Allama Iqbal Medical College Sarnia, Ontario, Canada
Introduction: Pancreatic adenocarcinoma, though a relatively uncommon malignancy, is one of the leading causes of cancer mortality. Rarely it metastasizes to the large bowel to present as intestinal obstruction, complicating its diagnosis. Herein we report a case of pancreatic adenocarcinoma presenting as intestinal obstruction due to sigmoid metastasis in a female patient.
Case Description/Methods: A 60-year-old female with a past medical history of diabetes presented with constipation for 2 weeks and obstipation for 1 day associated with left lower quadrant abdominal pain. On admission, vital signs were stable and physical examination revealed normal bowel sounds and mild tenderness in the left lower quadrant. CT abdomen revealed an obstructing sigmoid tumor with concerning pancreatic and liver lesions. Subsequently, the patient underwent exploratory laparotomy with en bloc sigmoid colectomy with primary colorectal anastomosis. Pathology report revealed poorly differentiated adenocarcinoma involving the colonic muscularis propria, pericolonic adipose tissue, serosa, and involvement of 5 out of 14 lymph nodes. Since immunohistochemical markers were more consistent with metastatic disease from a pancreatobiliary primary rather than a colorectal primary, an EUS/FNA of the pancreatic lesion was performed, revealing pancreatic adenocarcinoma and confirming the pancreas as the site of primary malignancy. MRI abdomen further elucidated an infiltrative mass at the body and tail of the pancreas with adjacent vessel encasement. Due to the involvement of the celiac axis exceeding 180 degrees, the tumor was deemed unresectable, and patient was started on FOLFIRINOX chemotherapy
Discussion: Pancreatic adenocarcinoma (PAC) is a rare but ominous diagnosis with less than 20% of patients presenting with an operable tumor and a 5-year survival approaching 5% [3]. PAC rarely presents as large bowel obstruction with 7 cases reported so far [4]. It can therefore be misdiagnosed as primary colorectal cancer. Knowing the true diagnosis beforehand in such a case can guide management, as palliative chemotherapy regimens, instead of local resection of colorectal disease, would be initiated if the pancreatic primary were first identified [5]. In our case, resection of the sigmoid mass was done to relieve symptoms of acute intestinal obstruction. Since patients with PAC are diagnosed after the disease has spread, palliative chemotherapy remains one of the few viable options for treatment.
