Decision Making in Bovine Abdominal Surgery

Surgery of the Bovine Digestive Tract

0749 -0720/90 $0.00

+ .20

Decision Making in Bovine Abdominal Surgery

Guy St. Jean, DMV, MS·

Abdominal surgery in cattle has been performed by large animal practitioners for many years. Accordingly, the differential diagnoses are of great importance to the bovine surgeon. When evaluating a cow with an abdominal disorder, the veterinarian should determine: 1. 2. 3. 4. 5.

The etiology of the disorder An appropriate treatment The necessity for surgical intervention The probability for survival and return to function Economic options

SIGNS OF DIGESTIVE DISTURBANCE Signs of digestive disease include abnormalities of prehenSion, mastication or swallowing, fever, abdominal discomfort, change in fecal consistency and volume, abdominal distention, tenesmus, and abnormalities of hunger and thirst. 15.32 Inappetence is among the earliest signs seen. Appetite decreases with infection, pain, or obstruction of the digestive tract. Cows with left displaced abomasum (LDA) usually prefer forage rather than concentrate. In milking cows, a drop in milk production and acetonemia may be noted with digestive disorders. 29•32 Vomiting is rarely observed in cattle. If observed, it is usually associated with a disturbance of the forestomach. Salivation can be associated with stomatitis, foreign bodies lodged in the mouth, pharynx, or esophagus, and neurological diseases such as listeriosis and rabies. 32 Changes in fecal consistency and elimination are frequently asso*Assistant Professor, Department of Surgery and Medicine, Kansas State University College of Veterinary Medicine, Manhattan, Kansas Veterinary Clinics o/North America: Food Animal Practice-Vol. 6, No.2, July 1990

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ciated with digestive disorders. In one report, 23.5 per cent of cows with LDA had diarrhea. 64 Diminished or scant feces may suggest the presence of a functional obstruction such as abomasal volvulus, abomasal displacement, or intussusception. With an intussusception, fecal elimination will cease after about 12 hours, and clotted blood and thickened mucus may be expelled. 51 Signs of gradual obstruction (days to weeks) are observed with extraluminal constriction of the spiral colon. 45 Tenesmus may accompany rectal irritation from excessive trauma during rectal examination, intestinal obstruction, and acute enteritis and colitis from causes such as salmonellosis and coccidiosis. Abdominal distention is often noted with digestive disturbances. Distention of the left paralumbar fossa will be associated with ruminal tympany or high left displacement of the abomasum (Fig. 1). Distention of the right ventral aspect of the abdomen may be due to abomasal atony or impaction. 32 "Papple" appearance of the abdomen is associated with true vagal indigestion. The right paralumbar fossa may become distended if cecal dilatation, cecal volvulus, abomasal volvulus, or torsion of the root of the mesentery are present. 45 Pain is sometimes shown by cattle with digestive disturbances. It may be seen by expiratory grunt, arching of the cow's back, contraction of the neck, an anxious expression, elbow abduction, reluctance to

Figure 1. Arrow indicates distention of the left paralumbar fossa with a left displaced abomasum.

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move, alternate standing and lying down, and kicking at the abdomen with a rear leg. 28 Cows with LDA often have concurrent disease such as ketosis, hypocalcemia, retained fetal membranes, mastitis, and metritis. 24 Fever may be a sign of a digestive disturbance (reticuloperitonitis or liver abscess) or may be associated with a concurrent disease. Calves with abomasal disorders will often show reduced appetites, diarrhea, abdominal distension, and poor weight gain. 9

METHODS OF DIAGNOSIS The diagnosis of a surgical lesion of the digestive system is based on an accurate history, physical examination findings, and pertinent laboratory data. A presurgical definitive diagnosis may not be obtained in every case because of the similarity of several abdominal diseases. For the large animal practitioner, it is extremely important to determine the surgical nature of a lesion so it can be differentiated from a nonsurgical lesion such as ileus, indigestion, or enteritis. To accomplish this goal and establish a diagnosis, many physical and laboratory parameters may be evaluated: History. One or more signs of digestive disturbance may be noted initially. Depression, separation from the herd, anorexia, or decrease in appetite are signs often noted. 32 With dairy cows, a decrease in milk production will often stimulate the owner to watch more closely. With torsion of the root of the mesentery, the diagnosis is sometimes based on a history of casting and rolling followed by the acute onset of clinical signs. 45 Feeding history and knowledge of previously administered medication by the owner will be important information. Sometimes the history can be confounding; a cow with an LDA was found to be clinically normal for half a year .1,34 Signalment will aid in identification of animals at high risk for certain diseases. 13 Although LDA can be seen in all age groups and breeds of cattle, the mature dairy cow within the first 6 weeks post partum is most likely to develop a displacement. 29,41 The age of the animal can also be important; lymphosarcoma of the abomasum and pathologic fat necrosis most commonly affect mature cattle. Sex predisposition is observed in diseases such as LDA, which is more common in females while inguinal hernias are more common in males. 29,39 Observation of the animal often provides the first clue as to the nature of the disease. 21 Visual inspection from behind the animal is important for observing abdominal contours. A sudden increase in abdominal size is usually evidence of a serious condition. If the abdomen is full and distended despite the animal being anorectic for more than 2 days, an obstructive disease must be considered. Cecal dilatation, cecal volvulus, and abomasal volvulus of long duration will give distention of the right paralumbar fossa. Intussusception, duodenal obstruction, and atresia coli cause progressive bilateral distention of

