The Success Rates of the Localization Techniques
ZO 40 60 80
Percent of Patients with True Positive Results
ZO 40 60 80
Figure 13-14. Success rates of insulinoma localization at our institution using various localization techniques. CT = computed tomography; MRI = magnetic resonance imaging; THPVS = transhep-atic portal venous sampling. Reproduced with permission from Boukhman MB et al.33
tionship to the pancreatic ducts, the portal vein, the common bile duct, and the superior mesenteric vessels. This helps in removal of the tumor and decreases the risk of a postoperative fistula. The body and tail of the pancreas are mobilized by incising the peritoneum at the inferior border of the gland and gradually dissecting beneath its entire posterior surface. This is also the approach that is frequently used to expose the left adrenal gland.
If a small pancreatic tumor is found, enucleation is often possible with gentle dissection of the exocrine parenchyma away from the islet cell tumor. Use of the Bovie electrocoagulation unit and clips might lessen the risk of a pancreatic fistula.35 Before removal of a suspected solitary adenoma, the entire pancreas should be carefully examined because insulinomas are occasionally (approximately 18%) multiple. As mentioned previously, they are only rarely found in extrapancreatic sites.
Pathologists can usually confirm that the removed tumor is an islet cell tumor on frozen section but usually cannot determine whether it is benign or malignant. Following removal, the blood sugar level usually rises and the insulin level falls, indicating a successful operation.
At UCSF medical centers, we have had an 89% success rate at initial pancreatic exploration for insulinomas, including a 96% (46 of 48) success rate in patients with benign solitary tumors.5 This success rate is similar to the results reported by others.23,36 Among the patients who had initial pancreatic exploration for insulinoma, 3 of 5 with multiple tumors and 6 of 7 with malignant tumors were successfully treated. Reoperations are not as successful as we and others have reported.5 The main reasons for failure in our experience5,37 and that of others were (1) islet cell cancer or metastatic disease, (2) nesidioblastosis/hyperplasia, (3) multiple neoplasms that are especially common in MEN type I patients, and (4) solitary adenomas that are small or soft deeply situated in the pancreas. Some patients have more than one reason for failure. Because of the higher failure rate in patients requiring reoperation, we recommend preoperative localization studies, including transgastric ultrasonography and the Ima-mura-Doppman procedure in these patients.
Table 13-2. ADVANTAGES OF INTRAOPERATIVE ULTRASONOGRAPHY IN PATIENTS WITH INSULINOMA*
Identified insulinomas with 91% sensitivity Is more sensitive than intraoperative palpation
(91% vs 76% sensitivity) Identified 9 nonpalpable and nonvisible insulinomas, thus increasing operative success Decreased the risk of missing multiple tumors Low false-positive rate; therefore, useful for persistent or recurrent disease Helped visualize relationship of the tumor to the pancreatic duct; therefore, possibly decreased incidence of postoperative fistula
*From the University of California-San Francisco institutional experience.
Adapted from Boukhman MB et al.33
For patients with sporadic insulinoma and solitary tumors, we recommend local incision; for massive tumors in the head of the pancreas, a Whipple procedure is indicated. Patients with MEN should be treated by enucleation of tumors from the head of the pancreas and distal pancreatectomy. For patients with nesidioblastosis, an extensive subtotal or near-total pancreatectomy should be done.
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