Gastric Dilatation

Gastric dilatation (GD) is a pathological condition characterized by abnormal accumulation of gas, fluid, or foam within the stomach, leading to marked distension of the gastric lumen. It is a life-threatening emergency, particularly in large and giant breed dogs, and is often a precursor to gastric dilatation-volvulus (GDV), where the stomach rotates on its mesenteric axis, compromising blood supply and leading to ischemia, necrosis, and rapid cardiovascular collapse. In veterinary medicine, gastric dilatation is recognized as a distinct clinical entity but is frequently discussed in the context of GDV due to shared risk factors and pathophysiology. The condition can be classified as acute or chronic, with acute gastric dilatation being a medical emergency requiring immediate decompression and stabilization. Chronic gastric dilatation may be associated with delayed gastric emptying, pyloric dysfunction, or dietary factors. The systemic relevance of gastric dilatation extends beyond the gastrointestinal tract, as severe distension can impair venous return to the heart, reduce cardiac output, cause hypovolemic shock, and trigger systemic inflammatory response syndrome (SIRS) and multi-organ dysfunction.

The exact etiology of gastric dilatation is multifactorial and not fully understood. Primary causes include excessive ingestion of air (aerophagia) during rapid eating, especially in anxious or competitive eaters, and fermentation of ingested carbohydrates by gastric bacteria, producing gas. Dietary factors such as feeding a single large meal per day, feeding dry kibble that expands in the stomach, and diets high in fat or fermentable fibers have been implicated. In some cases, gastric dilatation may be secondary to mechanical obstruction, such as pyloric stenosis, gastric foreign bodies, or gastric neoplasia, which impede gastric emptying. Functional causes include gastric motility disorders, delayed gastric emptying due to autonomic neuropathy, or gastroparesis. In addition, certain medications, such as anticholinergics, can reduce gastric motility. In dogs, a genetic predisposition is suspected, with certain breeds having a higher risk. In cats, gastric dilatation is rare but can occur secondary to underlying diseases like inflammatory bowel disease or gastrointestinal lymphoma. Infectious agents are not primary causes, but bacterial overgrowth can contribute to gas production. Toxins, such as ingestion of certain plants or chemicals, may also cause gastric dilatation by inducing ileus or excessive gas production.

Gastric dilatation is predominantly a disease of dogs, with a strong breed predisposition. Large and giant breed dogs with deep, narrow chests (deep-chested) are at highest risk, including Great Danes, German Shepherds, Standard Poodles, Doberman Pinschers, Weimaraners, Irish Setters, and Bloodhounds. The incidence is higher in males than females, and older dogs (middle-aged to geriatric) are more commonly affected. A familial predisposition has been identified, with first-degree relatives of affected dogs having a higher risk. The condition is less common in cats, and when it occurs, it is often associated with underlying gastrointestinal disease. There is no significant geographic variation, but seasonal trends may be observed, possibly related to increased outdoor activity and dietary changes. The lifetime risk of GDV in large breed dogs has been estimated at 15-20%, and gastric dilatation is considered a precursor in many cases. In a study of Great Danes, the incidence of GDV was 42.9% in first-degree relatives of affected dogs compared to 24.5% in controls. The mortality rate for GDV ranges from 15% to 33% even with treatment, and gastric dilatation without volvulus carries a better prognosis if treated promptly.

The pathophysiology of gastric dilatation involves a cascade of events leading to severe gastric distension and systemic compromise. Initially, gas and fluid accumulate in the stomach due to aerophagia, fermentation, or impaired emptying. As intragastric pressure rises, the stomach expands, compressing the caudal vena cava and portal vein, reducing venous return to the heart. This leads to decreased cardiac output, hypotension, and hypovolemic shock. The gastric wall becomes ischemic due to increased intramural pressure and reduced blood flow, leading to mucosal damage, necrosis, and eventually perforation if untreated. In cases that progress to volvulus, the stomach rotates (usually clockwise when viewed from the caudal aspect) around the gastroesophageal junction and pylorus, causing complete obstruction of the cardia and pylorus, trapping gas and fluid. The splenic vessels may become twisted, leading to splenic congestion and infarction. Ischemia of the gastric wall triggers the release of inflammatory mediators, including cytokines and reactive oxygen species, leading to systemic inflammatory response syndrome (SIRS), endotoxemia, and multi-organ dysfunction. Reperfusion injury occurs when blood flow is restored, exacerbating tissue damage. Cardiac arrhythmias, particularly ventricular premature contractions, are common due to myocardial ischemia, electrolyte imbalances, and acid-base disturbances. The release of myocardial depressant factors from ischemic gastric tissue further compromises cardiac function.

