Page 1378 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

The foal 1353

VetBooks.ir evidence of localised or systemic infection should urachus failing to seal at birth (persistent ura-
chus) or due to reopening and resumed patency
have the umbilicus examined carefully, including
the internal remnants, using transabdominal ultra-
urachus).
sonography (Figs. 14.18–14.20). The internal ves- after an initial urachal closure (acquired patent
sels remain visible for about 4 weeks after birth. The
normal umbilical vein running cranially to the liver Aetiology/pathophysiology
is <10 mm in diameter and the umbilical arteries run- The urachus is present in the fetus to drain urine
ning caudally to the bladder are normally <12 mm from the bladder into the allantoic cavity during
in diameter. Infected vessels are enlarged, contain gestation. It normally closes and involutes at par-
hypoechoic, echogenic or anechoic material depend- turition; urine flow should cease within 24 hours.
ing on the nature of the purulent material within the The exact mechanism whereby closure fails or
vessels, and may have thickened walls. Blood samples the urachus reopens is not known, but possible
for haematology to assess WBC count (leucocytosis causes include: umbilical disorders such as torsion;
or leucopenia), acute phase proteins (increased serum increased length; early severance or ligation of the
amyloid A [SAA] and fibrinogen) and IgG are help- umbilical cord rather than natural rupture; exces-
ful in assessing the severity of disease and detect- sive foal straining (e.g. meconium retention or rup-
ing SIRS and sepsis, in addition to determining the tured bladder); excessive or improper lifting of the
immune status of the foal, respectively. Some cases of foal’s abdomen; localised urachal/umbilical infec-
localised external infection show minimal changes in tions; systemic infections; prolonged recumbency;
the haematological and inflammatory profiles. and reduced movement or stall confinement. Patent
urachus is one of the most common complications
Management of hospitalisation for foals requiring intensive care.
When infection is confined to the external remnants It can also occur when irritant agents are applied to
and there are no signs of systemic involvement, encour- the external umbilical remnant, which causes tissue
aging drainage of the abscess and broad-spectrum necrosis and leaves the urachus and umbilical vessels
bactericidal antibiotics, preferably based on sensitivity exposed.
testing, is often effective. The case should be carefully
monitored and reassessed using transabdominal ultra- Clinical presentation
sound and bloodwork. Up to 14–21 days of antibiotics Urine is often observed leaking from the umbili-
may be required. If there is significant involvement of cal remnants continually or when the foal urinates.
the internal umbilical vessels and/or poor response to The umbilical area is continually wet, and this may
medical therapy or overwhelming signs of systemic lead to urine scalding and dermatitis of the ventral
involvement, then surgical resection of the internal abdominal skin. In some cases, the umbilical rem-
and external umbilical remnants should be performed. nants are necrotic (Fig. 14.21). The foal may pos-
Correct care of the umbilicus at foaling is criti- ture and strain frequently to urinate due to irritation
cal, as is early ingestion of high-quality colostrum. or local infection of the urachus.
General management issues such as providing a
clean foaling environment and minimising foal con- Differential diagnosis
tact with sources of contamination (wash the teats Other umbilical disorders; ventral abdominal
and udder pre-foaling) should be addressed. oedema; localised cellulitis.

PERSISTENT OR PATENT URACHUS Diagnosis
Clinical signs are usually adequate for diagnosis.
Definition/overview Ultrasonographic examination may reveal evidence
Patent urachus is a condition whereby the urachus of an umbilical remnant infection or a dilated urachus
is open and urine leaks from the external umbili- continuous with the bladder. Urinalysis and culture
cal remnants. This may occur as a result of the will identify any infection within the urinary tract.