Acute abdomen describes multiple painful disorders and disease processes around or in the abdomen. Some of these are acutely life threatening, others can be self-limiting. Multiple causes have to be considered in the diagnostic work-up.

During the initial assessment, the following questions should be answered:

• Is the patient dying?
• What is the patient dying from?
• What can I do to improve the patient’s survival and well-being?
• Does the case require surgical or medical management?
• Does the patient require in-house management or is outpatient care also possible?

Initial assessment includes triage and secondary survey, including physical examination, minimum database, and diagnostic imaging.

Triage

Airway

Usually airways are not affected in patients presenting with acute abdomen. In some cases, vomited material or mucous can be found in the oral cavity. In these cases, the material should be removed.

Breathing

Intra-abdominal disorders may lead to pulmonary complications. Abdominal masses or gas filled organs cause compression of the diaphragm, which may lead to atelectasis, decreased tidal volume, polypnoea, and hypoxaemia. Patients with severe vomiting and salivation may aspirate vomited material or saliva. These can cause aspiration pneumonia. Additionally, inflammatory causes of acute abdomen, like severe pancreatitis, may lead to systemic inflammation and disseminated intravacular coagulation, which are predisposing factors for acute respiratory distress syndrome. Emergency treatment consists of adequate oxygen therapy.

Circulation

In most cases of acute abdomen, patients suffer from significant fluid losses including hypovolaemic and distributive shock. Clinical diagnosis focusses on the clinical shock parameters. Keep in mind that cats often react with hypothermia and bradycardia to shock.

Adequate fluid therapy is mandatory to keep the patient alive. Especially if the patient is in distributive shock, potentially decreased colloid osmotic pressure should be noted and therapeutically addressed. These patients may require colloids, plasma, or albumin substitution.

Other

Abdominal pain is a major finding. It should be actively looked for. Adequate analgesia should be initiated very early during the patient´s resuscitation and diagnostics. The author prefers pure µ-agonists, like methadone or fentanyl.

The use of antiemetics in the acute abdomen accompanied by vomiting and nausea is often controversial. Antiemetics improve the well-being of the patient. On the other hand, symptoms will be less severe, which may convince some owners and inexperienced vets not to work up the patient and send it home with symptomatic treatment. Therefore, initiation of patient work-up should be decided on the basis of the initial symptoms and not on the basis of the symptoms after antiemetics.

Secondary Survey

History

History should focus on duration of the symptoms, ingestion of foreign material, frequency of vomiting, consistence and colour of the material, pre-treatment, and or signs of pre-existing diseases.

Physical Examination

Physical examination aims to find the cause and sequelae of the acute abdomen. It should include assessment of volume and hydration status, temperature, rectal examination, and proper abdominal palpation. Be prepared to look for localized, painful structures especially in cats.

During physical examination, acute abdomen should be differentiated from spinal pain. A proper neurologic examination is helpful. Some patients with respiratory disorders show signs of abdominal discomfort during palpation. Respiratory diseases should be included in the differentiation.

Initial Blood Work

Initial blood work should consist of Hct, WBC count, electrolytes, lactate, glucose, and creatinine and/or urea. It is often helpful to include a differential WBC count and a blood gas analysis. Blood gas values help to access severity of hypoperfusion and may give further information on the underlying cause, e.g., hypochloraemic metabolic alkalosis is often seen in proximal intestinal obstruction.

Diagnostic Imaging

Diagnostic imaging should be initiated in the early course of the case work-up, because some diseases presenting as acute abdomen may require immediate surgical intervention. In recent years, point-of-care ultrasound has gained increasing recognition in the emergency world, not only for trauma patients. It helps in the diagnosis of free fluid, free gas, large masses, and intestinal obstruction. The choice between performing ultrasound or doing radiography depends on the clinician’s experience with the technology and the most likely underlying disease. The next lecture will focus on this topic.

Free Abdominal Fluid Analysis

Free abdominal fluid analysis is a large area of interest in the acute abdomen. It is often helpful in differentiating surgical indication from conventionally manageable diseases. Leukocytosis >10,000/µl, intracellular bacteria, karyolitic neutrophils, decreased glucose concentration, and increased lactate concentration in the fluid are indicative of a septic or severe inflammatory process as peritonitis or intestinal wall injury. A PCV in the fluid that is greater than the blood PCV indicates haemoabdomen. An increase of creatinine or bile in the fluid more than 2-fold compared to the blood concentration indicates uroabdomen or bile peritonitis.

Indications for surgical management of the non-traumatic acute abdomen are:

• Free air
• Septic peritonitis
• Bile peritonitis
• Necrotizing pancreatitis
• Foreign body, sub-ileus
• Volvulus
• GDV
• Non-traumatic, non-coagulopathic haemoabdomen
• Some neoplasia
• Abscess
• Uroabdomen with significant urinary tract perforation
• Torsion of abdominal organs such as spleen, liver, uterus, or intra-abdominal testes

Conservative treatment can be initiated for e.g.,

• Pancreatitis
• Moderately dilated intestines without obstruction
• Paralytic ileus
• Uroabdomen without significant urinary tract perforation

In-patient care should be considered if the patient suffers from severe systemic abnormalities as follows:

• Dehydration >8%
• Severe ongoing fluid losses
• Hypothermia
• Hypoglycaemia
• Severe hypokalaemia
• Moderate to severe pain
• Paralytic ileus

Regular reassessment of the patient is mandatory, especially in compensated intestinal diseases, peritonitis, sepsis, and diseases with fluid losses that may decompensate in a short time. This should not only include clinical examination but also imaging such as ultrasound and laboratory analysis.