Clinical, hematological, and necropsy results suggested a classification of VI with respect to pres- ence or absence of ... Can Vet J Volume 41, October 2000. 777 ...... technicians of the Departments of Clinical Sciences ... Textbook of Veterinary.
Etiology, forms, and prognosis of gastrointestinal dysfunction resembling vagal indigestion occurring after surgical correction of right abomasal displacement Nicolas Sattler, Gilles Fecteau, Pierre Helie, Jean-Martin Lapointe, Luc Chouinard, Marie Babkine, Andre Desrochers, Yvon Couture, Pascal Dubreuil Abstract The objectives of this study were to determine the etiology and types of vagal indigestion (VI) occurring after right displacement of the abomasum or abomasal volvulus (RDA/AV), and the prognosis for each type. Data of cows presented for RDA/AV from a retrospective (n = 288) and a prospective (n = 132) study were used. Vagal indigestion occurred in 39 and 22 cows in each study, respectively. A necropsy was performed in 29 cases. Gastric compartment dilation compatible with VI type III or IV occurred in 23 cases. An abnormal gastric wall was detected in 22 cases. Peritonitis was present in 18 cows. Vagal nerve lesions were present in 5 out of 13 cases studied. Clinical, hematological, and necropsy results suggested a classification of VI with respect to presence or absence of peritonitis. Gastric wall damage, peritonitis and vagal nerve lesions appear important in the etiology. Considering peritonitis occurrence, antimicrobial therapy appears necessary in the treatment of RDA/AV.
Resume Etiologie, formes et pronostic des indigestions vagales survenant a la suite d'une correction chirurgicale d'un deplacement de la cailiette. L'etiologie, les types d'indigestion vagale (IV) et le pronostic de chaque type d'IV survenant apres un deplacement a droite ou un volvulus de l'abomasum (DDA/VA) furent etudies en utilisant les donnees provenant d'etudes retrospective (n = 288) et prospective (n = 132). Une IV fut observee dans 39 et 22 cas, respectivement. Une autopsie fut realisee sur 29 animaux. Une dilatation des compartiments gastriques compatible avec une IV type III ou IV etait presente chez 23 bovins. La paroi gastrique etait anormale dans 22 cas. Une peritonite etait presente chez 18 animaux. Des lesions du nerf vague furent observees dans 5 des 13 cas etudies. Les donnees cliniques, hematologiques et pathologiques suggeraient une classification des IV fondee sur absence ou presence de peritonite. Dommage structural a la paroi gastrique, presence de peritonite et lesions du nerf vague apparaissent etre des facteurs importants dans l'etiologie. Fondee sur la prevalence de peritonite, l'utilisation d'antibiotiques semble necessaire dans le traitement des DDA/VA. (Traduit par les auteurs) Can Vet J 2000;41:777-785
Introduction A bomasal displacement has a multifactorial etiology and constitutes the most common cause of surgical gastrointestinal disorders in dairy cattle (1). Left displacement of the abomasum (LDA) is more frequent than right displacement (RDA) or volvulus (AV), accounting for 85 to 95.8% of all cases (1). The prognosis
Departement de sciences cliniques, Faculte de medecine v'terinaire, Universite de Montreal, 3200, rue Sicotte, SaintHyacinthe, Quebec J2S 7C6 (Sattler, Fecteau, Babkine, Desrochers, Couture, Dubreuil); Laboratoire de pathologie animale, MAPAQ, 3220, rue Sicotte, Saint-Hyacinthe, Quebec J2S 7X9 (Helie, Lapointe, Chouinard). Address correspondence and reprint requests to Dr. Nicolas Sattler, Clinique veterinaire St-Vallier, 400, Montee de la station, St-Vallier, Quebec GOR 4SO. This research was partly funded by the Fonds du Centenaire de la Faculte de medecine veterinaire, Universite de Montreal. Can Vet J Volume 41, October 2000
for LDA is good with 95% of cattle returning to normal production (1). For RDA or AV, the prognosis is guarded: 75.5% of cattle return to normal production (2). Simple abomasal volvulus, or abomasal volvulus involving omasum or omasum and reticulum, have a worse prognosis than RDA with a mean survival rate of 61% (3). In recent studies, a survival rate of 64.7% (4) and a return to normal production rate of 73.8% (5) for AV were observed. While some animals die of hypovolemic (6-8) or septic (2,4) shock shortly after surgical correction of RDA/AV, others survive the acute postsurgical period but develop other related problems. The most frequent postoperative complication encountered with RDA/AV is a gastrointestinal dysfunction resembling vagal indigestion (GDRVI), which occurs in 14% to 21% of cases (4-6,9-12). This syndrome has a high case fatality rate with only 11.5% to 20% of affected cattle returning to production (4,5,13). Medical treatment for this condition includes prokinetics, laxatives, and fluids, and has a low success rate (5,12,13). The success rate for surgical 777
treatment of this condition, including pyloromyotomy, pyloroplasty, abomasoduodenostomy, and chronic abomasal or ruminal fistula, is not better (5,12,13). Four main causes of clinical signs compatible with vagal indigestion (VI) following surgical correction of AV have been proposed in the literature: vagus nerve damage, overstretching of the abomasal wall with neuromuscular junction alterations and autonomic motility modification, thrombosis and abomasal necrosis, and peritonitis (5,9,13,14). These hypotheses are based on a report by Habel (14) on AV cases euthanized prior to surgery. Constable et al (5) found an acute generalized peritonitis associated with necrotizing abomasitis at necropsy in 4 cases that survived for 6 to 9 d after surgical correction of AV. The objectives of this study were to determine and describe the etiology of the different forms of GDRVI that follow surgical correction of RDA/AV, based on clinical, laboratory, and postmortem data, and to estimate the prognosis for each form.
