MANAGEMENT OF THE ANIMAL WITH AN ACUTE ABDOMEN

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1 MANAGEMENT OF THE ANIMAL WITH AN ACUTE ABDOMEN Theresa W. Fossum DVM, MS, PhD, Diplomate ACVS Professor of Veterinary Surgery; Vice President for Research and Strategic Initiatives, Midwestern University, Glendale, AZ Animals that present with an acute abdomen may have a variety of underlying causes. Prompt diagnosis and therapy are key to reducing mortality and morbidity. This lecture used a cased based approach to detail management of animals presenting with an acute abdomen. PERITONITIS Any age, gender, or breed of dog or cat may develop peritonitis. It is particularly common in young animals that have perforating foreign bodies and in those that suffer abdominal injury, such as vehicular trauma or bite wounds. In a recent study of feline peritonitis, the median age of affected cats was three years with 74% being under five years of age. The history often is nonspecific. The animal may not show signs of illness for several days after the traumatic episode. Mesenteric avulsions often do not cause clinical signs of peritonitis for 5 to 7 days after the injury. Animals with traumatic bile peritonitis may be asymptomatic for several weeks after injury. Previous gastrointestinal surgery with associated dehiscence is a common historical finding in affected animals. Most animals are presented for treatment of lethargy, anorexia, vomiting, diarrhea, and/or abdominal pain. In cats with peritonitis, lethargy, depression, and anorexia may be more common presenting signs than abdominal pain or vomiting. Clinical signs of SEP are vague and non-specific (e.g., anorexia, vomiting, lethargy, weight loss, ascites, or all of these). Note: Be sure to evaluate any sick intact female dog for pyometra. Abdominal palpation often causes pain in affected dogs. The pain may be localized; but, generalized pain is more common, and the animal often tenses or splints the abdomen during palpation. Cats with septic peritonitis may be less likely to show evidence of pain on abdominal palpation than similarly affected dogs. Vomiting and diarrhea may be noted. Abdominal distension may be noted if sufficient fluid has accumulated. Pale mucous membranes, prolonged capillary refill times, and tachycardia may indicate that the animal is in shock. Dehydration and arrhythmias may also occur. Critically ill patients are often difficult to evaluate because they may have distracting injuries, be obtunded, have respiratory or cardiac failure, or other significant pathology that makes imaging difficult. CT has been determined to be the most useful diagnostic test for human patients with intraabdominal infections, with the exception of injuries of the biliary tract, where ultrasonography is generally more useful. The classic radiographic finding in animals with peritonitis is loss of visceral detail with a focal or generalized ground glass appearance. The intestinal tract may be dilated with air or fluid or both. Free abdominal air may occur due to rupture of a hollow organ and sometimes from infection with gasproducing anaerobic bacteria. Localized peritonitis may occur secondary to pancreatitis and can cause the duodenum to appear fixed and elevated ( sentinel loop ). Ultrasonography is useful for localizing fluid accumulation and assisting in obtaining a sample for analysis. Abdominal radiography and ultrasonography should be performed before diagnostic peritoneal lavage. Ultrasonography is also a valuable tool to evaluate the abdomen and surgical site in dogs. Most abdominal organs can be assessed Page 1 of 10

2 ultrasonographically 24 hours postoperatively; the limiting factor to evaluating affected animals is often pain. The most common laboratory finding in animals with peritonitis is a marked leukocytosis; however, the neutrophil count may be normal or low in some cases. The predominant cell type is the neutrophil, and a left shift is often but not always present. Other abnormalities may include anemia, thrombocytopenia, dehydration, hypoglycemia or hyperglycemia hyperbilirubinemia, and/or electrolyte and acid-base abnormalities. In a recent study of peritonitis in cats, lactate levels at the time of diagnosis were found to be a useful prognostic indicator. Non-survivors had a significantly higher blood lactate concentration than survivors in the aforementioned study median lactate at the time of diagnosis of septic peritonitis being 1.4 mmol/l in survivors and 3.5 mmol/l in non-survivors. The activity of circulating anticoagulant proteins (protein C and antithrombin) are often significantly lower in dogs with sepsis. C-reactive protein (CRP) and procalcitonin (PCT) are biomarkers that have been studied extensively in humans with septic peritonitis; PCT may be a superior biomarker