The farm animal service at St-Hyacinthe Veterinary School is a referring center for Eastern Canada bovine practitioners. Approximately 1000 cases are referred each year to the hospital. Amongst the clinician team, there are 2 Diplomates of the ACVIM and 1 Diplomate of the ACVS. The following concepts and description of the acute abdomen are the result of clinical experience and interaction between specialists. Many aspects discussed in the presented cases apply only in a teaching institution. Nevertheless, some hints and tips remain relevant for the bovine practitioner which is confronted with the field reality every day.
Certainly amongst the most challenging situations in bovine medicine, the acute abdomen can become a nightmare and result in difficult situations with client, especially in valuable animals. The acute abdomen represents both a diagnostic and therapeutic challenge. In some species, because of the cost and risks of surgery, the necessary medical work up is done in hopes of avoiding surgery. In the bovine, the cost and risk of a standing laparotomy is such that in many situations, it almost appears more economical to quickly move toward a surgical approach since both diagnostic and therapeutic purposes can be achieved simultaneously. "Where do you draw the line between being too conservative and being too aggressive?"
First Things First
What do you need to approach the case in a logical manner?
Theoretical background information: Excellent knowledge of the abdominal anatomy and good understanding of the pathophysiology of abdominal pain and the possible/probable causes
Good clinical skills: Recognition of need for immediate surgery and initiate necessary medical treatment prior to or during surgery.
Critical analysis: If surgery is postponed, determine when and how the monitoring will be performed to facilitate decision making and constant elaboration and revision of the differential list as other tasks are being realized.
Good client communication skills: Discuss with the client the prognosis and cost estimate, explain the risks of waiting and the risks of early intervention and communicate frequent summaries as the case evolves, particularly in critical situations.
A systematic approach based on adequate signalment and history, complete physical examination and judicious choice of ancillary tests represents the tools available to the clinicians.
Quick Review of Abdominal Pain in Ruminants
Abdominal pain may be a consequence of excess distension of a hollow viscus, spasm of intestinal smooth muscle, stretching of the mesenteric supporting structure, intestinal ischemia, or chemical irritation of the visceral or parietal peritoneum. Abdominal pain may be classified into visceral pain (hollow viscus and solid organs) and parietal pain (parietal peritoneum, abdominal muscles, rib cage). Pain sensation from the parietal peritoneum travel through the peripheral spinal nerves and usually localizes over the affected area. Since parietal pain is exacerbated by pressure and tension modification, the patient is reluctant to move and have a tonic reflex contraction of the abdominal muscles. In most cases, no active clinical signs of colic are recognized. Some pain fiber endings are located in the submucosa and muscle layers of hollow viscus (intestines, bladder), and in the capsule of solid organs (kidney, liver). Consequently, distention, forceful contraction or traction will produce pain in a hollow viscus. Capsule stretching will create pain in a solid organ. Visceral pain is associated with active manifestation of colic: kicking at the abdomen, treading with the rear feet, lying down or standing and stretching out. Visceral pain is transmitted via sensory fibers in the autonomic nerves and is often diffuse and difficult to localize.
Differential diagnosis for abdominal pain in ruminants may be first categorized into abdominal or extra-abdominal origin. Extra-abdominal causes include thoracic pain, laminitis and myopathy. The abdominal causes can then be sub-categorized into digestive or non digestive origin. The non digestive causes include pyelonephritis and uterine torsion while the classical abdominal digestive causes include abomasal torsion, intussusception and ileus.
When Surgery is the Only Option
If surgery is the only possible treatment offering a complete recovery and a long term positive outcome, there is no reason to delay the intervention. A good example is a case of abomasal volvulus where the definitive diagnosis is clinically achievable in some situations and where the rate of recovery using medical treatment alone is 0%. Unfortunately, in most acute abdomen, the certainty of the clinical diagnosis is not as great as in cases of abomasal volvulus and medical treatment could appear promising at first. This is why in all species, clinical and clinico-pathological criteria have been studied in hopes of defining an evidence-based approach.
I will share with you some of the criteria to which I give the most importance: 1) rapidity of the evolution since the first clinical sign, 2) severity of colic and its response to therapy if attempted prior to referral, 3) the severity of the abdominal distention, 4) the heart rate and the rectal palpation findings and 5) when available, the serum chloride and calcium are of great interest.
When Medical Treatment is Necessary
If immediate surgery is not necessary, there is time to establish a medical treatment that will either treat successfully the condition or improve the general condition of the patient. Also, diagnostic procedures should be considered and performed during the action of medical therapy. The goal of supportive therapy is to correct hemodynamic and metabolic imbalances, to control pain and to prevent or treat infection if suspected.
