Veterinary Clinical Medicine-I (General and Systemic)

PATHOGENESIS

Dilatation and displacement phase

• Abomasal atony occurs initially, resulting in the accumulation of fluid and gas in the viscus
• This leads to gradual disten­sion and displacement in a caudal direc­tion on the right side (dilatation phase).
• There is continuous secretion of hydrochloric acid, sodium chloride, and potassium into the abomasum. These causes gradual distension and the secreations do not evacuate into the duodenum.
• Leading to dehydration and metabolic alkalosis with hypochloremia and hypokalemia.
• Increased luminal pressure cause mucosal injury by local vascular occlusion and affect the prognosis.
• In com­plicated cases : hemocon­centration, hypovolemia and dehydration and marked metabolic alkalosis with a severely distended abomasum.
• Severe and prolonged abomasal volvulus: paradoxic aciduria with metabolic alkalosis associated with abo­masal disease.

Volvulus phase

• The distended abomasum  twists in a clockwise or anticlockwise (viewed from the right side) direction in a vertical plane around a horizontal axis.
• Degreeof volvulus is of 180-270* causing a  acute obstruc­tion with local circulatory impairment and ischemic necrosis of the abomasum.
• Sometimes abomasum and oma­sum are  distended and form a loop with the cranial part of the duodenum. Pressure and tension damage to the ventral vagal nerve trunk and to the blood vessels are responsible for the poor prognosis in severe cases