to CRP in humans with sepsis. CRP has been most studied in dogs. Its usefulness in differentiating septic and non-septic conditions in small animals is uncertain and warrants further investigation. Bile peritonitis usually causes elevations of alkaline phosphatase, alanine transaminase, and total bilirubin concentrations. Little or no abdominal effusion may be seen in early cases of peritonitis. When effusion is present, abdominocentesis should be performed and fluid retrieved for analysis. Toxic degenerative neutrophils with intracellular or extracellular bacteria are indicative of bacterial peritonitis, as is plant material (from feces). Leukocyte morphology and the presence of bacteria are more important than leukocyte numbers. If total nucleated cell counts (TNCC) are performed, they should be done on fluid that has been placed in an EDTA (lavender top) tube. Bacteria are sometimes not seen in patients with bacterial peritonitis, especially if they have been receiving antibiotics. Differentiating between these effusions and those due to pancreatitis may be difficult because large numbers of degenerative white blood cells can be seen with both. A concentration difference greater than 20 mg/dl between blood and peritoneal fluid glucose concentration has been reported to reliably differentiate between septic peritoneal effusions and nonseptic peritoneal effusions in dogs and cats. Lactate concentrations greater 2.5 mmol/l were indicative of septic peritoneal effusions in dogs in another study; however, lactate concentrations were not accurate tests for detecting septic peritoneal effusions in cats. MEDICAL MANAGEMENT The goals of management of animals with peritonitis are to eliminate the cause of the contamination, resolve infection, and restore normal fluid and electrolyte balances. Food should be withheld if the animal is vomiting. Intravenous fluid replacement therapy should be initiated as soon as possible, particularly if the animal is dehydrated or appears to be in shock (in dogs, 60 to 90 ml/kg/hour; in cats, 40 to 60 ml/kg/hour). Synthetic colloids such as hetastarch and dextran 70) may be beneficial, particularly if vasculitis is present. Hypokalemia and hyponatremia may be present and require intravenous supplementation. Hypoglycemia is common in animals with systemic inflammatory response syndrome (used to be called septic shock), and glucose may need to be added to the fluids (i.e., 2.5% to 5% dextrose). Standard shock therapy should be initiated (i.e., fluid replacement and antibiotics). Bicarbonate therapy can be detrimental, and should only be used if acidosis is so severe as to be immediately life-threatening. Steroid therapy was once considered standard for SIRS patients. Then it was almost universally rejected. Currently, there appears to be a place for judicious use of steroids in septic patients in SIRS that are not responding to standard resuscitative therapy. Broad-spectrum antibiotic therapy should be initiated as soon as the diagnosis is made. Escherichia coli, Clostridium spp., and Enterococcus spp. are commonly isolated from animals with peritonitis, and ampicillin plus enrofloxacin typically is an effective antimicrobial combination. However, amikacin plus either clindamycin or metronidazole may be necessary. A second generation cephalosporin (e.g., cefoxitin), also has a reasonable Gram-negative and anaerobic spectrum. If renal compromise is present in an animal with a resistant bacterial infection, imipenem may be considered. The initial antibiotic therapy should be altered according to the aerobic and anaerobic culture results of lavage fluid or cultures Page 2 of 10

3 obtained at surgery. Septic peritonitis typically causes DIC, and plasma administration to replace clotting factors is probably one of the most beneficial therapies in such patients. Low-dose heparin increases survival and significantly reduces abscess formation in experimental peritonitis. The inflammatory process in peritonitis is associated with an outpouring of fibrous exudate that causes intraabdominal loculation of bacteria. The loculated bacteria are protected from host defense mechanisms, and antibiotics that may not be able to penetrate the fibrin clots. Although the exact mechanism of its beneficial effect is still unknown, heparin appears indicated in patients with severe peritonitis. Heparin may also be incubated with plasma and given to animals with disseminated intravascular coagulation (DIC). Low molecular weight heparin (enoxaprin, dalteparin) differs from unfractionated heparin in its mechanism of action and may be more effective; however, large clinical studies are lacking. SURGICAL TREATMENT Exploratory surgery is indicated when the cause of peritonitis cannot be determined or when bowel rupture, intestinal obstruction (e.g., bowel