Swelling from the Inside Out: Atypical AKI Triggered by Gastrointestinal Hereditary Angioedema Flare

Introduction: Hereditary angioedema (HAE) is a rare disorder caused by C1 esterase inhibitor deficiency, resulting in episodic vascular permeability and tissue edema. Gastrointestinal attacks, though underrecognized, can present with severe abdominal symptoms and mimic intra-abdominal pathology. In patients with pre-existing chronic kidney disease (CKD), these episodes can precipitate significant volume shifts, posing a risk for acute kidney injury (AKI). This case highlights the diagnostic and therapeutic challenges of HAE-related gastrointestinal edema with secondary AKI. Case Description: A 75-year-old male with HAE type 1, CKD stage 4 (baseline Cr 4.46) due to focal segmental glomerulosclerosis, and adrenal insufficiency, presented with two weeks of abdominal pain, bloating, and dysphagia. He had missed his scheduled Takhzyro prophylaxis for over five weeks. CT imaging revealed duodenal and proximal small bowel dilation with findings consistent with localized ileus and inflammation. Laboratory workup demonstrated leukocytosis (WBC 26.68) and anuric AKI (Cr 7.13). Physical exam noted a distended abdomen; surgery was consulted to evaluate for abdominal compartment syndrome. Conservative management was pursued, and IV fluids were initiated for pre-renal AKI due to poor oral intake and third-spacing from gastrointestinal edema. Immunosuppressive agents (Cellcept, Acthar) were held. Despite fluids and antibiotics, symptoms persisted. Allergy consult confirmed an HAE flare. He received two doses of Firazyr, resulting in rapid improvement of GI symptoms, decreased NG output, and recovery of renal function to baseline. NG tube was removed, and immunosuppression was safely restarted. Discussion: This case emphasizes the nephrologic relevance of gastrointestinal HAE flares in patients with advanced CKD. In such individuals, volume depletion due to third-spacing and reduced oral intake can precipitate severe pre-renal AKI. Early recognition of non-infectious, non-surgical causes of GI symptoms is critical in avoiding unnecessary interventions and preserving renal function. Bradykinin-mediated GI angioedema should be considered in the differential of unexplained AKI in patients with known or suspected HAE. Prompt treatment with Firazyr can reverse systemic symptoms and facilitate renal recovery, underscoring the importance of multidisciplinary collaboration in complex cases.