Predisposing factors for gastric dilatation include both intrinsic and extrinsic elements. Intrinsic factors include breed conformation (deep-chested), genetic predisposition, age (older dogs), and male sex. Dogs with a history of gastric dilatation are at higher risk for recurrence. Extrinsic factors include dietary practices such as feeding one large meal per day, rapid eating, and using elevated food bowls, which have been associated with increased risk. Exercise immediately before or after meals may also contribute. Stress and anxiety, such as during boarding or competition, can lead to aerophagia. Concurrent diseases that impair gastric motility, such as inflammatory bowel disease, gastritis, or pyloric stenosis, increase susceptibility. Medications that reduce gastrointestinal motility, such as anticholinergics, can also predispose. In cats, risk factors include underlying gastrointestinal disease, such as inflammatory bowel disease or neoplasia, and possibly hairballs causing obstruction. Obesity may increase intra-abdominal pressure and contribute to gastric distension. Environmental factors, such as changes in routine or diet, may trigger episodes in susceptible individuals.

Clinical signs of gastric dilatation can be peracute, acute, or chronic. In peracute cases, the dog may collapse suddenly due to cardiovascular shock. Acute signs include non-productive retching, hypersalivation, restlessness, anxiety, abdominal distension (visible tympanic enlargement), and pain on palpation. The dog may assume a 'praying' position (front legs down, rear up) to relieve pressure. As the condition progresses, signs of shock develop: pale mucous membranes, prolonged capillary refill time, tachycardia, weak femoral pulses, and dyspnea. In chronic gastric dilatation, signs may be intermittent and include inappetence, weight loss, vomiting (often undigested food), and borborygmi. In cats, signs are similar but may be more subtle, with lethargy, anorexia, and vomiting. Physical examination reveals a tense, tympanic abdomen on percussion. In advanced cases, cardiac arrhythmias may be auscultated. If gastric rupture occurs, signs of peritonitis (fever, severe abdominal pain, and septic shock) may be present.

Differential diagnoses for gastric dilatation include: 1) Gastric dilatation-volvulus (GDV) - distinguished by radiographic evidence of pylorus displacement (e.g., 'double bubble' sign) and inability to pass a stomach tube; 2) Gastric foreign body - may cause similar distension but is often associated with vomiting and can be identified on radiographs or ultrasound; 3) Pyloric stenosis - chronic vomiting and delayed gastric emptying, confirmed by barium contrast studies or endoscopy; 4) Gastric neoplasia - may cause obstruction and distension, with mass lesions visible on imaging; 5) Intestinal obstruction (e.g., foreign body, intussusception) - may cause gastric distension secondary to ileus, but abdominal radiographs show dilated loops of small intestine; 6) Peritonitis - can cause ileus and abdominal distension, but systemic signs are more severe and imaging shows free fluid; 7) Splenic torsion - may present with abdominal distension and shock, but radiographs show a large spleen and gastric displacement; 8) Acute pancreatitis - can cause gastric dilation due to ileus, but serum lipase and pancreatic imaging are diagnostic; 9) Mesenteric volvulus - rare but causes severe abdominal distension and shock, with radiographic evidence of intestinal malposition; 10) Diaphragmatic hernia - may cause gastric displacement into the thorax, leading to respiratory distress and abnormal thoracic radiographs.

