition, surgical management may als o be complicated by the absence of palpable tumors or the presence of multiple tumors. We report the value of the euglycemic clamp technique for diagnosis and surgical treatment in 21 patients with confirmed in sulinomas. Data were compared with 12 controls, and nine patients were retested after surgery. During the euglycemic hyperinsulinic clamp, t he mean C-peptide value was 3.6 +/- 2.2 ng/ml and it remained high (3. 8 +/- 2.5 ng/ml), despite exogenous hyperinsulinemia (1762.7 +/- 233.2 mu U/ml for the highest plateau). In contrast, the C-peptide concentr ation declined in 12 control patients (0.3 +/- 0.1ng/ml, P < 0.001) an d after successful surgery in nine retested patients (0.3 +/- 0.2 ng/m l, P < 0.01). During continuous glucose monitoring, successful removal of the insulin-secreting tumor was accompanied by an increase in plas ma glucose concentrations and a loss of requirement for endogenous glu cose within 36min (range 28-43min). The continuing requirement for glu cose after the ablation of the tumor revealed the existence of additio nal and initially undetected tumors in four patients, among whom two h ad the multiple endocrine neoplasia type I (MEN I) syndrome. We conclu de that the euglycemic hyperinsulinic clamp is a reliable and convenie nt diagnostic test for insulinoma, as it is both safe (no hypoglycemia ) and relatively brief (3x90min). Glucose monitoring and glucose clamp ing provide a reliable indicator of complete removal of insulin-hypers ecreting tissue, especially in patients with occult or multiple tumors .