Materials and methods Inclusion criteria All medical records from adult dairy cows > 22 mo of age presented for RDA/AV l'H6pital veterinaire d'enseignement (HVE) of l'Universite de Montreal were studied. In the retrospective and prospective parts of the study, data from cases that died during surgical correction or hospitalization, or were euthanized, are presented. For the prospective part of the study only, data from cases with a poor prognosis at discharge, after surgical correction of a RDA/AV, are also reported. Cases presented at the hospital with clinical signs compatible with VI following surgical correction of RDA/AV at the farm were also included in the prospective part of the study. Definitions For the purpose of this study, RDA/AV is used to describe all types of volvulus and right abomasal dilation. The definitions of Constable et al (5) were used to establish the diagnosis of right displacement of the abomasum (RDA), abomasal volvulus (AV), omasoabomasal volvulus (OAV), or reticulo-omaso-abomasal volvulus (ROAV), based on the surgical or necropsy findings. A fatal outcome was defined as death or euthanasia during hospitalization. Cattle that were slaughtered after hospital discharge were not included in this definition and were considered to be survivors. The most important clinical signs for diagnosis in cattle with VI are apple-shaped abdomen, abnormal ruminal motility (atony, hypomotility, or hypermotility), absent or very scant feces, and L-shaped rumen on rectal examination (13,15,16). For the present study, cows were identified as suffering a GDRVI if the association of 3 of the 4 previously listed clinical signs were observed during the postsurgical period. Abnormal gastric wall was used to describe any of the following histological lesions: inflammatory cell infiltrate, ulcer, or vascular damage (edema, necrosis, thrombosis, hemorrhage). Abomasal ulcer was used to 778
Figure 1. Abomasal vascularization and localization of vascular lesions observed at necropsy in cases presenting clinical signs compatible with vagal indigestion following surgical correction of abomasal dilation or volvulus. A - abomasum; 0omasum; R - reticulum; Ru - rumen; 1 - aorta; 2- cranial mesenteric artery; 3 - celiac artery; 4 - left gastric artery; 5 - left gastroepiploic artery; 5' - accessory reticular artery; 6 - hepatic artery; 7 - right gastric artery; 8 - gastroduodenal artery; 9 - cranial pancreaticoduodenal artery; 10 right gastroepiploic artery; 11 - splenic artery; 12- left ruminal artery; 13 - reticular artery; 14 - right ruminal artery. CD : localization of the lesions in the major vessels (adapted from Dyce (17)).
Figure 2. Abomasal innervation and localization of vagus nerve lesions observed at necropsy in cases presenting clinical signs compatible with vagal indigestion following surgical correction of abomasal dilation or volvulus. C - cardia; D diaphragm; 0 & A - omasum and abomasum; R - reticulum; E - esophagus; CMA: cranial mesenteric artery; DRSB: diaphragmatic reticular surface branches; GACB - great abomasal curvature branch; IB - intestinal branch; LACB lesser abomasal curvature branch; LGA - left gastric artery; LGB - liver and gallbladder branches; MRSB - medial reticular surface branch; LPB - long pyloric branch; RDB ruminal dorsal branch; P & G - celiac and cranial mesentc`plexus & ganglia; RGA - right gastric artery; RRA - right ruminal artery; VDT - vagal dorsal trunk; VVT - vagal ventral trunk.
-I
I
*
*
__,
sES
Figure 3. Normal section of the vagal ventral branch in a cow with a gastrointestinal dysfunction resembling vagal indigestion following abomasal volvulus (Bielschowsky's stain). Bar = 50 gim.
Figure 4. Lesions observed in another vagal ventral branch section in the same cow as in Figure 3: fragmentation and loss of axons, edema, and slightly increased numbers of Schwann cells (Bielschowsky's stain). Bar = 50 ,um.
the abdomen or if bacteriological culture of the peritoneal fluid was positive. Peritonitis was defined as generalized, if it was diffuse or multifocal; localized, in every other situation; and chronic, if there were fibrous, nonreducible adhesions. The term vascular lesions was used if hemorrhages or thrombosis of the gastric or gastroepiploic vessels, or hemorrhages in the omentum were observed (Figure 1). Vagus nerve lesions were detected on macroscopic or histological examination and localized according to Figure 2.
seen, 2.5-cm-long sections were taken at about 10-cm intervals in the main branches, and smaller branches were randomly selected. Bielschowsky's and luxol-fast-blue stains were used on selected slides. In all cases, sections of the nerve and the nervous plexuses in the abomasum and forestomachs were evaluated by one of the authors (PH).
