(viral, bacterial or parasitic), foreign bodies, previous surgery, adhesions, or neoplasia [2, 3, 6]. Often, no predisposing cause can be identified [2, 7]. Gastroesophageal intussusception has been reported to occur most commonly in young German Shepherd dogs (33% dogs in one study) and has been associated with esophageal dilation or megaesophagus [8]. Advanced imaging may be required to confirm a diagnosis and after appropriate emergency stabilization, surgical intervention is usually indicated.
Clinical Presentation
The main clinical signs associated with intussusception in dogs and cats are anorexia, lethargy and vomiting [2, 3, 5, 9]. Less commonly reported signs include diarrhea with or without blood, hematemesis and weight loss [2, 3, 5, 9]. Animals suffering from gastroesophageal intussusception may present with history of regurgitation and dyspnea [8]. The severity and type of clinical signs are partially dependent on patient factors, duration of the intussusception, and whether the obstruction is complete or incomplete.
Common physical exam findings associated with intussusception include dehydration and abnormal findings on abdominal palpation, such as pain, abdominal mass, or intestinal thickening and distention. Hypothermia may be a common finding in cats, as 40% of cats in one study presented with low body temperatures [3]. Some animals with intussusception may present with signs of shock, such as abnormalities in heart rate, pale mucous membrane color, and poor pulse quality [3, 5].
Diagnosis
In animals with a suspicion of intestinal Intussusception, careful abdominal palpation may reveal a tubular structure within the cranial or mid‐abdomen. Commonly reported bloodwork abnormalities include hyponatremia, hypochloremia, and hypokalemia [5, 9]. Other reported relevant clinicopathologic abnormalities in dogs include hemoconcentration, hyperlactatemia, hypoalbuminemia, and leukocytosis with neutrophilia [5, 6, 10]. Clinicopathologic findings will vary with location of the intussusception, duration and severity of clinical signs, as well as any concurrent disease processes at the time of intussusception. Lateral and dorsoventral abdominal radiographic projections may reveal a mass effect and evidence of obstruction (Figure 6.1). Gastroesophageal intussusception may be evident on radiographs as a mass effect in the caudal esophagus. Barium contrast material (orally or via enema) may confirm a diagnosis of intussusception and obstruction [11] but ultrasound provides a superior sensitive and specific method for accurate diagnosis [12, 13]. In transverse section, ultrasonographically the intussusception appears as a target like structure consisting of a hyperechoic or anechoic center surrounded by multiple hyper‐ and hypoechoic concentric rings (Figure 6.2). In longitudinal sections, the segment appears as multiple hyper‐ and hypoechoic parallel lines (Figure 6.3) [12, 13]. Color Doppler may be a useful method for predicting reducibility by detecting venous and arterial blood flow in the mesenteric vessels supplying the affected area, although adhesion formation may preclude reducibility even when blood flow is present [14]. To avoid misdiagnosis, multiplane scanning of the lesion is vital. Identification of a semi‐lunar or G‐shaped hyperechoic center of the target lesion, together with confirmation of an overall width greater than 8–9 mm of the concentric rings appear useful in supporting the diagnosis of intussusception [15].
Figure 6.1 Lateral radiographic projection of a cat with an obstruction and gastric dilation secondary to pylorogastric intussusception.
Figure 6.2 Transverse ultrasound image of small intestinal intussusception.
Figure 6.3 Longitudinal ultrasound image of small intestinal intussusception.
More recently, a report of dual‐phase computed tomography (CT) illustrated the superiority of this modality when compared with ultrasound in confirming the diagnosis of a lead‐point intussusception related to an intestinal carcinoid tumor in a dog [16]. The lead point refers to the abnormality in the intestinal anatomy that incites the intussusception. It might be especially prudent to consider dynamic CT in geriatric patients presenting for an intussusception to look for underlying neoplasia, as well as using it as a staging tool. Megaesophagus and aspiration pneumonia are frequent findings in dogs with gastroesophageal intussusception; thus, in cases where such intussusception is identified, or if there is evidence of abnormalities pertaining to the respiratory system (tachypnea, increased respiratory effort, hypoxemia, abnormal thoracic auscultation), thoracic imaging may be indicated.
Initial Stabilization
Thorough physical examination is essential to the establishment of an adequate resuscitation plan. Hemodynamic stability should be assessed, which is reflected in pulse quality, mucous membrane color, heart rate, level of consciousness, and body temperature, as well as difference in temperature between the trunk and the extremities. Blood pressure and lactate measurement are useful bedside tests that aid in assessment of perfusion. If a patient is assessed as hypoperfused and no obvious contraindications to fluid therapy exist, a fluid bolus of isotonic crystalloid at approximately 10–20 ml/kg can be administered intravenously. Perfusion parameters should be reassessed after the bolus is delivered and fluid therapy altered as needed.
If the patient is hemodynamically stable but is dehydrated, body weight, percent dehydration, and continuing losses should dictate the intravenous fluid rate. Dehydration should be corrected quickly (over one to four hours) to optimize the patient as an anesthetic candidate (Figure 6.4).
At the time of intravenous catheter placement, blood may be collected for initial evaluation, and should at a minimum include a packed red blood cell volume, total solids, and blood glucose. Ideally, venous blood gas, electrolytes, and blood lactate level should be sampled. At that time, blood can also be collected and submitted for a complete blood count and serum chemistry. Intravenous fluid choice can then be tailored to the individual patient's needs, and, if any acid–base or electrolyte abnormalities are present, they can be appropriately addressed prior to and during the surgical procedure. For example, if metabolic alkalosis is present due to vomiting and chloride sequestration in the gastrointestinal (GI) tract, the fluid of choice should be physiologic (0.9%) saline to provide chloride necessary to excrete bicarbonate and reestablish normal acid–base balance. Careful attention should be paid to sodium levels, as sodium has frequently been reported to be low in animals with intussusceptions [5–7]. If hyponatremia is present and the patient requires a fluid bolus, a fluid most isotonic to the patient should be administered to minimize sudden fluid shifts and deleterious neurologic sequelae of rapidly correcting hyponatremia. Unless a normal sodium level has been reported in the patient within 48 hours of presentation, it should be assumed that hyponatremia is chronic, and care should be taken not to raise the sodium level more than 8–10 mEq in 24 hours to avoid central pontine myelinolysis [17].