SELECTIVE ARTERIAL CALCIUM INJECTION FOR LOCALIZATION OF

OCCULT INSULINOMA Resident: Sarah Hicks Allgeier, MD, PhD

Attending: Kyung Cho, MD, FSIR

Program/Dept: University of Michigan Health System, Department of Radiology

CHIEF COMPLAINT & HPI

Chief Complaint and/or reason for consultation 37 year old male with chief complaint of hypoglycemia resulting in loss of consciousness while exercising. Blood glucose measured 42 mg/dL by EMS called to scene.

History of Present Illness Episodes of confusion, diaphoresis, tremors, and feeling unwell beginning 3-4 hours after eating or during exercise.

Has modied behavior such that he eats higher volumes of food and eats more frequently to maintain blood glucose, which has caused him to gain weight.

RELEVANT HISTORY

Past Medical History Hypoglycemia.

Past Surgical History None.

Family & Social History Aunt with Type 1 Diabetes Mellitus. No family history of neuroendocrine tumors. Recreational alcohol consumption. Never smoker. No occupational exposures.

Review of Systems Other than HPI, within normal limits for all 10 systems queried.

Medications None.

Allergies None.

DIAGNOSTIC WORKUP

Physical Exam Normal physical exam.

Laboratory Data Measured Value (Reference Range) Insulin 11.5 uIU/mL (1-23) Proinsulin 260 pmol/L (3-20) C-peptide 4.3 ng/mL (1.1-4.4) Chromogranin A 48 ng/mL (

DIAGNOSTIC WORKUP - CT ARTERIAL PHASE

Axial images from contrast-enhanced CT abdomen during the arterial phase demonstrate no evidence of hyperenhancing pancreatic mass.

DIFFERENTIAL DIAGNOSIS FOR HYPERINSULINEMIA

Factitious hypoglycemia Familial persistent hyperinsulinemic hypoglycemia Nesidioblastosis (primary islet cell hyperplasia) Noninsulinoma pancreatogenous hypoglycemia Insulinoma

DIAGNOSIS INSULINOMA

Meets Whipples Triad, highly suggestive of hyperinsulinism due to insulinoma 1. Symptoms known or likely to be caused by hypoglycemia especially after fasting or heavy exercise 2. A low plasma glucose measured at the time of the symptoms 3. Relief of symptoms when the glucose is raised to normal

INTERVENTION

Selective Arterial Calcium Injection (SACI) of potential feeding arteries supplying the occult pancreatic insulinoma (30 minutes between injections) Celiac Artery (CA) Supplies all but caudal head and uncinate process Common Hepatic Artery (CHA) Supplies neck and cranial head as well as liver Proximal Splenic Artery (PSA) Supplies body and tail Distal Splenic Artery (DSA) Supplies tail Gastroduodenal Artery (GDA) Supplies head and cranial uncinate process Superior Mesenteric Artery (SMA) Supplies caudal head and uncinate process Replaced Right Hepatic (RHA) Supplies liver (rule out metastases)

Hepatic vein venous sampling at 0, 30, 60, 90, and 120 seconds following injection Quantication of insulin and C-peptide in hepatic vein blood samples

DSA of the celiac artery demonstrating: Dorsal pancreatic artery arising directly from celiac artery Pancreatica magna artery arising from proximal splenic artery Caudal pancreatic artery arising from distal splenic artery Common hepatic artery giving rise to gastroduodenal and left

hepatic arteries Absence of right hepatic artery (replaced to SMA) Cobra catheter in right hepatic vein for venous sampling

INTERVENTION

INTERVENTION

Superior mesenteric artery angiogram demonstrating: Replaced right hepatic artery Anterior/posterior inferior pancreaticoduodenal arcade o rst jejunal branch

Proximal splenic artery angiogram demonstrating proximal location of pancreatica magna artery origin

INTERVENTION

Distal splenic artery angiogram demonstrating perfusion of the caudal pancreatic artery

INTERVENTION

Gastroduodenal artery angiogram demonstrating anterior/posterior superior pancreaticoduodenal arcade

Replaced right hepatic artery angiogram

Insu

lin Lev

el (

U/m

L)

Time After Calcium Injection (sec) Reference range 1.0-21.0 U/mL

HEPATIC VEIN INSULIN LEVELS

C-pe

ptide Le

vel (ng

/mL)

Time After Calcium Injection (sec) Reference range 1.0-5.2 ng/mL

HEPATIC VEIN C-PEPTIDE LEVELS

CONCLUSIONS DRAWN FROM SACI

Hepatic vein insulin and C-peptide levels signicantly increase following celiac, proximal splenic and distal splenic selective arterial calcium injections.

The aforementioned arteries supply increasingly specic regions of the pancreas, with the celiac supplying the majority of the pancreas, the proximal splenic supplying the body and tail, and the distal splenic supplying only the tail.

The fact that selective calcium injection of the distal splenic artery resulted in signicant increases in hepatic vein insulin and C-peptide eectively localized the patients tumor to the tail of the pancreas.

CLINICAL FOLLOW UP

Laparotomy with identication of mass in the pancreatic tail which could not be enucleated and required distal pancreatectomy/splenectomy

Frozen section at time of surgery conrmed neuroendocrine tumor Final pathology conrmed insulinoma Blood glucose rose from 70 to 145 mg/dL within 30 minutes after removal of the insulinoma, consistent with biochemical cure.

SUMMARY & TEACHING POINTS

Insulinomas are rare tumors that cannot always be localized using conventional imaging modalities such as ultrasound, CT, and MRI

SACI is a useful minimally-invasive tool for localizing these occult insulinomas

REFERENCES & FURTHER READING

Doppman, JL et al. Insulinomas: localization with selective intraarterial injection of calcium. Radiology (1991); 178: 237-241.

Doppman, JL et al. Localization of insulinomas to regions of the pancreas by intra-arterial stimulation with calcium. Ann Intern Med (1995); 123: 269-273.

Pereira, PL et al. Insulinoma and islet cell hyperplasia: value of the calcium intrarterial stimulation test when ndings of other preoperative studies are negative. Radiology (1998); 206: 703-709.

Imamura, M et al. Usefulness of selective arterial secretin injection test for localization of gastrinoma in the Zollinger-Ellison syndrome. Ann Surg (1987); 205: 230-239.