Retrospective study All medical records between January 1, 1989, and December 31, 1994, were reviewed looking for the diagnosis of RDA, AV, OAV, or ROAV. Information retrieved included surgical observations (lesions detected, localization of the volvulus), diagnosis, clinicopathological findings, treatments, outcome, and necropsy findings.
Prospective study All adult cows admitted to the hospital between January 1, 1995, and September 15, 1998, with a final diagnosis of RDA, AV, OAV, or ROAV, were included. Information compiled included surgical observations, diagnosis, clinicopathological results, treatments, outcome, and necropsy findings. A standardized surgery report focusing on specific information was used (available upon request). For all cases presenting clinical signs compatible with VI when discharged, the owners were contacted to assess the long-term
Materials and methods In both the retrospective and prospective parts of the study, the etiology of the forestomach or abomasal dysfunction was determined based on the lesions observed at necropsy. Characterization of the syndrome was based on the pattern of gastric compartment distention identified at necropsy and on the surgical, clinical, and clinicopathological data. In the prospective study, postsurgical outcome and data were used to assess the success rate of the treatments attempted and the prognosis. Because postmortem examination was standardized in the prospective study, necropsy findings of the retrospective and the prospective parts of the study were analyzed separately. For the other data, differences between the 2 parts of the study were statistically tested. If there were no statistically significant differences, the data were combined for analysis and presentation.
Statistical analysis A chi-squared test was used to compare the frequencies and Wilcoxon's rank sign test was used for the median comparisons. The value of a was 0.05.
outcome.
Branches of the vagus nerve to the forestomachs and the abomasum were evaluated systematically during necropsy. The 2 major branches of the vagus nerve were dissected from the heart to the forestomachs and the abomasum. They were fixed in 10% buffered formalin prior to standard preparation for microscopic examination. Sections (5 ,um) were stained with hematoxylinphloxin-safran. In cases where macroscopic lesions were present (hemorrhage, thinning), only affected sections were recut. When macroscopic lesions were not Can Vet J Volume 41, October 2000
Results General results and necropsy findings of the retrospective study Two hundred eighty-eight cases of RDA/AV were retrieved from the medical archives. The RDA/AV case fatality rate was 12.8% (n = 37). A GDRVI was present in 13.5% of cows (n = 39). Death or euthanasia occurred either during or less than 6 h after surgical correction of RDA/AV in 17 of the 37 fatal cases. 779
Table 1. Results of the retrospective study: Number of cases with a gastrointestinal dysfunction resembling vagal indigestion following surgical correction of right abomasal displacement or volvulus (n = 16), where one lesion or a combination of lesions was present at necropsy Description
Table 2. Results of the prospective study: Number of cases with a gastrointestinal dysfunction resembling vagal indigestion following surgical correction of right abomasal displacement or volvulus (n = 13) where one lesion or a combination of lesions was present on postmortem examination Description
Number
Gastric compartments dilated
Rumen Rumen and omasum Rumen, omasum, and abomasum
3 3 7
5 3
Peritonitis
Generalized Localized
5 5
Abomasal necrosis Abomasal ulcers Multifocal gastric compartment necrosis Nonsuppurative infiltration or edema Reticulum ulcer
3 5 1
Abnormal gastric wall (1 or more lesions present for each case)
Abomasal or omasal necrosis Abomasal ulcers Edema, abomasitis or polymorphonuclear infiltration Ostertagiosis
3 3 6
Hemorrhages and thrombosis in the greater omentum near the abomasal wall
2
Multiple omental hemorrhages Left gastric vein thrombosis (omasal branch) Left and right gastroepiploic vein and artery thrombosis
2 I
Gastric compartments dilated
Rumen Rumen and omasum Rumen, omasum, and abomasum
Peritonitis
Generalized Localized
Abnormal gastric wall (1 or more lesions present for each case)
3 1 12
3
Lesions in the branches of the vagus nerve No relevant lesions detected
Have been examined only once and were normal
Lesions in the branches of the vagus nerve 4
Twenty cows died or were euthanized more than 6 h postsurgery (2 deaths; 18 euthanasia). The median survival time was 5 d (range, 2 to 31 d). Sixteen of these fatal cases displayed clinical signs compatible with VI. Eighteen necropsy reports were available, including those from all of these 16 cows. Necropsy findings from the 16 cases with clinical signs compatible with VI are listed in Table 1. Peritonitis was septic in 6 cases. Adhesions associated with peritonitis were reducible, except in one case.