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the abdomen. 6 ,12,31 Enlargement of the neck of the scrotum may be observed with inguinal hernia. 39,45 Auscultation of the gastrointestinal tract is important to obtain an accurate diagnosis. In many digestive problems rumen motility will be decreased (less than three contractions every 2 minutes) or absent. Reticuloperitonitis, abomasal volvulus, cecal volvulus, and intussusception, to name a few, will decrease rumen motility. In external hernias, the hernia sac can be auscultated for the presence of gut sounds. 45 Auscultatory percussion is the process of simultaneously auscultating and percussing the abdomen. The presence of a tympanic resonance, or "ping," denotes three basic characteristics about the structure from which the sound originates. 50,56 First, the structure must be a hollow viscus or cavity with a significant free gas component under pressure. 56 Second, the viscus must lie next to the parietal peritoneal surface. 56 Last, the body wall being percussed must be sufficiently thin to allow the energy from the fingertip to reach the gas-filled viscus and return a resonant sound. 56 Differential diagnosis of a left-side "ping" includes an LOA, rumen or uterine gas, or pneumoperitoneum. 21 ,49 A right-side tympanic resonance may be caused by abomasal dilatation or volvulus, cecal dilatation or volvulus, atony or obstruction of spiral colon, small intestinal intussusception, distention of cranial duodenum, gas in the rectum or uterus, and pneumoperitoneum. 21 ,56 A right-side "ping" is often elicited in addition to a left-side "ping" in cattle with LOA. The right-side "ping" is probably secondary to gas accumulation in the intestine resulting from ileus secondary to the LOA. A number of articles have been published describing the identification of structure and conditions responsible for tympanic resonance in cattle. 21 ,32,56 Ballottement consists of rapidly pushing in on the flank with the clenched fist such that a hard structure such as an impacted organ may be felt either during the pushing motion or as the organ rebounds. With abomasal impaction the increase in size, weight, and firmness of the abomasum can be felt in the lower cranial right portion of the abdomen. 32 Succussion consists of shaking the body in order to elicit a splashing sound in a cavity containing both gas and fluid. Superficial splashing sounds are heard with right dilatation of the abomasum, abomasal volvulus, and cecal volvulus. Deeper splashing sounds are heard with enteritis, rumen atony, and distention of the ventral sac of the rumen. Rectal examination. Detectable abnormalities in a rectal examination include alterations in the nature or quantity of feces, a displaced or distended viscus, and altered tension on mesenteric bands. With intestinal intussusception, a sausage-shaped mass can often be palpated in the right abdominal cavity and multiple loops of gas-distended small intestine are also present. 51 With cecal dilatation and volvulus, the rectal findings of the distended cecum in the posterior quadrant of the right abdominal cavity are characteristic and diagnostic. 16 With vagal indigestion, the posterior ventral blind sac of the rumen often extends

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to the right of the abdomen. 42 Abomasal volvulus can be detected in the right dorsal abdomen. , Feces. The quantity, consistency, color, and odor of feces are important. Diarrhea with a normal odor may indicate simple indigestion or parasitism. 29 Diarrhea with an abnormal odor may indicate salmonellosis. A decreased amount of dry feces is often noted with abomasal impaction. Melena is often noted with abomasal ulcers.29 Small amounts of feces covered by mucus may indicate an obstruction or paralytic ileus. Colic pain. Continuous, unrelenting signs of pain are usually associated with serious conditions. Visceral pain is mediated by the sympathetic nervous system. 57 Parietal pain is mediated by the somatic nervous system. 57 Parietal pain tends to render the abdomen "splinted," and external pressure will cause discomfort. The severity of signs of pain depend on the temperament of the animal. With intussusception the pain is due to stretching and tension of the muscular wall of the bowel and also to traction on the mesentery. As congestion and necrosis increase, signs of colic disappear and give way to depression. 49,51 With reticuloperitonitis, pain is usually manifested when the area over the reticulum, that is, the xyphoid region, is palpated and pressure is applied. Abdominal pain can also be seen in cattle with strangulated hernia, cecal torsion, torsion of the root of the mesentery, abomasal ulcers, atresia coli, urolithiasis with urethral or bladder distention, pyelonephritis, and uterine torsion. 28 Heart rate. In cases of severe abdominal pain and septic or hypovolemic shock, the heart rate tends to become elevated. Torsion of the root of the mesentery, abomasal volvulus, abomasal ulcer, intussusception, proximal duodenal obstruction, reticuloperitonitis, and lactic acidosis will cause tachycardia. 20,29 Vagal indigestion is usually associated with bradycardia. 42 Abdominocentesis. Turbid peritoneal fluid containing at least 90 per cent mature neutrophils has been frequently associated with a diagnosis of peritonitis. 68 Only in extreme cases is the white blood cell count of the peritoneal fluid and total protein a useful indication of peritonitis in the cow. Fluid that clots readily following collection can generally be assumed to be an indication of elevated fibrinogen. It has been reported that peritoneal fluid analysis is better than measurement of plasma fibrinogen as a diagnostic test for peritonitis. 68 Hydration. The skin resiliency test and position of the eye in the orbit are quick ways to estimate the status of total body hydration. Dehydration is associated with decreased resiliency of the skin and a sunken eye in the orbit. Dehydration may be observed with many digestive disorders. Body temperature. Hyperthermia may be observed with reticuloperitonitis, liver abscess, and peritonitis. Hypothermia is commonly noted in animals with shock, as in severe abomasal volvulus and perforated abomasal ulcers. Rumen contents. Sampling and analysis of rumen content via oral

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tube or percutaneous puncture can supply considerable diagnostic information. 7,8 Ruminal content is examined for color, odor, and viscosity. A methylene blue reduction test can be done to provide a crude measurement of the redox potential of the ruminal fluid. 7 The redox potential reflects the level of activity of anaerobic bacterial flora. The diet influences the test time; the established value for a high-concentrate ration is 1 to 3 minutes, and for an all-hay diet, 3 to 6 minutes. Digestive disturbances prolong the test reaction up to 15 minutes or longer. 7,8 Increases in rumen chloride indicate abnormal transit of chloride content in abomasal fluid, as in abomasal volvulus, some cases of LDA, and proximal duodenal obstruction. Chloride concentration in ruminal fluid is normally less than 25 mEq per liter. 7 The pH of rumen content usually ranges from 6 to 7, although feedlot animals on a high concentrate diet can have a rumen pH of 5.5. If rumen pH is less than 6, lactic acidosis or accumulation of hydrochloride from abnormal abomasal transit should be suspected. 7 ,32 Paracentesis (liptak test). This test can be performed to distinguish between a ruminal "ping" and an abomasal "ping." A few drops of liquid is aspirated percutaneously from the ventral margin of the "pinging" area and tested with a pH paper. A pH less than 5 would indicate the abomasum was aspirated. 30 Radiography. Abdominal radiography can be used as a diagnostic aid in the young calf because of the inability to perform a rectal examination. In adults, radiography is often helpful in identifying metallic foreign bodies in the reticulum and for determining whether reticular penetration has occurred.10,1l Unfortunately, radiography is impractical to use in the field because of low voltage of portable equipment. l l ,28 Metal detector. Metal detectors help demonstrate the presence of a metallic foreign object in the reticulum. Failure to demonstrate a metallic object can help to avoid a celiotomy and rumenotomy. One should remember that many cows have metallic foreign bodies unassociated to clinical disease. 28 A compass also can be used to examine for presence of a magnet in the reticulorumen. Capillary refill time. Capillary refill time, in conjunction with palpation of the extremities, can be used to assess the status of peripheral tissue perfusion. An abnormal capillary refill time is that greater than 3 seconds. Laparotomy. Laparotomy can be used as a diagnostic aid. Enterolith of the spiral colon is suspected during rectal examination with distended spiral colon, but the final diagnosis is obtained during the laparotomy, as in the case of lymphosarcoma with involvement of the abomasum. Endoscopy. An endoscope inserted into the paralumbar fossa after production of a moderate pneumoperitoneum has been used for diagnosis of abomasal disorders. This method requires the abomasum to be displaced high enough so it can be seen. 65 In the author's opinion, this technique has very limited applications and he prefers to perform a laparotomy instead. Ultrasonography. The use of ultrasonography to examine the spa-

