Gastric Dilatation-Volvulus

Gastric dilatation-volvulus (GDV) is an acute, life-threatening surgical emergency characterized by abnormal accumulation of gas and/or fluid in the stomach (gastric dilatation) followed by rotation of the stomach around its longitudinal axis (volvulus), leading to complete or partial obstruction of the gastroesophageal junction and pylorus, compromised gastric blood supply, and rapid progression to cardiovascular shock, gastric necrosis, and death if untreated. The condition is most commonly seen in large and giant breed dogs with deep-chested conformations. The stomach typically rotates in a clockwise direction (when viewed from the ventrodorsal aspect) around the axis of the esophagus and duodenum, resulting in a 90 to 360-degree torsion. The spleen, which is intimately attached to the greater curvature of the stomach via the gastro-splenic ligament, often becomes displaced and may also torse, leading to splenic congestion and infarction. The disease is classified based on the degree of rotation (e.g., 90°, 180°, 270°, 360°) and the presence of gastric necrosis, which is a critical determinant of prognosis. Surgical intervention, specifically derotation and gastropexy, is the definitive treatment, and prompt recognition and stabilization are essential for a successful outcome.

The exact etiology of GDV is multifactorial and not completely understood. Anatomical predisposition is the most significant factor, with deep-chested, narrow-waisted breeds such as Great Danes, Weimaraners, Saint Bernards, Gordon Setters, Irish Setters, and Standard Poodles being at highest risk. The suspensory ligaments of the stomach (gastrohepatic, gastrosplenic, gastrocolic, and gastrophrenic) are relatively lax in these breeds, allowing excessive gastric mobility. Functional factors include aerophagia (excessive swallowing of air) secondary to stress, anxiety, or rapid eating, which leads to gastric dilatation. Gastric outflow obstruction at the pylorus or gastroesophageal junction can precipitate dilatation, and a 'one-way valve' mechanism at the lower esophageal sphincter may trap gas and fluid. Other proposed mechanisms include abnormal gastric motility, delayed gastric emptying, and altered myoelectric activity. Dietary factors such as feeding a single large meal per day, feeding dry food with limited moisture, and using elevated food bowls have been implicated, though recent studies have questioned the role of elevated bowls. Exercise after eating, stress, and a history of gastric dilatation (bloat) without volvulus are also risk factors. Genetic factors may play a role, as certain breeds have a higher incidence, and a familial predisposition has been suggested. Traumatic events, such as blunt abdominal trauma, are rare causes but can lead to gastric displacement. Iatrogenic causes are uncommon but may include prior abdominal surgery that alters gastric positioning.

GDV predominantly affects dogs, with a strong breed predisposition for large and giant breeds with deep thoracic conformations. The Great Dane has the highest lifetime risk, with an estimated incidence of 40-50%. Other high-risk breeds include Weimaraners, Saint Bernards, Gordon Setters, Irish Setters, Standard Poodles, Basset Hounds, and Doberman Pinschers. The condition is rare in cats and small breed dogs, though it can occur in any dog. Age of onset is typically middle-aged to older, with a mean age of 7-10 years, but it can occur in young adults. There is no clear sex predilection, though some studies suggest a slight male predominance. Body weight and conformation are significant: dogs weighing over 23 kg are at increased risk, and those with a thoracic depth-to-width ratio greater than 1.4 are particularly susceptible. The condition is more common in purebred dogs than mixed breeds. Activity level and temperament may also play a role, with anxious or hyperactive dogs being at higher risk. The mortality rate for GDV ranges from 15% to 40% even with prompt surgical intervention, and it is higher in cases with gastric necrosis, peritonitis, or delayed treatment. Recurrence rates are high (up to 80%) if gastropexy is not performed at the time of derotation.