Crystalloid solutions (0.9% NaCl, Ringer's solution) are indicated initially to replenish fluid loss and improve the circulating blood volume. In our clinics, we often use a volume of 20 L of isotonic saline in adult cows (20 L IV in 60-90 minutes). Intravenous administration of hypertonic saline provides a rapid resuscitation in dehydrated or endotoxemic ruminants (Constable, 1999). A rate of 4-5 mL/kg of hypertonic solution should be administered IV through the jugular vein over 4-5 minutes. In our clinics, unless the animal is unable to stand or showing clinical signs of acute blood loss, hypertonic solutions are not used routinely in case of acute abdomen. Ideally, correction of electrolytes imbalance should be based on laboratory results. Most patients with acute abdomen suffer of metabolic alkalosis associated with hypochloremia and hypokalemia. Hypocalcemia is common in dairy cattle with gastrointestinal diseases. Calcium ions are of particular importance in gastrointestinal motility. In our clinics, the intravenous solution used for the medical treatment of an acute abdomen is most often an isotonic saline to which calcium borogluconate is added. It is not unusual for a patient to receive 60 L over the first 24 hours.
Pain is a primary cause of gastrointestinal hypomotility. Gastrointestinal pain increases sympathic tone causing general inhibition of the gastrointestinal tract (Bueno, 1997)(Guyton and Hall, 2000b)(Malone and Graham, 2002). Peritoneal inflammation or irritation and associated pain is an initiatory factor of ileus in several species (Bauer, 2002) (Bueno, 1997). Consequently, analgesic and anti-inflammatory drugs are often considered in the management of the bovine acute abdomen. These drugs must be used with the complete knowledge of their possible side-effects. Non steroidal anti-inflammatory drugs (NSAIDs) may induce abomasal ulcers particularly in an anorexic patient. Analgesics may also alter clinical signs (pain, fever) used to decision making. Anderson and Muir report that based on clinical observation flunixin provides an excellent visceral analgesia (Anderson and Muir, 2005). In our clinical experience, flunixin and ketoprofen are both adequate to control visceral pain in cattle. Sedatives and analgesics such as xylazine, detomidine and medetomidine could also be used. In a cow with large intestinal obstruction, signs of abdominal discomfort disappear immediately after the administration of a single dose of xylazine (0.05 mg/kg, IV) for at least 1 hour (Steiner, 1994). Xylazine is reported to have significant effects on the gastro-intestinal tract in cattle, altering reticuloruminal and intestinal motility (Steiner, 2003). Because of the associated hemodynamic changes, these drugs must be used with caution in patients in arterial hypotension or/and in shock (Gross, 2001). In our clinics, ketoprofen is administered to virtually all cases of acute abdomen very shortly after initial assessment. When possible, the referral veterinarians administer the drug prior to referral.
Bacterial translocation from the intestines may occur in cases of mechanical or functional ileus secondary to bacterial overgrowth, inflammation and impairment of barrier function of the intestinal wall (Madl and Druml, 2003)(Bauer, 2002). There is no debate on the need of antimicrobial therapy prior to surgery however the duration of treatment post surgically remains to be determined. In human medicine, prolonged broad spectrum antibiotic therapy in case of surgical acute abdomen does not appear beneficial (Fabers, 1997)(Gleisner, 2004). Prevention of infective complication was not affected by prolonging the antibiotic course of treatment (Gleisner, 2004). In cattle with rumenotomy, there was no significant difference on post operative complications between animals that received only a single preoperative dose of antibiotic and those additionally treated for 7 days post surgery (Haven, 1992). In human medicine, the current recommendation is a single prophylactic antibiotic administration when there is no or minimal evidence of contamination and a 5 to 7 days regimen when infection is identified during the procedure (localized or diffused) (Gleisner, 2004). In our clinics, patients going to surgery in reason of an acute abdomen will receive antimicrobial prior to surgery and immediately after and then for a minimum of 3 days. The choice of antimicrobial is variable but the IV route is always the first choice.
The use of laxatives in cases of suspected gastrointestinal obstruction or ileus is at the least controversial since the intestines are already filled with gas and fluid. In human medicine, laxatives are frequently used for the treatment of postoperative ileus, however there is no study that could demonstrate their true benefit (Luckey, 2003). Braun et al. reported that the use of laxatives in the treatment of cecal disorders delays the time to first defecation (Braun, 1989). Magnesium hydroxide may induce metabolic alkalosis and hypermagnesemia (Kasari, 1990), increased ruminal pH (Smith, 2004) and decreased rumen microbial activity (Smith, 2004). We do not use laxatives since our population are exclusively referral.