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tial relationships of organs might also be helpful as a diagnostic aid. 7 Abnormalities need to be located near or adjacent to the peritoneal surface or rectum.

HEMATOLOGIC ALTERATIONS IN DIGESTIVE DISEASES The determination of hematologic alterations will often give valuable information about the nature of an abdominal disorder. An elevated packed cell volume (PCV) and total protein suggest acute dehydration (hemoconcentration) as in acute grain overload, severe profuse diarrhea, intussusception, or abomasal volvulus of long duration. Serial estimation of PCV and plasma protein will be useful to assess hydration and monitor fluid therapy. Most subacute inflammatory disorders are characterized by a low normal PCV and mild hyperproteinemia. Cases of chronic infection may have a moderate anemia and high total protein. Severe anemia is often found in cows with abomasal ulcers. A normal PCV with a low total protein suggests a protein-losing enteropathy (paratuberculosis), body cavity sequestration of protein (diffuse peritonitis), or renal protein loss (amyloidosis). Most cows with LDA will show a normal hemogram. However, leukopenia or leukocytosis can be observed in cows with LDA and severe concurrent diseases. Cows with LDA and leukopenia often have a severe inflammatory reaction somewhere in the body (often uterus or udder) and have decreased ability to cope with the stress of surgery.63.64 Polymorphonuclear leukocytes from cattle with LDA with or without concurrent infection have depressed phagocytic function when compared with polymorphonuclear cells from healthy cattle. 25 A leukogram should be taken in cattle with LDA and severe concurrent disease to evaluate whether the animal is a good surgical risk. Surgical correction of an LDA should be delayed in cattle with concurrent infectious disease until the leukogram is normal (greater than 4000 cells/mm3) and the clinical status of the animal appears acceptable. 63.64 In the acute phase of traumatic reticuloperitonitis, a moderate leukocytosis (12,000 to 16,000 cells/mm3) with neutrophilia and a left shift is often observed. The number of white cells rapidly returns to within normal range if the process becomes localized. Elevation of plasma fibrinogen can also help to differentiate traumatic reticulitis from other noninflammatory digestive disorders. In acute diffuse peritonitis, the total circulating white blood cell count may be very low. A complete blood count might indicate lymphosarcoma if lymphocytosis is present. 42 The total white blood cell count and differential varies with intussusception depending on the degree of intestinal necrosis and peritonitis present. Usually cows with intussusception will show leukocytosis, which is sometimes accompanied by a left shift in response to the intestinal devitalization. 51

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DECISION FOR SURGERY Necessity for Surgical Intervention The basic criteria used for decision making in celiotomy include assessment of the history, clinical signs, physical finding, and confirmation of suspicions using laboratory tests. 13,32 Gradually progressive abdominal distention, especially if the abomasum, cecum, or intestines seem involved and presence of a high heart rate, abdominal pain, scant or absent feces, and abnormal finding on rectal examination are suggestive of the necessity for surgical intervention. The sensitivity and positive predictive value of the abomasum (volvulus, dilatation) as the source of the tympanic resonance "pingH were 98 per cent and 96 per cent, respectively. 56 For the cecum and ascending colon, the sensitivity and predictive value were both 87 per cent. 56 Failure to recognize the nature of right-side "pingH can result in improper medical treatment or unnecessary surgery. Prognosis and Prognostic Indicators Accurate prognosis is important in deciding whether surgery should be attempted. Unfortunately, few studies have been completed examining prognosis and prognostic indicators in bovine abdominal surgery. The most complete studies have involved cattle with LDA or abomasal volvulus. There is currently a need for more studies examining prognosis and prognostic indicators in conditions such as cecal torsion, intussusception, or abomasal impaction. Left Displaced Abomasum Many cows with LDA have concurrent diseases. This often results in a less favorable prognosis and lengthens the time required for return to a maximal production. 24,64 In a study by Wallace, the death rate was two times greater in 74 cows with LDA, concurrent disease, and diarrhea than in cows only affected with LDA.63,64 Many of the cows that died had leukopenia. The recurrence rate for LDA was not different in cows that initially presented with diarrhea than in the group as a whole or for cows not showing diarrhea. 64 Several methods are available for the surgical treatment of LDA. All of them are highly successful in terms of recovery and nonrecurrence. Gabel reported an 85 per cent success rate for correction of LDA by right-sided omentopexy in 147 cows. IS Dirksen reported a 90 per cent success rate in 50 cattle with LDA using a right-sided omentopexy. 46 Using a left flank approach for an abomasopexy, Ames reported 100 per cent success in 14 cows, whereas Gertsen reported that 80 per cent of 45 cows returned to satisfactory production. 46 Right paramedian abomasopexy success rates of 83.5 per cent, 92 per cent, and 94 per cent have been reported. 46 Hull reported a 93 per cent success rate in 44 cases, whereas Grymer reported an 8l.5 per cent success rate in 27 cows with LDA using the closed suture technique or bar suture technique. 22,33

