Acute Gastric Dilatation-Volvulus in Dogs

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Definition

Overdistention of stomach with gas, fluid, or ingesta with rotation of stomach on long axis.

Systems. Stomach can become devitalized, circulatory system compromised, and forms of shock can occur. Transient dysfunction of esophagus occasionally.

Genetic implications. Families are thought at greater risk if first-degree relative (sibling, offspring, parent) has had an episode.¹

Incidence/Prevalence. Common among large- and giant-breed dogs, especially purebreds. Relative risk 1.271 comparing size of dog (i.e., giant vs. large breed). A lifetime incidence of 24% in large breeds, 21.6% in giant breeds: life expectancy of 10 and 8 years, respectively.¹

Geographic distribution. Worldwide.

Signalment

Species. Dogs and rarely cats.

Breed predilection. See box below.

Age and Range. Dogs >5 years at much greater risk.¹ Giant-breeds tend to have signs at earlier age than large breeds.² Incidence increases in large/giant breeds with age.

Gender. Male dogs, even if neutered, are slightly more prone.

Causes

Appears multifactorial. Gastric dilatation presumed to result from impaired ability to empty gas from stomach and eructate when excessive gas-primarily swallowed air-accumulates. Dilatation may also result from delayed emptying of solid material.

Risk Factors

Personality traits. Temperament seems directly related. Fearful or "unhappy" personality and hyperactivity help precipitate GDV, as does stress.¹

Body condition. In giant but not large breeds, thin or lean body condition is a risk factor.

Anatomical factors. Deep, narrow thorax in some breeds,³ high abdominal depth in large/giant breeds, high ratio of thoracic depth to abdominal depth in large breeds, and high abdominal depth-to-width ratio in large/giant breeds are risk factors.^1,4 Some evidence links lax gastric ligaments to GDV.

Diet and associated events. Intake of large amount of food or liquids once thought to precipitate a GDV event. More recently speed of eating, eating from raised bowl, restricting water intake before and after eating have been implicated.¹ In large (but not giant) breeds, restricting exercise before/ after eating and moistening dry food increased risk.¹

Pathophysiology

Distention probably results in some degree of obstruction. Aerophagia, ingesta, gastric secretions, and eventually transudate from venous obstruction contribute to distention. Stomach usually rotates in clockwise direction when viewing animal from behind. Short gastric vessels may become twisted, or thrombosis or avulsion may occur. Avulsion can contribute to hemoabdomen within hours of initiation of GDV. Over time, increased intragastric pressure results in decreased blood flow to stomach wall/necrosis. Distention becomes so great that occlusion of caudal vena cava and portal vein occurs, decreasing venous return from abdomen to heart. Cardiac output, myocardial hypoxia, hypovolemic shock, and hypotension result, eventually leading to arrhythmia requiring treatment.

Cardiac and hypotensive conditions can lead to increased rate of endotoxin release by gram-negative bacteria. Bacteria and toxins cross mucosal barrier entering circulation via intestinal or diaphragmatic lymphatics or peritoneal surfaces. Concurrent portal vein occlusion decreases ability of reticuloendothelial system to handle toxins and translocated bacteria. Hypoventilation results from impaired diaphragmatic movement. Congestion, thrombosis, necrosis and torsion of spleen can occur. One report describes GDV occurring after splenic torsion in two dogs.⁵ Reperfusion injury may be associated with GDV as a result of significant tissue damage.

Signs

History. Recent self-limited, mild/moderate gastric distention; anorexia; or occasional vomiting common. Restlessness, retching, excessive eructation or flatulence possible. Environmental stress-transportation to/from dog shows, introduction of new animal or person into household, boarding, recent surgery, hospitalization.

Physical examination (See box above). Painful abdomen most commonly associated with distended stomach, but even after decompression, remains a factor and should be monitored/ treated aggressively.

Diagnosis

Definitive diagnosis. Based on history, clinical signs, and physical findings. Radiography (right lateral view recommended) confirms diagnosis but is always postponed until after patient is stabilized. Pylorus is seen dorsally, cranially, and to left of midline; fundus is ventrally displaced. Spleen often large and located in right dorsal position. Although rarely necessary, barium can be given orally if position of stomach questionable or foreign body suspected. Abdominal effusion (usually blood from torn short gastric vessel) may be noted. Free gas signals probable gastric perforation.

