Equine Colic Cases Flashcards
You have been asked to examine a horse which has mild signs of colic. These have been apparent for approximately 18 hours; however, the owner was reluctant to call you out as she was worried about cost. The horse has recently become more uncomfortable but has remained standing.
•How would you go about your initial examination?
What parameters do you want to investigate and record?
•Full clinical exam:
–HR
–TPR – should be done early
–Nasogastric intubation – should be done early on too (shows If there is fluid or gas)
–MM/peripheral perfusion
–Asucultation of upper loer right, left paralumbar regions and ventral abdomen
–Evidence of Pain
–Look at behaviour – to do this we cannot restrain them
–Abdominal silhouette – pear shaped suggests fluid filled
–External palpation or ballotment of the abdomen
–History?
–Rectal exam – will need restraint for this
How would you position yourself, the horse and the horse handler to provide the safest means of performing a rectal examination. You will need to think about where you need to be, how to minimise horse movement, how to prevent yourself being kicked (or at least reduce the chance of it causing serious injury).
- What methods of restraint can you apply?
- Can you use the environment in an appropriate manner to increase the safety of all concerned?
–Ideally use stocks
–Minimum – head collar and lead rope
–Twitch
–Crossties
–Lifting a limb
–Chemical restraint
- Over half door (P)—may protect from kick but if horse goes down, you lose your arm.
- Around corner (P)—safe but may lose some reach.
Describe what you would feel on the left side of the abdomen for a rectal palpation?
- The aorta can be felt at the 12 o’clock position on the roof of the pelvis and on the dorsal aspect of the abdomen. The caudal pole of the kidney can be identified just to the left of the aorta at an arm’s length from the anal sphincter. A prominent ligament (nephrosplenic ligament) can be felt as it connects the ventral aspect of the kidney to the dorsomedial aspect of the spleen. The ascending colon can move from its normal ventral position and become abnormally entrapped in the potential space created by this ligament. Having identified the spleen, its caudal border can be palpated in a vertical position against the left body wall.
- The left ascending colon can be identified just ventral to the spleen against the left body wall. The ascending colon is a “horseshoe-shaped” piece of large intestine that has dorsal and ventral segments. During examination per rectum, the dorsal (without bands and sacculation) and ventral (with bands and sacculation) component can be distinguished by the presence or absence of broad fibrous bands and sacculation. The pelvic flexure connects the left ventral colon to the left dorsal colon, and often can be identified in the lower caudal aspect of the left side of the abdomen. The pelvic flexure is a narrowed portion of the ascending colon and a common problem area in horses with signs of colic due to impacted ingesta.
- The small intestine is usually collapsed and therefore not palpable in the normal horse. The mesenteric sheet of the jejunum (the tissue that suspends the small intestine from lumbar region of the dorsal body wall) is quite long and enables the small intestine to be highly mobile. The majority of the small intestine is usually contained within the center of the “horseshoe-shaped” ascending colon, and towards the left hand side of the horse’s abdomen. The descending (small) colon can be found in several locations in the dorsal aspect of the caudal left and right abdomen, and is identified by the presence of formed fecal balls and a prominent ventral band.
- When listening for intestinal sounds with a stethoscope in the left flank, you hear sounds from the small intestine in the upper quadrant, and colonic sounds (left ascending colon) in the lower quadrant.
Describe what you would feel on a rectal palpation on the right side
•Using the aorta to identify the center of the abdomen, the stalk (mesenteric root) that suspends the small intestine can be identified as a taut structure just to the right of center at an arm’s length from the anal sphincter. At mid-arm’s length from the anal sphincter, the base of the cecum can be identified and is firmly attached to the right dorsal aspect of the body wall In the normal horse it is not possible to distinguish the ileum (the terminal end of the small intestine) as it empties into the medial (left side) aspect of the cecum, although this might be abnormally distended in the horse with signs of colic. The medial cecal band can be identified on the left side of the body of the cecum and directs the veterinarian’s hand from the right side of the abdomen downward and towards the apex of the cecum on the midline of the abdomen. In the normal horse, the cecal band and the ventral band of the ascending colon are the only bands that can be easily identified during examination per rectum.
Although the inguinal rings can be difficult to find in the normal horse, they can be identified at the 4 and 8 o’clock position just in front of the floor of the pelvis. These structures can entrap small intestine in the intact male. When listening for intestinal sounds with a stethoscope in the right flank, one hears sounds from the base of the cecum in the upper quadrant, and colonic sounds (right ascending colon) in the lower quadrant.
•Are there any things that you shouldn’t do during the rectal examination of a horse? Are there any pharmacological agents that could potentially make the examination safer? How do they work?
