Severe Long-Segment Ischemic Colitis Associated with an Underlying Colonic Vascular Malformation in a Patient with a Synchronous Rectal Tubulovillous Adenoma with High-Grade Dysplasia: A Case Report

Background: Ischemic colitis is the most common form of intestinal ischemia and usually affects elderly patients with vascular risk factors. Although most cases respond to conservative treatment, severe ischemia complicated by transmural necrosis, abscess formation, or impending perforation requires emergency surgical intervention. Colonic vascular malformations are uncommon vascular lesions that have rarely been associated with ischemic injury and may present with nonspecific clinical and radiological features that overlap with colorectal malignancy or inflammatory bowel disease. We report a rare case of severe long-segment ischemic colitis involving the descending and sigmoid colon, associated with an underlying colonic vascular malformation, in a middle-aged woman with a synchronous rectal tubulovillous adenoma with high-grade dysplasia. Case Presentation: A 48-year-old woman with a 10-year history of diabetes mellitus presented with intermittent left-sided abdominal pain, altered bowel habits, constipation, and intermittent rectal bleeding. Ultrasonography suggested a pelvic bowel mass, and colonoscopy demonstrated an irregular anorectal lesion together with a polypoid upper rectal lesion. Histopathological examination revealed chronic nonspecific colitis in the anorectal lesion and a colonic adenoma with high-grade dysplasia in the upper rectal lesion. Endoscopic snare polypectomy confirmed a tubulovillous adenoma with high-grade dysplasia without invasive carcinoma. Despite treatment, she subsequently developed recurrent abdominal pain, fever, leukocytosis, anemia, and worsening renal function. Contrast-enhanced computed tomography demonstrated marked long-segment mural thickening involving the descending and sigmoid colon with inflammatory changes and ascites. Emergency laparotomy revealed extensive edema of the descending and sigmoid colon with retrocolic abscess, patchy ischemic changes, inflammatory fixation, and impending perforation. Resection of the affected colon with primary stapled colorectal anastomosis and diverting transverse loop colostomy was performed. Histopathological examination showed chronic colonic ulceration with peritonitis, impending perforation, and underlying colonic vascular malformation without evidence of malignancy, consistent with severe long-segment ischemic colitis. The patient recovered well and underwent successful colostomy closure five months later. Conclusion: This case highlights severe long-segment ischemic colitis involving the descending and sigmoid colon, associated with an underlying colonic vascular malformation and complicated by retrocolic abscess, peritonitis, and impending perforation in a patient with a synchronous tubulovillous adenoma with high-grade dysplasia. Early recognition, repeated clinical reassessment, and timely surgical intervention are essential for achieving favorable outcomes.