The acute abdomen (Proceedings)

Acute abdominal pain is often associated with a variety of disorders in small animals. Abdominal pain can be the result of many different underlying diseases processes, many of which can be life threatening. Clinical signs can range from abdominal distension, prayer-type postures, vomiting and diarrhea, to more serious findings such as collapse, hypovolemic shock, hypothermia, and difficulty breathing. Acute abdominal pain thus requires rapid and efficient diagnostic evaluation with proper treatment to facilitate patient survival.

Diseases causing severe abdominal pain can be categorized by the abdominal viscera:

Gastrointestinal

     √ Pancreatitis

     √ Gastric dilation or volvulus

     √ Mesenteric volvulus

     √ Intestinal obstruction

     √ Intussusception

     √ Gastrointestinal perforation

     √ Hemorrhagic gastroenteritis

     √ Parvovirus

     √ Neoplasia

Hepatic

     √ Trauma

     √ Neoplasia

     √ Abscess

     √ Cholelithiasis

     √ Cholestasis

     √ Biliary obstruction or stasis

Spleen

     √ Splenic torsion

     √ Neoplasia

Urogenital

     √ Rupture or leakage

     √ Prostatic abscess

     √ Testicular torsion

     √ Pyometra

     √ Uterine torsion or rupture

     √ Dystocia

     √ Obstruction

Pain associated with any such disease processes can be the result of inflammation of the abdominal viscera or the peritoneum. Inflammation can be secondary to infection, ischemia, distension or organ rupture or torsion. In addition, malperfusion or poor perfusion of the abdominal region can result in tissue hypoxia and subsequent organ failure.

Diseases causing acute abdominal pain can affect multiple organ systems, specifically the cardiovascular, respiratory, renal and neurologic systems. Physical evaluation of each system is paramount to successful therapy. Rapid stabilization techniques should be instituted as life threatening problems are identified.

The most common life-threatening problem associated with acute abdominal pain is hypovolemia or septic shock. Clinical signs of hypovolemia include dull mentation, pale mucus membranes, poor pulse quality, and a rapid heart rate. Signs of septic shock typically include a rapid capillary refill time, hyperemic or bright red mucus membranes, and bounding peripheral pulses. Aggressive fluid therapy is the initial treatment for either hypovolemic or septic shock. A large-bore cephalic catheter should be placed and blood samples obtained prior to fluid resuscitation. Initial laboratory analysis should include the hematocrit, total protein, dipstick BUN (AZO), blood glucose, electrolytes, and lactate. If a CBC cannot be performed in a timely fashion, a blood smear should be analyzed. Interpretation of the laboratory data can be summarized as follows:

Combination crystalloid and colloid therapy should be administered based on perfusion parameters such as blood pressure, heart rate, body temperature, capillary refill time, and mucus membrane color. Recommended fluid therapy guidelines for the treatment of shock is listed are listed as follows:

Note that rapid fluid administration for patients in hypovolemic or septic shock should not contain any additives such as potassium chloride or dextrose. Hypoglycemia is managed with a bolus of 0.5g/kg of intravenous dextrose diluted in a crystalloid suspension at a 1:10 ratio.

Triaging such patients also requires examination of the respiratory system, as aspiration pneumonia can occur in animals with acute abdominal pain. Abnormal lungs sounds will often be present, with dyspnea or hypoxia requiring supplemental oxygen administration. Thoracic radiographs should be obtained if pneumonia is suspected, with a bronchial lavage or transtracheal wash for culture and cytology once the patient is stabilized.

Once the patient is stabilized, an accurate and thorough patient history should be obtained. Duration of the abdominal pain, possible exposure to toxins or trauma, history of any dietary indiscretion, current drug therapy, vaccination status, and any relevant health problems should be addressed.

Revaluation of the patient after the triage phase is crucial. Physical examination should include lung sounds, respiratory effort, mucus membrane color, capillary refill time, patient mentation, and pulse quality. Laboratory evaluation of the PCV/TS, blood glucose, lactate, and electrolytes should be performed. Gentle palpation of the abdomen may help patient diagnosis; for example, organomegaly may indicate neoplasia, and bowel distension may indicate intussusception or foreign body. Pain localized to the right cranial quadrant of the abdomen is suspicious of pancreatitis. Obvious abdominal distension indicates either fluid or air accumulation; either a quick abdominal centesis or ultrasonic imaging can help identify the cause of the distension. Fluid can indicate hemorrhage, uroabdomen, or septic peritonitis. Cytology of the fluid should be immediately performed. Gas or air in the abdominal cavity is highly suggestive of gastric-dilation volvulus (GDV) and is a surgical emergency. Rectal examination should also be performed to identify melena, prostatomegaly, hematochezia, or possible ingestion of foreign material.

