Molly is a nine year old Boxer. In January her owners called the hospital to report that she was having episodes of muscle tremors, sometimes severe enough to cause her legs to collapse. Dr. Lyn Lemieux spoke with her owners and recommended that Molly come in for a physical examination, blood work to rule out metabolic disorders, and a cardiac workup.
Molly’s physical examination was normal with the exception of a rapid heart rate (180 beats per minute). Her chest x-rays and EKG suggested right atrial heart enlargement. Abnormalities on her blood count included increased red blood cells and hemoglobin and a high PCV (packed cell volume) of 64 (normal 37-55). On serum profile her globulin was slightly elevated (3.4 – normal range 2.1-3.2). Her blood glucose was 62, which is near the low end of the normal range (54.5 – 118.1).
Four days later Molly had a more severe episode of tremors and weakness. Her blood glucose was 43, this time well below the normal range, and her PCV remained high at 61.2. The differential diagnosis for hypoglycemia (low blood sugar) in older dogs includes diseases such as liver insufficiency, pancreatic neoplasia, extrapancreatic neoplasia, hypoadrenocorticism, and sepsis. The differential diagnosis for polycythemia (increased PCV) includes pulmonary disease, cardiac shunts, hyperadrenocorticism, neoplasia (especially renal neoplasia), and bone marrow disease. A tumor search was undertaken with radiographs and ultrasound examination of the chest and abdomen. No grossly visible tumors were identified.
To narrow the differential diagnosis a serum insulin level was submitted. The insulin level was extremely high at 60.7 (normal is 15-35). This greatly increased the probability of an insulin secreting pancreatic tumor as the cause of Molly’s hypoglycemia.
After discussing the medical and surgical options with Molly’s owners, a decision was made to attempt medical management of her hypoglycemia. Molly was sent home with instructions to feed her four times a day. She continued to have episodes of tremors especially before eating. After further discussions with Molly’s family, a decision was made to perform exploratory surgery. If Molly’s low blood sugar was caused by a pancreatic tumor it might be possible to remove the tumor and part of the pancreas. Pancreatic tumors in dogs may be single or multiple and are often very small. The tumors may be barely palpable within the pancreas.
During the exploratory Molly’s pancreas was closely examined. A small firm tumor was found mid pancreas. The remainder of the pancreas appeared quite normal except for diffuse 1-2 mm densities palpable throughout the organ. The primary nodule was surgically removed and four additional biopsies of pancreas were taken. These small nodular areas were worrisome. If these densities were early spread of the primary tumor, Molly would have little chance of recovery. Liver, spleen, kidneys, and mesenteric lymph nodes appeared normal.
Molly was considered an increased surgical risk because of her persistent low blood sugar and her mild heart enlargement. During the presurgical, surgical, and postsurgical period Molly was maintained on an IV pump that delivered 5% Dextrose to keep her blood sugar within normal limits. Her oxygen saturation, heart rate, and pulse pressure were monitored closely throughout the surgery. Her body temperature was maintained with the use of circulating warm water blanket. Her condition was stable throughout the surgical procedure. Her postoperative comfort was insured with the use of pain relief.
Molly did very well throughout the postoperative period. Her blood sugar stabilized and we were pleased to send her home four days after surgery.
Molly’s tissue samples were sent to Tufts University Veterinary Pathology Lab for examination. We now anxiously awaited the pathology report.
Histopathological examination of the tumor submitted revealed islet cell tumor. This is an insulin secreting mass. Four additional sections of pancreatic tissue were examined. All showed essentially normal structure. Normal pancreatic ducts were also present in addition to a few pancreatic islets. No evidence of neoplasia was present in these sections. This report was very encouraging. Pancreatic tumors have a high rate of metastasis or spread. Even though no secondary tumors were found by the pathologist, it was possible very early microscopic secondary tumors existed elsewhere in the pancreas. Only time would tell how well Molly would do after surgery.
Ten days later Molly was re-examined and her owners reported that she was doing very well and had had no episodes since surgery. Her blood glucose was 116.3 and her PCV was 46, both within normal limits. To date Molly continues to do well. Her prognosis remains somewhat guarded because of the possibility of small, unidentified tumors within the pancreatic tissue.
Of note is the fact that her elevated PCV returned to normal after excision of the pancreatic mass. Polycythemia has not been reported to be related to islet cell tumors of the pancreas.