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Abomasal Volvulus The prognosis for abomasal volvulus is based on the preoperative condition of the animal, the degree of distention of the abomasum, the severity of the twist, and the time lag between the volvulus and the correction. Published recovery rates following surgical correction of abomasal volvulus vary from 30 to 80 per cent, with an overall mean of 61 per cent.4.17.19.38.40.44.47.55 A more accurate prognosis for recovery and productivity can be based on the preoperative condition of the cow and observation at the time of surgery. Cows treated early and without an abomasotomy and drainage of the abomasum have better prognoses. Because of the deSirability of a presurgical assessment that would help determine whether surgery is justified, several variables have been tested for their merit in developing an accurate prognosis for abomasal volvulus. Serum chloride concentration, base excess, anion gap, heart rate, and abomasal fluid content have proved of value in assessing prognosis (Table 1). In a review of 212 cattle with abomasal Table 1. Prognostic Indicators with Abomasal Volvulus PROGNOSTIC

NUMBER OF

INDICATORS

CATTLE

HR> 100 beats/min

86

HR < 96 beats/min Serum CI < 84 mEqfL

86 58

Serum CI <79 mEqfL

65

Serum CI <75 mEqfL

58

Serum CI > 80 mEqfL

65

Serum CI > 75 mEqfL

58

Base excess <-0.1 mEqfL Base excess < 0 mEqfL

102 58

Base excess < -25 mEqfL Base excess >-2.5 mEqfL

58 58

Anion gap >32.5 mEqfL

58

Anion gap> 30 mEqfL

58

Abomasum distended principally with gas Abomasum distended with gas and fluid> 30 L

100 100

OUTCOME

44 % productive 72% survivor 75% productive 38% survivor Sensitivity 0.56 Specificity 0.85 18% productive 45% survivor 38 % survivor Sensitivity 0.28 Specificity 0.93 74% productive 83% survivor 74% survivor 89% survivor 50% survivor 57% survivor Sensitivity 0.667 Specificity 0.6 < 11 % survivor 80% survivor Sensitivity 0.56 Specificity 0.83 0% survivor Sensitivity 0.83 Specificity 1. 00 16% survivor Sensitivity 0.89 Specificity 0.93 97% productive 100% survivor 12% productive 35% survivor

REFERENCES

55 55 19 55 19 55 19 47 19 19 19 19 19 55 55

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Table 2. Heart Rate as a Prognostic Indicator for Abomasal Volvulus HEART RATE

CATTI..E

(BEATS/ MIN)

SURVIVORS

35 69 30 41 37

<60 61-80 81-100 101-120 >120

100.0% 89.9% 80.0% 78.0% 56.8%

NUMBER OF

volvulus examined at the Ohio State University Veterinary Teaching Hospital (P. Constable, personal data), preoperative heart rate appeared to be an accurate predictor of postoperative outcome (Table 2). A prospective study examining a number of preoperative prognostic indicators in cattle with abomasal volvulus has also found heart rate to be a very good predictor of surgical outcome. 5 Abomasal intraluminal pressure determined percutaneously or at surgery is currently being investigated by the author as a prognostic indicator in LDA and abomasal volvulus. After correction of the volvulus, an edematous, discolored and atonic abomasum often indicates irreparable loss of function, the result of damage to the vasculature, musculature, and nerve supply.19,26 Such changes result in postoperative abomasal motility impairment and appear more related to the degree of twisting and stretching of the abomasum and vagal nerve than to the degree of metabolic derangement. 19,44 This suggests that the prognosis for obtaining a productive animal is more accurately determined by intraoperative findings than by indicators relying on alteration of serum electrolytes. Abomasal Impaction Abomasal impaction frequently goes unnoticed until terminal stages because the onset is so gradual. Treatment is often effective only in the early stages. The prognosis is guarded to poor even after successful surgery because of the possibility of vagal nerve damage. Abomasal Ulcers The mortality rate with perforating abomasal ulcers can be expected to exceed 50 per cent, and death is usually due to diffuse peritonitis and endotoxic shock. 62 The successful surgical resection of a nonperforating abomasal ulcer has been described in an adult cow. 58 Cecal Dilatation and Volvulus The prognosis for cattle with cecal dilatation and volvulus is good (dilatation 80 per cent, volvulus 75 per cent) following surgery unless there is vascular compromise of the cecum and resection is required. 16,45 In one study there was a recurrence rate of 10 per cent. 16

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Intussusception Intussusception carries a good prognosis, provided the patient is not severely dehydrated or hypochloremic, the cow has no evidence of severe peritonitis at surgery, and if good surgical technique and appropriate postoperative medical care are employed. The animal should pass feces within 24 hours following surgical anastomosis. 45.51 Volvulus of the Root of the Mesentery In the case of volvulus of the root of the mesentery, the prognosis is fair when early diagnosis and surgery can be accomplished. 45 A 60 per cent survival rate was obtained in five calves (age: 12 hours to 9 weeks) following surgical correction of volvulus of the root of the mesentery.61 Immediate death of the animal following surgical correction of mesenteric root volvulus is probably due to rapid release of tissue metabolites and toxins into the blood stream. 45 Intestinal Adhesions The prognosis of adhesions of the small intestine will vary, depending upon the location and extent of these adhesions. A cow with a localized lesion that can be resected has a good prognosis. Cattle with extensive peritonitis and adhesion formation with inaccessible lesion have a very poor prognosis. 45 Fat Necrosis The prognosis in cows with obstruction of the digestive tract resulting from fat necrosis with extensive involvement is very poor. Spiral Colon Obstruction of the spiral colon by extraluminal constriction carries a fair prognosis if the obstruction is bypassed by side-to-side anastomosis.43.45.52 Successful correction of an intussusception of the spiral colon in a calf has been described. 27 Hernia The prognosis for the repair of external and internal hernias varies from good to poor depending on location and size, the amount of intestine involved, and whether the bowel is incarcerated or devitalized. 45 The prognosis for inguinal herniorrhaphy in the bovine male is reported as being excellent. 39 Fourteen beef bulls operated for inguinal hernias had excellent general recovery, and 12 of 14 settled cows had satisfactory results. 39 Vagal Indigestion Although vagal indigestion implies a generally poor prognosis, the cause is important. 42 In valuable animals, surgical therapy and adequate surgical aftercare give the best chance for recovery. In one report of 112 cows affected with vagal indigestion, 29.5 per cent of the animals made a complete recovery after treatment. 42 Vagal indigestion second-