incarceration, neoplasia), or mesenteric avulsion is suspected. Serosal patching and plication reduce the incidence of intestinal leakage, dehiscence, or repeated intussusception. Animals that require surgery and have peritonitis secondary to intestinal trauma (disruption of mesenteric blood supply, bowel perforation, chronic intussusception, foreign body) often are hypoproteinemic. The role that protein levels play in healing intestinal incisions is not understood. However, most surgeons are concerned that hypoproteinemic patients may not heal as quickly as patients with normal protein levels despite the fact that similar complication rates are typically seen among euproteinemic and hypoproteinemic animals. Most experimental evidence has shown that retardation of wound healing is only seen with severe protein deficiencies (less than 1.5 to 2 g/dl). Although the practice of lavaging the abdominal cavity of animals with peritonitis is controversial, lavage generally is indicated with diffuse peritonitis. Lavage should be done with care in animals with localized peritonitis to avoid dissemination of infection. When lavage is performed, as much of the fluid as possible should be removed, because fluid inhibits the body s ability to fight off infection, probably by inhibiting neutrophil function. Historically many different agents have been added to lavage fluids, especially antiseptics and antibiotics. Povidone-iodine is the most widely added antiseptic; however, its use may be contraindicated with established peritonitis. Furthermore, no beneficial effect of this agent has been shown in repeated experimental and clinical trials in animals. Although a great many antibiotics have been added to lavage fluids over the years, there is no substantial evidence that their addition benefits patients being treated with appropriate systemic antibiotics. Warmed sterile physiologic saline is the most appropriate lavage fluid. In a meta-analysis of human patients, it was determined that peritoneal lavage was of no benefit in people with severe pancreatitis despite isolated reports of its clinical benefit in some centers. Open abdominal drainage (OAD) may be useful for managing animals with peritonitis. Reported advantages include improvement in the patient s metabolic condition secondary to improved drainage, fewer abdominal adhesions and abscesses, and access for repeated inspection and exploration of the abdomen. Disadvantages include hypoalbuminenmia, hypoproteinemia, anemia, and nosocomial infections. With this technique the abdomen is left open, and sterile wraps are placed around the wound. The frequency of wrap changes depends on the amount of fluid drained and external soiling. Complications of open abdominal drainage include persistent fluid loss, hypoalbuminemia, weight loss, adhesion of abdominal viscera to the bandage, and contamination of the peritoneal cavity with cutaneous organisms. Because of the effort and time involved in OAD, it is less commonly performed; although with highly exudative effusions it may be more effective than closed-suction drainage. Nonetheless closedsuction drainage is often effective in dogs and cats with generalized peritonitis, particularly if the effusion is serous in nature, and it involves far less time and effort. Animals with peritonitis often are endotoxic and hypotensive. Small amounts of endotoxins are normally absorbed from the intestine and transported via the portal system to the liver where they are removed Page 3 of 10

4 and destroyed by hepatocytes. Hypotension in dogs is associated with intense portal vasoconstriction. This vasoconstriction causes breakdown of the intestinal mucosal barrier, allowing more intestinal endotoxin to be absorbed. If hepatic function is impaired, a common condition in septic animals, small doses of endotoxin that normally would be harmless may be lethal. Therefore, hypotension should be corrected before and prevented during and after surgery in animals with peritonitis. Animals with less than 4 g/dl total protein or 1.5 g/dl albumin may benefit from perioperative colloid administration. Colloids (e.g., hetastarch) may be given preoperatively, intraoperatively, or postoperatively for a total dose of 20 ml/kg/day (dog) or 10 to 15 ml/kg/day (cat). Colloids such as hetastarch are less apt to cause coagulation abnormalities than older products (e.g., dextrans). However, large volumes of either crystalloid or colloid are given, clotting factors may be diluted. Clotting profiles, PCV, and TS should be checked frequently, regardless of which volume replacement therapy is used, when treating severe dehydration, hypotension, fluid loss, and blood loss. Fresh frozen plasma should be considered when clotting tests are prolonged. Blood should be considered when PCV is in the low 20 s. PANCREATIC