–Shouldn’t splay your hands they should be flat at all times
–Chemical restraint options include sedation with alpha-2 agonists, spasmolytics and analgesics. Acepromazine should not be used for sedation. The choice of alpha-2 agonist and the dosage used should be based on the required duration of action and any potential concerns over hypovolaemia. Doses of up to 0.5mg/kg of xylazine IV can be useful for short durations (15 to 30 minutes) to enable initial assessments and then re-evaluation of clinical signs. Detomidine or romifidine may be preferred if a longer duration of sedation is required for more prolonged procedures or transport of the patient. The impact of chemical restraint on clinical parameters should always be considered. Alpha-2 agonists will cause a reduction in heart rate and respiratory rate, decreased gastrointestinal borborygmi and some visceral analgesia.
You are called to re-evaluate a horse that the partner in your practice has seen earlier in the day. She feels that the horse may have a left dorsal displacement.
•What would she have felt on rectal examination that would lead her to this conclusion (hint: how would it feel different from a normal horse). The partner has also suggested you take some additional equipment from the practice, which is well equipped, to help you confirm your diagnosis. What might this kit be and explain how you would go about using it?
–On rectal examination the pelvic flexure or left colon can be felt in the nephrosplenic space, the spleen is often displaced towards the midline. The displaced colon becomes distended with gas due to compression over the nephrosplenic ligament.
–Ultrasound exam: the left colon can be identified in the nephrosplenic space, it may partially or completely obscure the left kidney.
–Put the probe on the body wall in the position of the left kidney?
•You decide that in order to help you determine whether the gut remains healthy that you will perform an abdominocentesis. What are the landmarks for this procedure? Is there anything that you might need to alter about your technique in this case? Again, where will you position yourself and the handler to make things as safe as possible?
–Standing, sedated horse, preferably in a stock
–The best site for abdominocentesis is the most dependent part of the abdomen, midline and usually around 5 cm caudal to the xiphoid. The use of ultrasound for selecting the pockets of peritoneal fluid within the abdomen is ideal as it not only indicates how thick the body wall is but the location of viscera to be avoided. However, peritoneal fluid can still be extracted even if it is not apparent on ultrasound. A right paramedian approach at the most dependent area of the abdomen is the best site if ultrasound is not available. This approach should avoid accidental puncture of the spleen. The selected area should be generously clipped and a sterile scrub performed. At minimum a twitch, or sedation if the horse is more fractious, should be used for restraint. Sterile gloves should be worn to maintain sterility. The veterinarian should stand next to the horse and insert the needle with a quick action through the skin. Then the needle can be gently and carefuly advanced through the linea alba, into the peritoneal cavity. If fluid is present, then drops should be seen in the needle hub. If this is not the case, reposition and twist the needle. Alternatively, a sterile syringe can be attatched and the fluid can be aspirated. Once the fluid is noted, it should be allowed to drop freely into the EDTA and plain tubes for analysis. The fluid may also be submitted for microbiological culture and sensitivity, peritoneal lactate and glucose concentrations if necessary.
You are called to re-evaluate a horse that the partner in your practice has seen earlier in the day. She feels that the horse may have a left dorsal displacement.
•Assuming you are able to confirm this diagnosis there are several treatment options available for treatment of a nephrosplenic entrapment. These range from doing nothing through to surgical intervention. There are two intermediate options. What might these be? (These will require a certain degree of lateral thinking.).
- The condition can usually be resolved with medical management, IV fluids and analgesia in the form of NSAIDs should be given to correct hydration status and make the horse comfortable.
- Mild displacements may respond to the withdrawal of feed, allowing the colon to empty and return to a normal position. This can be aided by the intra-venous administration of phenylephrine which causes splenic contraction, significantly reducing its size and allowing the colon to relocate. Light exercise can also be beneficial to encourage movement of the abdominal contents. Circling on the left rein is considered particularly helpful, as it increases the potential space between the spleen and the body wall, allowing more room for the colon to return to its normal location.
- In some cases a rolling technique may be used to try and correct the displacement. The procedure involves anaesthestising the horse and placing it on its right side, lifting it with a hoist and returning it onto the left side. Rectal manipulations can aid the relocation of the colon but it is not always successful.
- Where conservative management has failed or in severe cases of left dorsal displacements, surgical exploration and correction is indicated.
•Work out what the problem is with a left dorsal displacement, why the colon is stuck where it is, and indeed how it got there in the first place?
–The exact cause is unknown but it is thought that changes in the ingesta, gas content and motor activity of the colon are important factors.
–It has been theorized that the colon initially becomes distended with gas, the spleen contracts in response to abdominal pain, the colon becomes displaced dorsally, and the spleen refills with blood and “traps” the colon
•Is there anything that you could suggest to the owner if the horse was suffering from a third or fourth episode of nephrosplenic entrapment. It is an athletic horse so a colopexy is contraindicated. How else could you prevent this type of colic (think about the anatomy)?
- Provide a diet that will help prevent gas buildup or alterations in the normal activity of the bowel that might have initiated the previous displacements
- Nephrosplenic space ablation (surgical closure of the nephrosplenic space) helps to prevent recurrence. This can be performed by standing flank laparotomy, but is usually performed by standing laparoscopy and typically is performed in horses with previous nephrosplenic entrapment events. Methods of laparscopic closure have included suturing the space closed, using mesh, and barbed suture
Same practice, different day. The partner in your practice, thrilled at how well you managed to treat her previous case with colic has asked you to go and check another horse that she had seen earlier in the morning. At the time of the initial examination the horse was only mildly uncomfortable with normal clinical parameters. There had been no further signs of colic after the administration of a small amount of phenylbutazone. During her examination she was convinced that she could feel a right dorsal displacement.
