DMN 2: Lesson 94 Pathogenesis of Gastric Dilation Volvulus in Dogs

What is GDV?

A life threatening disorder characterized by abnormal twisting of the stomach on its mesenteric axis, with subsequent gastric gas accumulation and distention 

Commonly referred to as “bloat” or “gastric torsion”

What are the characteristics of simple gastric dilation (simple bloat)?

Distention of the stomach alone

Can resolve on its own

Can be life threatening depending on the duration and severity

What are some characteristics of GDV (bloat with volvulus)?

Very rapid gas filled stomach twist upon itself

Can occur if simple bloat is not corrected

Life threatening if not corrected immediately

What is an intrinsic factor?

An internal characteristic of an animal that increases its likelihood of a disease or condition developing

What is an extrinsic factor?

An external or environmental factor that increases the likelihood of a disease or condition developing

What are some intrinsic factors of GDV?

Breed predisposition

Body conformation

Genetics

Age and Sex 

What are breed disposition intrinsic factors for GDV?

Large, deep-chested breeds

Irish setters, Standard poodles, great danes

What are body conformation intrinsic factors for GDV?

Dogs with a deep and narrow thoracic cavity increases the risk of stomach torsion

More room for stomach to move and rotate

German shepards

What are genetic intrinsic factors for GDV?

Family history of GDV suggests a hereditary component

What are age and sex intrinsic factors for GDV?

Middle-aged to older dogs have a higher risk

Males slightly higher risk then females

Previous medical history or existing GI abnormalities, a history of splenic torsion or GI surgeries 

What are some extrinsic factors for GDV?

Feeding practices

Food characteristics

Stress or anxiety

Timing and level of activity

Why does feeding practices influence GDV?

Eating one large meal per day instead of multiple small meals can cause delayed gastric emptying and lots of gas accumulation from a large meal

How does the food characteristics relate to GDV?

Rapid eating, swallowing air, or consuming large kibble pieces

Dry foods with oils or fats listed within first 4 ingredients

How does stress or anxiety influence GDV?

Boarding, travel, or changes in routine increasing nervous behavior —> increase sympathetic stimulation —> decrease motility

How does timing and level of activity influence GDV?

Vigorous exercise immediately before or after eating due to increased gastric motility and gas accumulation, which can contribute to stomach torsion

Pathogenesis of GDV

Gas accumulation in the stomach

Stomach rotation (gastric torsion/volvulus)

Obstruction of blood flow

Splenic displacement and vascular damage

Gastric wall ischemia and necrosis

Systemic circulatory collapse

Multi-organ failure and acidosis

Reperfusion injury and sepsis risk

What is the first change that occurs in the stomach during GDV?

Stomach fills with gas and twists on its axis, leading to displacement of the stomach and spleen

What is the second change that occurs in the stomach during GDV?

The twisting of the stomach causes mechanical obstruction of local blood vessels, particularly those supplying the stomach and spleen

What is the third change that occurs in the stomach during GDV?

Increased tension in the stomach walls results in drop in the gastric perfusion pressure —> leads to venous congestion as blood cannot drain properly 

What is the fourth change that occurs in the stomach during GDV?

The displacement of the stomach and spleen further contributes to avulsion of the gastrosplenic ligament —> resulting in hemorrhage

What is the fifth change that occurs in the stomach during GDV?

Due to obstruction, blood flow slows down and thickens, leading to clot formation (thrombosis) —> formation of clots can cause splenic infarction

What is the sixth change that occurs in the stomach during GDV?

The blood vessels within the stomach wall collapse, leading to ischemia in the gastric wall

What is the seventh change that occurs in the stomach during GDV?

If untreated, can result in necrosis and perforation of the stomach wall, leading to sepsis and shock 

How does GDV affect the cardiovascular system?

Significant decrease in venous return to the heart results in hypovolemic state —> decreased CO to organs resulting in organ hypoxia and tissue damage and death

Decreased myocardial perfusion and increases in inflammatory mediators —> cardiac arrhythmias —> VPC’s

How does GDV affect the respiratory system?