Motility-modifying agents may be used in the management of gastro-intestinal disorders. Steiner reviewed the different prokinetics that can be used in ruminant medicine and their clinical implication (Steiner, 2003). In our clinics, we do not tend to use prokinetic in acute abdomen patients and rarely in the post surgical period.
Useful Diagnostic Procedures: I Need More Information!
Ancillary diagnostic tests mainly serve three purposes: assessment of the patient's immediate requirements, attainment of an etiological diagnosis and help determining prognosis. The following procedures are the ones we find most useful in the management of an acute abdomen patient.
Complete Blood Count (CBC)
Haematological profiles are useful for assessing hydration and for indicating the presence of inflammation. Of particular interest is the relationship between plasma protein concentration and PCV. An increased PCV combined to a normal to decreased plasma protein concentration often indicate an active secretion of protein-rich fluid into the peritoneal cavity. The severity of endotoxemia is also of importance since secondary ileus is commonly observed with acute endotoxemia. On the other hand, endotoxemia may develop secondary to an abdominal problem.
Serum Biochemistry Profile (SBP)
Most gastrointestinal impairment leads to sequestration of the high-chloride abomasal contents into the upper gastrointestinal system. Some degree of systemic hypochloremic hypokalemic metabolic alkalosis eventually develops in several situations. The diagnostic value of this finding is limited since it does not bring precise information on the possible etiology and has controversial value as a prognostic indicator. Serum calcium concentration is of great interest since it is commonly low in anorexic periparturient dairy cattle. It is so important in gut motility that we feel we cannot ignore even a marginal diminution.
Abdominocentesis and Peritoneal Fluid Evaluation
Abdominocentesis is a simple and practical procedure helpful to manage acute abdomen. However, one should remember some bovine particularities. Absence of peritoneal fluid does not rule out the possibility of peritonitis. A large volume of peritoneal fluid is abnormal. Normal bovine peritoneal fluid should be clear, with a specific density less than 1.016. Protein content should be less than 3 g/dl, although some authors have reported normal values up to 6.3 g/dl (the major part being albumin). Nucleated cells count should be less than 10 000 cells per µl, with a majority of macrophages. Lymphocytes, eosinophils and desquamated mesothelial cells may also be present. Neutrophils are rare. Periparturient cattle have significantly more peritoneal fluid with a lower protein concentration. When macroscopic examination is not diagnostic, cytological examination of the peritoneal fluid is useful. As an example, in some cases of lymphoma, abnormal lymphocytes may be observed in the peritoneal fluid. Very little is known on the most common bacteria isolated from acute or chronic peritonitis, however since Arcanobacter pyogenes is commonly isolated from abscesses in the bovine, one could assume that it may be of importance in chronic abcedative cases.
Medical Imaging: Ultrasound Examination, Laparoscopic Procedures and Cranial Abdominal Radiography
Ultrasound is used to image soft tissues of the abdominal cavity. The potential of this tool is enormous. The size and anatomic relationship of lesions may be delineated. Knowledge of the underlying anatomy is essential. Abscesses, tumors, large amount of free fluid and intussusceptions have been identified in our clinic using ultrasound.
Laparoscopic procedures are also of importance and allow visualization without the invasive procedure. This is a field in development and the future possibilities appear promising.
Radiology of the cranial abdomen is a useful diagnostic aid when traumatic reticuloperitonitis is suspected. It is however limited to reference centers with high quality equipment due to the difficulty to penetrate the depth and density of tissues involved.
When Surgery is Part of the Solution
Exploratory laparotomy is a valuable ancillary diagnostic procedure in ruminants. Information obtained from the physical examination and laboratory data is often indicative of a diagnosis but does not provide a specific cause. Cattle are particularly amenable to exploratory surgery as the procedure is performed standing and with care towards asepsis is associated with little complications. The approach for exploratory celiotomy is determined by the suspected location of the problem. Standing flank procedures are the least compromising to the patient. A squeeze chute with or without sedation, and a regional anesthesia (e.g., paravertebral) is usually required for beef cattle. Dairy cattle often only require a set of stocks and local analgesia.
"When to cut or when to wait" is not an easy decision and remains a challenge for most food animal practitioners. Optimal management depends of multiple factors, some of which are under the direct control of the veterinarian while others are totally independent. Complete physical examination and judicious use of ancillary tests remains the best ally. It is important to keep in mind that exploratory laparotomy is sometimes an economical option. However, to remember that it is not the only option to get to the final diagnosis is also relevant...
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