Transmural Ileal Fibroplasia Causing Mechanical Obstruction in a Dog: Surgical Management, Histopathology, and Molecular Findings

Small bowel obstruction (SBO) in dogs is most commonly caused by foreign bodies or neoplasia; however, SBO secondary to transmural fibroplasia remains a rare clinical complication of canine chronic enteropathy. This report describes the complex case of mechanical SBO caused by transmural ileal fibroplasia and inflammation at the ileocolic junction in a 9-year-old mixed-breed dog with concomitant hyperadrenocorticism (HAC). The primary presentation involved chronic severe weight loss and intermittent anorexia, contrasting with the acute presentation typical of most SBO cases. Imaging studies revealed severe, circumferential thickening up to 10 mm of the small intestine wall at the ileocolic junction (ICJ), resulting in complete luminal stricture and marked proximal dilation. Surgical intestinal resection and anastomosis were performed for alleviation of the obstruction, and histopathology confirmed severe mural and serosal enteritis with extensive fibroplasia extending into the adjacent mesentery, thereby excluding neoplastic processes. Quantitative PCR analysis demonstrated a significant upregulation of mRNA expression for <i>PDGFRB</i> and <i>FGFR</i> compared to normal tissue. Postoperative recovery was rapid; although soft feces persisted for one month, normal stool consistency was subsequently restored, and the patient achieved significant weight gain. This case underscores the diagnostic and therapeutic challenges associated with non-neoplastic, inflammation-driven SBO and suggests that activation of the PDGFR-β/FGFR pathways may play a key role in fibroplasia-related intestinal strictures, offering a novel molecular perspective beyond conventional SBO etiologies.