The pathophysiology of GDV involves a cascade of events leading to severe cardiovascular compromise and tissue ischemia. Initially, gastric dilatation occurs due to accumulation of gas and fluid, which may be secondary to aerophagia, fermentation of gastric contents, or impaired outflow. As the stomach distends, it rotates, typically clockwise (when viewed from the ventrodorsal aspect), causing the pylorus to move ventrally and to the left, while the fundus moves dorsally and to the right. The rotation can be 90 to 360 degrees, and the spleen, attached to the greater curvature, is often displaced and may torse as well. The torsion creates a closed-loop obstruction at the gastroesophageal junction and pylorus, preventing decompression. Gastric distension leads to increased intragastric pressure, which compresses the gastric wall and impairs venous drainage. Venous congestion causes edema, hemorrhage, and ultimately arterial ischemia, leading to gastric wall necrosis, which can be focal or diffuse. The compromised gastric mucosa allows bacterial translocation and endotoxin absorption, contributing to systemic inflammatory response syndrome (SIRS) and sepsis. The distended stomach also compresses the caudal vena cava and portal vein, reducing venous return to the heart, leading to decreased cardiac output, hypotension, and hypovolemic shock. Additionally, the spleen may become congested and infarcted, releasing inflammatory mediators. Reperfusion injury occurs upon derotation, generating reactive oxygen species that further damage the gastric wall and other organs. Cardiovascular collapse, disseminated intravascular coagulation (DIC), and multi-organ failure can ensue if not rapidly corrected.

Predisposing factors for GDV can be divided into intrinsic and extrinsic categories. Intrinsic factors include breed and conformation: large and giant breeds with deep, narrow chests (high thoracic depth-to-width ratio) have increased risk due to laxity of the gastric suspensory ligaments. Age is a factor, with older dogs (7-10 years) being more commonly affected. Genetic predisposition is suggested by breed-specific incidence and familial clustering. Body weight over 23 kg is a risk factor. Gastric motility abnormalities, such as delayed emptying or altered myoelectric activity, may predispose to dilatation. Extrinsic factors include dietary practices: feeding one large meal per day, rapid eating, and dry food diets with limited moisture have been associated with increased risk, though recent evidence is conflicting. Elevated food bowls have been historically implicated, but a large study found no increased risk and possibly a protective effect. Exercise or vigorous activity immediately after a meal may increase risk. Stress and anxiety, such as during boarding or travel, can lead to aerophagia. A history of gastric dilatation (bloat) without volvulus is a significant risk factor for future GDV. Prior abdominal surgery, particularly splenectomy, may alter gastric positioning and increase risk. Trauma is a rare cause. Prevention strategies, such as prophylactic gastropexy in high-risk breeds, are recommended to mitigate these risks.

Clinical signs of GDV are acute and rapidly progressive. The most common presenting signs include non-productive retching or attempts to vomit, abdominal distension (tympanic on percussion), hypersalivation, restlessness, anxiety, and signs of abdominal pain (pacing, looking at the abdomen, groaning). As the condition progresses, dogs may exhibit weakness, collapse, pale mucous membranes, prolonged capillary refill time, tachycardia, weak femoral pulses, and signs of hypovolemic shock. In some cases, the stomach may not be visibly distended if the torsion is partial or if the dog has a deep chest. Respiratory distress may occur due to abdominal distension impinging on the diaphragm. Cardiac arrhythmias, particularly ventricular premature contractions, are common due to myocardial ischemia, electrolyte imbalances, and acid-base disturbances. On physical examination, the abdomen may be tense and painful, and a splenic mass may be palpable if the spleen is displaced. In advanced stages, signs of peritonitis (fever, severe pain, abdominal fluid) may be present if gastric rupture has occurred. The severity of clinical signs correlates with the degree of gastric distension, duration of torsion, and presence of gastric necrosis. Prompt recognition of these signs is critical for survival.