ABSCESSES Pancreatic abscesses are a collection of purulent material and necrotic tissue within and extending from the pancreatic parenchyma. Pancreatic pseudocysts are collections of pancreatic secretions and cellular debris enclosed within a wall of granulation tissue or fibrous sac that lacks an epithelial wall. Pancreatic pseudocysts have also been called pancreatic cysts. Pancreatic pseudocysts are a common complication of acute pancreatitis in human beings but are rarely diagnosed in small animals. They may be associated with recurrent bouts of pancreatitis or trauma. Fluid in the cysts is a combination of blood, pancreatic fluids, and enzymes. These are not true cysts because the fluid is thought to leak from damaged pancreatic ducts and vessels rather than being secreted by the lining of the cyst. Pancreatic pseudocysts may be incidental findings or may be associated with nonspecific abdominal signs, such as pain and vomiting. Complications such as infection, rupture, or acute hemorrhage may occur in people and are associated with a high mortality rate. Large pancreatic masses in symptomatic or asymptomatic animals may be pseudocysts or sterile abscesses; cancer is a much less common event. Do not recommend euthanasia solely on the basis of a radiographic finding of an abdominal mass. Pancreatic abscesses/pseudocysts probably arise after acute pancreatitis; therefore, the signalment of these animals closely parallels that of animals diagnosed with acute pancreatitis. Most animals are middle-aged or older, and dogs are more commonly affected than cats. Animals with pancreatic abscesses/pseudocysts may have a previous history of acute onset of anorexia, depression, diarrhea, or vomiting; some have previously been treated for gastroenteritis that probably was pancreatitis. Other clinical findings may include ataxia, anorexia, abdominal pain, or pyrexia. These patients may have dramatic acute signs, or vague, smoldering, chronic signs, or they may be asymptomatic. Typical findings with pancreatic abscesses/pseudocysts may include pain during abdominal palpation, depression, icterus, pyrexia, palpable cranial abdominal mass, or abdominal distention. Some animals may be weak and reluctant to stand. Pyrexia is an uncommon finding. However, some animals are asymptomatic. Diagnostic Imaging The most consistent finding with pancreatic abscess/pseudocyst on survey abdominal radiographs is an ill-defined increase in soft tissue density in the right cranial abdominal quadrant. If peritonitis is present, Page 4 of 10

5 a generalized increase in soft tissue opacity and loss of visceral detail in the right quadrant or throughout the abdomen may be observed. Abdominal ultrasonography is more sensitive and usually reveals a mass in the area of the pancreas. Gallbladder and bile duct distention may also be noted. Ultrasonography may also identify pancreatitis. Gastric outflow obstruction is rarely observed on contrast studies of the upper gastrointestinal tract. Ultrasonography is the best tool for identifying pancreatic abscess/pseudocyst; however, differentiation of pseudocysts from other fluid-filled masses is not possible without evaluation of the fluid. Percutaneous fine needle aspiration of masses is reasonable in dogs because of the extremely low incidence of septic pancreatitis in this species. Risk must be weighed against the advantage of a preoperative diagnosis. Resolution of pancreatic abscess/pseudocysts after percutaneous, ultrasound-guided drainage is possible. Hematologic and serum biochemical findings with pancreatic abscess/pseudocyst are inconsistent but may include leukocytosis, neutrophilia with or without a left shift, lymphopenia, or monocytosis. Serum biochemical abnormalities may include hyperbilirubinemia and high serum alkaline phosphatase caused by extrahepatic cholestasis, high alanine aminotransferase, hypocholesterolemia, hyponatremia, hypochloremia, and hypokalemia. Serum lipase and serum amylase are insensitive and nonspecific; they should not be requested. Bilirubinuria often is present. MEDICAL MANAGEMENT Pancreatic abscesses/pseudocysts have classically been considered surgical diseases. However, we now realize that in some patients they can be resolved with percutaneous drainage, and others (typically those fortuitously diagnosed on abdominal ultrasound for some other reason) may need no treatment. These lesions are almost invariably sterile in dogs, but septic abscesses can occur in cats. The mortality rate in human beings with pancreatic abscesses is nearly 100% when medical therapy without drainage is used; with surgical treatment, mortality has been reduced. Similar studies have not been reported in dogs or cats. Some pancreatic abscesses/pseudocysts may resolve spontaneously without therapy. SURGICAL TREATMENT