Diagnostic imaging, including radiographs and ultrasound, should be instituted after patient stabilization in order to provide proper therapy. Both lateral and ventral dorsal radiographs should be obtained, but keep in mind both patient comfort and stability. Ultrasound is the most valuable diagnostic tool, as imaging can detect phenomena that cannot be detected on radiographs or abdominal palpation. Areas of particular interest in the acute abdomen include fluid accumulation between organs, such as between liver lobes, between the body wall and the spleen, and the apex of the bladder. Pocketing of fluid is common among certain disease processes such as pancreatitis, wherein fluid is found in the right cranial quadrant near the duodenum. Retroperitoneal fluid accumulation can be indicative of hemorrhage or urethral leakage. Fluid pockets can be easily aspirated with ultrasonic guidance and cytology performed to facilitate patient diagnosis.

If ultrasonic imaging is not available, and abdominal effusion is suspected based on palpation and/or radiographs, an abdominal centesis can be performed for fluid retrieval and analysis. The abdomen should be clipped and prepped as if for a sterile surgical procedure. A four-quadrant technique is suggested to optimize the chances of obtaining free fluid for diagnosis. Either four open, 20 gauge needles are used to place through the skin and into the peritoneal cavity and allowed to accumulate fluid, or a syringe is attached to the needles and aspirated for fluid collection. The open needle method is preferred as the attachment of a syringe may prevent the capillary action of the needle from drawing small amounts of liquid into the needle hub. If abdominal disease is suspected despite a positive abdominal centesis, a diagnostic peritoneal lavage may be performed.

Diagnostic peritoneal lavage detects smaller amounts of fluid as opposed to the abdominal centesis. A fenestrated or multilumen dialysis catheter is placed into the peritoneal cavity after a surgical prep, an infusion of lidocaine into subcutaneous tissue around the umbilicus, and a small scalpel blade incision made just caudal to the umbilicus. 20ml/kg warm saline may be infused through the catheter to help facilitate fluid collection for diagnostic purposes. A sterile collection system can be added to allow all of the fluid to drain out of the abdomen. The catheter may be sutured in if additional lavage therapy is indicated.

Cytology of the abdominal fluid should be analyzed for inflammatory cells, bacteria, or vegetable fibers. Degenerate neutrophils and the presence of bacteria are considered a surgical emergency. In addition, abdominal effusion with a glucose of less than 50mg/dl, pH less than 7.2, a P02 less than 50mmHg, and a lactate greater than 5.0mMol/l is highly suggestive of bacterial presence. A high packed cell volume is suggestive of hemoabdomen, typically a result of trauma or rupture of an intra-abdominal neoplastic mass. However, abdominal bleeding can occur with liver disease, coagulopathies, or disseminated intravascular dissemination. Medical management includes stabilization with blood component therapy, and placement of an external bandage to increase intra-abdominal pressure to prevent tamponade. Abdominal wraps should not be placed in patients with respiratory deficiencies or suspected diaphragmatic hernias. Abdominal wraps should be removed slowly over a 4-6 hour period once the patient is stable and bleeding monitored via serial PCV/TS, prothrombin time, and platelet count. Surgery should be performed if the bleeding cannot be controlled.

Patients with suspected foreign bodies or other gastrointestinal obstructions may require radiographic barium contrast studies or fluoroscopy. If renal or ureter trauma is suspected, an intravenous pyelogram can be performed for diagnostic purposes. After survey radiographs and ultrasound are obtained, an iodinated contrast is injected intravenously, with radiographs taken at 0, 5, and 20 minutes apart. If lower urinary tract leakage is suspected, contrast cystography or urethrography can be performed by placement of a urinary catheter followed by injection of contrast dye. Leakage can be evaluated by visualization of the dye into the entire abdominal cavity as the dye leaks into the peritoneum.

In summary, the patient with an acute abdomen can present with multiple symptoms and in varying forms of stability from dehydration to hypovolemic shock. Basic principles and protocols of critical care should be applied to each patient for a successful outcome. Note that any portion of the abdomen can be a source of pain; thus, diagnostic procedures including patient history, physical examination, blood work, radiographs, abdominal ultrasound with possible contrast studies, abdominal centesis, or peritoneal lavage are essential in order to provide proper therapy.

References Available Upon Request