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The article by F. Beccati et al. (2011)‘Is there a statistical correlation between ultrasonographic findings and definitive diagnosis in horses with acute abdominal pain?’ in the Equine Colic Supplement published in August 2011 contains several errors. The text below replaces the sections containing errors.

Results, paragraphs 3–7.

Univariable analysis

The stomach (n = 3), peritonitis (n = 6), nonstrangulating obstruction (n = 7), intussusception (n = 6), large colon impaction (n = 7), caecal disease (n = 6), small colon impaction (n = 6), inflammatory bowel disease (n = 6) and adhesions were excluded from the statistical analysis because of the low number of cases in these categories.

Increased free peritoneal fluid (OR 2.52, 95% CI 1.05–6.06, P<0.05), reduced duodenal motility (OR 3.70, 95% CI 1.18–11.60, P<0.05), completely distended appearance (OR 9.84, 95% CI 2.66–36.38, P<0.0001) and absent motility (OR 8.40, 95% CI 2.81–25.15, P<0.0001) of SI loops were significantly associated with strangulating obstruction of the SI. Increased free peritoneal fluid (OR 3.25, 95% CI 1.51–7.02, P<0.001), reduced (OR 4.48, 95% CI 1.43–13.95, P<0.001) and absent (OR 6.51, 95% CI 1.55–27.39, P<0.01) duodenal motility, completely distended appearance of SI loops (OR 43.55, 95% CI 10.79–175.72, P<0.0001), reduced (OR 3.42, 95% CI 1.18–9.89, P<0.05) and absent motility (OR 29.25, 95% CI 9.24–92.50, P<0.0001) of SI loops were significantly associated with definitive diagnosis involving SI. Colon appearance, colon motility and visualisation of the left kidney were associated with a reduced risk of strangulating obstruction of the SI and definitive diagnosis involving SI.

There was a tendency to fail to identify SI loops in association with right dorsal displacement of the LC (P = 0.08). Completely distended appearance and reduced motility of SI loops and increased free peritoneal fluid were associated with a reduced risk of right dorsal displacement of the LC. LC distension (OR 3.87, 95% CI 1.08–13.85, P<0.05) and absent visualisation of the left kidney (OR 30.78, 95% CI 6.41–147.80, P<0.0001) were significantly associated with renosplenic entrapment. Thickening (OR 9.41, 95% CI 1.67–52.81, P<0.01) and absent motility (OR 7.84, 95% CI 1.83–73.81, P<0.05) of the LC were significantly associated with strangulating LC volvulus. Amotile LC (OR 4.08, 95% CI 1.93–17.74, P<0.05) and failure to visualise SI (OR 4.66, 95% CI 1.24–17.43, P<0.05) were significantly associated with nonstrangulating LC volvulus.

Multivariable analysis

The final multivariable logistic regression models for each disease category are shown in Table 3.

Table 3.  Statistically significant findings on multivariable logistic regression analysis of the associations between abnormal abdominal ultrasonographic findings and disease categories obtained in 158 horses with colic
VariableOdds ratio95% CIP value
  1. NA = not applicable.

Strangulated obstruction
Loop appearance   
 NormalReferentNANA
 Completely distended11.662.33–58.19<0.001
Colon appearance   
 NormalReferentNANA
 Thickened0.080.01–0.74<0.05
Small intestine
Increased peritoneal free fluid   
 NoReferentNANA
 Yes33.991.80–64.69<0.05
Loop appearance   
 NormalReferentNANA
 Completely distended38.248.25–270.15<0.001
Duodenum motility   
 NormalReferentNANA
 Reduced7.61.23–60.30<0.01
Thickened wall loops   
 NoReferentNANA
 Yes5.42.65–43.64<0.05
Right dorsal displacement
Increased peritoneal free fluid   
 NoReferentNANA
 Yes0.330.11–0.95<0.05
Colon appearance   
 NormalReferentNANA
 Distended4.421.22–15.97<0.05
Nephrosplenic entrapment
Visualisation left kidney   
 YesReferentNANA
 No38.177.31–99.34<0.001
Increased peritoneal free fluid   
 NoReferentNANA
 Yes0.230.05–0.94<0.05
Large colon strangulating volvulus
Colon appearance   
 NormalReferentNANA
 Thickened23.21.40–82.17<0.05
Colon motility   
 NormalReferentNANA
 Absent18.232.13–96.42<0.05
Large colon nonstrangulating volvulus
Colon motility   
 NormalReferentNANA
 Absent3.971.89–17.79<0.05
Visible loops of small intestine   
 YesReferentNANA
 No4.041.96–16.99<0.05

