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.
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.
The final multivariable logistic regression models for each disease category are shown in Table 3.
|Variable||Odds ratio||95% CI||P value|
|Increased peritoneal free fluid|
|Thickened wall loops|
|Right dorsal displacement|
|Increased peritoneal free fluid|
|Visualisation left kidney|
|Increased peritoneal free fluid|
|Large colon strangulating volvulus|
|Large colon nonstrangulating volvulus|
|Visible loops of small intestine|
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.
|Definitive diagnosis||Total number of horses||Sensitivity||Specificity||PPV||NPV|
|Completely distended SI loops||76%||73%||55%||87%|
|Right dorsal displacement||25|
|Not visualised left kidney||87%||83%||42%||98%|
|LC strangulating volvulus||9|
|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%|
|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
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.