ABOMASAL DISPLACEMENT AND ABOMASAL VOLVULUSOverview of the Condition
Because cows live on a high fiber diet, they have a specialized
digestive system that helps them process their food. Like all
ruminants, cows have four distinct compartments to their stomachs- the
rumen, reticulum, omasum, and abomasum. Much of the fiber in their
diets is slowly broken down by bacteria in the rumen before it passes
in to the remaining compartments. The abomasum is referred to as the
“true” stomach of the cow; here, digestive juices help to extract as
many of the remaining nutrients as possible.
The abomasum moves easily within the cow because it is suspended by
loose attachments. Unfortunately, this means the abomasum can
potentially move out of its normal position, resulting in bloating
(filling up with gas) and even life threatening obstruction. Three
types of abnormal position are commonly seen, including left abomasal
displacement (LDA), right abomasal displacement (RDA), and “volvulus”
(twisting) of the abomasum on the right side (RVA). Abomasal
displacements typically occur in high production dairy cows, but also
have been recognized infrequently in calves, dairy bulls, and beef
cattle. Abomasal displacement to the left is by far the most common.
No one knows exactly what causes the abomasum to move out of its normal
position. The majority of abomasal disorders occur in dairy cows during
the first three months of lactation (milk production). It is possible
that changes in diet, exercise, or amount of space in the belly, or
problems such as inflammation in the mammary glands or uterus or fat
build-up in the liver, could slow down normal movement in the stomach
and intestines, resulting in bloating and subsequent change in the
position of the abomasum.
Signs/Clinical Presentation/DiagnosisAdult dairy cows with abomasal displacement or volvulus lose their
appetites and produce less manure. Milk production also drops.
The classic diagnosis of LDA or RDA is made by performing simultaneous
“auscultation and percussion” or “pinging” of the abdomen. This is done
by “snapping” or thumping the abdomen with the thumb and third finger
while listening with a stethoscope. A pinging noise is heard when there
is a gas filled organ up against the body wall, such as a displaced
abomasum. Other digestive organs can cause a ping in cattle, so it is
important to carefully identify the area producing the noise. The
classic left and right-sided DA ping is between the ninth and
thirteenth rib (on the left and right side respectively), on a line
angling between the tuber coxae (the pointy hip bone) and the elbow
(Figure 1). If the diagnosis of displaced abomasum is still unclear
there are other tests that can confirm, or help to confirm, the
diagnosis including passage of a nasogastric tube (a tube through the
nose into the stomach), testing the fluid from the rumen, and
evaluating blood work for abnormalities.
Figure 1: A typical area of ping outlined in a cow with an LDA
(Photo courtesy of Dr. T.J. Divers).
Differential DiagnosisOther conditions that can cause signs similar to abomasal displacement
include gas distension of the rumen, which causes air entrapment on the
left side of the belly, or in the cecum or intestines, which causes air
entrapment on the right side. These conditions are differentiated from
abomasal disorders by the location of the ping and sometimes by rectal
palpation. Animals with abomasal volvulus often have fluid collecting
in the belly that can be detected on physical examination. If fever
accompanies the signs of LDA, a perforating abomasal ulcer (Figure 2)
could be present along with abomasal displacement.
Figure 2: A perforating abomasal ulcer in a cow. A full thickness hole
in the abomasum allowed food particles to leak into the abdomen. The
hole will be sewn closed to prevent further leakage.
Treatment OptionsTreatment goals for abomasal displacement or volvulus include moving
the abomasum to a normal position, preventing it from ever displacing
again, and keeping the procedure as inexpensive as possible for the
owner. Abomasal displacements can be corrected by open (surgical) or
closed (nonsurgical) techniques. Closed techniques are less expensive
and relatively quick and simple to perform. They include rolling the
cow to flip the abomasum back in place, or securing the abomasum to the
body wall with a blind tack (a holding stitch in the abomasum that is
placed without opening the belly) or a toggle pin (a special device to
fix the abomasum in place). Rolling is not an effective long-term
treatment because most cows will have a recurrence.
With the blind tack or toggle pin technique, the cow is rolled onto her
back to help shift the abomasum back into place before it is tacked to
the body wall by suture or toggle pin. Some surgeons may use a
laparoscope during closed procedures, which helps them see into the
cow’s belly while they are tacking the abomasum. Both blind tacking and
toggle pin techniques prevent recurrence of the displacement but they
can have very high complication rates, including infection or damage to
internal organs. Closed techniques should not be used in cows that are
having difficulty breathing or that are valuable to the herd.
With open techniques, an incision is made through the side or belly of
the cow so that the surgeon can anchor the abomasum to the body wall
internally (Figure 3). Whether the surgery is performed with the cow
standing or lying down depends on the surgeon’s preference, temperament
of the cow, its physical condition, and the surgery facilities that are
available.
Before surgery can be performed, it may be necessary to stabilize the
animal with fluid therapy, calcium and/or dextrose (sugar) solutions,
and antimicrobials (i.e. antibiotics). Conditions such as mastitis
(mammary gland inflammation or infection) and metritis (uterine
inflammation or infection) must be treated as well.
Figure 3: The abomasum being examined at surgery with the cow on her back.
Abomasal VolvulusOnce the abomasum starts to twist (abomasal volvulus), the cattle get
much sicker, with rapid heart rates, greater amounts of gas and fluid
collection on the right side, loss of appetite, scant manure
production, and dehydration. These cows must undergo an open, surgical
procedure to return the abomasum to its normal position and they may
require temporary tube placement into the abomasum to empty it (Figure
4) before it can be repositioned.
Figure 4: A stomach tube placed in the distended abomasum to empty it
before returning the abomasum to the correct position. (Photo courtesy
of Dr. D.F. Smith)
Because blood vessels can be damaged when the abomasum is twisted, the
prognosis for abomasal volvulus is poorer than with a simple
displacement and the cow will require more intensive therapy. Cows that
are stressed and have increased heart rates (>100 beats/min.) may
not do as well as those that are treated early in the disease.
Potential Complications of SurgeryIn some animals, the fixation to the body wall may fail, or the cow may
develop an infection at its incision site. Animals that have other
illnesses or health problems such as respiratory (lung) disease or that
are severely dehydrated are more likely to have complications after the
surgery.
AftercareAfter surgery, cows are returned to the herd with no special
post-operative management unless drugs were used that require a
specific withdrawal time. It is necessary to monitor the surgical wound
and, in rare instances, deal with an incisional complication.
Additionally, cows may have other diseases such as mastitis that
require specific treatment.
Prognosis and PreventionGenerally the outcome following surgery for abomasal displacement is
quite favorable, regardless of the technique chosen. Short-term success
rates are reported to be as high as 85-95%; how the cows will do
long-term is not well known. The prognosis following abomasal volvulus
is more guarded.
Unfortunately no one knows how to prevent the onset of abomasal
displacements. Rapid changes in diet should be avoided. There has been
some suggestion that heredity may play a role in development of
abomasal displacement, so breeding lines should be examined closely.
موضوع: ABOMASAL DISPLACEMENT AND ABOMASAL VOLVULUS 
الثلاثاء أغسطس 26, 2008 9:20 pm