Symptomatic dogs with abscesses or pseudocysts probably benefit from drainage procedures; however, many dogs with pancreatitis have hypoechoic areas in the pancreas that do not represent fluid accumulations that can be drained. Generalized, sterile peritonitis is present in some dogs with pancreatic abscess/pseudocyst; if septic peritonitis or pancreatitis is present, a thorough search should be made for a primary cause such as a perforated duodenum. On opening the abdomen, a mass is observed originating from the pancreas in the cranial portion of the abdomen. The mass may be firm and fibrotic or friable. Multiple adhesions to omentum and adjacent loops of small or large intestine often are present. These lesions can look malignant; however, a vast majority of pancreatic lesions and masses are inflammatory without malignancy, regardless of how bad they appear. Adhesions may be present if the lesion has ruptured and re-formed. If the abscess or pseudocyst is surgically resolved, omentalization is preferred over external drainage. PREOPERATIVE MANAGEMENT If clinically apparent pancreatitis is present, medical management should be initiated before surgery (percutaneous drainage may proceed if deemed important). A broad-spectrum antibiotic can be administered intravenously before surgery if sepsis is believed to be present, but this is seldom necessary. If infection is found by cytology or culture, then antibiotics should be used for at least 10 to 14 days postoperatively. Perform a midline abdominal laparotomy that extends from the xiphoid cartilage caudally to distal to the umbilicus. Gently explore the abdomen. Locate the pancreatic mass and obtain cultures of infected tissue. Gently break down adhesions in the intestine and omentum as needed to visualize the lesion. Preserve the pancreatic ducts, common bile ducts, and adjacent vascular structures during dissection. Débride necrotic or purulent areas of the pancreas using a combination of sharp and blunt dissection. Resect as much of the necrotic pancreas as possible without damaging adjacent blood vessels or tissue. Once the lesion has been débrided, place a piece of omentum in it and secure it with sutures. If possible, Page 5 of 10

6 loop the omentum through a tunnel in the pancreatic tissue and suture it back to itself. Determine common bile duct patency by gently expressing the gallbladder. If the common bile duct is not patent, catheterize the duct and try to obtain flow or perform a cholecystoenterostomy. Make sure you do not ligate the common bile duct. If generalized peritonitis is present, lavage the abdomen thoroughly with warm, sterile saline or lactated Ringer s solution. If peritonitis is present close the abdomen, insert a drain, or leave it open for drainage. POSTOPERATIVE CARE AND ASSESSMENT The patient should be treated for pancreatitis, as described previously. Antibiotic therapy should be continued if infection is found. Animals should be monitored postoperatively for signs of worsening inflammation. Clinical assessment of these patients (i.e., presence or absence of fever, abdominal pain, anorexia, vomiting, and icterus) is more important than the CBC or ultrasonographic appearance. Repeat operations may be required occasionally. Blood cultures are warranted if bacteremia is suspected. Pancreatitis is a potential complication of any surgery involving the pancreas. PROGNOSIS The prognosis in animals with inflammatory pancreatic lesions is guarded. Mortality rates appear to be higher with necrotic mass lesions of the pancreas and pancreatic abscesses than with pancreatic pseudocysts. Cats undergoing surgery because of extrahepatic biliary obstruction secondary to severe acute pancreatitis that does not respond to medical management may have a good prognosis. Postoperative complications that have been described include progression of diabetes mellitus, septic peritonitis, local gastrostomy tube stoma inflammation, local gastrostomy tube stoma infection, and mild dermal suture reaction. SPLENIC NEOPLASIA The spleen is composed of a variety of tissues, and splenic neoplasia may arise from blood vessels, lymphoid tissue, smooth muscle, or the connective tissue that makes up the fibrous stroma. In a recent study of 249 dogs with splenic masses nearly half were found to have non-malignant disease. The most common splenic tumor in dogs is HSA; this tumor is more commonly diagnosed in large dogs (>27.8 kg) than small dogs. The pathogenesis of canine HSA may be related to mirna dysregulation. Other malignant tumors of the spleen in dogs include liposarcoma, fibrohistiocytic nodules, lymphoma, blastoma, and adenocarcinoma. Non-malignant masses include nodular hyperplasia, hemangioma, hematoma, and splenitis. Dogs with hemoperitoneum have a higher frequency of splenic neoplasia; similarly cats