Study Notes on Gastric Dilatation-Volvulus (GDV)

Gastric Dilatation-Volvulus (GDV)

Objectives

  • Discussion of the proposed etiology of gastric dilatation and volvulus (GDV) and its risk factors.

  • Understanding the pathophysiology of GDV and reperfusion injury.

  • Determination of the most common type of gastric displacement and its determination during surgery.

  • Discussion and understanding of:

    • History of GDV

    • Clinical signs of GDV

    • Appropriate diagnostics

    • Initial stabilization

    • Treatment goals for GDV patients.

  • Characterization of the surgical principles and components of surgical management of a GDV patient.

  • Differentiation between the various gastropexy techniques and understanding their surgical principles.

  • Acknowledgment and recall of recurrence rates with and without gastropexy in patients undergoing this procedure.

  • Discussion of what a gastropexy can prevent and what it cannot prevent in post-operative GDV patients.

  • Understanding postoperative monitoring and management of GDV patients:

    • When to treat cardiac arrhythmias.

    • Most prevalent arrhythmias and the rationale for their treatment and methods used.

  • Discussion of reasons for postoperative death and prognosis for patients with GDV, including survival and mortality percentages.

Definition

  • Gastric Dilatation:

    • Distension of the stomach with fluid, food, and/or gas, leading to increased intragastric pressure.

  • Medical Dilatation (Dilation):

    • Enlargement of the stomach typically without rotation on its mesenteric axis (malposition/twisting). This condition may resolve spontaneously or with medical management.

  • Surgical Dilatation-Volvulus:

    • A life-threatening condition characterized by gastric distention and anatomical displacement (twisting) of the stomach on its long axis, requiring immediate surgical intervention.

Etiology

  • **Initial Conditions: (What comes 1st?)

    • Normal stomach

    • Primary Gastric Dilatation

    • Volvulus/GDV. Primary gastric dilatation can progress to volvulus, especially when gastric outlet obstruction or impaired eructation is present.

    • Dysfunction in: Gastroesophageal sphincter (GES) and pylorus, which can either prevent gas from escaping (eructation) or delay gastric emptying, leading to accumulation of contents.

Factors Contributing to Gastric Dilatation

  • Accumulation of:

    • Gastric HCl and carbohydrates, which can ferment and produce gas.

    • Salivary bicarbonate.

    • Gas primarily through aerophagia (swallowing air, often caused by nervousness, rapid eating, excitation).

  • Abnormal gastroesophageal function contributing to delayed gastric emptying, allowing ingesta and gas to accumulate over a longer period.

  • Diet:

    • Composition that includes a large volume of ingesta, high fat/oil content in food (which slows gastric emptying), and dry kibble that absorbs water and expands in the stomach, or foods that ferment readily.

  • Anatomical & Behavioral Factors:

    • Laxity of gastric ligaments (e.g., hepatoduodenal, hepatogastric, gastrosplenic), which typically anchor the stomach, allows for increased gastric mobility and potential rotation.

    • Deep-chested breed conformation (high thoracic depth-to-width ratio) provides more intra-abdominal space for the stomach to distend and rotate.

    • Post-prandial exercise leading to increased abdominal pressure, reduced gastric motility (atony), and subsequent dilatation.

Risk Factors

  • Dogs with first-degree relatives with a history of GDV are at significantly increased risk due to genetic predisposition.

  • Genetics:

    • Increasing age is a risk factor. Identification of genetic markers associated with gut microbiome that modulate immune functions suggests a complex genetic component.

  • Studies referencing genetic predisposition (Genes 2020, 11, 1313; doi:10.3390/genes11111313) highlight the heritable nature of GDV.

Dietary Precautions

  • Feeding Practices:

    • Divide daily food intake into multiple smaller meals rather than one large meal to reduce acute gastric distention.

    • Avoid rapidly consumed meals by using slow feeder bowls.

    • Avoid raised food bowls unless specifically indicated for certain dogs (e.g., megaesophagus), as some studies suggest they may increase GDV risk in predisposed breeds.

    • Supplements:

    • Fish or egg protein supplements can potentially decrease GDV risk, possibly due to their digestibility and effects on gastric emptying.

Impact of Exercise

  • Historically, vigorous exercise immediately after eating was considered a significant risk factor for GDV due to increased abdominal pressure and reduced gut motility.

