Findings:
Abdominal ultrasound:
- The small intestine is moderately to severely distended with fluid exhibiting to- and fro- motion.
Survey radiograph:
- Multiple gas-dilated small intestinal segments are noted throughout the caudal abdomen. Gas is seen to fill the rectum, with an abruptly, convex caudal margin of the rectum at the level of the obturator foramen (yellow outline). No evidence of gas is seen extending caudal to this region.
Positive contrast colonogram:
- A catheter has been placed within the anus, and positive contrast medium (nonionic, iodinated, 300 mg I/mL) was injected through the catheter. The catheter can be seen extending 1 cm cranially, within the soft tissues dorsal to the gas-distended convex margin of the rectum described above. Contrast medium fills the rectum, extending cranially to the level of the obturator foramen, with multiple circumferential linear filling defects throughout the rectum. There is acute tapering of the cranial margin of the contrast-filled rectum, with no communication with the cranially located gas-filled rectum (blue outline). On the ventrodorsal projection, contrast medium is superimposed over the soft tissues of the perineal and left thigh region.
Conclusions:
- Atresia recti with gastrointestinal mechanical obstruction.
Necropsy:
- Atresia coli and rectum, congenital, dorsal large colon and small colon.
A little bit more…
- Atresia ani/coli: part of the intestine fail to develop in utero (Haggett et al., Hepworth‐Warren et al.). Atresia coli is most common.
- Pathogenesis of intestinal atresia is poorly understood and multiple theories have been proposed:
- vascular insufficiency resulting in ischemic necrosis of the intestine
- hereditary
- developmental arrest
- If vascular in origin, intussusception, volvulus, herniation or strangulation of the intestines during pregnancy may resulting interruption of the blood supply to a segment of intestine and subsequent segmental atrophy embryonically (Hepworth‐Warren et al., Azizi et al.).
- Discontinuity of the intestine is most commonly found between the left ventral and dorsal colon (Haggett et al.).
Types of atresia ani:
- Congenital anal stenosis (type I)
- Imperforate anus alone (Type II)
- Combined with a more cranial termination of the rectum as a blind pouch (Type III)
- Discontinuity of the rectum orad with normal anal and terminal rectal development (Type IV)
- On rare occasions, concurrent defects within the urinary tract may be seen (Haggett et al.)
- Foals are usually normal at birth and present 4–24 hours after birth with a progressive moderate to severe colic (slower onset of clinical signs for more aborad defects) (Haggett et al., Gillen et al.).
- A diagnosis may be achieve with ultrasound (identify obstructive pattern) and survey radiographs followed by a contrast enema (Haggett et al., Hepworth‐Warren et al.).
- Fatal disease; however, surgery has been attempted in some cases (Haggett et al.).
References:
- Haggett, Emily, and Victoria Scott. “The foal.” Equine Clinical Medicine, Surgery and Reproduction. CRC Press, 2019. 1329-1368.
- Hepworth‐Warren, Kate L. “Congenital Disorders of the Equine Gastrointestinal Tract.” Equine Neonatal Medicine (2024): 421-435.
- Azizi, S., et al. “Atresia coli in an Arabian foal.” Trakia Journal of Sciences 15.2 (2017): 179.
- Gillen, Alexandra. “The Acute Abdomen in the Neonatal Foal.” Equine Neonatal Medicine (2024): 495-524.