with hemoperitoneum commonly have abdominal neoplasms and HSA is the most common malignant splenic tumor in cats. NOTE: Incidentally found, nonruptured splenic masses or nodules without associated hemoperitoneum are most commonly benign. Surgery is warranted in these dogs as the prognosis is often fair or good. Canine splenic HSA may be seen in more than a third of dogs presenting with acute nontraumatic hemoabdomen. Because HSAs arise from blood vessels, they may form in several different sites in the body (e.g., spleen, right atrium, subcutaneous tissue, liver). The incidence of concurrent splenic and right atrial HSA is unknown, but was recently reported to be as low as 8.7%. Splenic HSAs are aggressive tumors that frequently metastasize to the liver, omentum, mesentery, and brain. Most dogs with HSA have gross evidence of metastatic disease on initial presentation. Splenic hematomas vary in size and are encapsulated, blood- and fibrin-filled masses that often are grossly and ultrasonographically indistinguishable from HSAs. Histologically, the cavities are surrounded by congestion, fibrosis, and areas of necrosis. They may result from trauma, may occur spontaneously, or may develop secondary to other diseases (e.g., nodular hyperplasia). Hemangiomas and HSAs may be difficult to distinguish histologically, but because the prognosis for these lesions is very different, it is important that they be accurately differentiated. Splenic masses with evidence of malignant neoplastic Page 6 of 10

7 endothelial cell proliferation can be easily identified as HSAs. However, multiple sections of a malignant mass may be studied without finding malignant cells. More importantly, a proliferation of plump endothelial cells that resemble neoplastic endothelium, but do not have evidence of mitotic activity, may be misdiagnosed as HSA. Hyperplastic nodules are also a common finding at necropsy. Mastocytoma, lymphosarcoma, myeloproliferative disease, and HSA are the most common neoplasms of the feline spleen. Splenic involvement is a consistent finding in cats with noncutaneous systemic mastocytosis. It is not associated with the feline leukemia virus (FeLV) and is primarily a disease of older cats. Mast cell infiltrates may be recognized in other organs (i.e., liver, lymph nodes, and bone marrow), and circulating mastocytosis may be present in 50% of affected cats. Splenomegaly is one of the most common gross findings in feline mast cell disease, which usually is diagnosed by finding neoplastic cells in the circulation or on bone marrow examination. Splenic HSA is less commonly recognized in cats than in dogs. Extra-abdominal metastasis of mast cell tumors, particularly to the myocardium, appears to be common. DIAGNOSIS Signalment. Splenic tumors may occur in large or small breed dogs. Dogs weighing less than 27.8 kg may be less likely to be diagnosed with HSA than larger dogs. There are conflicting reports on the effect of sex on disease prevalence. Canine splenic HSAs occur mainly in older animals. A predisposition is described for German shepherd and Labrador retriever dogs; boxers, Bernese mountain dog, German shorthaired pointers, and flat coated retriever may also have a high relative risk. No breed or sex predisposition has been reported in cats with HSA, and no obvious breed or gender predilection has been observed in dogs with nonangiogenic and nonlymphomatous splenic sarcomas. The mean age of occurrence of HSA in dogs is 8 to 13 years and from 8 to 10.5 years in the cat. History. Dogs with HSA may be presented because of abdominal enlargement, anorexia, lethargy, depression, and/or vomiting, or they may have acute signs of weakness, depression, anorexia, and hypovolemic shock caused by splenic rupture and hemorrhage. The clinical signs of splenic hematoma are similar, except that rupture leading to collapse and anorexia are less common because large masses frequently become apparent before rupture occurs. The most common clinical signs of disease with other types of sarcomas include diminished appetite, abdominal distention (as a result of peritoneal effusion or tumor mass or both), polydipsia, vomiting, and/or lethargy. In contrast to dogs with HSA, splenic rupture and hemorrhage are uncommon in dogs with nonangiogenic and nonlymphomatous splenic tumors. The most common presenting signs in cats are a palpable abdominal mass and anorexia. Physical Examination Findings The physical examination findings include lethargy, weakness, abdominal distention, and possibly splenomegaly or a splenic mass. If a splenic mass is palpated, it should be handled gently to prevent iatrogenic rupture. If abdominal effusion is present, it is not always possible to palpate the enlarged spleen. If rupture occurs, the animal may have signs of hypovolemic shock (tachycardia, pale