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ary to abomasal volvulus carries an extremely poor prognosis. In a retrospective study only 3 of 23 patients had a good outcome. 42 Atresia Coli The prognosis in most cases of atresia coli is fair (40 per cent) if the condition is recognized and treated early. As the course of the disease progresses, peritonitis and toxemia may develop, resulting in a poor prognosis. 6,12,31 With atresia coli, failure of passive transfer of immunity is often observed. An atretic colon could interfere with absorption of immunoglobulin by leading to intestinal stasis. Atresia Ani Atresia ani is suspected to be hereditary in cattle and is often associated with other abnormalities. The surgery should be performed on nonbreeding animals only, and the prognosis is good. The owner should be warned about the possibility of stricture formation. General Conclusions It is the author's opinion that if surgery is required for a lesion, the earlier the surgery is performed after stabilization of the animal, if necessary, the greater the likelihood of a successful outcome. In general, a heart rate near 100 beats per minute, progressive dehydration, and recumbency carry a poor prognosis. The growth of gram-negative or anaerobic bacteria from an abdominocentesis in cattle has been associated with mortality. 61

ECONOMICS Because surgery is relatively expensive and occasionally is accompanied by a poor outcome, the animal's value should warrant surgical intervention before surgery is undertaken. 13 The practitioner should identify the economic feasibility of surgery as early as possible to increase the chance of a successful outcome. Financial consideration should include the animal's value, transportation cost if referred, medical and surgical expenses, and loss of use. 13 For a cow of marginal value, it may be more economically sound for the owner to market such a cow when the chance of a successful surgical correction is small. Left Displaced Abomasum: Probability for Return to Function In a cow with LDA in which surgical correction is performed, an overall decrease in milk production (250 to 500 kg) during that lactation is often observed. Most cows, following corrective surgery for LDA, complete the lactation. However, 9 to 1 7 per cent of affected cows following surgery for LDA do not complete a 240-day lactation and produce at least 2000 kg less milk than expected. 36,37 In the lactation subsequent to LDA, cows tended to increase their production, both in actual amounts and relative to their production in the lactation prior to the occurrence of LDA.36,37 Subsequent to LDA surgery, cull time relative to controls was not altered. 36,37 In one report it was

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estimated that, considering the cost of surgical correction and estimated drop in milk production, the monetary loss resulting from LDA is approximately $350 per COW. 23 Decision Analysis Large animal practitioners often face the decision to attempt to save a seriously ill animal, to advise sending the animal to an abattoir, or to perform euthanasia on the farm. 14,36,67 The question is more relevant with animals of minimal economic value. 14,35 Decision analysis is a technique for formally structuring and solving problems. 3 ,66,67 The de-

Chance node

Survive (FAVORABLE) - - - - - . . . . . ; . - - - - - - - VF-C,

P,

SURGERY

. Die (UNFAVORABLE) '---------------------Vu-C, (1-P,)

decision node Survive (FAVORABLE) - - - - - - - - - - - - - - - - - - V F -C 2 P2 MEDICAL TREATMENT

Die (UNFAVORABLE)

-----------------------VU-C (1-P 2)

P,

= Prognosis for a favorable outcome following

2

surgery

P2 = Prognosis for a favorable outcome following medical treatment VF

Vu

C,

= Revenue obtained = Revenue obtained = Cost of surgery

from a favorable outcome from an unfavorable outcome

C2 = Cost of medical treatment

o

o

= Choices; decision maker may elect one of several alternative courses of action = Event not under the control of the decision maker, probability

Figure 2. Decision tree for surgery versus medical management. (Adapted from Weinstein MC, Fineberg HV: Clinical Decision Analysis. Philadelphia, WB Saunders, 1980, p 15, Fig. 2-4; P 188, Fig. 7 -2.)

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cision is represented using a decision tree (Fig. 2). The expected values can be expressed algebraically as follows: for surgery, PI (VF-C I) + (I-PI) (VU-C I); for medical treatment, P 2 (VF -C 2 ) + (I-P 2 ) (VU-C 2 ). The information needed to construct a decision tree is the value of each outcome, the cost to reach each outcome, and the probability of reaching that outcome. 14,35,66,67 The probabilities are derived from the literature or from expert opinion. 66,67 The decision maker should take the intervention with the path with the highest expected value. By doing so, one should maximize profit over a series of such choices. 14,35,66,67 The accuracy of the results depends on the data and assumptions used to create the analysis. The weakness of applying decision analysis is the reliance on assumptions based on limited data. As an example of decision analysis, let us assume a mature Holstein cow 3 weeks after calving has an LDA. Should one do an abomasopexy to correct and stabilize the displacement, or should one attempt to replace the abomasum by the rolling technique? Whatever the treatment' presume that the cow will either recover fully or be sold for salvage. Menard reported a success rate of 92 per cent following abomasopexy in a large series of cases. 38 The charge for the surgery would be $120. Hoffsis and Ames reported a probability of favorable outcome with rolling of 25 per cent and the cost is arbitrarily fixed at $20. The cow's replacement value would be $1300 and her salvage value $500 (Ohio, March 1989) (Fig. 3). After calculation, the expected value for an abomasopexy is $1116 and for rolling is $675. The surgery would be the better economic option. If the cow's replacement value was less, the analysis needs to be redone to determine the expected value of each intervention. If economics dictate that a cow of marginal value with LDA does not justify an expensive surgical procedure, the blind-suture procedure or the bar suture technique may be used as an inexpensive alternative. 2,59 The question is often whether to treat an animal with a poor prognosis or to send the animal for salvage. Let us suppose a mature Holstein cow early in lactation has an abomasal volvulus. Should a veterinarian do a surgical correction and an omentopexy or suggest selling the animal to an abattoir? Whatever the treatment, presume that the cow will either recover fully, die, or be sold for salvage. In a series of 272 cows with abomasal volvulus, Garry reported a probability of 75 per cent for recovery.19 The charge for surgery and postoperative care would be approximately $200. An assumption is made that the cow's replacement value would be $1300 and her salvage value $500 (Fig. 4).