•What would you expect to feel on rectal examination on this occasion?
–On rectal examination a gas distended colon is palpable in the right caudal abdomen, the caecum is displaced towards the midline and the pelvic flexure cannot be palpated as it has moved cranially towards the diaphragm. If the displacement is accompanied by a 270° volvulus then the colonic walls will be thickened and oedematous.
–The bands on the colon will be running transversely across the pelvic inlet
•If the horse is showing further signs of discomfort how would you choose to proceed?
–What factors would affect your decision?
–Prompt surgical treatment is necessary for correction. The displaced colon can be relocated after decompression of the colon and the caecum. In cases where significant impaction has developed, the colon should be evacuated via a pelvic flexure enterotomy. If a concurrent volvulus occurred, causing ischemic damage to the colon then resection of the affected portion must be performed.
–Medical treatment with IV fluids and analgesia
–Factors affecting choice: cost of the procedure, whether the owner would refer, if the referral is close by????
You decide to pass a nasogastric tube since you remember at the back of your mind that sometimes horses can reflux with right dorsal displacements even in the absence of any other small intestinal distension.
•What is the reason for this?
–The horse’s stomach is relatively small, holding about 10 to 15 L. It is positioned on the left side of the horse’s abdomen beneath the ribcage. Because of the peculiar arrangement of the junction of the esophagus and the stomach, horses cannot vomit. As a result, distention of the stomach with excessive amounts of gas or buildup of fluid from the small intestine can cause the stomach to rupture.1 This is why a nasogastric tube is passed in horses that show signs of colic. The junction between the stomach and the first portion of the small intestine is formed by the muscular pyloric sphincter
You decide to pass a nasogastric tube since you remember at the back of your mind that sometimes horses can reflux with right dorsal displacements even in the absence of any other small intestinal distension.
•How would you position everyone to ensure maximum safety?
–No one in the kick zone
–No one at the end of the tube, watch the horse doesn’t hit your head and break your nose..
–Adequate restraint
What are the landmarks for passing the NG tube?
The horse should be adequately restrained in stocks or in the stable. The veterinarian may need a twitch or chemical restraint. The NGT should be immersed in the bucket of warm water to make it clean and flexible. Some veterinarians may lubricate the end of the NGT for a smoother, atraumatic passage. The veterinarian should stand on the horses left and place the right hand over the nose. The veterinarian’s right thumb can be used to reflect the alar fold of the left nostril, without obstructing the airflow to the right nostril. The NGT is introduced ventrally into the ventral nasal meatus. The tube is advanced slowly and the veterinarian should not use force if there is resistance. Once the tube is at the level of the epiglottis in the pharynx, there may be some resistance. Most horses swallow the tube immediately, but if this is not the case then the veterinarian should carefully bump the epiglottis with the tube or blow down the tube. The tube may need to be rotated 180 degrees to pass down the esophagus.
Passage of a nasogastric tube, with the introduction of the tube into the ventral nasal meatus(Courtesy of Potter K, SPANA)
It is very important to check that the tube is in the esophagus and not in the trachea. The tube is visible passing down the left neckline when it is in the esophagus. It is not visible if it is in the trachea. There is negative pressure in the esophagus when suction is applied to the tube. There is no negative pressure in the trachea during suction. If the tube is in the esophagus, there should be some resistance its passage. There is no resistance when the tube is advanced down the trachea and the tracheal rings are palpable.
Once at the cardia, the veterinarian must blow into the tube to enter the stomach. There is a characteristic smell in the tube of ingesta and blowing on the tube will cause a bubbling noise. These are key to ensure that the tube is in the stomach.
To obtain reflux, the tube must become a siphon by creating a complete tube of water from the stomach to the end of the tube. This is achieved by filling the tube with warm water using the syringe, and then aspirating a bit of the fluid. The gastric fluid can be encouraged to flow out at a faster rate by quickly pulling the tube out by 10 to 15 cm. Gastric reflux should be collected into a separate bucket so that the volume can be measured and a sample is available for analysis. The tube may need to be left in place in certain conditions whereby more gastric fluid will be produced. This can be achieved by coiling the tube and taping it to the headcollar with zinc oxide tape. The horse should have the gastric fluid repeatedly removed to prevent rupture of the stomach.
Picture of a nasogastric tube taped in place to allow for repeat refluxing(Courtesy of Potter K, SPANA)
If no reflux is obtained then the medications may be administered. It is important that any oral fluids or medications are warmed to body temperature prior to administration. Ensure that all of the fluids in the tube are in the stomach before removing it. Crimp the tube prior to its removal to ensure that no fluid is deposited in the pharynx.
A normal horse will have less than 2 litres of reflux.