Associations between disease categories and abdominal US findings

Various ultrasonographic findings were associated with specific disease categories (Table 3): The presence of completely distended SI loops was associated with strangulating obstruction of the SI (P<0.0001); the presence of distended LC was associated with right dorsal displacement of the LC (P<0.05); thickened appearance (P<0.001) and absent motility (P<0.05) of the LC were associated with strangulating LC volvulus, visualisation of SI loops (P<0.05) and amotility of the LC (P<0.05) were associated with nonstrangulating LC volvulus while lack of visualisation of the left kidney was associated with renosplenic entrapment (P<0.001). Records of peritoneal fluid assessment were available for 141 horses, SI motility for 90 horses, and SI distension and thickening for 135 horses. Horses with increased free peritoneal fluid (SI 43 of 55; LI 46 of 86, P<0.001), reduced duodenal motility (SI 11 of 36; LI 6 of 54, P<0.001), completely distended SI loops (SI 47 of 59; LI 11 of 76, P<0.0001), and thickened SI wall (SI 22 of 59; LI 8 of 76, P<0.05) were more likely to have SI rather than LI disease.

The sensitivity, specificity, and positive (PPV) and negative (NPV) predictive values for US findings that were significantly associated with specific disease categories are summarised in Table 4.

Table 4.  Sensitivity, specificity, positive and negative predictive values of abdominal ultrasonographic findings significantly associated with specific disease categories
Definitive diagnosisTotal number of horsesSensitivitySpecificityPPVNPV
  1. SI = small intestine; LC = large colon; PPV = positive predictive value; NPV = negative predictive value

Strangulated obstruction 45    
 Completely distended SI loops 76%73%55%87%
Right dorsal displacement 25    
 Distended LC 38%70%40%85%
Renosplenic entrapment 16    
 Not visualised left kidney 87%83%42%98%
LC strangulating volvulus 9    
 Thickened LC 67%86%87%97%
 Absent motility of LC 63%77%77%96%
LC nonstrangulating volvulus 13    
 No visible SI loops 46%91%33%95%
 Absent motility of LC 58%76%23%94%
SI disease 58    
 Increased peritoneal free fluid 79%49%50%78%
 Completely distended SI loops 83%85%85%83%
 Reduced duodenum motility 28%89%65%62%
 Thickened wall loops 37%82%60%60%

Discussion, Paragraphs 9 and 10

Large intestine

The results of multivariable analysis of renosplenic entrapment demonstrate that failure to visualise the left kidney was highly significantly associated with this condition. In agreement with other authors (Santschi et al. 1993), in horses with renosplenic entrapment the presence of gas-filled colon dorsal to the spleen precluded imaging of the kidney. There are no published data on the sensitivity, specificity, PPV and NPV of this US finding, but in this study the values were 87, 83, 42 and 98%, respectively. The low PPV is a consequence of false positive findings (18/143), and a similar finding was reported in a previous study (Busoni et al. 2010). Recent transrectal examination often obscures visualisation of the left kidney (Reef 1998a); in our practice, transrectal examination precedes abdominal US examination. Failure to visualise the left kidney was the only parameter assessed and analysed in this study. Other authors recommend assessment of several ultrasonographic features for the diagnosis of left dorsal displacement of the LC (Santschi 1993; Reef 1998a).

In the multivariable model for right dorsal displacement a distended LC was significantly associated with this condition. In LC displacements, which are nonstrangulating conditions, because of the impaired flow of ingesta over time, gaseous distension becomes more significant and the distension of the LC is a common feature. With regard to renosplenic entrapment, it could be very interesting to evaluate whether there is a difference in US appearance of the LC in medical vs. surgical cases, since there are no published data. Strangulated LC volvulus causes complete obstruction of venous drainage, which causes the LC wall to become oedematous and thickened (Snyder et al. 1989). In agreement with Pease et al. (2004), the ultrasonographic finding of thickened LC was sensitive and specific for the presence of strangulated LC volvulus, with good PPV and NPV. In contrast, changes in the ultrasonographic appearance of the LC wall was not associated with nonstrangulating volvulus. In nonstrangulation obstruction (and in displacement) of the LC, the viscus could become distended with gas and ingesta but, because the vasculature is not compromised, the wall does not become thickened as it does in LC torsion (Hackett 1983). Absent motility of the LC had moderate sensitivity, specificity and high NPV for both strangulated and nonstrangulated volvulus, with better PPV for strangulated volvulus.

Reference

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  2. Reference
  • Beccati, F., Pepe, M., Gialletti, R., Cercone, M., Bazzica, C. and Nannarone, S. (2011) Is there a statistical correlation between ultrasonographic findings and definitive diagnosis in horses with acute abdominal pain? Equine vet. J., Suppl . 39, 98-105.