Page 1373 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1348 CHAPTER 14

VetBooks.ir faecal retention and/or gaseous distension proximal the colon. This presentation may be seen in foals
suffering from NMS. Historically, it was reported
to the site of the intestinal occlusion. Contrast radi-
ography with a barium enema can be useful for con-
foal, but this may not be true, and many filly foals
firming the location of the atresia. Proctoscopy or that the condition was more common in the male
colonoscopy will usually confirm the lesion. In some are also affected. The exact reason why the condi-
cases, an exploratory laparotomy is required to con- tion affects some foals is not clear.
firm diagnosis of more proximal lesions and to deter-
mine what (if any) treatment options are available. Clinical presentation
Foals with meconium retention usually present
Management with mild to severe colic from 6–36 hours post
The location of the abnormality partly determines partum (Fig. 14.15). The foal may become recum-
the possibility of surgical correction. In true atresia bent, with rolling and struggling movements.
ani, surgical reconstruction of the anus may be possi- There is persistent unproductive straining to pass
ble. Colostomy and anastomosis techniques have been faeces, with tail swishing or lifting, squatting and
attempted in a few published cases, but the results have crouching (with a rounded back). Affected foals
been poor, particularly as many cases have extensive develop progressive gas abdominal distension and
intestinal motility problems. Most cases are not ame- are either intermittently, or completely, off suck.
nable to surgery because of the degree of atresia, and The passage of some meconium does not rule out
the prognosis is therefore hopeless. meconium retention because there may still be
material present more proximally in the intestinal
MECONIUM RETENTION tract.

Definition/overview Differential diagnosis
Meconium consists of the digested amniotic fluid Congenital deformities of the GI tract where there
and cell debris accumulated during fetal life and is is segmental aplasia produce similar signs. Foals with
usually passed within 12 hours of birth. It is usu- a ruptured bladder may present in a similar way, but
ally pelleted or occasionally tarry, dark brownish/ these foals are usually older and passing milk faeces.
green or black faecal material. It is followed by the An abdominal crisis caused by an obstruction usu-
yellowish material formed from milk products after ally presents with severe unrelenting pain and sud-
the first few sucks. den onset.

Aetiology/pathophysiology Diagnosis
Retention of meconium most commonly occurs in Clinical examination and history are important.
the rectum but can also occur more proximally in Careful digital rectal examination may reveal pel-
lets of meconium. The full extent of the retention
is often underestimated by this technique, how-
ever. Ultrasonographic examination of the abdo-
14.15 men is very useful to visualise the meconium (very
echogenic [almost sparkly] round balls within
the bowel) and the site of retention (Fig. 14.16).
Meconium in the rectum and small colon can be
visualised in the caudal abdomen adjacent to the
bladder, while retention more cranially can be seen
within the colon on the ventral abdomen, almost
as far as the sternum. Barium enema radiographs
Fig. 14.15 A foal showing marked signs of colic due may be useful to confirm the diagnosis in refrac-
to meconium retention. tory cases.