The diagnostic algorithm for gastric dilatation begins with immediate triage and stabilization. On presentation, assess vital signs (heart rate, respiratory rate, mucous membrane color, capillary refill time, pulse quality) and perform a rapid physical examination. If the patient is unstable, initiate intravenous fluid resuscitation with isotonic crystalloids (e.g., lactated Ringer's solution) at shock doses (90 ml/kg in dogs, 40-60 ml/kg in cats) and provide oxygen supplementation. Attempt gastric decompression via orogastric intubation or percutaneous needle decompression (trocarization) if intubation is not possible. Obtain orthogonal abdominal radiographs (right lateral and ventrodorsal) to confirm gastric distension and assess for volvulus. In GDV, the stomach appears as a large, gas-filled viscus with a 'double bubble' sign (two gas-filled compartments separated by a soft tissue band) and the pylorus is displaced craniodorsally. If radiographs are inconclusive, perform abdominal ultrasonography to evaluate gastric wall thickness, blood flow (Doppler), and the presence of free fluid. Blood work should include a complete blood count, serum biochemistry panel, blood gas analysis, and lactate measurement. Elevated lactate (>6 mmol/L) indicates poor perfusion and is a negative prognostic indicator. Electrocardiography (ECG) should be performed to detect arrhythmias. If the patient is stable and chronic gastric dilatation is suspected, further diagnostics such as barium contrast radiography, endoscopy, or CT may be indicated to identify underlying causes. Definitive diagnosis of GDV is made at surgery or via imaging showing malposition of the stomach.

Laboratory findings in gastric dilatation reflect the severity of systemic compromise. Hematology may show hemoconcentration (increased packed cell volume and total protein) due to dehydration, and leukocytosis with a left shift in cases of inflammation or necrosis. Serum biochemistry often reveals electrolyte imbalances, including hypokalemia, hyponatremia, and hypochloremia due to vomiting and sequestration of fluids in the stomach. Metabolic alkalosis is common initially due to loss of hydrogen ions in vomitus, but metabolic acidosis may develop with shock and tissue hypoperfusion. Blood gas analysis may show mixed acid-base disturbances. Elevated blood lactate (>6 mmol/L) is a marker of poor tissue perfusion and is associated with a worse prognosis. Liver enzymes (ALT, AST) may be elevated due to hepatic ischemia. Renal parameters (BUN, creatinine) may be increased due to prerenal azotemia. Cardiac troponin I may be elevated in cases of myocardial ischemia. In chronic cases, hypoproteinemia may be present due to malnutrition or protein-losing enteropathy. Urinalysis may show concentrated urine with casts and proteinuria due to prerenal factors. Specific biomarkers such as C-reactive protein (CRP) may be elevated in inflammatory states. In cats, feline pancreatic lipase immunoreactivity (fPLI) may be useful to rule out pancreatitis.

Imaging is crucial for diagnosis and management. Abdominal radiography is the primary modality. In gastric dilatation, the stomach is markedly distended with gas, often appearing as a large, air-filled viscus occupying the cranial abdomen. In GDV, the classic 'double bubble' sign is seen on the right lateral view, with the pylorus displaced craniodorsally and the fundus caudoventrally. The stomach may appear compartmentalized. On ventrodorsal view, the pylorus may be seen on the left side of the midline. Radiographs can also reveal free abdominal gas if gastric rupture has occurred. Ultrasonography is useful to assess gastric wall thickness (normal <5 mm in dogs), wall layering, and blood flow using Doppler. In GDV, the stomach may be fluid-filled, and the wall may appear hypoechoic due to edema. The spleen may be enlarged and displaced. Computed tomography (CT) provides detailed anatomical information and can accurately diagnose GDV, but is often not feasible in unstable patients. Endoscopy is not recommended for diagnosis of GDV due to the risk of perforation, but may be used in chronic cases to evaluate the gastric mucosa and pylorus. Fluoroscopy with barium contrast can assess gastric emptying and motility in chronic cases. Echocardiography may be indicated to evaluate cardiac function in patients with arrhythmias or underlying cardiac disease.

Cytology and histopathology are not typically performed for acute gastric dilatation, as the diagnosis is based on clinical and imaging findings. However, in cases where gastric neoplasia or chronic gastritis is suspected, fine-needle aspiration (FNA) of gastric masses or thickened wall may be performed under ultrasound guidance. Cytological evaluation of gastric aspirates may reveal inflammatory cells (neutrophils, lymphocytes, plasma cells) or neoplastic cells (e.g., adenocarcinoma, lymphoma). Histopathological examination of gastric biopsies obtained via endoscopy or surgery can identify underlying causes such as chronic gastritis, pyloric stenosis, or neoplasia. In cases of gastric necrosis due to GDV, histopathology of resected gastric tissue shows ischemic necrosis, hemorrhage, and inflammatory infiltration. Special stains may be used to identify infectious agents, such as Helicobacter spp. (Warthin-Starry silver stain). In chronic gastric dilatation, histopathology may reveal atrophy of gastric glands, fibrosis, or hypertrophy of the pyloric muscle.