  • Recent Findings:

    • New studies contradict this, suggesting no significant impact or even a decreased risk of GDV associated with moderate postprandial activity. However, it is still generally advised to avoid strenuous exercise directly after large meals.

Bloat Risk Ranking for Dog Breeds

  • Various breeds have varying risks of developing GDV, with Great Danes showing a 42% lifetime risk.

  • Notable breeds and ranks include:

    • Great Dane: High (e.g., Irish Setter, Weimaraner, Standard Poodle, German Shepherd)

    • St. Bernard: Moderate

    • Doberman Pinscher: Moderate to Low

    • Other breeds are ranked by their risk levels, indicating a greater predisposition in deep-chested breeds with a high thoracic depth-to-width ratio.

Conformation Factors

  • The increased thoracic depth to width ratio, characteristic of deep-chested dogs such as the Great Dane, provides more room for the stomach to swing and rotate, significantly contributing to the risk of GDV.

Temperament Influences

  • Feeding practices were suggested to be mitigated by the dog's temperament.

  • “Happy” dogs demonstrate a decreased risk of GDV, while heightened anxiety or aggression in pets correlated with an increased risk, possibly due to stress-induced aerophagia or altered gastric motility.

Implications of Splenectomy

  • Reports indicate that dogs undergoing splenectomy, particularly those at high risk for splenic torsion, may develop GDV secondarily. Possible mechanisms include the loss of the gastrosplenic ligament's stabilizing effect or changes in intra-abdominal space.

  • Study Findings:

    • 4% incidence of GDV in splenectomized dogs compared to 1.4% in controls.

    • Odds of developing GDV in previously splenectomized dogs are 5.3 times higher than those without this history.

Pathophysiology of GDV

  • Physiological Impact:

    • Thoracic and diaphragmatic impingements, resulting from the severely distended stomach pushing against the diaphragm, lead to decreased tidal volume, ventilation-perfusion mismatch (impaired respiratory function), gastric atony, and intestinal ileus.

    • Gastric ischemia and compromised blood flow to the portal vein occur due to vascular compression (splenic, gastric, and portal vessels) as the stomach rotates, leading to cellular death (necrosis), blood loss (from mucosal sloughing), and subsequent systemic shock from toxin release and hypovolemia.

  • Multi-Organ Systems Affected:

    • GI system (necrosis, hemorrhage), liver (hypoperfusion), respiratory (dyspnea), and cardiovascular systems (arrhythmias, shock) are all severely impacted.

    • Potential to develop SIRS (Systemic Inflammatory Response Syndrome) due to inflammatory mediator release, MOFS (Multiple Organ Failure Syndrome) if untreated, and DIC (Disseminated Intravascular Coagulation) from widespread endothelial damage and activation of the coagulation cascade.

Reperfusion Injury

  • Occurs when blood flow returns to previously ischemic tissues after detorsion, leading to:

    • Anaerobic metabolism product accumulation (e.g., lactic acid) during ischemia.

    • Release of cellular toxins (e.g., reactive oxygen species or free radicals, inflammatory cytokines) into circulation, followed by changes in capillary permeability, microvascular occlusions (especially in the stomach wall), and widespread endothelial damage, exacerbating systemic shock and organ damage.

Types of Gastric Displacement

  • Clockwise Rotation:

    • Most common displacement (80-90% of cases) characterized by the pylorus moving left along the abdominal wall and coverage by the greater omentum, which visually obscures the stomach when the abdomen is opened surgically. The fundus moves ventrally and to the right.

  • Counterclockwise Rotation:

    • Less common (<5% of cases), often associated with chronic GI signs before acute collapse. The pylorus moves to the right and ventrally, while the fundus moves to the left and dorsally, typically without omental coverage of the pylorus.

Clinical Signs

  • Acute Symptoms of GDV:

    • Restlessness (trying to get comfortable), hypersalivation (nausea/pain), 'praying' posture (bowing, head down, rear up, indicating abdominal pain), vomiting with nonproductive retching (attempting to vomit without producing anything), weakness, and collapse due to hypovolemic and obstructive shock.

Physical Examination Findings

  • Distended, painful, and tympanic (drum-like sound when tapped) abdomen upon palpation due to gas accumulation. Visible collapse, and varying degrees of shock upon exam—ranging from compensatory (tachycardia, strong peripheral pulses) to decompensatory (bradycardia, weak pulses, hypotension, pale mucous membranes) responses.

