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Equine veterinary journal2026; doi: 10.1002/evj.70147

Intra-rater and inter-rater reliability of ultrasonographic intestinal wall thickness measurements in healthy horses.

Abstract: Abdominal ultrasound is widely used to evaluate the intestinal tract of horses. Despite being a routine examination, there is limited data on the reliability of this diagnostic procedure. Objective: To investigate intra- and inter-rater reliability of ultrasonographic intestinal wall thickness measurements in healthy horses. A second aim was to assess variance within repeated measurements to determine threshold values that distinguish whether differences between repeated examinations are true findings versus solely due to measurement variation. Methods: In vivo reliability study. Methods: Eight healthy horses (7 Standardbreds, 1 Warmblood) were ultrasonographically examined in six intestinal regions: duodenum, right dorsal colon (RDC), right ventral colon (RVC), caecum, jejunum and left ventral colon (LVC). In each horse, triplicate measurements of intestinal wall thickness were performed by three sonographers on three consecutive days. Intra-class correlation coefficient (ICC) was calculated to assess intra- and inter-rater reliability. Results: Intra-rater ICC was <0.5 for all regions except the duodenum (0.52). Inter-rater ICC was <0.5 for duodenum, caecum and jejunum and between 0.5 and 0.75 for RDC, RVC and LVC. The standard deviation of repeated measurements was low (0.33-0.45 mm). Across all regions, 95% (±2 SD) of all reported measurements were within a 1 mm range. Conclusions: Homogenous study group and use of healthy horses may limit generalisability to clinical populations. Conclusions: Ultrasonographic measurements of intestinal wall thickness show limited consistency but low absolute variation. Differences of less than 1 mm fall within expected repeated measurement variability. This study supports the use of repeated ultrasonographic intestinal wall thickness measurements in clinical practice and provides a practical cut-off value of 1 mm to differentiate expected variability within and between observers from true changes in intestinal wall thickness.
© 2026 EVJ Ltd.
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Publication Date: 2026-01-04 PubMed ID: 41486579DOI: 10.1002/evj.70147Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated the consistency of ultrasound measurements of intestinal wall thickness in healthy horses by examining how reliably the same and different sonographers could measure the thickness over multiple days.
  • It further aimed to identify a threshold to discern whether differences in repeated measurements were due to true changes or just measurement variability.

Introduction and Purpose

  • Abdominal ultrasound is a common diagnostic tool for assessing horses’ intestines.
  • Despite routine use, there was a lack of data on how reproducible intestinal wall thickness measurements are via ultrasound in horses.
  • Primary objectives included:
    • Evaluating intra-rater reliability (consistency when the same sonographer measures repeatedly).
    • Evaluating inter-rater reliability (consistency between different sonographers).
    • Determining the extent of variability in repeated measurements and establishing a practical threshold to identify true anatomical changes versus measurement noise.

Methods

  • Subjects:
    • Eight healthy horses (7 Standardbreds and 1 Warmblood).
  • Measurement regions:
    • Duodenum.
    • Right dorsal colon (RDC).
    • Right ventral colon (RVC).
    • Caecum.
    • Jejunum.
    • Left ventral colon (LVC).
  • Procedure:
    • Ultrasound examinations were performed on each horse in each region.
    • Three different sonographers each took three measurements (triplicate) per region on three consecutive days.
  • Analysis:
    • Calculated intra-class correlation coefficient (ICC) to quantify both intra-rater and inter-rater reliability.
    • Assessed variation across repeated measurements to decide meaningful threshold values.

Results

  • Intra-rater reliability (same sonographer over time):
    • ICC was less than 0.5 for all regions except duodenum (0.52), which indicates poor to moderate reliability.
  • Inter-rater reliability (between sonographers):
    • ICC was less than 0.5 for duodenum, caecum, and jejunum, showing poor reliability.
    • ICC between 0.5 and 0.75 (moderate reliability) for the right dorsal colon (RDC), right ventral colon (RVC), and left ventral colon (LVC).
  • Measurement variability:
    • Standard deviation of repeated measurements was low (ranging from 0.33 to 0.45 mm).
    • 95% of all measurements fell within ±2 standard deviations, roughly corresponding to a 1 mm range of variability.

Conclusions and Clinical Implications

  • The study group was homogeneous (healthy horses only), which may limit applicability to horses with intestinal diseases or broader clinical populations.
  • Ultrasound measurements of intestinal wall thickness have limited consistency between and within raters but show low absolute variation in measurements.
  • Differences of less than 1 mm in repeated measurements likely represent expected variation rather than true anatomical changes.
  • Thus, repeated ultrasonographic measurements can be useful clinically, with a practical cut-off of 1 mm difference to differentiate between measurement noise and actual changes in wall thickness.

Cite This Article

APA
Hansen T, Kendall A, Finne R, Law E, Ringdahl A, Nostell K. (2026). Intra-rater and inter-rater reliability of ultrasonographic intestinal wall thickness measurements in healthy horses. Equine Vet J. https://doi.org/10.1002/evj.70147

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Hansen, Tina
  • Mälaren Equine Clinic, Sigtuna, Sweden.
Kendall, Anna
  • Mälaren Equine Clinic, Sigtuna, Sweden.
Finne, Rebecca
  • Mälaren Equine Clinic, Sigtuna, Sweden.
Law, Ellen
  • Diagnostic Imaging Clinic, University Animal Hospital, Uppsala, Sweden.
Ringdahl, Agnes
  • Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Nostell, Katarina
  • Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.

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