Abomasal Displacement

The clinical presentation of abomasal disease seen in calves varies. The abomasum can displace without volvulus to the left or right (LDA or RDA) of its normal position by swinging, folding, or stretching the lesser omentum and attached structures. Figure 14.1-1 shows that the abomasum and its attachments can stretch to the point at which the abomasum can be exteriorized almost completely through the left paralumbar fossa. In addition, dilation without apparent displacement is also described in calves. Abomasal volvulus (RVA) is seen in calves and seems to progress quickly if untreated. Finally, abomasal perforations secondary to abomasal ulcers are prevalent in calves.

Figure 14.1-1 Standing left paralumbar fossa celiotomy in a 6 month old calf with LDA. The abomasum is exteriorized before decompression.

(Courtesy of Dr. Norm G. Ducharme; Cornell University.)

Left displacements are recognized occasionally in beef and dairy calves, most commonly between 3 weeks and 4 months of age, but the dietary predisposing factors are different; high amounts of starch in milk replacer and abomasal ulcers have been reported as factors in the pathogenesis of LDAs. The prevalence of abomasal ulcers in veal calves has been estimated at 39% of LDA cases.

DIAGNOSIS

Clinical signs of left displacement are less well-described in calves but are more variable than in adults. They include nonspecific signs such as reduced appetite, poor weight gain, recurrent tympany, and variable fecal consistency. Unlike adult cattle, the distended abomasum typically fills the left flank in affected calves and can cause distinct asymmetry when viewed from behind or above (Figure 14.1-2). The ping detectable by simultaneous auscultation and percussion may be less high-pitched than in adult cattle, thus making it easily confused with ruminal distention. This may be why the diagnosis is sometimes delayed in calves. Sometimes the area of percussion is lower than one would expect adding to the diagnostic difficulty (Figure 14.1-3). Calves may also have concurrent diseases typical of their age group including pneumonia and diarrhea. As noted above, calves do not consistently demonstrate the hypochloremic metabolic alkalosis shown by adult ruminants with LDA, and laboratory evaluation is highly recommended if possible. Ultrasound evaluation can be very useful as well.

Figure 14.1-2 3-month-old calf with large LDA viewed from above. Note the prominent left-sided abdominal distention.

(Courtesy of Dr. Thomas Divers; Cornell University.)

Figure 14.1-3 LDA in a 3-month-old calf. The “ping” is outlined with white markers.

(Courtesy of Dr. Thomas Divers; Cornell University.)

Abomasal Volvulus

Calves with either an RDA or RVA typically present to the herdsman with signs very similar to those described for LDAs (i.e., partial or complete anorexia, abdominal distension, and decreased fecal output with altered consistency [fluid or pasty]). However, in the case of an RVA, the progression of signs may be very rapid, and a subset of affected calves will first present with signs of severe depression, anorexia, and dehydration.

The presence of a tympanic area (ping) centered over the 10th to 13th ribs and on a line from elbow to tuber coxae is the primary diagnostic sign of an RDA or RVA. This ping must be differentiated from other sources of right-sided pings, which include cecal dilation/torsion, gas accumulation in the duodenum, spiral colon, ascending colon or small intestine, or right flank abscess. An abomasal ping generally can be differentiated from pings associated with other structures by combining information about ping location, size, and pitch. The cecum, colon, and small intestines are limited in their mobility by their mesenteric attachments to the dorsal body wall, whereas the abomasum and ascending duodenum are limited by more cranial attachments at the duodenal sigmoid flexure and the reticular connection to the diaphragm. Cecal, colonic, and small intestinal pings will generally be centered on a point in the paralumbar fossa, more caudal than that for the abomasum or duodenum. The cecum is the only structure that has the potential to dilate to the maximum size possible for the abomasum and is the primary differential for single-pitched pings greater than 10 cm in diameter. In addition, to differentiate the ping’s center by location, the outline of the cecum can usually be seen through a right paralumbar fossa with the calf in lateral recumbency (see Figure 14.2.3-1). Small intestinal pings are typically a collection of small diameter pings of varying pitch. Spiral colon pings also tend to involve multiple areas that vary in pitch. Ultrasound evaluation may be very useful to differentiate the right sided viscus. The presence of tachycardia (>130/min) and colic have been reported to be more consistent with RVA in calves; however, controlled studies are lacking.

