Intestinal Ultrasonographic Measurements in Cats Diagnosed with Lymphoplasmacytic Enteritis and Low-Grade T-Cell Lymphoma Based on Either Histology/Immunohistochemistry or Clonality Testing—And Assessment of the Effects of Therapy on Wall Layering After 3 and 6 Months of Treatment

It is unknown whether intestinal ultrasonographic measurements differ between lymphoplasmacytic enteritis (LPE) and low-grade intestinal T-cell lymphoma (LGITL) in cats if the diagnosis is based either on histology/immunohistochemistry (IHC) or on clonality assay results. The effects of treatment on intestinal ultrasonographic measurements are also unknown. Therefore, we prospectively compared small intestinal wall layering between cats with LPE and LGITL and investigated whether there were differences between the groups when the diagnostic gold standard was either histology/IHC or clonality testing. We evaluated the effects of standardized treatment in a subset of cats. The thicknesses of the total wall, mucosa, muscularis, and submucosa were measured in the duodenum, jejunum, and ileum, and ratios (muscularis to submucosa, muscularis to total wall thickness) were calculated. The thickness of the largest mesenteric lymph nodes was also determined. Ultrasonographic measurements from duodenal and jejunal segments were grouped together, and ileal segments were assessed separately. Sixteen cats with standardized full-thickness biopsies from the stomach, duodenum, jejunum, and ileum were included. Samples for clonality testing were fresh-frozen and analyzed later, and the standardized treatment was based on histologic/IHC diagnoses. Ultrasonographic measurements were compared between LPE and LGITL when diagnoses were either based on histology/IHC or clonality testing using a linear mixed model. Repeated ultrasonographic measurements of segments were available for seven cats after 12 weeks (five LPE, two LGITL) and five cats after 24 weeks (three LPE, two LGITL) of standardized treatment. We found that none of the ultrasonographic measurements differed between LPE and LGITL regardless of the diagnostic gold standard used. During treatment, only the ratio of lamina muscularis thickness to total wall thickness decreased significantly in LPE cats after 12 and 24 weeks compared to baseline. In conclusion, the herein evaluated ultrasonographic variables did not differ between LPE and LGITL and the diagnostic gold standard used had no influence on the results. The detected change over time during treatment in LPE cats requires further study.