General results and necropsy findings of the prospective study One hundred thirty-two cases of RDA/AV were studied. The RDA/AV case fatality rate was 15.9 % (n = 21). Death or euthanasia occurred either during or less than 6 h after surgical correction of RDA/AV in 6 of the 21 cases. In the 126 cows that survived surgery, the rate of GDRVI occurrence was 17.5% (n = 22). According to the medical records, 31.8% of cases with this syndrome postsurgery (n = 7) had severe ruminal dilation prior to surgical correction of the RDA/AV. However, ruminal dilation was observed prior to surgery in only 10% of cases witbout GDRVI postsurgery (n = 10; P = 0.03). On rectal examination, performed when clinical signs compatible with VI were present postsurgery (n = 22), the abomasum was never palpable. Nine of the 22 (41%) animals were discharged, even if a GDRVI was present. Only one had a favorable long-term outcome (2 y survival), according to the owner. Thus, the long-term case fatality rate of this syndrome was 95.5 %. 780
1
I
Vascular lesions Vascular lesions
Number
Lesions in the nervous plexuses
Wallerian degeneration, thrombosis, hemorrhage, and vascular necrosis located in: Ventral trunk (long abomasal branch) Dorsal trunk (omasal endings) Ventral and dorsal trunks Abomasal plexus: loss of ganglial cells Abomasal plexus: lymphoplasmocytic perivascular cuffing
I
3 I
1
3 4
The 15 cases with a fatal outcome that survived > 6 h after surgery (1 death, 14 euthanasia) had a median survival time of 5 d (range: 2 to 14 d). Thirteen displayed clinical signs compatible with VI. Necropsy findings are presented in Table 2. Peritonitis was septic in all cases. Adhesions associated with the peritonitis were reducible in all cases. Sections from all gastric compartments, except the reticulum, were available in each case, allowing for examination of nervous plexuses.
Clinical examination findings and hematological results For these data, there were no statistically significant differences between the cases in the retrospective and the prospective parts of the study. Thus, these results were combined for analysis and presentation. Clinical signs of the 29 cases presenting a GDRVI the day prior to death are summarized in Table 3. The relationship between the surgical diagnosis and the gastric compartments found dilated at necropsy for these cases is reported in Table 4. According to the medical records, in most cases, the rumen was either hypomotile or hypermotile before becoming atonic during the Can Vet J Volume 41, October 2000
Table 3. Results from clinical examination of the cows presenting a gastrointestinal dysfunction resembling vagal indigestion following surgical correction of right abomasal displacement or volvulus, on the day of their death or euthanasia Parameter Rectal temperature °C (median) 37.8 T< 39.0 39.039.5
Number of cases of both studies (Total = 29)
(38.8) 17 7 5
Heart rate bpm (median) 56 4 contr/2 min and weak contr) Absent: (0 contr / 2 min)
10 8 11
Fecal appearance Dry or mucous or doughy Absent Diarrhea Normal Not available
14 6 5 1 3
bpm - beats per minute; brpm - breaths per minute; contr -contractions
postsurgical hospitalization. The rumen was hypermotile on the day prior to death in 54.5% of cases without peritonitis (n = 6), but in only 11% of cases with peritonitis (n = 2) (P = 0.05). There was no statistically significant association between clinical signs on the day prior to death and the surgical diagnosis (RDA, AV, OAV, ROAV). There was no other statistically significant association between the clinical signs on the day prior to death and the necropsy findings. Available results of the complete blood cell count and serum biochemical analysis performed less than 48 h prior to euthanasia or death are presented in Tables 5 and 6. All but 7 animals were receiving IV fluids at the time of sampling. The median serum sodium concentrations were 141.1 mmol/L and 135.8 mmol/L for cases treated and not treated with fluids, respectively (P = 0.01). The median fibrinogen concentration was 5 g/L and 7 g/L (normal range, 2 to 4 g/L) for cases treated and not treated with fluids, respectively (P = 0.02). There was a statistically significant difference between serum glucose concentration (P = 0.01) and neutrophil count (P = 0.02) for cases with or without peritonitis detected at necropsy (Figure 5). There was a statistically significant difference between cases with or without abomasal ulcer for the anion gap (P = 0.04). There was a statistically significant difference between albumin concentration (P = 0.02), calcium concentration (P = 0.03), and hematocrit (P = 0.01) for cases with or without abomasal dilation. There was no statistically sigCan Vet J Volume 41, October 2000
Table 4. Relationship between surgical diagnosis and the gastric compartments dilated at necropsy for cows that developed a gastrointestinal dysfunction resembling vagal indigestion following surgical correction of right abomasal dilation or abomasal volvulus Exact diagnosis of the abomasal dilation (at surgery) (n = 27)a
Gastric compartment dilated
RDA (n = 2)
AV (n= 17)
OAV (n = 6)
ROAV (n = 2)
Rumen Rumen and omasum Rumen, omasum, and abomasum
0 1 1
3 3 11
1 0 5
1 0 1
a2 diagnoses are missing for the prospective study because surgery was performed on the farm. RDA - right abomasal displacement, AV - abomasal volvulus, OAV - omaso-abomasal volvulus, ROAV - reticulo-omasoabomasal volvulus
nificant association between hematological parameters on the day prior to death and surgical diagnosis. There was no other statistically significant association between hematological values and necropsy findings. Treatments attempted in some cows presenting a GDRVI included IV fluids, metoclopramide (Metoclopramid; Wyeth-Ayerst, Saint-Laurent, Quebec), 0.1 mg/kg body weight (BW), SC, q8h; neostigmine (Stimuline; Distrivet, Roxton Falls, Quebec), 2 mg, IM, q4h; cisaprid (Prepulsid; Janssen-Ortho, North York, Ontario), 0.1 mg/kg BW, per rectum, q12h for 3 treatments, exercise, laxatives (magnesium oxide or magnesium sulfate), and supportive care. No surgical treatment was attempted. No clinical improvement was observed in any case, based on the daily records of fecal output, appetite, milk production, and physical examination.