Gastric dilation and increased intra-abdominal pressure severely reduces the total thoracic volume —> prevents the caudal movement of the diaphragm and reduces lung volume —> poor ventilation

How does GDV affect the GI system?

Decreased perfusion —> ischemic necrosis —> necrosis and perforations —> eventually septic peritonitis

What area is most commonly affected by gastric necrosis?

The fundus 

How does GDV affect the lymphatic system?

The spleen is commonly affected due to its close relationship with the stomach. The spleen becomes congested. Shorts gastric arteries are avulsed because of splenic torsion.

How does GDV affect coagulation dysfunction?

DIC can occur, putting them at risk of complications associated with thrombosis in the early hypercoagulable state and hemorrhage in the subsequent hypocoagulable state

Body runs out of clotting factors and platelets

How does GDV cause decreased venous return to the heart?

Mechanical obstruction of blood flow to caudal vena cava and hepatic vein 

What happens when CO decreases?

Reduced tissue perfusion

Acidosis and metabolic imbalances

Hyperlactatemia

Oliguria to anuria (kidney failure)

How does reperfusion injury occur after de-rotation of the stomach/spleen?

If the stomach is surgically repositioned, reactive oxygen species are released —> reperfusion injury

What does reperfusion injury cause?

Endothelial damage

DIC

Systemic inflammatory response syndrome

Monitoring post surgical intervention of GDV

Close monitoring for at least 24-48 hours is critical after decompression due to the risk of life-threatening complications 

What are some early clinical signs of GDV?

Restlessness and pacing

Panting

Retching and/or vomiting

Hypersalivation

Mild to moderate distention of abdomen

Abdominal pain

What are some progressive signs of GDV?

Tachycardia

Rapid shallow breathing

Weak pulses

Dark red mucous membranes

severe abdominal distention

Depressed mentation, weakness/lethargy

Cardia Arrythmias

What are severe/late clinical signs of GDV?

Hypothermia

Coma

Collapse

Evidence of metabolic disturbances

White or blue MM

Why should signs of GDV be considered an emergency?

Stomach can perforate and spleen can die

Circulatory blood flow is compromised —> other organs at risk of dying

Respiratory system is affected —> poor ventilation

What can we use to diagnose GDV?

Signalment and physical exam findings

Blood analysis

Radiography

ECG

What does the order in which tests are performed depend on?

The condition of the patient

What should we do with severely affected GDV patients?

Stabilization and correction may be performed before or in conjunction with diagnostic tests 

When is radiography for GDV performed?

Only when the patient is stable

What is the key feature in radiographs that differentiates gastric dilation from gastric volvulus?

The location of the pylorus

What should we compare in radiographs for GDV?

Left and Right lateral views

What should volvulus look like on radiographs?

Displacement of the pylorus dorsally and to the left, creating a shelflike partition of soft tissue that appears to compartmentalize the stomach 

What are the therapeutic goals of GDV?

Restore and support circulation

Decompression of the stomach

Establish whether volvulus or simple dilation is present

Rapidly correction of the volvulus if present

Provide prophylaxis —> surgically or environmentally

What are the two treatment options for GDV?

1. Gastric decompression/deflation

2. Emergency surgery gastropexy

Gastric decompression/deflation

Stomach tube

Percutaenous trocarisation

Emergency surgery gastropexy for GDV

Incisional

Belt loop

Circumcostal 

Laparoscopic

How to prevent GDV?

Feed several small meals a day rather than one large meal

Avoid stress while feeding

Restrict exercise before and after meals

Do not use an elevated dog bowl

Do not breed dogs with a first degree relative that has a history of GDV

Consider prophylactic gastropexy of high-risk breeds

What happens if GDV is diagnosed and treated quickly?

Many dogs recover well with a 98% survival rate

What happens if gastric necrosis is present in GDV?

Guarded prognosis —> 66% survival rate

What does the poorest prognosis of GDV entail?

Evidence of DIC, sepsis, heart arrhythmias, and severe damage and/or perforation of the stomach