Dorsal displacement of the pylorus (black arrow) and ventral displacement of the fundus (white arrow) confirm GDV.

Differential diagnosis. See box below.

Laboratory Findings

Most abnormal laboratory data nonspecific for GDV. Hemoconcentration common. Hypokalemia most common electrolyte disorder. Acid-base status varies, but metabolic acidosis due to decreased circulating blood volume is most common. Metabolic alkalosis may result from sequestration of hydrochloric acid in stomach, but normal blood pH possible as acidosis/alkalosis offset each other. Plasma lactate concentration reported to predict gastric necrosis/survival.⁶ Concentration with gastric necrosis(6.6 mmol/L) significantly higher than without necrosis (3.3 mmol/L).

Treatment

Medical Management. Rapid decompression with orogastric tube. Moving animal to different positions may assist in passage of tube. If distention severe, pass tube quickly:I usually allow about 2 minutes before resorting to trocarization, usually done on left side with 18-gauge hypodermic needle. Left side should NOT be used if a "ping" is not heard at site of penetration; this could indicate presence of spleen. After trocarization, retry passing stomach tube; usually easily accomplished even if some distention remains.

Two large-bore intravenous catheters are placed in front legs concurrent with decompression, allowing rapid administration of balanced electrolyte solution (100 ml/kg the first hour) or hypertonic saline alone or with colloids, followed by crystalloids. Brief oxygen therapy routinely given via nasotracheal catheter during initial stabilization.

Surgical Management. Recurrence with medical management alone reported 75% to 80%; thus, definitive treatment with gastropexy highly recommended. Anatomical repositioning of stomach/spleen followed with right-sided gastropexy. I prefer incision gastropexy because of its simplicity, speed, predictable results.⁷ If spleen or stomach devitalized, splenectomy or partial gastrectomy, respectively, is done.

Medications

Give analgesic early (I prefer fentanyl, 0.005 mg/kg IV). If surgery anticipated, fentanyl transdermal patch placed. Broad-spectrum antibiotics indicated: combination therapy with enrofloxacin, 2.5 to 5.0 mg/kg IV, and ampicillin, 20 mg/kg IV, or cefoxitin alone, 20 mg/kg IV. Because of risk for megaesophagus/subsequent aspiration pneumonia with surgery, I recommend administering injectable metoclopramide (0.3 mg/kg SQ) and injectable antacid (famotidine, 0.5 to 1.0 mg/kg IV, or ranitidine, 0.5 to 2 mg/kg IV). This regimen starts before surgery, continuing for at least 24 hours. When mild/moderate gastric compromise detected during surgery (hyperemia or "blushing" of serosal surface of stomach), I do not recommend partial gastrectomy but continue systemic antacid another 7 to 10 days.

For pain, I continue injectable fentanyl for 24 hours after surgery until transdermal patch effective. Constant-rate infusion of ketamine preferred for managing pain, along with fentanyl as described in recent publication.⁸I administer loading dose of ketamine (0.5 mg/kg IV) after induction of anesthesia followed by infusion of crystalloid solution spiked with 60 mg ketamine/L as long as fluid rate is between 5 to 20 ml/kg/hr. This regimen continues for several days postoperatively.

Follow-Up

I monitor electrocardiogram (arrhythmias) for 24 to 48 hours; add potassium chloride (60 mEq/L) to crystalloid solution when fluid therapy decreased to maintenance levels. Antibiotics continue for 48 to 72 hours after surgery. If aspiration pneumonia occurs, antibiotics continue longer, with nebulization/coupage. Transtracheal wash usually indicated in these cases.

Dogs presenting again 3 to 7 days after surgery with distended abdomen, lethargy, fever, and vomiting are evaluated for perforation secondary to gastric erosion or ulcer. Dogs with postoperative esophageal signs (regurgitation, drooling) are treated for megaesophagus, often transient. I treat these cases aggressively with antacids; prokinetic agents, such as metoclopramide or cisapride (if available); and cytoprotectants (sucralfate suspension).