mucous membranes, and weak peripheral pulses). Hemoabdomen is more commonly associated with HSA than with hemangioma or hematoma. In fact, dogs with nonruptured splenic masses or nodules, without associated hemoperitoneum, are more likely to have benign splenic lesions than malignant tumors. Some dogs with HSA will have cutaneous metastasis (dark reddish-purple mass). Sometimes a murmur is heard in patients with HSA in the right atrium; pericardial effusion due to such an HSA may cause muffled heart sounds or a jugular pulse. Diagnostic Imaging Abdominal masses usually are detected radiographically in dogs with HSA and nonangiogenic and nonlymphomatous sarcomas; however, peritoneal fluid may make locating the lesion in the spleen difficult. Masses involving the tail of the spleen are typically identified in the cranial ventral abdomen on the lateral radiographic projection. Thoracic radiographs (or thoracic CT) should be taken in animals with Page 7 of 10

8 splenic masses to detect pulmonary or thoracic neoplasia. Ultrasonography is more definitive than radiography in locating lesions in the spleen and in detecting abdominal metastases; however, differentiation of hematomas from neoplastic lesions is unreliable. Finding internal septation and encapsulation or apparent metastasis may help differentiate hematoma from HSA. Contrast-enhanced ultrasound can improve the characterization of focal or multifocal lesions of the spleen. The most useful criterion was the hypoechogenicity of the lesion in the washout phase combined with the presence of tortuous feeding vessels, which is observed in association with malignancy. Magnetic resonance imaging (MRI) may be a useful tool for differentiating benign and malignant splenic lesions in dogs. Computed tomography (CT) and positron emission tomography PET/CT may also be useful diagnostic imaging modalities for evaluation of focal canine splenic masses. Note Before surgery, it may be wise to obtain an echocardiogram of the heart to look for right atrial HSA in dogs with splenic masses. Laboratory Findings Neutrophilic leukocytosis may be present in some dogs. Mild or moderate anemia associated with chronic disease or hemoperitoneum also is common. Other hematologic abnormalities caused by HSA may include numerous nucleated RBCs (inappropriate numbers for the degree of anemia), Howell-Jolly bodies, poikilocytosis, acanthocytosis, schistocytosis, and/or thrombocytopenia. Dogs with hemoabdomen and HSA may have lower total solid concentrations and platelet counts on admission than dogs with other causes of hemoabdomen. Hemostatic disorders, particularly thrombocytopenia caused by DIC, are common in dogs with splenic tumors. Abdominal effusion generally is serosanguinous or hemorrhagic. Cytologic analysis of abdominal fluid rarely reveals tumor cells. Note Histologic diagnosis of splenic HSA may require review of several sections of the mass. MEDICAL MANAGEMENT Surgical resection is the mainstay of therapy in dogs with splenic HSA; however, postoperative chemotherapy or immunotherapy may prolong survival. Readers are referred to an oncology text for discussion of protocols and treatment regimens used in dogs with HSA. SURGICAL TREATMENT Splenectomy is the treatment of choice for animals with splenic hematoma and hemangioma. It is also the treatment of choice for animals with HSA in which evidence of extensive metastasis or other organ failure does not preclude the short-term benefits of removing the enlarged or ruptured spleen. Laparoscopy is a more sensitive method of detecting visceral HSA metastasis than imaging and can be done before surgery to decide whether surgery is appropriate for a given patient. Splenectomy may not be warranted in dogs with concurrent right atrial tumor; therefore careful preoperative examination (e.g., echocardiogram) of patients is necessary. Dogs with splenic lymphoma and clinical signs associated with massive splenomegaly, splenic rupture, and hemoperitoneum may also benefit from splenectomy. Gastropexy may be performed concurrently NOTE: Importantly, large splenic masses may be more likely to be benign than malignant. Dogs with benign splenic masses often have larger and heavier spleens than dogs with HAS. Preoperative Management Anemic animals may require blood transfusions before surgery, and they should be preoxygenated. An electrocardiogram should be performed to determine whether ventricular arrhythmias requiring preoperative or intraoperative therapy are present. Ventricular arrhythmias are present in some dogs with splenic masses, and anemia and hemoabdomen may be strongly associated with arrhythmia development. Hydration, electrolyte, and acid-base abnormalities should be corrected before induction of anesthesia, but it must be remembered that fluid therapy may result in worsening of previously mild anemia; the hematocrit must be re-examined shortly before anesthesia. Perioperative antibiotics (e.g., Page 8 of 10