Discussion In veterinary medicine, VI has been used to refer to a clinical syndrome (16,20-23). Multiple etiologies are then associated with this syndrome (16,20-23). Vagal indigestion has also been used to refer to a specific diagnosis based on the demonstration of lesions in the vagus nerve, such as those depicted by Hoflund (24-26). For the purpose of this paper, VI refers to the latter definition. In this study, the overall RDA/AV survival rate at discharge from the hospital of 86.2% (362/420) is higher than that given in previously published reports (3,4). However, definition of outcome or duration of followup may be different from one study to another, making comparisons difficult. Development of a GDRVI was associated with delayed fatal outcome after the surgical correction of RDA/AV in most cases (83% of all delayed fatal outcome cases). The case fatality rate for this VI-like syndrome reported in the prospective part of this study (95.5%) is in the range already published (80% to 100%) (4,5,13). None of the surgical treatments for VI proposed in the literature were attempted because of the poor reported results (5,12,13). 781
Table 5. Results of complete blood cell count (n = 19) performed less than 48 h prior to euthanasia or death for cases presenting a gastrointestinal dysfunction resembling vagal indigestion following surgical correction of right abomasal displacement or abomasal volvulus Values Hematocrit Thrombocytes Monocytes WBC Lymphocytes Fibrinogen Neutrophils Left shift Toxic neutrophils
Units L/L x 109 cells/L x 109 cells/L
X 109 cells/L x 109 cells/L g/L x 109 cells/L
Population Percentage of 5%-95% population in the range reference range
Reference rangea
Median
0.24-0.46 100-800 0-0.8 4.0-12.0 2.5-7.5 2-5 0.6-4.0 Absent Absent
0.32 463 0.41 9.39 2.6 6 5.7 Present in 7 cases Present in 4 cases
0.25-0.40 191-830 0.1-1.6 4.7-21.4 1.2-4.2 4-8 2.4-18.1
96.5 94.1 84.2 74.2 52.7 42.6 35.9
WBC - White blood cell count aFrom the laboratory of the Faculte de medecine veterinaire
Table 6. Results of serum biochemistry (n = 25) performed in the 48 h prior to euthanasia or death for cows presenting a gastrointestinal dysfunction resembling vagal indigestion following surgical correction of right abomasal displacement or abomasal volvulus Values
Phosphorus Creatinine Sodium Anion gapb Urea Glucose Globulin Total protein ALP Potassium Albumin Calcium Chloride Total bilirubin Total CO2 AST GGT CK
Units
Reference rangea
mmol/L pmol/L mmol/L mmol/L mmol/L mmol/L g/L g/L U/L mmol/L g/L mmol/L mmol/L pmol/L mmol/L U/L U/L U/L
1.05-2.83 54-132 134-147 7-18 1.61-6.51 2.6-4.9 26.2-45.2 59.5-80 0-100 3.86-5.28 27.7-40.4 2.22-2.70 96-109 0.1-14.0 22-33 30-104 9.5-39 0-310
Median
Population 5%-95% Range
Percentage of population in the reference range
1.65 81 139.5 12.01 4.4 2.9 33.1 61.5 94 3.96 27.5 2.18 105 17.6 24.8 184 62 683
1.04-2.41 62.2-138.5 133.2-147.8 5.5-17.99 2.4-17.4 1.8-4.4 20.6-50.5 44.5-79.8 52-305 2.86-4.63 21.7-32 1.85-2.44 81.5-113.6 7.7-57.4 13.9-41.9 77-787 30-97 180-6791
94.9 93.8 92.6 81.7 77.7 77.3 74.3 58.2 55 52.9 44 44 39.1 35.4 34.8 13.3 12.8 12
ALP - alkaline phosphatase activity; AST - aspartate amino transferase activity; GGT - gamma glutamyl transferase activity; CK - creatine kinase activity aFrom the laboratory of the Faculte de medecine veterinaire bAnion gap = ([Nal] + [K+]) - ([CI-] + [HCO3-i)
In order to define the different forms of gastrointestinal dysfunction following RDA/AV, the combination of clinical examination findings, hematological results, and necropsy findings was used. Only in cases that were different for the presence or absence of peritonitis were the clinical signs (rumen motility and heart rate) and hematological results (blood glucose, neutrophil count) also different. Cows with or without abomasal ulcers at necropsy differed only for the anion gap. Cows with (VI type Ill or IV (16,27)) or without (VI type 11 (16,27)) abomasal dilation at necropsy were only different for nonspecific hematological results (albumin level, hematocrit, and calcium value). Thus, for cows presenting a GDRVI following RDA/AV, a classification based on the presence or absence of peri782
