Sonographic Evaluation of Coprostatic Impaction with Sand and Ingesta in Draft Equids

India has second largest population of equines in world. Simultaneously, the incidences of equine abdominal emergencies are very common. Colic is an important cause of morbidity and mortality in the equine population. Due to the topography of the country these animals are quite common in use for transportation of construction materials and as public transport. Due to the feed scarcity these animals are not fed properly and they are deprived even from the maintenance ration. So in order to meet their physiological demands, these animals get habit of eating unusual things like horses employed at construction sites have access to the grazing area heavily laden with dust, sand and gravel. Similarly, horses used for public transportation have been seen peeping into garbage bins and eating whatever they get there like polythene bags, ropes, metallic objects etc. At the same time owners do not provide them proper care like deworming, dental hygiene, palatable water which further increases the risk for abdominal emergencies and they end up with obstruction or impaction of the gastrointestinal tract. Finally it becomes a challenge for the veterinarian to diagnose the exact etiology as there are very few diagnostic techniques available with the veterinarians which include radiography and rectal examination (Farooq et al., 2018a). But unfortunately these techniques have their own limitations, like due to the large size of abdomen the utilization of radiography is precluded and only 40 to 50% of the cases can be diagnosed by rectal examination, that too if the etiology lies within the caudal abdomen. Under such limited diagnostic options, diagnostic ultrasonography seems to fulfill the promise without wasting time in symptomatic treatment because time is the important factor for the survival of the animal in case of equine abdominal emergencies. 
       
Ultrasonography is a valuable diagnostic modality for the diagnosis of gastrointestinal disorders and disease involving the abdominal organs and urogenital tract. It is useful ancillary test for assessing the animal with colic and is more sensitive than per rectal palpation for identifying abdominal disorders. Ultrasonographic examination of the abdomen in the adult equids yield information about the gastrointestinal tract and abdominal organs that is difficult or impossible to obtain through other diagnostic modalities (Farooq et al., 2018b). Ultrasonographic assessments about the luminal contents, motility and wall thickness help the surgeon to decide in a colicky horse if surgical intervention is necessary or not (Reef et al., 2004). Ultrasonography enables the veterinary surgeon to image regions of the abdomen that are inaccessible to the rectal palpation. It allows abnormal rectal findings to be confirmed and in many cases provide further information based on which a surgeon can distinguish between surgical and non surgical colic. (Freeman, 2002).
       
However, no predictive model is 100 per cent accurate and clinicians have to rely on clinical evidence and instinct and to use various diagnostic and prognostic procedures only as guides for case management. Thus the objective of this study was to perform the detailed ultrasonographic examination of equids suffering from abdominal discomfort and to identify which measurable parameters were important in reaching a diagnosis of small intestinal abnormality and determining treatment options.

Twenty five mules (age 10-13 years) with history of cessation of defecation ranging from 2-4 days were presented. The initial signs of colic were manifested by kicking at belly, stamping at the ground, frequent rolling, sweating, muscle tremors especially of hind quarters and repeated attempts to void faeces but could only pass scanty mucus. Other associated symptoms were anorexia and reduced urine output. On physical examination all the animals were dull, depressed and dehydrated (status of dehydration was calculated as per (Barton, 2002) with mild congestion of conjunctival mucus membranes and gum perfusion time (GPT) of 2 seconds. Heart rate and respiration rate were slightly increased. Mild distention of the left side abdomen was seen along with hypothermia in two animals. In 18 cases, abdominal auscultation revealed mild tinkling and fluid splashing sounds of borborygmi whereas no audible sound was heard in seven animals. A thorough physical examination followed by hematological, biochemical analysis and electrocardiography was performed. The animals were stabilized by administering intravenous fluids. Once the animals were stabilized, lubrication of the rectum with liquid paraffin was done and transrectal examination was performed, which revealed absence of faecal material with dryness of rectal mucosa and distended intestinal loops. But impaction could not be ascertained due to animal’s intense straining, frequent attempts to lie down and apprehension of rectal tear. Following physical examination, the animals were prepared for ultrasonography.

On ultrasonography the left ventral colon wall was found flattened against the ventral body wall with loss of normal sacculations and peristaltic movement in 22 animals [Fig 1.1(a,b)]. while in two animals the sacculations were present but the wall of left ventral colon was seen edematous with increased wall thickness of 2.4 mm and absence of peristaltic activity [Fig 1.2(a,b)]. which is above the normal range 1.3 mm in Himalayan hill mules (Farooq et al., 2018b). Similar findings were reported by Freeman (2002). In one animal the investigation of the more cranio-dorsal portion of the LVC revealed normal wall thickness with presence of mixed echogenic ingesta [Fig 1.3(a,b)]. Reef et al., (2004) stated that the bowel wall may be of normal thickness or may be thicker than the normal and there is a large acoustic shadow cast from the impacted ingesta adjacent to the colonic mucosa. The impaction of left ventral colon in all animals was imaged as hyperechoic intraluminal structure casting a strong acoustic shadow [Fig 1.1(a,b)]. A consistent observation of small pinpoint hyperechoic structures on the mucosal surface were seen casting small acoustic shadows and reverberation artifacts in different directions depending upon the fanning of the beam were highly suggestive of sand impaction [Fig 1.4(a,b)]. Korolainen and Ruohoniemi (2002) also found that impactions appear as hyperechoic line casting an acoustic shadow from the mucosal surface, whereas small hyperechoic particles causing reverberation artifacts are consistent with sand impaction.
 

 

 

 

       
Reef (1998) reported similar findings and in addition to this he also found fluid distention of the more proximal small intestine in horses with large colon or caecal impactions. In all  animals the loops of small intestine were observed in transverse as well as longitudinal sections as hypermotile distended with fluidy ingesta and hyperechoic feed particles swirling inside that fluidly ingesta [Fig 1.5(a,b)]. The presence of dilated multiple loops of intestine in a single scanning area was also observed in few animals. This happens due to excessive entrapment of gases as well as ingesta in the lumen of the intestinal segments proximal to the obstruction [Fig 1.6(a, b)]. Thus ultrasonography proved to be a useful tool in diagnosis of left ventral colon impactions. After proper diagnosis all the animals were treated conservatively.
 

 

The conclusive sonographic findings giving an indication of sand colic are the flattening of left ventral colon wall against the ventral body wall with loss of normal sacculations with loss or absence of peristaltic activity. The impaction of left ventral colon in all animals was imaged as hyperechoic intraluminal structure casting a strong acoustic shadow with increase in wall thickness. A consistent observation of small pinpoint hyperechoic structures on the mucosal surface seen casting small acoustic shadows in different directions were highly suggestive of sand impaction. Based on the above findings the surgeon/clinician can be able to differentiate the true and false colic, which will help in accurate diagnosis and formulation of a precise and efficient therapeutic plan.