9 cefazolin 22 mg/kg IV) may be indicated in some animals undergoing splenectomy. Surgical Technique Total splenectomy, rather than partial splenectomy, is warranted in animals with malignant and benign masses. After exploring the abdomen, exteriorize the spleen and place moistened abdominal sponges or laparotomy pads around the incision under the spleen. Double ligate and transect all vessels at the splenic hilus with absorbable (preferred) or nonabsorbable suture material or use a vessel sealant device such as the LigaSure. If possible, preserve the short gastric branches supplying the gastric fundus. As an alternative, open the omental bursa and isolate the splenic artery. Identify the branch or branches supplying the left limb of the pancreas. Double ligate and transect the splenic artery distal to this vessel (or these vessels) Laparoscopy has been used to remove splenic HSA; however, only surgeons proficient in interventional laparoscopy should attempt this procedure. A hepatic biopsy is likely to be of low-yield in a dog with HSA that has a normal appearing liver. In one study, no dogs with grossly normal livers had metastasis detected on liver pathology; however, nodules (be they multiple, dark-colored, and/or actively bleeding) were highly associated with malignancy. Note It is difficult to differentiate HSA from hematoma. Several samples of the mass must be submitted for histopathologic evaluation. Postoperative Care and Assessment Animals with splenic HSA should be closely observed for DIC after splenectomy. Fluid therapy should be continued until the animal can maintain its own hydration. The hematocrit should be monitored and blood transfusions provided if the PCV falls below 20%. Septic complications after splenectomy appear to be rare, and antibiotic therapy can be discontinued within 24 hours in most animals. Note Be prepared to treat cardiac arrhythmias, particularly if hemoabdomen or anemia or both are present. Prognosis Life expectancy of dogs with splenic masses, as one might expect, is determined largely on whether the mass is benign or malignant. In one study, the median life expectancy of dogs with benign and malignant lesions was 436 and 110 days, respectively. In the aforementioned study, the median life expectancy of dogs with HSA was 132 days; only 7 of these 18 dogs received adjunctive chemotherapy. Vascular tumors of intermediate malignancy, termed hemangioendotheliomas, appear to have a better prognosis than HSAs. Because most tumors of the spleen cannot be differentiated on gross inspection alone and survival of dogs with hematomas is much longer than that of dogs with HSA-associated lesions, surgery should not be denied dogs in which a definitive diagnosis of HSA has not been made. Survival of dogs with HSA may be influenced by clinical stage; dogs with hemoperitoneum at the time of diagnosis may have a shortened survival. Dogs that are anemic or thrombocytopenic at presentation, or that develop ventricular arrhythmias during surgery may have a worse prognosis. 29 Affected dogs typically die from uncontrolled bleeding from metastatic lesions and thrombotic and coagulation disorders. Although the histologic pattern of growth does not appear to affect survival, dogs with cavernous tumors have a shorter survival because of the increased propensity for these tumors to rupture and bleed. Median survival time of dogs with splenic HSA treated with splenectomy alone was 1.6 months in a recent study. When the entire follow-up period was considered, there was no significant difference in survival time between dogs treated with surgery alone and dogs treated with surgery and chemotherapy. However, during the first 4 months of follow-up, after adjusting for the effects of clinical stage, survival Page 9 of 10

10 time was significantly prolonged among dogs receiving any type of chemotherapy and among dogs receiving both conventional and metronomic chemotherapy. Over 50% of dogs with splenic lymphoma treated by splenectomy alone will survive at least one year, and animals surviving to a year are unlikely to die of this disease. Marginal zone lymphoma and mantle cell lymphoma were the most common histologic B cell lymphoma subtypes in one study. Pre- or postoperative adjuvant chemotherapy is unlikely to provide a survival benefit. Median survival time (MST) after splenectomy in cats was 197 days, with a range of 2 to 1959 days, in one study. Preoperative weight loss was the only factor that had prognostic significance for survival following splenectomy in the aforementioned study. For cats with weight loss, the MST was 3 days; for those without weight loss, the MST was 293 days. Page 10 of 10