tonitis seems more valid than does the classification used for VI based on the site of digestive transit obstruction (16,27). This would be important in the management of these cases and to determine treatment. As the peritonitis was septic in most cases, antimicrobial therapy would appear to be desirable and recommended in the treatment of RDA/AV. However, the usual classification of types of VI (16,27) was useful in describing the forms of digestive transit obstruction observed at necropsy. In the literature, clinical signs compatible with VI following RDA/AV are usually referred to as type III (abomasal paralysis) or type IV (pyloric outflow failure) vagal indigestion (13). In this study, the digestive transit seemed to be obstructed at 3 different sites: the reticulo-omasal Can Vet J Volume 41, October 2000
1Ruminal moUtity.-
)..e
i
."tff 140
1132
120
.I I.'''40
OU
tE10
e
$04
M.
.-'.
0.
-
.
Pelb
'
*m 3. Tempoertur OpfOM)
lb-
t
.Oi=0.02.
4L
p, L -fhato0bhI coulOmOmt
.
24
25
416"
17,
14
14
.4,
2 0
~4,0
33
567 2.3 .2.6
Figure 5. Clinical signs and hematological values on the day prior to death for cases presenting a gastrointestinal dysfunction resembling vagal indigestion and with peritonitis at necropsy (n = 16) and without peritonitis at necropsy (n = 13). Extremities of the whiskers are values of the 0 and 100th percentiles of the population. Limits of the box are values of the 25th and 75th percentiles of the population. The line in the box is the median (50th percentile).
opening (reticuloruminal dilation alone), the omasoabomasal opening (reticuloruminal and omasal dilation), or the pylorus (dilation of all the gastric compartments). The cases with reticuloruminal dilation only (n = 6) were similar to the description of type II vagal indigestion (failure of omasal outflow) (13). According to our results, it appears that a gastrointestinal dysfunction resembling type II vagal indigestion could occur after RDA/AV. Can Vet J Volume 41, October 2000
In order to hypothesize about the etiology of clinical signs compatible with VI in these cows, each necropsy finding was studied. Structural abomasal wall damage was the most frequent finding. When abomasal necrosis is observed, it can be considered as a cause of pyloric outflow failure, as it will be associated with a failure of the abomasal outflow (16,23,26). It is not possible to determine the precise role of the other abomasal wall lesions observed in this study in the pathophysiology of VI 783
following RDA/AV. These lesions were associated with abnormal intramural nervous plexuses in only 2 cases. Except for abomasal necrosis, all abomasal wall lesions observed appeared to be reversible. However, these lesions were diffuse and were found up to 28 d after surgery. Peritonitis was the second most frequent lesion noted on postmortem examination of cows presenting a GDRVI. In 14 of 18 cases with peritonitis, the process was septic. Necrosis of the abomasal wall and bacterial translocation were probably responsible for the infection. This observation has already been reported by Constable (5) but was not observed in other reports (4,13,14). It was not possible from the results of this study to establish a causal relationship between this lesion and the clinical signs compatible with VI that were observed, because the frequency of peritonitis in cows without VI following RDA/AV was not known. Moreover, according to Cable et al (28), peritonitis due to abomasal ulceration is not associated with the clinical signs of VI. Lesions in the major abomasal vessels (thrombosis or hemorrhage) were detected in 6 (21 %) cases at necropsy. However, these lesions were only associated once with abomasal necrosis. Because the abomasal wall has a dual arterial supply (Figure 1), it is possible that thrombosis of a single major vessel does not result in loss of viability of the abomasal wall. One could hypothesize that development of abomasal necrosis is dependent more on the tightness of the volvulus and/or the duration of ischemia to the abomasum than on the presence of a thrombosis or rupture of a major vessel. According to the results of the prospective study, VI (presence of vagus nerve lesions) following RDA/AV occured in 5 (38.5%) cases. The lesions observed in the vagus nerve were focally extensive and associated with hemorrhages, probably due to the volvulus. In all cases, they were seen on gross examination. In one case, a lesion of the vagus nerve (Figure 4) was found in the ventral vagal trunk, associated with omasal necrosis and fibrinous peritonitis. This favors the hypothesis that peritonitis and vagus nerve lesions could coexist as distinct consequences of the volvulus. All observed lesions of the vagus nerve were severe, considered active, and not in the repair stage. However, as physiological studies were not performed, it is not possible to conclude that the electrical transmission