14 Gastroenteric Conditions Most cases of choke are easily diagnosed by the owner, but the clinician then has a dilemma: if the owner or the patient is very distressed then immediate attention is indicated, but if the owner is sensible and the horse relatively calm, I think it is quite reasonable for the practitioner to delay visiting the case: many cases of choke will have cleared within a few minutes. It is very important that the client knows that a horse that is choked has a blocked oesophagus and is not in an immediate life-threatening situation, unlike a human, who can become choked with a blocked trachea. A choked human needs application of the Heimlich manoeuvre immediately. Assuming that the horse is still choked on your arrival, you will readily observe the classic action of arching of the neck and failure to swallow. Rarely is the heart rate raised above 48 beats/min, and the mucous membranes will appear normal; however, saliva and food material will be running intermittently down the nose. There will appear to be no abdominal pain and gut sounds will be normal; rectal temperature will be normal and the anal sphincter will have a normal tone. In a study of 100 cases of choke attended in general practice between September 1997 and April 2003, 100% showed drooling and nasal return of saliva and food. Equally, 100% made repeated attempts to swallow, 92% had a palpable mass on the left lateroventral aspect of the neck, while 81% had repeated spasm of the neck muscles. Marked anxiety and distress was not a feature, with only 5% affected; 11% had a cough. It will be rare that you will have a problem with diagnosis. However, the possible differentials are: • colic; • grass sickness; • tetanus; • chronic lead poisoning. Other causes of dysphagia are: • dental abnormalities; • guttural pouch disease; • foreign bodies in the naso-/oropharynx; • palatal defects. Choke is normally caused by dry concentrate feed, particularly pelleted feed, but the very worst cause is dry sugarbeet pulp. Accepted wisdom is to attempt to pass a nasogastric tube to confirm your diagnosis. This is obviously sensible if there is any doubt in your mind but, if there is no doubt, caution should be exercised. First of all, the owner will assume that you are going to clear the obstruction, which is rarely the case; you are then faced with an even more worried owner who will want a result. Secondly, you will find the tube harder to pass into the rostral oesophagus in a choked case than in a normal one; this will cause you some anxiety and the owner even more anxiety. A better approach, therefore, is to sedate choke cases with romifidine (e.g. 1 ml Sedivet/100 kg i/v) after normal clinical examination. This dose will cause the horse to lower its head, thus reducing the risk of aspiration pneumonia; a full oral examination should then be performed. It is prudent to give the horse antibiotics by injection to guard against the danger of inhalation pneumonia. Strict instructions should be given that the animal is to be stabled with a non-edible bed. All food is to be removed, as some horses will start to eat again even if the choke remains. Ask for the water to be removed. The rationale is that many horses will play in the water, so that after 4 h the owner will not be able to see whether the animal has drunk or not. It is much better to present the water to the animal on a regular basis; one can then see whether the animal has drunk and therefore swallowed. Reassure the owner that you will visit the following day, unless you receive a telephone call to say the horse has recovered: this is an advantageous psychological ploy – the owner does not get the impression that you think the horse will be clear within 24 h. In a study of 100 horses treated in general practice without passage of a nasogastric tube (see Fig. 14.1), 71 were clear within 12 h and a further 15 within the next 12 h. The other 14 horses had to be visited after 24 h; these were not sedated again but received i/v antibiotics and NSAIDs. In temperate countries it is reasonable to wait a further 24 h, but in hot climates the horse that has been choked for 24 h will require i/v fluids at that stage. Of those 14, nine had managed to clear the obstruction within a further 24 h, leaving five horses out of the original 100 still choked and obstructed after 48 h. The lesson from this study is that the majority of choke cases will clear themselves. The clinician has two options if the horse is still choked. First, the horse can be given a general anaesthetic following premedication, then intubated with an endotracheal tube; the cuff is next inflated and the anaesthesia maintained with gaseous agents. A nasogastric tube