Figure 14.2.3-1 Holstein-Friesian calf in left lateral recumbency. Note the distended paralumbar fossa secondary to cecal distension proximal to a spiral colon obstruction.

(Courtesy of Dr. Susan Fubini; Cornell University.)

A right paracostal approach can be used to perform an abomasopexy (preferred procedure) in calves positioned in left lateral recumbency. A rolling procedure with percutaneous decompression (as described for LDAs previously) has been reported to be effective in calves with right-sided pings; however, this is risky should the calf have an RVA or involvement of another right-sided viscus. The veterinarian should be prepared to move to an open approach within 2 to 3 hours if clinical signs do not improve. A modified right flank or right paracostal omentopexy (Figure 14.1-4) can be used to correct abomasal displacement or volvulus in calves in left lateral recumbency. However, the limited holding power of the omentum in calves makes this a less desirable approach than the right paramedian or right paracostal abomasopexy described earlier.

Figure 14.1-4 Abomasal volvulus in a calf viewed from a right paralumbar fossa. Note the distended omasum (O) and abomasum (A) with the abaxial surface covered by greater omentum which is seen only if a volvulus is present.

(Courtesy of Dr. Mary Smith; Cornell University.)

Luminal Obstruction

Intraluminal obstructions are more common in calves than in adult cattle. Grooming behavior in group-housed calves can result in multiple cases of trichobezoars (hairballs) (Figure 14.1-5). As for LDAs in calves, the specific acid-base and electrolyte changes that result from outflow obstruction are more variable.

Figure 14.1-5 Trichobezoar removed from a calf’s abomasum.

(Courtesy of Dr. Brad L Njaa; Cornell University.)

Ileus can lead to abomasal dilatation. Excessive milk consumption and changes in nutrition from milk to solid feed have also been suggested as a cause of abomasal distention without displacement in calves. Abomasitis is recognized as an inflammatory condition in young calves presumably as a result of infection with Clostridium perfringins, Sarcina sp., or Salmonella typhimurium. Affected calves present with signs of toxemia, including dehydration, abdominal distention, tachycardia, and a fluid filled abomasum in normal position on ultrasound examination (Figure 14.1-6).

Figure 14.1-6 An ultrasound image of a calf with abomasitis presumed to be caused by Clostridium perfringens. The liver is imaged (L); the abomasum (A) is distended with fluid, and the abomasal wall is thickened and edematous (arrows).

(Courtesy of Dr. Thomas Divers; Cornell University.)

Surgical access to the pyloric area in calves can be achieved from a right flank, right paracostal, or right paramedian approach with the calf positioned in left lateral recumbency (flank or paracostal) or dorsal recumbency (paracostal or paramedian). This allows an incision over or near the site of obstruction and extraction of the obstructing material with minimal contamination.

Abomasal Ulceration

In one study of calves with clinically apparent abomasal ulceration, 17 of 118 animals had bleeding ulcers. Perforating ulcers (Types 3 and 4) appeared to be most common in veal calves, beef calves, and yearling feedlot cattle (Figure 14.1-7). The incidence in beef and veal calves was highest at 4 to 8 weeks of age, with most cases occurring by 12 weeks of age. Of clinically apparent ulcers in a 3-year study of calves, 81 of 118 were perforating. The occurrence of perforating ulcers in beef calves is highest in the spring, reflecting the age of greatest risk. The incidence of fatal ulcers (Types 2, 3, and 4 combined) was highest in the winter in yearling feedlot cattle but occurred throughout the year. Ninety-three percent of 209 fatal ulcers in beef calves were perforating.

Figure 14.1-7 Type III abomasal ulceration in a calf. Note distended rumen covered by greater omentum (R). Note fibrin surrounding abomasum (A).

(Courtesy of Dr. Susan Fubini; Cornell University.)