Differential diagnoses for GDV include other causes of acute abdominal distension and vomiting in dogs. These include: 1) Gastric dilatation without volvulus (simple bloat), which presents with similar signs but without gastric torsion; differentiation is made by radiography or response to decompression. 2) Splenic torsion, which can occur alone or with GDV; it may present with abdominal pain and distension, but radiography and ultrasound can differentiate. 3) Intestinal obstruction (foreign body, intussusception, neoplasia) can cause vomiting and abdominal distension, but the onset is usually less acute, and radiography may show obstructive patterns. 4) Peritonitis (septic or sterile) from other causes (e.g., pancreatitis, gastrointestinal perforation) can cause abdominal pain and distension, but systemic signs may be more prominent. 5) Acute pancreatitis can cause vomiting and abdominal pain, but abdominal radiography may show a mass effect in the right cranial quadrant, and serum lipase/PLI is elevated. 6) Mesenteric volvulus is rare but can cause rapid abdominal distension and shock; it is often fatal and diagnosed at surgery. 7) Gastric neoplasia (e.g., leiomyosarcoma) can cause chronic vomiting and weight loss, but acute distension is uncommon. 8) Diaphragmatic hernia can cause respiratory distress and abdominal organ displacement, but thoracic radiography will reveal the hernia. 9) Hepatomegaly or liver mass can cause abdominal distension, but the onset is usually chronic. 10) Urethral obstruction can cause abdominal distension due to a distended bladder, but the bladder is palpable, and the dog is unable to urinate. Definitive diagnosis of GDV is made by passing an orogastric tube (which may be difficult to pass due to torsion) and by abdominal radiography showing a 'double bubble' or 'hourglass' stomach shape, with the pylorus dorsally positioned and the spleen displaced.

The diagnostic algorithm for GDV begins with a rapid triage assessment, including evaluation of cardiovascular status (heart rate, pulse quality, mucous membrane color, capillary refill time, blood pressure) and respiratory status. If the dog is unstable, immediate stabilization with intravenous fluid therapy (e.g., isotonic crystalloids at shock doses, 20-30 ml/kg boluses) and oxygen supplementation is initiated. A brief history and physical examination are performed, noting the signalment, onset of signs, and abdominal palpation. An orogastric tube is passed to decompress the stomach; if resistance is met, it may indicate torsion, but passage does not rule out GDV. Abdominal radiographs (right lateral and ventrodorsal views) are the gold standard for diagnosis, showing a distended stomach with a compartmentalized appearance (double bubble) and the pylorus positioned dorsally and to the left of the fundus. If radiography is inconclusive, abdominal ultrasound can be used to assess gastric wall thickness, splenic position, and the presence of free abdominal fluid. Blood work, including a complete blood count, serum biochemistry, lactate, and blood gas analysis, is performed to assess for shock, electrolyte imbalances, and tissue hypoxia. A coagulation panel (PT/aPTT) and thromboelastography (TEG) may be indicated if DIC is suspected. Electrocardiography (ECG) is performed to monitor for arrhythmias. Once the diagnosis is confirmed, the dog is stabilized further, and surgical intervention is planned. In cases where the dog is too unstable for surgery, temporary percutaneous decompression (trocarization) may be performed, but this is a temporizing measure. The definitive diagnostic and therapeutic step is exploratory celiotomy, which allows direct visualization of the gastric torsion and assessment of gastric wall viability.

Laboratory findings in GDV reflect the severity of shock and tissue ischemia. Hematology may show hemoconcentration (elevated packed cell volume) due to dehydration, but with fluid resuscitation, PCV may decrease. Leukocytosis with a left shift may be present due to stress and inflammation. Thrombocytopenia may occur due to consumption or DIC. Serum biochemistry often reveals electrolyte imbalances, particularly hypokalemia, hyponatremia, and hypochloremia due to vomiting and sequestration of fluids in the stomach. Metabolic acidosis is common due to lactic acidosis from poor tissue perfusion, but metabolic alkalosis can occur if vomiting is prominent. Blood gas analysis may show a mixed acid-base disturbance. Serum lactate is a valuable prognostic indicator; elevated lactate (>6 mmol/L) is associated with gastric necrosis and a poorer prognosis. Liver enzymes (ALT, AST) may be elevated due to hepatic ischemia. Renal parameters (BUN, creatinine) may be elevated due to prerenal azotemia. Coagulation abnormalities, including prolonged PT/aPTT, elevated FDPs, and D-dimer, may indicate DIC. Inflammatory biomarkers such as C-reactive protein (CRP) and serum amyloid A (SAA) may be elevated. Synovial fluid analysis is not relevant in GDV. Urinalysis may show proteinuria or casts due to renal ischemia. These laboratory findings help guide fluid therapy, electrolyte replacement, and monitoring for complications.