The expected value for surgical correction and omentopexy is $775 and for immediate salvage is $500. The surgery would be the better economic choice. Some cows with abomasal volvulus have abnormal abomasal motility following surgical correction and are sold for salvage value. In a series of 100 cases, Smith reported a probability of 68 per cent for the animal being productive, 14 per cent to be salvaged, and a probability

DECISION MAKING IN BOVINE ABDOMINAL SURGERY

349 Net value of outcome

Recover

,------------$1,300-$120 0.92 $1,116

Salvage

------------$500-$120 0.08 Abomasopexy

Rolling Recover

,------------$1,300-$25 0.25 $675

Salvage

~----------$500-$25

0.75 Figure 3. Decision tree for abomasopexy versus rolling for left displaced abomasum.

of 18 per cent for dying after surgery. 55 If all the other parameters are kept equal, the decision tree will now be that shown in Figure 5. The surgery would be the better economic choice. Although decision analysis is a major simplification of the decision process in veterinary practice, it portrays the choices made daily by the practitioner. 14,35,67 For more information on clinical decision analysis, the reader should consult the references.

PREOPERATIVE PREPARATION FOR ABDOMINAL SURGERY Bovine abdominal surgery is more feasible for the large animal practitioner than equine abdominal surgery. One of the reasons is the docile nature of many cows allows for many surgeries in the standing position while they are under regional anesthesia. The management of patients with abdominal disorders depends on an assessment of the nature and quantity of metabolic abnormalities and dehydration. To be successful, surgical therapy must often be accompanied by excellent metabolic supportive care.

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Net value of outcome Recover -----------$1,300-$200 0.75

$775

Died ~----------$0-$200

Correction and omentopexy

0.25

Sell for salvage

~-------------$500

Figure 4. Decision tree for intervention versus sale for salvage of cows with abomasal volvulus.

Facilities The surgical area should be clean and dust free and should include an adequate means of restraining the animal for the operation. The surgical site should be clipped liberally and cleaned and scrubbed with an antiseptic solution. Cattle are not more resistant than horses to surgical infection, and all efforts should be made to prevent it. Equipment should be available for the administration of intravenous fluids during the procedure. A few drugs (emergency pack) and surgical equipment should be kept adjacent to the operating room in case they are needed during the surgical procedure. Possible complications should be anticipated and plans developed to cope with them prior to the start of the surgery. Equipment and Assistant Several retaining devices have been developed specifically for the rumenotomy procedure: Michael and McKinley rumenotomy ring, rubber rumenotomy shroud, Gabel rumen retractor board, and Merillat Vulsellum forceps. Vulsellum forceps are also useful, in the author's opinion, in performing an omentopexy. Decompression is very useful if the intestinal tract is heavily dis-

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Net value of outcome Productive

------------$1,300-$200 0.68 $754

Salvaged

.......- - - - - - - - - - - - - $ 5 0 0 - $ 2 0 0 0.14 Died

Correction and omentopexy or abomasopexy

-------------$0-$200 0.18

Sell for salvage

---------------------$500 Figure 5. Decision tree for intervention versus sale for salvage of cows with abomasal volvulus, according to data from Smith DF: Right-sided torsion of the abomasum in dairy cows: Classification of severity and evaluation of outcome. J Am Vet Med Assoc 173:108, 1978.

tended with fluid or gas. Decompression of the rumen may involve using a very large diameter rubber stomach tube (Kingman) passed orally to siphon off the rumen contents. It may also involve incision and evacuation of the contents of an organ prior to manipulative procedure. Decompression of gas from an organ during a surgical procedure usually involves using a 14-gauge needle. In most cases, centesis can be performed without taking any special precautions to guard against leakage subsequent to the withdrawal of the needle from the organ. A sterile impervious sleeve should be worn while exploring the abdomen. Procedures involving incision into the organs often require an assistant to hold the organ while the surgeon completes the procedure. An assistant is needed for an abomasopexy from the left flank. 46 The assistant directs the surgeon for correct suture placement and also ties the suture on the ventral abdomen. Elective versus Emergency Surgery Some conditions are considered emergencies and require immediate surgical intervention, such as omasal-abomasal volvulus and volvulus of the root of the mesentery and cecum. Surgery for digestive

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disorders such as LDA and laparotomy-rumenotomy are elective procedures and may allow some preoperative therapy to stabilize or improve the animal's condition prior to surgery and may yield improved prognosis for return to function. In elective surgery, deprivation of food for 12 to 24 hours may help to decrease the volume of gastric contents and thus facilitate exploratory surgery, but this often is not done by the author. If general anesthesia is used, water and food deprivation is desirable to decrease contents and the rate of fermentation in the reticulorumen. Supportive Therapy It is imperative that cows in shock from hypovolemia be administered fluid intravenously through a well-secured aseptically placed indwelling catheter. In most cases of gastrointestinal disorders, fluids given orally are useless because of bowel stasis and pooling of fluid in the gastrointestinal tract. Intravenous fluid administration for intussusception during surgery and in the immediate postoperative period helps increase the survivability of the animal. When deciding whether to use intravenous fluid in a cow with abomasal volvulus, a distinction between the severity of the cases should be made. Uncomplicated cases of early volvulus have normal hydration and a slight disturbance of the electrolyte and acid-base balance (metabolic alkalosis). The general condition of these animals is good, and the abomasum is only distended with gas. They start eating and drinking rapidly after surgery, and acid-base and electrolyte balances return to normal value. If the abomasal volvulus is of long duration, the animals are dehydrated and show signs of hypovolemia. These animals generally have pronounced changes in the electrolyte and acid-base balance. After surgery the animals often refuse to drink or eat, and intravenous fluids and electrolytes must be given to rehydrate them. Sepsis and peritonitis can be prevented during digestive surgery by avoiding leakage of ruminal, abomasal, or intestinal contents and adhering to good surgical techniques. Depending on the risk of contamination, broad-spectrum antibiotics should be administered parenterally prior to surgery to ensure adequate tissue levels during the operative procedure. If there is a possibility of salvaging the animal based on operative findings, antibiotics may be withheld until the disposition of the animal is decided. Ketosis is a common concurrent problem in lactating or pregnant cattle with digestive disorders. Intravenous solution of glucose should be given in such cases. ANALGESIA FOR ABDOMINAL SURGERY The choice of anesthetic technique for abdominal surgery involves many considerations, the most important being abolition of pain for the patient. 40,48 Local and Regional Analgesia Local and regional analgesia is possible because of the cow's willingness to accept mechanical restraint without inflicting severe injury