is passed and the blockage cleared with large volumes of water. This is a hazardous procedure, as it is possible for water to inadvertently find its way into the trachea, even with an endotracheal tube in place, and to set up pneumonia. Secondly, the choke can be cleared without a general anaesthetic, but with sedation and a cuffed nasogastric tube. Fig. 14.1. Cuffed nasogastric tube. Clearance is relatively straight forward. There is good evidence that the use of neither oxytocin at 10 IU/100 kg i/v nor butylscopolamine and metamizole (Buscopan®) i/v helps the horse move the choke. To summarize, the best advice on treating cases of choke in horses is: 1. Pass a nasogastric tube only if the diagnosis is in doubt. 2. Time will solve 95% of cases. 3. A cuffed nasogastric tube is extremely useful in the choked horse, but has its limitations in the small pony. 4. Intravenous fluids are useful in preventing dehydration. The causes of colic will vary enormously, depending upon the part of the world in which you are working. Dry, sandy areas will predispose to sand colic, particularly after the annual rains have started, whereas in areas of high rainfall with lush pastures, gassy colics will predominate. There are in reality almost 100 different causes of equine colic. Age will have an influence: young animals are more prone to intussusception or larval cyathostomosis (see Section 14.3), while strangulating lipoma is seen in the older animal. Gender also has a marked influence: uterine torsion occurs only in the last trimester in the mare, while inguinal herniation and testicular rotation are seen only in the stallion. There have been few epidemiological studies on breed or type of horse influencing the cause of colic, although Standardbreds and Cleveland Bays appear to have a predisposition to inguinal herniation. A horse that has previously had colic is much more likely to suffer from colic a second time, though any horse that has undergone colic surgery is at a very high risk of repeated attacks of colic. Poor dentition or lack of dental care has been suggested as a predisposing cause of colic, although this has never been proved. On the other hand, the presence of tapeworms, particularly at the ileocaecal junction, has been shown to predispose to colic. Large redworms cause damage to the small intestinal arteries, leading to infarctions later. Obviously, cyathostomes that have become encysted will cause larval cyathostomosis. Administration of anthelmintics, particularly in the presence of large numbers of either roundworms or tapeworms, will trigger a colic episode. The influence of management factors, e.g. feeding and housing, is likely to influence the rate of colic attacks: the nearer a horse is kept to a natural environment the less likely it is that a colic episode is going to occur. Horses, left to fend for themselves, will feed and move for at least 18 h out of 24, and any change in this pattern will predispose to colic. All these factors will influence the numbers of colic attacks within a population. However, the actual cause of the majority of cases is never ascertained. Even with surgical intervention the original cause is often not established, e.g. why a volvulus has occurred (see Section 14.6), why an enterolith has formed, why there is an intussusception or even why a horse has developed grass sickness (see Section 14.7). Of all the improvements made in equine surgery and medicine, the greatest have been in the treatment of equine colic. There have been massive benefits to both the horse and its owner, and these advancements have been brought about through excellent research, evidence-based medicine (EBM) and clinical audit (CA). The veterinary schools and referral practices are to be congratulated for all their hard work. Gone are the seemingly endless days and nights of worrying about horses with colic, although in areas of the world where there are no surgical facilities the practitioner has to do the best with the facilities available. Below is presented an approach to colic cases. With all these excellent advancements, it is still very important that we have in the forefront of our minds the welfare of the horse. The following questions need to be answered by the owner: 1. How old is the animal? 2. Has the animal had colic before and did it have surgery? 3. When did they last see it in a normal state? The clinician needs to make an assessment as to: 1. Whether the owner is prepared for considerable expense. 2. Whether the owner is prepared to care for the animal properly. 1. Check the general body condition and look for signs of trauma. 2. Measure heart rate and pulse; a raised pulse indicates pain, dehydration or enterotoxaemia. 