S6227 Between a Rock and a Hard Place: A Rare Case of Chronic Superior Mesenteric Artery Syndrome Secondary to Retroperitoneal Lymphoma Causing Severe Malnutrition and Cachexia

Introduction: Superior Mesenteric Artery (SMA) Syndrome is a rare condition characterized by compression of the third portion of the duodenum between the SMA and aorta, leading to partial or complete obstruction. It is typically associated with rapid weight loss and low mesenteric fat pad volume. Malignancy is an exceedingly rare secondary cause. We present a unique case of chronic SMA syndrome resulting from mass effect of retroperitoneal lymphoma, culminating in profound malnutrition and cachexia. Case Description/Methods: A 56-year-old man with no significant past medical history presented with 8 months of progressive postprandial abdominal pain, early satiety, bilious vomiting, and a 42-pound unintentional weight loss. Initial evaluations including esophagogastroduodenoscopy and basic labs were unremarkable. Computed tomography abdomen with contrast revealed significant narrowing of the aortomesenteric angle (18°) with duodenal compression and associated gastric dilation. A retroperitoneal soft tissue mass encasing the SMA and aorta was identified. Computed tomography -guided biopsy confirmed low-grade B-cell lymphoma. Discussion: The patient was diagnosed with secondary SMA Syndrome due to mass effect from retroperitoneal lymphoma. He was started on enteral nutrition via nasojejunal tube and referred to oncology for systemic therapy. Over 12 weeks, following initiation of chemotherapy, repeat imaging showed reduction in mass size and normalization of the aortomesenteric angle (38°). The patient’s oral intake improved, and he gained 19 pounds. Symptoms of obstruction resolved completely by week 16. He transitioned to oral nutrition and resumed baseline activity level. This case highlights an unusual etiology of chronic SMA syndrome, illustrating the importance of broad differential diagnosis in patients with nonspecific GI obstructive symptoms and significant weight loss. Malignancy-related external vascular compression is rare but should be considered, particularly when clinical progression is subacute and unresponsive to typical interventions. Timely recognition and multidisciplinary management involving nutrition, oncology, and gastroenterology were critical to the favorable outcome in this case.