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on itself. The technique is commonly used owing to economic necessity and good results. The standing position is optimal for reducing problems associated with bloat, regurgitation, and nerve or muscle damage. 43.46 Also, surgery of the alimentary tract, with few exceptions, is more satisfactorily performed with the patient under local or regional analgesia than under general analgesia. Regional analgesia is produced after perineural injection of major nerves. With proximal paravertebral analgesia, the dorsal and ventral roots of the last thoracic and first and second lumbar (LI and L2) spinal nerves are desensitized as they emerge from the intervertebral foramina. Occasionally, the nerve may be touched by the needle, which provokes a pain response from the animal. 43 Successful analgesia is demonstrated by an increase in skin temperature resulting from hyperemia. 43 Paravertebral analgesia, as compared with infiltration analgesia, offers the advantages of small doses of analgesic, wide and uniform area of coverage, and good muscle relaxation and allows easier manipulation of viscera, minimal intra-abdominal pressure, and no local analgesic agent in the operative margin. 43.46 In the distal paravertebral technique, the dorsal and ventral lateral rami of the spinal nerves T 13 , L I, and L2 are desensitized at the distal end ofLI' L2, and L4.46 The advantages of distal paravertebral analgesia include lack of risk of penetrating a major blood vessel, lack of scoliosis and minimal weakness in the pelvic limb or ataxia. The disadvantages of the technique are that large doses of anesthetic are needed and variations in efficiency exist. 43.46 Infiltration analgesia is achieved by injecting a local analgesic agent into the tissues at the surgical sites. A line block or inverted "L" block are commonly used in bovine practice. The advantage of the inverted "L" block compared with the line block is deposition of the analgesic away from the incision site, minimizing edema, hematoma, and possible interference with wound healing. The disadvantages of local infiltration analgesia include incomplete analgesia (particularly peritoneum), increased cost because of large doses of analgesic, and time required. 46 General (Inhalation) Anesthesia In cattle, general anesthesia may be considered desirable because it produces optimal relaxation of the abdominal musculature, abolishes painful stimuli associated with surgery of the peritoneal cavity and manipulation of the mesentery, commonly offers better exteriorization of intestinal lesions, minimizes intestinal prolapse through the incision, and obviates all other forms of restraint. 6o Anesthetic techniques such as induction procedures, endotracheal intubation, and maintenance procedures have been adequately described. 60 Most common hazards associated with general anesthesia of ruminants relate to the interaction of the digestive and respiratory systems. The large digestive reservoir of cows may in certain circumstances force the diaphragm cranial and drastically reduce lung volume. Food,

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water, or gas distention of the rumen may magnify the influence of dorsal recumbency and further depress respiratory function and lead to hypoxia. General anesthesia permits the regurgitation of ruminal content and possible inhalation. Preanesthetic fast and endotracheal intubation should diminish this problem. Cattle with prolonged recumbency and improper body position may have postanesthetic myopathy or neuropathy, even though it is observed less frequently than in horses. In comparison with the standing position, lateral or dorsal recumbency make abdominal exploration more difficult. The author is in accordance with what has been published by Smith for correction of an intestinal intussusception. 51 A standing celiotomy is done to ensure the diagnosis, especially if the preoperative diagnosis is not certain. The intussusception is found, the flank incision is temporarily closed, and the animal is placed in left lateral recumbency, preferably under general anesthesia. 51 The incision is reopened and intestinal resection and anastomosis performed. General anesthesia facilitates manipulation of the small intestine and traction on the mesentery and decreases the chance of abdominal contamination.

SELECTION OF SURGICAL APPROACHES FOR ABDOMINAL SURGERY The surgical approaches for entry into the abdominal cavity of cattle are an important consideration. Because of the size of their abdomen and the tight attachment of viscera by short mesentery and omenta, it is advantageous to enter the abdomen as close to the target organ as possible. 5 o,54 This stresses the importance of a correct diagnosis. Each surgical approach has its indications, advantages, and disadvantages. 46,50,53,54 The most common approaches for abdominal disorders are left paralumbar fossa celiotomy, right paralumbar fossa celiotomy, right paracostal celiotomy, and paramedian celiotomy (Table 3). Only certain portions of the intestinal tract can be exteriorized through a right paralumbar fossa incision. 50,54 These include: 1. The pylorus (unless the abomasum is abnormally full of ingesta or adhesions are present) 2. The distal 6 to 8 cm of abomasum and proximal 6 to 8 cm of the cranial duodenum 3. The descending duodenum 4. The jejunoileum (except the proximal 3 to 4 m of jejunum) 5. The cecum and most of the proximal loop of the ascending colon 6. The ileocecocolic junction and the cranial parts of the proximal colon. (more easily accomplished if the attachment of the greater omentum to the second segment of the proximal colon is incised) 7. The spiral loops of the ascending colon (accomplished by rotating the cecum and ileum craniad)

External factors, including physical facilities, available help, and

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Table 3. Surgical Approaches for Abdominal Surgery SURGICAL APPROACHES

INDICATIONS

Left paralumbar fossa

- access to rumen, reticulum - access and good visual inspection of the abomasum with left displacement (abomasopexy) - adhesion of the abomasum to the left body wall -left displaced abomasum in cows in the last trimester of pregnancy

Right paralumbar fossa

-most thorough exploration of the abdomen - access to small and large intestine (intussusception, torsion of the root of the mesentery, cecal dilatation and volvulus, enterolith) - access to left displaced abomasum (omentopexy) - access to right dilatation and abomasal volvulus; surgery can be done without an assistant (omentopexy) -evaluation of liver, gall bladder - good for undiagnosed problem and prophylactic omentopexy

Right paracostal

- access to pyloric part of the abomasum - access to cranial part of the duodenum

Paramedian

- good access to forestomachs - allows the most complete exteriorization of the abomasum (ulcer, impaction) - permits correction of left or right displacement or abomasal volvulus (abomasopexy) - preferred approach for abomasal problems in young calves because of their tendency to lie down - incision scar is not readily visible

postoperative care, must also be evaluated. It is unwise to perform a paramedian celiotomy if recovery is to take place in a contaminated wet area and expect optimal healing. 2 ,46 Regardless of the surgical approach, care must be exercised in the manipulation of digestive organs. Extensive pulling on the greater omentum during repositioning of an LDA will frequently cause extensive damage to the vessels and omental attachment along the greater curvature of the abomasum. Also, with every surgical approach chosen, it is important to isolate the organ being incised from the rest of the abdominal cavity during the procedure to avoid contamination. ACKNOWLEDGMENT

The assistance of Drs. Koenig, Constable, and Rings in the preparation of this article is gratefully acknowledged.