In General

Relative Cost*

Emergency care/stabilization:$1200 to $2000

Includes emergency call fees, fluid therapy, gastric decompression, narcotics/sedatives or short-acting anesthetic agents, laboratory costs, confirmatory radiographs, oxygen therapy, electrocardiographic monitoring, 2 to 3 days of critical care and case-management fees (including doctors' and technicians' salaries).

Including surgery: Additional $1500 to $2500

Includes all of the above with the addition of more electrocardiograph monitoring, preoperative medications, and postoperative sequelae management (disseminated intravascular coagulopathy, pain management, and aspiration pneumonia).

Prognosis

Fair/good with medical therapy alone short term but poor long term (high recurrence rate). With stabilization/surgical management (gastropexy) prognosis good (survival from 85% to 90%). Outcome worse if partial gastrectomy, splenectomy, or both are necessary. Based on gastric necrosis identified by plasma lactate concentrations, 98% without gastric necrosis survived; 66% with gastric necrosis.⁶ Even animals undergoing gastropexy occasionally have some abdominal distention afterward but usually self-limiting/rarely requiring veterinary care.

Future Considerations

Anticipate more studies designed to outline dietary-related factors/other conformational aspects associated with GDV. Predisposing factors identified thus far have been instrumental in identifying high-risk patients, thereby prompting many surgeons to perform prophylactic gastropexy using laparotomy, laparoscopy, or laparoscopic-assisted techniques.^9-11 Laparoscopic prophylactic gastropexy is a 1-day, "in-and-out" hospital procedure, so it seems prudent in dogs with partial or chronic volvulus to decrease the risk of a life-threatening episode.

Breeds at Greatest Risk for GDV

• Great Dane

• Saint Bernard

• Weimeraner

• Irish setter

• Golden retriever

• German shepherd dog

• Wolfhound

• Bloodhound

Common Signs of GDV

• Grossly distended stomach

• Abdominal pain

• Splenomegaly

• Circulatory shock (e.g., tachycardia, pale/muddy mucous membranes, prolonged capillary refill time, weak femoral pulses)

• Occasional Hyperpnea/dyspnea

• Depression (severe depression progresses rapidly to coma)

• Pulse deficits (cardiac arrhythmia)

Differential Diagnoses of GDV

• Gastric dilatation without volvulus

• Splenic torsion

• Splenic hemangiosarcoma

• Intestinal volvulus

• Diaphragmatic hernia

• Ileus from other causes, such as dysautonomia or peritonitis

Laboratory Findings in GDV

• Hemoconcentration

• Hypokalemia

• Metabolic acidosis and/or alkalosis

• Elevated plasma lactate concentration

TX ... at a glance

Medical Management

• Give oxygen via nasotracheal tube• Quickly decompress stomach (orogastric tube)• Conduct trocarization, if necessary• Place large-bore catheters in front legs• Administer electrolytes: 100 ml/kg in the first hour ORhypertonic saline alone or + colloids, then crystalloids• Administer analgesic: fentanyl 0.005 mg/kg IV• Give broad-spectrum antibiotics:-enrofloxacin 2.5-5.0 mg/kg IV and ampicillin 20 mg/kg IVOR-cefoxitin alone 20 mg/kg IV

Surgical Management

To preclude megaesophagus/ aspiration pneumonia, administer:• injectable metoclopramide0.3 mg/kg SQ and injectable antacid:-famotidine 0.5-1.0 mg/kg IV OR-ranitidine 0.5-2 mg/kg IV• Anatomically reposition stomach/spleen• Perform right-sided gastropexy

Postoperative Management

1. Continue injectable fentanyl for 24 hours after surgery, until patch becomes effective

2. Give constant-rate infusion ketamine, along with fentanyl, for pain management

3. After induction, give 0.25-0.50 mg/kg ketamine followed by 60 mg mixed in crystalloids, maintaining infusion rate at5 to 20 ml/kg/hr

4. Continue above regimen for several days after surgery.