Page 880 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.2 The lower gastrointestinal tr act 855

VetBooks.ir or stalls. Horses that are underfed or kept in over- occurs and sand is present, then a sand impaction is
almost invariably present.
stocked, closely grazed pastures may be at greater
risk. Some horses, particularly foals, may intention-
Sand accumulation may be evident radiographi-
ally ingest sand (pica). Following ingestion, sand can cally (Fig. 4.166), particularly in the cranioventral
settle in the large colon. Over time, and with contin- abdomen. Sand may also be evident ultrasonograph-
ued ingestion, sand can accumulate to such a degree ically within the large colon in the cranioventral
than partial or complete obstruction occurs, and abdomen.
signs of colic develop. The right dorsal colon is the The sand sedimentation test is commonly recom-
most common site of sand accumulation, but impac- mended but the presence of sand in faeces correlates
tions can develop in all sections of the large colon, poorly with accumulation in the large colon. As
and multiple sites may be involved. such, use of the test is not advised.

Clinical presentation Management
Signs of mild to severe colic may be observed. This Enteral fluid therapy is useful in most of cases
can be accompanied by varying degrees of anorexia, and removal of impacted ingesta as per a typical
depression and abdominal distension. Faecal produc- large-colon impaction should be performed prior
tion may be decreased and soft faeces may be present. to attempting to remove accumulated sand. Once
Signs of pain can be intermittent or continuous. the animal is comfortable and passing normal fae-
Concurrent large-colon displacement or volvulus may ces then specific therapy targeted at removing sand
be present and affect the clinical presentation. should be commenced.
Psyllium (1.0 g/kg) combined with magnesium
Differential diagnosis sulphate (1.0 g/kg) daily via a NG tube has been
Other causes of mild to moderate colic should be con- shown to be effective in the removal of sand accu-
sidered, including large-colon impaction or displace- mulations. Treatment is continued for 3–5 days fol-
ment, intestinal tympany, EGUS and enterolithiasis. lowed by repeat radiographic or ultrasonographic
examination. Following resolution, periodic evalua-
Diagnosis tion (every 3–6 months) via abdominal radiography
A history of potential exposure to sand is usually or ultrasonography should be considered, particu-
present; however, sand impaction can be difficult larly if management changes are not feasible.
to differentiate from other causes of colic. During Intermittent administration of psyllium may
abdominal auscultation, characteristic ‘sand help reduce sand accumulation but the response
sounds’ can be heard, particularly over the ventral between individuals is highly variable. Medical
abdomen. Sand sounds are similar to friction rubs treatment is usually effective, but surgical inter-
or movement of sand in a paper bag. Identification vention may be required in horses with intractable
of these sounds is a relatively sensitive and specific pain, poor response to medical therapy or deterio-
indicator of sand accumulation. Haematological rating cardiovascular status. Feed should be gradu-
changes are uncommon, non-specific and not ally re- introduced after the impaction has resolved.
diagnostic for sand impaction. It is often difficult A discussion of management practices is important
to detect sand impactions p/r because they tend to avoid further sand impactions.
to be located cranially. Gaseous distension of the
large colon and caecum is often palpable with sand Prognosis
impactions, but this may also indicate a large-colon The prognosis is good; however, compared with
displacement or volvulus. ingesta impactions, sand impactions tend to be more
Abdominocentesis should only be performed if difficult to treat, are more likely to require surgery
it is an important part of the diagnostic plan and and have a higher mortality rate. Rupture of the
should be done with care because of concerns about large colon during attempts to exteriorise it during
lacerating the distended colon. If enterocentesis surgery is not uncommon.