# 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

## TL;DR

This study compares intestinal ultrasound measurements in cats with enteritis and lymphoma, finding no differences between conditions and a treatment-related change in wall layering.

## Contribution

The study is the first to assess ultrasonographic wall layering changes in cats with enteritis and lymphoma during treatment.

## Key findings

- No ultrasonographic differences were found between enteritis and lymphoma in cats.
- Treatment led to a significant decrease in muscular layer thickness ratio in enteritis cats.
- Diagnostic method (histology vs. clonality) did not affect ultrasonographic results.

## Abstract

It is unclear whether ultrasonographic examinations of the small intestines differ between cats with chronic enteritis and lymphoma if the diagnosis is made either histologically or based on lymphocyte clonality testing. Effects of treatment on ultrasound results have also never been assessed. We compared wall layer thicknesses between cats with enteritis and lymphoma diagnosed either with histology or clonality testing and also examined the effects of therapies in a subset of cats. Wall layering was measured in the duodenum, jejunum, and ileum, and ratios of individual layers were calculated. The thickness of the largest abdominal lymph node was also determined. Sixteen cats with surgical biopsies from stomach, duodenum, jejunum, and ileum were included. Medical treatments were based on histologic diagnoses. Ultrasonographic measurements were compared between enteritis and lymphoma when final diagnoses were either based on histology or clonality testing. The same ultrasonographic measurements were available for seven cats after 12 weeks and five cats after 24 weeks of medical treatment. No measurement differed between enteritis and lymphoma regardless of the diagnostic gold standard used. During treatment, only the ratio of muscular layer thickness to total wall thickness decreased significantly in cats with enteritis after 12 and 24 weeks compared to baseline. The change over time during treatment in cats with enteritis warrants further study.

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.