Use of radiographic and histologic scores to evaluate cats with idiopathic megacolon grouped based on the duration of their clinical signs

Abstract

Since the duration of clinical signs could be used to identify cases of chronic constipation, in addition, prolonged duration is often associated with irreversible changes. Thus, the main objective of this study was to determine whether the duration of clinical signs of idiopathic megacolon in cats affected their diagnosis and prognosis after treatment. Medical records of cats that either had confirmed megacolon for an unknown cause (cat patients) or with normal bowels (control cats) were reviewed. Cat patients were grouped based on the duration of their clinical signs (constipation/obstipation) to cats <6 months and ≥6 months. For all feline patients, abdominal radiographs (for colonic indexes) and resected colon specimens (for histology) were assessed vs. control cats. Treatment applied to cat patients was also evaluated. Cat patients were older (p = 0.0138) and had a higher maximum colon diameter (MCD; mean 41.25 vs. 21.67 mm, p < 0.0001) and MCD/L5L ratio (1.77 vs. 0.98, p < 0.0001) than controls. Compared to cats with <6 months, cats ≥6 months showed a higher MCD (43.78 vs. 37.12 mm, p < 0.0001) and MCD/L5L ratio (1.98 vs. 1.67, p < 0.0001). Histologically, increased thickness of the smooth muscularis mucosa (54.1 vs. 22.33 μm, p < 0.05), and inner circular (743.65 vs. 482.67 μm, p < 0.05) and outer longitudinal (570.68 vs. 330.33 μm, p < 0.05) smooth muscular layers of the muscularis externa was noted only in cat patients with ≥6 months compared to controls. Similarly, fewer ganglion cells (0.93 vs. 2.87, p < 0.005) and more necrotized myocytes (2.25 vs. 0.07, p < 0.005) were observed in cats with ≥6 months. In contrast to <6 months, the majority of cats (94.4%) with ≥6 months duration did not show any response to medical treatment and therefore underwent surgery with favorable results. In conclusion, this study suggests that the duration of clinical signs should be considered in conjunction with maximal colon scores to evaluate cats for idiopathic megacolon and determine the level of treatment. Functional abnormalities of the colonic smooth muscles may be a possible cause of idiopathic megacolon in cats.

Keywords: cats; histopathology; idiopathic megacolon; radiography; signs duration.

Figure 1

A representative lateral abdominal plain radiograph of a 4.5-years-old 5.7-kg Persian intact male normal healthy cat. Measurements for the body length of the fifth lumbar vertebra (L5L, labeled a, 21.1 mm), and maximum colon diameter (MCD, labeled b, 25.8 mm) are displayed by solid yellow lines.

Figure 2

A representative lateral abdominal plain radiograph of a 6.9-years-old 4.6-kg domestic shorthair castrated male cat with idiopathic megacolon and constipation/obstipation. Measurements for the body length of the fifth lumbar vertebra (L5L, labeled a, 21.7 mm), and maximum colon diameter (MCD, labeled b, 40.5 mm) are displayed by solid yellow lines.

Figure 3

Box-and-whiskers plots of MCD (A), L5L (B), MCD/L5L ratio (C), body weight (D), and age (E) for cats that had confirmed idiopathic megacolon (n = 30) or healthy without evidence of either gastrointestinal or vertebral column diseases (controls; n = 30). The line represents the median, the cross represents the mean, and the whiskers rep-resents the range. Significant at p < 0.0001 and p < 0.005.

Figure 4

Box-and-whiskers plots of MCD (A), L5L (B), MCD/L5L Ratio (C), body weight (D), and age (E) for cats that had confirmed idiopathic megacolon with a duration of constipation/obstipation <6 months (n = 12) or ≥6 months (n = 18). The line represents the median, the cross represents the mean, and the whiskers represent the range. Significant at p < 0.0001 and p < 0.005.

Figure 5

Photomicrograph of H&E colon sections from healthy cat colon showing: (A) normal histology of mucosa (M), submucosa (SM), inner circular (IC), and outer longitudinal (OL) smooth muscles. Scale bar 200 μm. (B) Numerous goblet cells within the lamina epithelialis (curved arrow), and no morphological changes in the submucosal layer (star label). Scale bar 100 μm. (C) Normal myenteric plexus (arrow) between the inner and outer muscular layers. Scale bar 100 μm.

Figure 6

Photomicrograph of H&E-stained sections from cat idiopathic megacolon that had <6 months duration of constipation/obstipation showing mild-moderate degenerative changes: (A–C) desquamated epithelium (arrow) and metaplastic changes of the colonic columnar epithelium into goblet cells (arrowheads). (D) Vacuolated (arrowhead) and necrotic enteric myocytes (arrow). Scale bar 200, 100, 20, and 100 μm, respectively.

Figure 7

Photomicrograph of H&E sections from cat idiopathic megacolon that had ≥6 months duration of constipation/obstipation showing moderate to severe degenerative changes. (A, B) The diphtheritic membrane is replaced by most mucosal layers (arrows). Scale bar 100 and 20 μm, respectively. (C, D) Neutrophils (curved arrows) and proteinaceous exudates within lamina propria and submucosa. Scale bar 20 and 10 μm, respectively.

Figure 8

Photomicrograph of H&E-stained sections from cat idiopathic megacolon that had ≥6 months duration of constipation/obstipation showing moderate to severe degenerative changes: (A, B) Catarrhal lesions in the colonic epithelium [desquamated colonic epithelium (arrowhead), inflammatory cells infiltrate (star) between degenerated and necrotized colonic glands and congested blood vessels (arrow)]. (C, D) Submucosal neutrophils infiltrations (arrows) and clearly visible adhered neutrophils to blood vessel endothelium (curved arrow) for the transmigration process. Scale bar 200, 100, 20, and 10 μm, respectively.

Figure 9

Measurements of the thickness of the muscularis mucosa, and the inner circular and outer longitudinal smooth muscle layers of the muscularis externa obtained from the transverse colon [TC, (A)] or descending colon [DC, (B)] in controls (n = 5) and case cats with idiopathic megacolon and grouped based on the duration of constipation/obstipation, <6 months (n = 3) and ≥6 months (n = 5). Necrotized enteric myocytes (C) and ganglion cells (D) mean scores in controls and grouped case cats with idiopathic megacolon. Data are given as mean ± SD. ns, not significant. *p < 0.05; **p < 0.005.