3. Measure respiratory rate; a high rate also indicates pain. 4. Assess the gut sounds; intermittent bursts of sound in the right quadrant are related to the caecum, while sounds in the left quadrant tend to relate to the small intestine or left colon. Either increased or decreased sounds are abnormal; the normal response of bowel proximal to an obstruction is hypermotility. 5. Look at the colour of the mucous membranes and gauge capillary refill time. 6. Take the rectal temperature (this is useful to assess the danger of a rectal examination. If a horse kicks when you take rectal temperature it will certainly kick when you perform a rectal examination). It will be raised in colic cases if there is anterior enteritis, colitis (Clostridium or Salmonella) or peritonitis. It is normal to perform a rectal examination, but the clinician should be mindful of the danger to the horse and to him- or herself. The use of a spasmolytic and analgesic, e.g. butylscopolamine and metamizole, or sedation, e.g. with a combination of detomidine and butorphanol, may well be the way forward. Clinicians with large hands and forearms should not attempt to perform a rectal on a small pony or donkey. When performing a rectal examination the serosal surfaces should be checked – these will feel tacky in cases of peritonitis or bowel rupture. The position of the bowel is then checked and any pain associated with palpation noted. The bowel is next checked for distension, i.e. gas or firm ingesta. Even at this stage the clinician should have the answers to the second group of history questions in the back of their mind. This information is required to decide whether at this initial visit the clinician is going to treat this as a surgical or a medical case. If it is decided that it is a surgical case, the decision has to be made whether the horse is going to be referred, surgery is going to be undertaken by the first-opinion veterinary surgeon or the owner needs guidance toward making the decision of euthanasia. The clinician may carry out nasogastric intubation. It is useful here to apply suction to create a siphon; drawing off a large volume of fluid may be lifesaving, as gastric rupture will be prevented. A large volume gives a poor prognosis, as this indicates gastric impaction or a blockage in the anterior section of the small intestine. In either of these conditions the horse will often sit in a dog-sitting position to relieve the pressure in the anterior abdomen. Very careful thought must be given before deciding that surgery should be undertaken: 1. There must be an upper age limit for colic surgery, which will vary depending upon whether the patient is a pony or a horse. Realistically, ponies over 25 and horses over 20 years of age are not suitable surgical cases. 3. The possible duration of the colic symptoms aid decision making: if the animal is known to have been well within the previous 2 h, a trial with analgesics is acceptable (obviously, if the signs have not indicated a surgical case). Otherwise, prompt referral is indicated if in any doubt. However, if the symptoms have been obviously long-standing and there is likelihood of severely damaged bowel, from a welfare point of view immediate euthanasia is the only option. Naturally, no practitioner should feel totally alone; if one is in doubt a second opinion from within the practice or from a neighbouring veterinarian is certainly worthwhile. Consideration must be given to assessment of the owner: 1. If the owner is not prepared for considerable expense, then everyone has a problem. The costs of sedation for a rectal, passing a nasogastric tube, performing a peritoneal tap, scanning the abdomen, etc. are going to enlarge the bill. Multiple visits might end up being more expensive than hospitalization. One thing is certain – immediate euthanasia may be the less expensive option and, from a welfare standpoint, cannot be faulted. Surgery is not an option. 2. If the owner is not prepared or is unable to provide adequate care for the animal, medical care at home is not an option. Lastly, we come to the vital signs, and these are useful guidelines: 1. Heart rate is a very good predictor. 2. A rising heart rate is an adverse sign. 3. A heart rate remaining high after analgesia is also an adverse sign. 4. Signs of pain, including the respiratory rate, are helpful but should be judged with care. 5. Absence of gut sounds, particularly after analgesia, is an adverse sign. 6. The presence of gut sounds that then disappear is an adverse sign. 7. The colour of the mucous membranes is a good predictor. 8. Dehydration is a bad prognostic sign.
14.1 Choke
14.2 Colic
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