Treatment of gastric dilatation is an emergency. The immediate goals are to decompress the stomach, restore cardiovascular stability, and correct electrolyte and acid-base imbalances. Intravenous fluid resuscitation is initiated with isotonic crystalloids (e.g., lactated Ringer's solution) at a shock dose of 90 ml/kg in dogs and 40-60 ml/kg in cats, administered as a bolus over 15-30 minutes, followed by a maintenance rate (5-10 ml/kg/hr) adjusted based on perfusion parameters. Colloids (e.g., hetastarch) may be considered in hypoproteinemic patients, but their use is controversial. Gastric decompression is performed via orogastric intubation: a well-lubricated stomach tube is passed to the level of the stomach, and gas and fluid are allowed to escape. If the tube cannot be passed due to torsion, percutaneous needle decompression (trocarization) using a large-bore needle (14-18 gauge) inserted through the skin into the stomach can provide temporary relief. After stabilization, surgical intervention is indicated if GDV is confirmed or if gastric rupture is suspected. Surgery involves derotation of the stomach, assessment of gastric wall viability, and gastropexy (e.g., incisional gastropexy) to prevent recurrence. Non-viable gastric tissue is resected. Postoperative care includes continued fluid therapy, pain management (e.g., opioids such as hydromorphone 0.05-0.1 mg/kg IV q4-6h), antiemetics (e.g., maropitant 1 mg/kg IV q24h), and gastroprotectants (e.g., omeprazole 1 mg/kg IV q12h). Antibiotics (e.g., ampicillin 22 mg/kg IV q8h and enrofloxacin 10 mg/kg IV q24h) are indicated if there is evidence of sepsis or gastric necrosis. Cardiac arrhythmias are monitored and treated if hemodynamically significant (e.g., lidocaine 2 mg/kg IV bolus followed by CRI at 50-80 mcg/kg/min for ventricular tachycardia). Nutritional support is initiated once the patient is stable, with small, frequent meals of a low-fat, easily digestible diet. In chronic cases, treatment of the underlying cause (e.g., pyloric stenosis surgery, dietary modification) is necessary.

The prognosis for gastric dilatation without volvulus is generally good if treated promptly. However, if it progresses to GDV, the prognosis is guarded to poor, with mortality rates ranging from 15% to 33% despite aggressive treatment. Negative prognostic indicators include: prolonged duration of clinical signs (>6 hours), elevated blood lactate (>6 mmol/L), gastric necrosis requiring resection, presence of cardiac arrhythmias, and development of peritonitis or sepsis. The survival rate for dogs with GDV that undergo surgery is approximately 80-85%, but drops to 50% or less if gastric necrosis is present. Recurrence of GDV is prevented by gastropexy, with a recurrence rate of less than 5% after surgery. In chronic gastric dilatation, the prognosis depends on the underlying cause; if a correctable lesion is found, the prognosis is good. Long-term management may be required for dogs with motility disorders.

Follow-up care is essential for patients recovering from gastric dilatation or GDV. Immediately postoperatively, patients are hospitalized for 24-72 hours for monitoring of vital signs, fluid balance, and arrhythmias. Serial blood work (CBC, biochemistry, blood gas, lactate) is performed every 12-24 hours until stable. ECG monitoring is continued for at least 24-48 hours postoperatively. After discharge, re-check examinations are scheduled at 7-14 days for suture removal and assessment of wound healing. A re-check at 4-6 weeks may include abdominal ultrasound to evaluate gastric wall healing and gastropexy site. Long-term management includes dietary modifications: feed small, frequent meals (2-3 times daily) of a high-quality, low-fat diet; avoid exercise for 1 hour before and after meals; and consider using a slow-feeder bowl to reduce aerophagia. Owners should be educated on signs of recurrence and the importance of immediate veterinary attention. For dogs with chronic gastric dilatation, regular monitoring of weight, body condition, and gastrointestinal signs is recommended. If underlying conditions such as inflammatory bowel disease are present, follow-up with appropriate therapy and monitoring is necessary.