Initial Stabilization Procedures

  • Fluid Therapy:

    • Use of large bore cephalic or jugular catheters for rapid fluid administration (>60-90 mL/kg/hr crystalloids, or hypertonic saline to quickly expand intravascular volume). Aggressive fluid resuscitation is crucial to combat shock.

    • Continual monitoring of blood pressure (BP), heart rate, and EKG is crucial during stabilization to assess response to therapy and detect arrhythmias.

Diagnostics Conducted

  • Tests include CBC (complete blood count- looking for hemoconcentration, leukocytosis), biochemistry profile (electrolytes, organ function) and monitoring lactate levels (a marker of tissue hypoperfusion), with lower lactate indicating better outcomes.

  • Lactate Study Conclusions:

    • Trends in lactate levels in response to fluid resuscitation are a better indicator of patient prognosis and response to therapy than absolute initial values.

Treatment Goals

  • Objective to stabilize the cardiovascular, respiratory, and renal systems through:

    • Fluid resuscitation (restoring circulating blood volume).

    • Gastric decompression (relieving pressure on diaphragm and vessels).

    • Pain management (using appropriate analgesics like opioids).

    • Surgical intervention as needed for definitive repositioning and gastropexy.

Gastric Decompression Techniques

  • Methods to Decompress Stomach:

    • Orogastric intubation is preferred; involves carefully passing a lubricated, appropriately sized orogastric tube after sedation into the stomach to release gas and fluid. Ensuring tube size and placement accuracy is vital, as is monitoring for esophageal trauma.

    • Trocharization is utilized if intubation fails or to provide immediate relief; involves percutaneously inserting a large bore needle or catheter (e.g., 14-16 gauge) into the stomach, typically at the point of maximal tympany on the right side of the abdomen, but may involve greater risk of complications such as splenic laceration or peritonitis.

Surgical Management Principles

  • Conduct surgery as soon as stabilization allows, often following a staged approach where initial shock is managed before definitive surgical repair to ensure effectiveness and reduce mortality risk.

  • Immediate gastric repositioning is critical to restore blood flow to the stomach and spleen, prevent further necrosis, and reduce the likelihood of cardiac arrhythmias.

Techniques in Gastropexy

  • Abilities of Gastropexy Techniques:

    • Gastropexy creates a permanent adhesion between the stomach and the abdominal wall, significantly reducing recurrence rates of GDV (e.g., with incisional techniques achieving a 4% recurrence versus 50% without).

    • Various techniques such as laparoscopic (minimally invasive), circumcostal (stomach wall sutured to a rib), or belt loop (a flap of stomach muscle is passed through the abdominal wall) approaches show similar success rates (~95%) in preventing recurrence.

Prophylactic Considerations

  • Assessing at-risk breeds for prophylactic gastropexy during elective surgeries such as ovary-hysterectomy (OVH) or castration may be advisable. This preventative measure can significantly reduce the lifetime risk of GDV in predisposed dogs.

Postoperative Care Protocols

  • Immediate Instructions:

    • NPO (nil per os - nothing by mouth) for ~12-24 hours to allow gastric rest.

    • Monitor for cardiac arrhythmias continuously, especially for the first 24-72 hours, as they are common and can be life-threatening.

    • Maintain fluid and electrolyte balancing, manage pain with multimodal analgesia, and monitor for potential hypotension, which can increase mortality risk if not aggressively addressed.

Postoperative Complications & Monitoring

  • Arrhythmias are common, predominantly ventricular types (e.g., ventricular premature contractions, ventricular tachycardia), and may require monitoring and treatment, commonly occurring 12-36 hours post-GDV due to reperfusion injury and circulating myocardial depressant factors.

  • Significant mortality rates/reactivity are associated with various factors such as gastric necrosis (requiring gastrectomy, which seriously worsens prognosis), severe reperfusion injuries, sepsis, and unrecognized complications (up to 40-50% mortality for patients with preoperative arrhythmias).

Conclusion on Prognosis

  • Current survival rates for uncomplicated GDV cases range from 80% to 90%. Rates for associated complications, particularly cardiac arrhythmias, gastric necrosis (which can require partial gastrectomy and often splenectomy), or severe reperfusion-related risks, can significantly escalate mortality chances (38%-55% mortality in severe cases, or higher if gastric resection is needed).