A variety of factors have been proposed as causative, including nutritional deficiencies, bacterial and fungal agents, abrasive agents, and stress. Copper deficiency has been the primary mineral incriminated, although a large study of western Canadian beef herds found a higher fatal ulcer incidence in calves in herds with adequate mineral supplementation. The incidence of ulcers in general increases 20% to 30% when calves are allowed access to roughage. Transition to solid feed and/or transition in abomasal function have been attributed with predisposing and protective effects in beef calves. Clostridium perfringens type A has been the pathogen most commonly incriminated in calves, although fatal ulceration may remain as a problem in herds that use consistent vaccination programs. Hairballs in extremely cold weather conditions and poor-quality roughage are the most commonly suggested abrasive agents. However, hairballs were as common in calves of the same age dying of other causes as they were in calves dying of perforating ulcers. Although nonspecific stress is commonly associated with development of diffuse nonpenetrating ulcers (Type 1), the association with focal perforating ulcers is less clear.

Prognosis

Information on the prognosis for surgical management of calves with perforating ulcers is limited. In one study of ten 4- to 6-week-old calves with perforating fundic and greater curvature ulcers, four were successfully treated with surgical intervention and aggressive supportive care.

Clinical Findings

Pharyngeal trauma can be diagnosed by physical examination findings that include swelling, dysphagia, and excessive salivation (see Section 10.1). Thoracic lesions can be identified based on physical examination and imaging studies. For example, signs of bronchopneumonia, such as coughing, tachypnea, abnormal auscultation (wheezes, squeaks, crackles or decreased lung sounds), and dullness on thoracic percussion, help identify a primary respiratory problem requiring treatment. Imaging of the head or thoracic cavity by ultrasonography or radiography could confirm a diagnosis of trauma or bronchopneumonia.

Rumen Fistula

Rumen fistulas are indicated to relieve free-gas bloat in calves. The procedure is most effective in calves free from other disease that respond to a stomach tube passed to relieve gaseous accumulation. Fistulas are also placed to allow alimentation for calves unable to eat because of another disease process (i.e., tetanus, pharyngeal trauma).

Calves that have had severe bronchopneumonia and subsequently develop free-gas bloat, presumably from vagal nerve damage, may benefit from a rumen fistula that gives gas an escape route until the thoracic inflammation subsides.

Commercial trocars can be used in free-gas bloat or in an emergency situation. For longer-term use, surgically placing a fistula is recommended.

Surgical Technique

The purpose of surgery is to allow decompression of the rumen, thus giving the primary condition an opportunity to resolve. The fistula should not be too ventral, or ingesta will tend to occlude the fistula, thus allowing ruminal distension to recur. The fistula is placed in the dorsal aspect of the left paralumbar fossa. However, the fistula should not be too dorsal if the rumen is empty (i.e., an animal with tetanus), or it will cause excessive tension on the suture line. The appropriate area on the left flank is identified, desensitized with a local block, and prepared for surgery. A 6-cm vertical skin incision is made. The external abdominal oblique and transversus muscles are incised sharply. The peritoneum is tented and incised.

Several surgical options are available, including the three-layer technique the authors use. We recommend the transversus abdominis (which is mostly fascia) and peritoneum be sutured to the dermis on each side of the incision for the first layer. This protects the muscle layers and is usually done with a size 0 absorbable suture on a cutting needle. For the second layer, the rumen wall is sutured circumferentially to the dermis to provide a “seal” between the rumen and the skin. For this layer, a cutting needle is required; and the suture line is “broken” several times to avoid a pursestring effect. For the third layer, the rumen is incised, and the wall is sutured to the skin in a simple interrupted pattern with size 0 nonabsorbable sutures. The ends are left long to facilitate removal. To keep the fistula patent, an appropriate-sized syringe case (with four holes in its collar) is fitted into the incision site. The syringe case is secured to the skin with umbilical tape placed through the preplaced holes in the collar to four separate “loops of sutures,” placed in the skin at four corners approximately 5 cm from the fistula (Figure 14.2-3).

Figure 14.2-3 Completed rumen fistula in a calf.

(Courtesy of Dr. Brett Woodie; Cornell University.)

The syringe case is capped when the primary cause of the ruminal distension appears to have resolved. If the ruminal distension does not recur after a few weeks, the syringe case is removed. In some calves, the fistula will close over the ensuing weeks. In other calves, the fistula will need to be resected en bloc and the rumen and body wall closed separately as described in Section 10.3 for a rumenotomy closure.