of the nerve impulse was totally interrupted (18,25). On another hand, the observed lesions of the vagus nerve were not always associated with the branches to the dilated gastric compartment(s). One explanation to that finding could be that no matter where the lesion in the vagus nerve is located, it will affect the motility of all gastric compartments, because the motility of the forestomachs and that of the abomasum are intimately related, and the vagus nerves are mainly sensory (16). The study of the relationship between the surgical diagnosis and the pattern of gastric compartment dilation (Table 4) could be useful in understanding the etiology of clinical signs compatible with VI following surgical correction of RDA/AV. However, in this study, a statistically significant association between the surgical diagnosis and the dilated gastric compartment(s) was not 784
observed. This could be an artifact due to manipulation of dead cows prior to necropsy or to the low number of cases. Another hypothesis is that direct involvement of the dilated compartment in the volvulus is not needed, as the dilation of a forestomach can be due to a dysfunction of that compartment or of the aboral one (13,16). As clinical signs compatible with VI occurred in 2 cows following surgical correction of a RDA (Table 4), it is possible that VI is not a consequence of abomasal volvulus in some cases. Simple RDA should have a prognosis similar to that of LDA and should not cause lesions inducing a VI-like syndrome (1,5). This could indicate that stoppage of pyloric outflow could be concomitant with or even the cause itself of RDA for some cows. It is also possible that AV was misdiagnosed as RDA in these cases. Due to the small number of cases and the high fatality rate, the prognosis of each form of GDRVI could not be determined in this study. However, as peritonitis can be prevented and treated by antimicrobial therapy, it should be ruled in or out in a cow developing clinical signs compatible with VI after abomasal dilation. Other studies are needed to assess that the prognosis of cases following RDA/AV is different, when peritonitis is associated with a VI-like syndrome. The type of vagus nerve lesions observed could be associated with the prognosis (29). In this study, neural lesions were always associated with vascular damages. This could indicate that even if regeneration occurs, it will not be associated with normal function (29). We were unable to document regeneration in vagus nerves in the cows studied (up to 5 d after surgical correction of the RDA/AV). If regeneration occurs in these cases, it is not known how much time it takes. However, since the long-term survival was only 4.5% in this study, it seems unlikely that function is regained in most cases. According to the lesions detected at necropsy, the main causes of clinical signs compatible with VI occurring after RDA/AV could be structural damage to the gastric wall, peritonitis, or a vagus nerve lesion. However, it was not always possible to link the observed lesions with the dilated gastric compartments. One explanation is that the dilation observed at postmortem is poorly correlated with the primary dysfunction and is not useful in defining it. Another hypothesis is that the syndrome observed in some cases is not the consequence but is unrelated to, or the cause of, the RDA/AV. The fact that severe ruminal dilation was detected statistically prior to surgery more often in cases that developed a syndrome similar to VI following surgical correction of RDA/AV could favor this hypothesis. When septic peritonitis is ruled out in a cow developing clinical signs compatible with VI after a surgically corrected abomasal dilation, treatment should aim to support the animal (ruminal fistula for decompression and nutritional and fluid support), but the prognosis is poor. However, aggressive antimicrobial therapy appears to be essential in all cases prior to and
following the surgical correction of RDA/AV. Prokinetics (metoclopramide, cisaprid, or others) are probably ineffective due to the presence of structural abomasal wall damage and the prevalence of nerve lesions. All these considerations need to be supported by other studies with Can Vet J Volume 41, October 2000
more cases and by physiological studies on the nerve lesions and abomasal wall.
Acknowledgments The authors wish to thank all members, students, and technicians of the Departments of Clinical Sciences and Pathology who were involved in the management of cvi these cases.