Imaging is crucial for the diagnosis and management of GDV. Abdominal radiography is the primary imaging modality. On a right lateral radiograph, the stomach appears as a large, gas-filled viscus with a 'double bubble' or 'hourglass' appearance, created by the compartmentalization of the fundus and pylorus. The pylorus is typically positioned dorsally and cranially, while the fundus is ventral and caudal. The spleen may be displaced, often appearing as a soft tissue mass in the mid-abdomen. On a ventrodorsal view, the stomach is distended and may be seen crossing the midline, with the pylorus on the left side. Radiography can also help rule out other causes of abdominal distension. Abdominal ultrasound is useful in cases where radiography is inconclusive or to assess gastric wall thickness and viability. Ultrasound may show a distended stomach with a thickened, hypoechoic wall, indicating edema or necrosis. The spleen may be enlarged and have a 'bicortical' appearance if torsed. Free abdominal fluid may be visualized, suggesting gastric rupture or peritonitis. Color Doppler ultrasound can assess blood flow to the gastric wall and spleen. Computed tomography (CT) is not typically used in the emergency setting but can provide detailed anatomical information and assess gastric wall perfusion if available. CT with contrast can identify areas of gastric wall ischemia. Magnetic resonance imaging (MRI) is rarely used due to time constraints. Thoracic radiography may be performed to evaluate for aspiration pneumonia or other thoracic pathology. Intraoperative imaging is not typically used, but fluoroscopy can be used to guide orogastric tube placement. Overall, radiography remains the most practical and widely available imaging modality for GDV.

Cytology and histopathology are not commonly used in the diagnosis of GDV, but they are valuable in assessing gastric wall viability and identifying complications. During surgery, if gastric necrosis is suspected, a biopsy of the gastric wall may be taken for histopathological examination. Histopathology of necrotic gastric tissue shows coagulative necrosis, hemorrhage, edema, and inflammatory cell infiltration. The mucosa may be sloughed, and there may be evidence of thrombosis in the gastric vasculature. In cases of gastric rupture, cytology of peritoneal fluid may be performed; it typically shows a septic suppurative inflammation with degenerate neutrophils and intracellular bacteria, confirming peritonitis. Histopathology of the spleen, if splenectomy is performed, may show congestion, infarction, and necrosis. In chronic cases or if there is an underlying gastric neoplasm, histopathology of the mass is diagnostic. Immunohistochemistry may be used to differentiate tumor types. However, in the acute setting, histopathology is rarely performed due to the need for rapid surgical intervention. Postoperative histopathology of resected gastric tissue can provide prognostic information, as the extent of necrosis correlates with outcome. In summary, cytology and histopathology are adjunctive tools in GDV, primarily used to confirm necrosis or peritonitis and to rule out underlying pathology.

Treatment of GDV is a surgical emergency. The initial management focuses on cardiovascular stabilization and gastric decompression. Intravenous fluid therapy with isotonic crystalloids (e.g., lactated Ringer's solution) is administered at shock doses (20-30 ml/kg boluses, up to 90 ml/kg in the first hour) to restore perfusion. Colloids (e.g., hetastarch) may be used if hypoproteinemia is present. Pain management with opioids (e.g., hydromorphone 0.05-0.1 mg/kg IV) is initiated. Gastric decompression is attempted via orogastric intubation; if this fails, trocarization (percutaneous needle decompression) may be performed. Once the dog is stabilized, surgery is performed as soon as possible. The surgical approach is a ventral midline celiotomy from the xiphoid to the pubis. The stomach is located and derotated by grasping the pylorus and rotating it back to its normal position (usually counterclockwise). The spleen is assessed; if it is torsed or severely congested, splenectomy may be necessary. The stomach is evaluated for viability; areas of necrosis are resected via partial gastrectomy (gastric wedge resection or incisional gastropexy). A gastropexy is always performed to prevent recurrence. The most common technique is the incisional gastropexy, where a full-thickness incision is made in the pyloric antrum and a corresponding incision in the transversus abdominis muscle, and the two are sutured together. Other techniques include belt-loop gastropexy, circumcostal gastropexy, and tube gastropexy. The abdomen is lavaged with warm sterile saline, and a closed-suction drain may be placed if peritonitis is present. Postoperative care includes continued fluid therapy, electrolyte monitoring, antiarrhythmic drugs (e.g., lidocaine CRI 25-80 mcg/kg/min) if arrhythmias occur, and early enteral nutrition. Antibiotics (e.g., ampicillin 22 mg/kg IV q8h and enrofloxacin 10 mg/kg IV q24h) are indicated if gastric necrosis or peritonitis is present. Analgesia is maintained with opioids and NSAIDs once the dog is stable. The prognosis is guarded to good depending on the extent of gastric necrosis and the timeliness of surgery.

