Ultrasonographic gastro-intestinal pattern of dogs with acute kidney injury

Canine Acute Kidney Injury (AKI) is a critical clinical condition that, beyond compromising renal excretory function, triggers a complex multi-organ dysfunction syndrome, due to the accumulation of uremic toxins, electrolyte imbalances, and release of inflammatory mediators. Among extra-renal complications, the gastrointestinal tract (GI) emerges as a primary target, although veterinary literature still lacks a systematic ultrasonographic characterization of the associated morpho-functional alterations. This prospective observational study aimed to systematically characterize the GI morpho-functional alterations in dogs with AKI through B-mode ultrasonography. Specifically, the study sought to determine the prevalence of structural abnormalities across different GI segments - stomach, small intestine, and colon - and to quantitatively assess gastrointestinal motility to identify specific patterns of dysmotility associated with uremia. This prospective study enrolled 39 client-owned dogs diagnosed with AKI based on IRIS (International Renal Interest Society) guidelines, which were referred to the veterinary teaching hospital between January 2025 and January 2026. Each patient underwent a standardized clinical workup and a comprehensive B-mode abdominal ultrasound using high-frequency linear or micro-convex probes. The methodology focused on measuring wall thickness and evaluating the echogenicity and integrity of the parietal layers. The cohort predominantly presented at advanced disease stages, with IRIS Grade IV being the most prevalent (33.3%). The GI tract was the most frequently affected system (97.4%). The small intestine was the most commonly involved segment (92.3%), followed by the stomach (61.5%) and colon (56.4%). Principal ultrasonographic abnormalities included parietal thickening and increased mucosal echogenicity across segments. Dynamic evaluation demonstrated profound motor impairment; peristalsis was completely absent in the stomach of 66.6% of evaluated patients and the small intestine of 50%. When present, contractions consistently exhibited a non-propulsive, bidirectional oscillatory pattern. These findings, including the early presence of hyperechoic mucosal bands in the stomach, suggest that uremic gastropathy is a common feature of acute injury. Furthermore, the high prevalence of accessory signs like mesenteric fat reactivity (41%) and biliary sludge (59%) underscores the activation of the renal-intestinal axis. In conclusion, abdominal ultrasonography should not be limited to renal parenchyma but must include a detailed analysis of the GI tract, as the early identification of atony and mucosal changes is fundamental to guiding therapeutic choices and nutritional support in dogs with AKI.