References 1. Trent AM. Surgery of the bovine abomasum. Vet Clin North Am Food Anim Pract 1990;6:399-448. 2. Fubini SL, Grohn YT, Smith DF. Right displacement of the abomasum and abomasal volvulus in dairy cows: 458 cases (1980-1987). J Am Vet Med Assoc 1991;198:460-464. 3. St-Jean G. Decision making in bovine abdominal surgery. Vet Clin North Am Food Anim Pract 1990;6:335-358. 4. Kumper H. Right displacement of the abomasum and abomasal volvulus in cattle. Part 1: Pathogenesis clinical symptoms and prognosis. Tierarzt Prax 1995;23:351-359. 5. Constable PD, St-Jean G, Hull BL, Rings DM, Hoffsis GF. Prognostic value of surgical and postoperative findings in cattle with abomasal volvulus. J Am Vet Med Assoc 1991; 199: 892-898. 6. Hjortkjaer RK, Svendsen CK. Right abomasal displacement in dairy cows: Clinical, clinical chemical and hemodynamic findings with special reference to prognosis and circulatory disturbance. Nord Vet 1979;31(Suppl. II): 1-28. 7. Smith DF. Abomasal volvulus. Bov Pract 1987;22:162-164. 8. Simpson DF, Erb HN, Smith DF. Base excess as a prognostic and diagnostic indicator in cows with abomasal volvulus or right displacement of the abomasum. Am J Vet Res 1985;46: 796-797. 9. Garry FB, Hull BL, Rings DM, Kersting K, Hoffsis GF. Prognostic value of anion gap calculation in cattle with abomasal volvulus: 58 cases (1980-1985). J Am Vet Med Assoc 1988;192:1107-1112. 10. Menard L, St-Pierre H, Lamothe P. Les affections de la caillette chez la vache laitiere au Quebec. II. Etude retrospective de 1000 cas. Can Vet J 1978; 19:143-149. 11. Poulsen JSD. Right sided abomasal displacement in dairy cows: pre- and post-operative clinical chemical findings. Nord Vet 1974;26:65-90. 12. Smith DF. Right-side torsion of the abomasum in dairy cows: classification of severity and evaluation of outcome. J Am Vet Med Assoc 1978;173:108-111. 13. Rebhun WC, Fubini SL, Miller TK. Vagus indigestion in cattle: clinical features, causes, treatments and long-term follow-up of 112 cases. Compend Contin Educ Pract Vet 1988;10:387-391. 14. Habel RE, Smith DF. Volvulus of the bovine abomasum and omasum. J Am Vet Med Assoc 1981;179 (5):447-455. 15. Garry FB. Diseases of the alimentary tract. In: Smith BP, ed. Large Animal Internal Medicine. 2nd ed. St. Louis: Mosby-Year Book 1996:830-834. 16. Radostits OM, Blood DC, Guay CC. Veterinary Medicine: A Textbook of the Diseases of Cattle Sheep Pigs Goats and Horses. 8th ed. London: Bailliere Tindall 1994:304-307. 17. Dyce KM, Sack WO, Wensing CJG. Textbook of Veterinary Anatomy. 2nd ed. Philadelphia: WB Saunders 1996:682-688. 18. Habel RE. A study of the innervation of the ruminant stomach. Cornell Vet 1956;46:555-633. 19. Barone R, Caillette. Anatomie Comparee des Mammiferes Domestiques. Marcy-l'Etoile: Laboratoire d'anatomie ENV Lyon 1976:367-373. 20. Fubini SL, Ducharme NL, Erb HN, Smith DF, Rebhun WC. Failure of omasal transport attributable to perireticular abscess formation in cattle: 29 cases (1980-1986). J Am Vet Med Assoc 1989;194:81 1-8 14.
Can Vet J Volume 41, October 2000
21. Kuiper R, Breukink HJ. Reticulo-omasal stenosis in the cow: differential diagnosis with respect to pyloric stenosis. Vet Rec 1986;1 19:169-171. 22. Rehage J, Kaske M, Stockhofe-Zurwieden N, Yalcin E. Evaluation of the pathogenesis of vagus indigestion in cows with traumatic reticuloperitonitis. J Am Vet Med Assoc 1995;207: 1607-1611. 23. Whitlock RH. Digestive diseases: vagal indigestion. In: Howard JL, Smith RA, eds. Current Therapy. Food Animal Practice. 4th ed. Philadelphia: WB Saunders 1998:517-527. 24. Blikslager AT, Bristol DG, Hunt EL. Abomasal impaction in cattle. Compend Contin Educ Pract Vet 1993;15:1571-1575. 25. Hoflund S. Investigations of functional defects of the ruminant stomachs caused by damage to the vagus nerve. Sven Vet Tidn 1940;45 (Suppl). 26. Radostits OM, Blood DC, Guay CC, eds. Diseases of the alimentary tract-II. In: Veterinary Medicine: A Textbook of the Diseases of Cattle Sheep Pigs Goats and Horses. 8th ed. London: Bailliere Tindall 1994:284-288. 27. Garry FB, Hull BL, Rings DM, Hoffsis GF. Comparison of naturally occurring proximal duodenal obstruction and abomasal volvulus in dairy cattle. Vet Surg 1988;17(4):226-233. 28. Cable CS, Rebhun WC, Fubini SL, Erb HN, Ducharme NL. Concurrent abomasal displacement and perforating ulceration in cattle: 21 cases (1985-1996). J Am Vet Med Assoc 1998;212: 1442-1445. 29. Summers BA, Cummings JF, de Lahunta A. Veterinary Neuropathology. St. Louis: Mosby-Year Book 1995:402-423.
The f11 shot is your best protection' against influenza. Talk to your doctor, nurse, pharmacist, local health unit or CLSC today. Get the vaccine. Not the flu. CA N AD IAN COALI TI O N FO R
N F L U E NZA I M M U N I ZATI O N
www. Inf1uenza. cpha. ca
785