The prognosis for GDV is guarded to good, with reported survival rates ranging from 60% to 90% with prompt surgical intervention. The most significant negative prognostic indicators include the presence of gastric necrosis, which is associated with a mortality rate of up to 50%, and the need for partial gastrectomy. Other negative factors include delayed presentation (>6 hours), severe cardiovascular compromise at presentation, elevated serum lactate (>6 mmol/L), and the development of postoperative complications such as peritonitis, DIC, and cardiac arrhythmias. The extent of gastric necrosis is the most critical determinant of outcome; dogs with full-thickness necrosis have a much poorer prognosis. Splenic torsion and infarction also worsen the prognosis. However, with aggressive fluid resuscitation, timely surgery, and appropriate postoperative care, many dogs recover fully. Long-term prognosis is excellent if the dog survives the perioperative period, with a recurrence rate of less than 5% if a gastropexy is performed. Dogs that undergo prophylactic gastropexy have a very low risk of developing GDV. Overall, the prognosis is favorable for dogs that are stabilized and treated surgically without significant gastric necrosis.

Follow-up care for dogs after GDV surgery is critical for monitoring recovery and preventing complications. Immediately postoperatively, dogs are hospitalized for 24-72 hours for intensive monitoring. Intravenous fluids are continued until the dog is hemodynamically stable and eating. Electrolytes and acid-base status are monitored regularly. Cardiac monitoring via ECG is continued for at least 24 hours, as arrhythmias can occur up to 72 hours postoperatively. Pain management is provided with opioids (e.g., fentanyl CRI 2-5 mcg/kg/hr) and later NSAIDs (e.g., carprofen 2.2 mg/kg PO q12h) once oral intake is tolerated. Antibiotics are continued if indicated. The surgical incision is checked daily for signs of infection. Suture removal is typically 10-14 days postoperatively. Dogs are fed small, frequent meals of a bland diet initially, gradually transitioning to their regular diet. Activity is restricted for 2-4 weeks to allow healing. A recheck examination is scheduled at 2 weeks for suture removal and assessment of wound healing, and at 4-6 weeks for a full physical examination and to discuss long-term management. Radiographs may be taken at 4-8 weeks to assess the gastropexy site if needed. Long-term follow-up includes monitoring for signs of recurrence, which is rare if gastropexy was performed. Owners are advised to avoid risk factors such as feeding one large meal per day, vigorous exercise after eating, and stress. Prophylactic gastropexy may be recommended for high-risk breeds. Overall, follow-up is straightforward, and most dogs return to normal function within a few weeks.

Clinical pearls for GDV management include: 1) Always pass an orogastric tube before radiographs to decompress the stomach, but do not delay radiographs if the tube cannot be passed; torsion is likely. 2) In unstable dogs, perform trocarization to decompress the stomach before surgery; this can be life-saving. 3) During surgery, derotate the stomach gently to avoid reperfusion injury; some surgeons recommend slow derotation over several minutes. 4) Always perform a gastropexy to prevent recurrence; incisional gastropexy is the preferred technique due to its low complication rate. 5) Assess gastric wall viability carefully; use intraoperative Doppler or fluorescein to evaluate blood flow. 6) If gastric necrosis is present, resect the affected area and perform a partial gastrectomy; do not leave necrotic tissue. 7) Monitor for cardiac arrhythmias postoperatively; treat with lidocaine if ventricular arrhythmias are frequent or hemodynamically significant. 8) Provide early enteral nutrition to promote gastrointestinal healing. Pitfalls to avoid include: 1) Delaying surgery for extensive diagnostic testing; GDV is a surgical emergency. 2) Failing to stabilize the dog adequately before surgery, leading to intraoperative cardiac arrest. 3) Attempting to pass an orogastric tube forcefully, which can cause gastric rupture. 4) Incomplete derotation, leaving the stomach twisted. 5) Not performing a gastropexy, leading to a high recurrence rate. 6) Overlooking splenic torsion; if the spleen is torsed, it must be derotated or removed. 7) Inadequate lavage of the abdomen if gastric rupture has occurred, leading to peritonitis. 8) Discharging the dog too early, as arrhythmias can occur up to 72 hours postoperatively. By adhering to these pearls and avoiding pitfalls, the surgeon can optimize outcomes.

