Ultrasonographic Examination Of Ruminants With Left Displacement Of Abomasum

Left displacement of abomasum (LDA) is a common disease in dairy cows. LDAcan reduce milk yield sharply and may lead to involuntary culling and death, causingfinancial loss. Risk of necrosis and adhesions make an early diagnosis necessary.Auscultation and simultaneous percussion on the left mid-flank area is a very usefuldiagnostic method.Although a diagnosis usually can be made directly, differentialdiagnoses for a ping in the left flank are necessary. In addition, some invasivemethods such as laparoscopic exploratory are required to make definite diagnosis inborderline cases. However, B-mode ultrasound can image internal organs of animalswhich in turn make a diagnosis of LDA non-invasively, if the knowledge of ultrasoniccharacteristics of abomasum is acquired. Therefore, in order to obtain moredifferentiating ultrasonic features for LDA, the present study was designed toultrasonographically examine the left abdomen of small-tail Han sheep withsurgery-induced LDA before and after displacement surgery; and cows with LDAbefore and after reposition surgery.Six nonpregnant adult small-tail Han sheep were equally divided into two groups.Group-I was assigned to experience a mild surgery-induced LDA, as well as Group-IIendured a serious LDA by surgery. The sheep were examined ultrasonographically todetermine the normal location and ultrasonogram of abomasum, and then the surgerywas performed. After that, ultrasonography was performed every two days for15days.The abomasum could be seen from linea alba and paramedian region in all the sheepin normal condition. The abomasum appeared as a heterogeneous, moderateechogenic structure with echogenic stippling and sometimes abomasal folds were seen.The rumen and the reticulum were visualized similarly as a curve echogenic band andno clear inner echogenic structures were observed. A remarkable difference could beidentified between abomasum and forestomach. In the animal models of LDA, thedisplacedabomasum was clearly seen between rumen and abdominal wall at left flank in both two groups. In Group-II the pylorus was found embedding between rumen andleft abdominal wall. No more changes were found in both groups except for one sheepin Group-II whose abomasums was repositioned naturally. The thickness of theabomasums which was trapped between rumen and left abdominal wall increased inGroup-II. The results showed that the abomasums could be easily differetiated fromthe surrounding organs in ultrasonogram before and after displacement.Forty-three suspectedLDA cows were examined ultrasonographically on the leftside, from the9th intercostal space (ICS) to the12th ICS as well as the ventral leftabdomen.40cows were confirmed LDA through right flank laparotomy and then aright flank pyloropexy was performed.Before the abomasal reposition surgery, theabomasum could be visualized in all of the left9th,10th,11th,12th ICS of37cows,and could be only identified in the left ventral abdomen region in3cows. Except for8,the abomasum of the cows with LDA appeared similar in ultrasonogram and couldbe particularly categorized as abomasal gas cap, abomasal ingesta, abomasal folds andpyloric canal. The abomasal gas cap was visualized from the9th to12th ICS andcharacterized by reverberation artifacts. The abomasal ingesta appeared ashomogenous hypoechogenic structures with scattered echogenic spots and weremainly visible in the median region and ventral region of the9th to11th ICS. Thepyloric canal was detected from the ventral left abdomen wall and appeared as a loopwith hypoechogenic wall and echogenic contents in cross section. After repositionsurgery all these findings disappeared, except that some reverberation artifacts werestill observed in the dorsal region of the ICSs.In conclusion, the left displaced abomasum of cows and sheep can display sometypical ultrasonograms and it is helpful to use ultrasonography to diagnose LDA.