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3. Anderson JR, Dillon JL, Hardaker JB: Agricultural Decision Analysis. Ames, The Iowa State Press, 1977 4. Baker JS: Right displacement of the abomasum in the bovine - a modified procedure for treatment. Bovine Pract 11:58, 1976 5. Constable PD, St. Jean G, Hull BL, et al: Preoperative prognostic indicators in cattle with abomasal volvulus. J Am Vet Med Assoc, in press 6. Constable PD, Rings DM, Hull BL, et al: Atresia coli in calves: 26 cases {19771987}. J Am Vet Med Assoc 195:118, 1989 7. Dirksen G, Garry FB: Diseases of the forestomachs in calves. Part II. Comp Cont Educ Pract Vet 9:173, 1987 8. Dirksen G, Garry FB: Diseases of the forestomachs in calves. Part I. Comp Cont Educ Pract Vet 9:140, 1987 9. Dirksen G: Left abomasal displacement in calves. Bovine Pract 17:75, 1982 10. Ducharme NG: Surgical considerations in the treatment of traumatic reticuloperitonitis. Comp Cont Educ Pract Vet 5:213, 1983 11. Ducharme NG, Dill SG, Rendano VT: Reticulography of the cow in dorsal recumbency: An aid in the diagnosis and treatment of traumatic reticuloperitonitis. J Am Vet Med Assoc 182:585, 1983 12. Ducharme NG, Arighi MF, Horney DF, et al: Colonic atresia in cattle: A prospective study of 43 cases. Can Vet J 29:818, 1988 13. Ducharme NG, Lowe JE: Decision for surgery. Vet Clin North Am [Equine Pract] 4:51, 1988 14. Fetrow J, Madison JB, Galligan D: Economic decision in veterinary practice: A method for field use. J Am Vet Med Assoc 186:792, 1985 15. Fox FH: Abomasal disorders. J Am Vet Med Assoc 147:383, 1965 16. Fubini SL, Erb HN, Rebhun WC, et al: Cecal dilatation and volvulus in dairy cows: 84 cases {1977-1983}. J Am Vet Med Assoc 189:96,1986 17. Gabel AA, Heath BR: Treatment of right-sided torsion of the abomasum in cattle. J Am Vet Med Assoc 155:642, 1969 18. Gabel AA, Heath BR: Correction and right-sided omentopexy in treatment of leftsided displacement of the abomasum in dairy cattle. J Am Vet Med Assoc 155:632, 1969 19. Garry FB, Hull BL, Rings DM, et al: Prognostic value of anion gap calculation in cattle with abomasal volvulus: 58 cows {1980-1985}. J Am Vet Med Assoc 192:1107,1988 20. Garry F, Hull BL, Rings DM, et al: Comparison of naturally occurring proximal duodenal obstruction and abomasal volvulus in dairy cattle. Vet Surg 17:226, 1988 21. Grymer J, Ames KN: Bovine abdominal pings: Clinical examination and differential diagnosis. Comp Cont Educ Prac Vet 3:311, 1981 22. Grymer J, Sterner KE: Percutaneous fixation ofleft displaced abomasum using a bar suture. J Am Vet Med Assoc 180:1458, 1982 23. Grymer J: Factors influencing left-displaced abomasum: An application of computer data. Bovine Clin 2{3}:1, 1982 24. Grymer J: Displaced abomasum-a disease often associated with concurrent diseases. Comp Cont Educ Pract Vet 11:290, 1980 25. Gyang EO, Markham RJF, Usenik EA, et al: Polymorphonuclear leukocyte function in cattle with left displaced abomasum. Am J Vet Res 47:428, 1986 26. Habel RE, Smith DF: Volvulus of the bovine abomasum and omasum. J Am Vet Med Assoc 179:447, 1981 27. Hamilton GF, Tulleners EP: Intussusception involving the spinal colon in a calf. Can Vet J 21:32, 1980 28. Henninger RW, Mullowney PC: Anterior abdominal pain in cattle. Comp Cont Educ Pract Vet 6:453, 1984 29. Hoffsis GF, McGuirk SM: Diseases of the abomasum and intestinal tract. In Howard JL {ed}: Current Veterinary Therapy, Food Animal Practice. Philadelphia, WB Saunders, 1980, p 891 30. Hoffsis GF, McGuirk SM: Right displaced abomasum and abomasal torsion {volvulus}. In Howard JL {ed}: Current Veterinary Therapy, Food Animal Practice, ed 2. Philadelphia, WB Saunders, 1986, p 726

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60. Tranquilli WJ: Technique of inhalation anesthesia in ruminants and swine. Vet Clin North Am [Food Anim Pract] 2:593, 1986 61. Tulleners EP: Surgical correction of volvulus of the root of the mesentery in calves. J Am Vet Med Assoc 179:998, 1981 62. Tulleners EP, Hamilton GF: Surgical resection of perforated abomasal ulcers in calves. Can Vet J 21:262, 1980 63. Wallace CI: Left abomasal displacement-a retrospective study of 315 cases. Bovine Pract 10:50, 1975 64. Wallace CI: Prognostic significance of diarrhea in cows with left displacement of the abomasum. Bovine Pract 11:62, 1976 65. Weaver AD: Left abomasal displacement in cattle. Br Vet J 126:194, 1970 66. Weinstein MC, Fineberg HV: Clinical Decision Analysis. Philadelphia, WB Saunders, 1980, p 12 67. White ME, Erb M: Treatment of ovarian cysts in dairy cattle-a decision analysis. Cornell Vet 20:247, 1980 68. Wilson AD, Hirsch VM, Osborne AD: Abdominocentesis in cattle: Technique and criteria for diagnosis of peritonitis. Can Vet J 26:74, 1980

Address reprint requests to Guy St. Jean, DMV, MS Department of Surgery and Medicine College of Veterinary Medicine Kansas State University Manhattan, KS 66506