Perioperative drug protocols for GDV are based on Plumb's Veterinary Drug Handbook and current veterinary guidelines. Preoperatively, intravenous fluid therapy with isotonic crystalloids (e.g., lactated Ringer's solution) is administered at shock doses: 20-30 ml/kg boluses, up to 90 ml/kg in the first hour, then 10-20 ml/kg/hr. Colloids (e.g., hetastarch 10-20 ml/kg IV) may be used if hypoproteinemia is present. Pain management includes opioids: hydromorphone 0.05-0.1 mg/kg IV, or fentanyl 2-5 mcg/kg IV bolus followed by CRI at 2-5 mcg/kg/hr. Antibiotics are indicated if gastric necrosis or peritonitis is suspected: ampicillin 22 mg/kg IV q8h and enrofloxacin 10 mg/kg IV q24h, or cefazolin 22 mg/kg IV q2h during surgery. Postoperatively, analgesia is continued with opioids (e.g., fentanyl CRI) and NSAIDs (e.g., carprofen 2.2 mg/kg PO q12h or meloxicam 0.1 mg/kg PO q24h) once the dog is hemodynamically stable and eating. Antiarrhythmic therapy: lidocaine 2 mg/kg IV bolus (over 2 minutes) followed by CRI at 25-80 mcg/kg/min for ventricular arrhythmias; if refractory, amiodarone 5 mg/kg IV over 15 minutes, then CRI at 10-20 mcg/kg/min. Gastroprotectants: pantoprazole 1 mg/kg IV q24h or omeprazole 1 mg/kg PO q12h to reduce gastric acid secretion. Antiemetics: maropitant 1 mg/kg IV q24h if vomiting. Prokinetics: metoclopramide 1-2 mg/kg/day CRI to promote gastric emptying. Electrolyte supplementation: potassium chloride added to fluids at 20-40 mEq/L to maintain serum potassium >3.5 mEq/L. In cases of DIC, fresh frozen plasma 10-20 ml/kg IV may be administered. All dosages should be adjusted based on patient response and monitoring.

The literature on GDV is extensive, with landmark studies guiding current management. A seminal study by Glickman et al. (1994) identified breed, thoracic depth-to-width ratio, and body weight as major risk factors, leading to recommendations for prophylactic gastropexy in high-risk breeds. Another key study by Brockman et al. (1995) demonstrated that gastric necrosis is the most significant predictor of mortality, with a survival rate of 50% in dogs with necrosis compared to 90% without. The role of serum lactate as a prognostic indicator was highlighted by de Papp et al. (1999), showing that lactate >6 mmol/L is associated with gastric necrosis and poorer outcomes. Regarding surgical techniques, a prospective study by Rawlings et al. (2002) compared incisional, belt-loop, and circumcostal gastropexy, finding that incisional gastropexy has the lowest complication rate and is the preferred method. A meta-analysis by Monnet et al. (2003) confirmed that gastropexy significantly reduces recurrence rates. The use of prophylactic gastropexy in high-risk breeds is supported by a study by Ward et al. (2003), which showed a 90% reduction in GDV risk. Recent studies have focused on the role of inflammatory mediators and reperfusion injury, with experimental models showing that antioxidants may reduce gastric damage. Consensus guidelines from the ACVS and ECVS recommend early surgical intervention, aggressive fluid resuscitation, and routine gastropexy. Overall, the evidence supports a standardized approach to GDV management, with surgical derotation and gastropexy as the cornerstone of treatment.