Pearls: 1) Always treat gastric dilatation as an emergency; rapid decompression and fluid resuscitation are life-saving. 2) In GDV, the stomach tube may not pass; do not force it, as it may cause perforation. 3) Measure blood lactate; a value >6 mmol/L indicates severe hypoperfusion and a worse prognosis. 4) Perform gastropexy during surgery for GDV to prevent recurrence; incisional gastropexy is the preferred technique. 5) Monitor for cardiac arrhythmias, especially ventricular premature contractions, in the first 24-48 hours postoperatively. 6) In chronic cases, consider underlying causes such as pyloric stenosis or gastric neoplasia. Pitfalls: 1) Do not delay surgery in confirmed GDV; prolonged anesthesia time increases mortality. 2) Avoid using corticosteroids for shock, as they are not effective and may worsen gastric mucosal injury. 3) Do not administer oral medications or food until gastric decompression is achieved and the patient is stable. 4) Do not overlook the possibility of gastric rupture; free abdominal gas on radiographs is an emergency. 5) Do not discharge the patient without owner education on preventive measures, as recurrence is possible without gastropexy.

Based on Plumb's Veterinary Drug Handbook, the following drug protocols are recommended for gastric dilatation and GDV: 1) Fluid therapy: Lactated Ringer's solution (LRS) or Normosol-R at shock dose (90 ml/kg IV in dogs, 40-60 ml/kg IV in cats) over 15-30 minutes, then CRI at 5-10 ml/kg/hr. 2) Analgesia: Hydromorphone (0.05-0.1 mg/kg IV q4-6h) or fentanyl (2-5 mcg/kg IV bolus, then CRI at 2-5 mcg/kg/hr). 3) Antiemetics: Maropitant (1 mg/kg IV q24h) or metoclopramide (1-2 mg/kg/day IV CRI). 4) Gastroprotectants: Omeprazole (1 mg/kg IV q12h) or pantoprazole (1 mg/kg IV q12h). 5) Antibiotics (if indicated): Ampicillin (22 mg/kg IV q8h) and enrofloxacin (10 mg/kg IV q24h) or cefazolin (22 mg/kg IV q8h). 6) Antiarrhythmics: Lidocaine (2 mg/kg IV bolus, then CRI at 50-80 mcg/kg/min) for ventricular tachycardia; if refractory, consider amiodarone (5 mg/kg IV over 15 minutes, then CRI at 10-20 mg/kg/day). 7) In cases of reperfusion injury, consider antioxidants such as S-adenosylmethionine (SAMe) (20 mg/kg PO q24h) or N-acetylcysteine (140 mg/kg IV loading dose, then 70 mg/kg q6h). 8) For chronic cases with delayed gastric emptying, metoclopramide (0.2-0.5 mg/kg PO q8h) or cisapride (0.5 mg/kg PO q8h) may be used. Dosages should be adjusted for renal or hepatic impairment, and drug interactions should be considered.

Key evidence-based literature on gastric dilatation and GDV includes: 1) A landmark study by Glickman et al. (1994) identified breed, age, and body conformation as risk factors for GDV in large breed dogs. 2) The same group (Glickman et al., 2000) demonstrated that gastropexy significantly reduces the risk of recurrence. 3) A study by Brockman et al. (1995) found that elevated blood lactate at presentation is a strong predictor of mortality in GDV. 4) The ACVIM consensus statement on GDV (2016) recommends early surgical intervention and gastropexy. 5) A study by de Papp et al. (1999) showed that prophylactic gastropexy is safe and effective in high-risk breeds. 6) Research on gastric motility and dietary factors has been summarized in a review by Monnet (2003). 7) Recent studies have investigated the role of inflammatory mediators and reperfusion injury, suggesting potential therapeutic targets. 8) A meta-analysis by Sharp et al. (2015) confirmed the benefit of incisional gastropexy over other techniques. 9) Guidelines for fluid resuscitation and management of shock in veterinary patients have been published by the Veterinary Emergency and Critical Care Society (VECCS). 10) The use of lidocaine for arrhythmias in GDV is supported by clinical experience and retrospective studies.