The oesophageal stricture is a rare condition, and due to the nonspecific signs, rarity of occurrence and not very common use of endoscopy in veterinary clinical diagnostics very frustrating and difficult to manage for clinicians and owners (Willard 2004).
Oesophageal strictures are often secondary to an inflammatory process. Moreover, previous studies have also reported that the oesophageal strictures in both, humans and animals can occur after oral administration of tetracyclines (specifically doxycycline tablets), as it most probably was in the presented case (Carlborg and Densert 1980; Carlborg and Densert 1983; Bissett et al. 2009; McGrotty and Knottenbelt 2002; Willard 2004).
The results of previously described experimental study have shown that doxycycline and oxytetracycline administrations produced areas of deep ulceration in the oesophagus (Carlborg and Densert 1980; McGrotty and Knottenbelt 2002). Moreover, doxycycline capsules, not tablets were mostly associated with oesophageal damage. This observation was probably associated with a longer retention time in the oesophagus of this form of drugs (Carlborg and Densert 1983; McGrotty and Knottenbelt 2002). Furthermore, the oesophageal retention time can be minimized by administering capsules and tablets with food or providing large amount of water after the drug administration (McGrotty and Knottenbelt 2002).
During the described case the patient was treated with several drugs due to the diagnosed panleukopenia. The patient was treated with enrofloxacin intravenously and an injectable penicillin drug. This treatment strategy did not improve the patient's condition so it was changed for tetracyclines (mostly because of a broad spectrum of activity and action against gram – bacteria). Most probably the cause of the oesophageal stricture in the present case was long-term doxycycline treatment without water administration as described previously (German et al. 2005; Sasaki et al. 2017). Unfortunately, due to better access to doxycycline tablets and the lack of possibility of daily intravenous administration of drugs for a long time, it was decided to use this solution, despite the risk of oesophageal stricture. The owner was informed about the need to give large amounts of water or food after taking the tablet, but it is most likely that this practice was not fully followed. In veterinary medicine several treatment methods can be used in the cases of oesophageal strictures. The conservative treatment relies on special, semi-liquid diet, high positioning of the bowl and treating the underlying disease (Wesdorp and Bartelsman 1982; Gallagher and Specht 2013). Moreover, the oesophageal stricture can be treated pharmacologically with the anti-inflammatory drugs (including steroids) and antibiotics. This method is extrapolated from human medicine, but its effectiveness in veterinary patients has not been confirmed yet (Yan et al. 2019). Finally, the oesophageal stricture may be resolved mechanically that is through surgical operation or endoscopy. Surgery includes resection and anastomosis, oesophagoplasty or reconstructive procedures (patch grafting), and is indicated when conservative treatment fails or in the case of neoplastic or tubular strictures. Surgery can be an effective method of the treatment for the oesophageal stricture, but it is not commonly performed due to the complexity of the treatment, the specialized surgical equipment requirements, and the potentially poor outcome (Johnson et al. 1992; Fingeroth 1993).
Therefore the endoscopic methods, which are less risky and less invasive than surgical operation and more effective than drug therapy are the preferred methods of treating oesophageal strictures in dogs and cats. However, the procedures involving the mechanical expansion of oesophageal strictures may need to be performed several times to consolidate the effect, which is associated with the need of repeated anesthesia and great discomfort for the patient (Adamama-Moraitou et al. 2002; Bissett et al. 2009; Gallagher and Specht 2013). Therefore, the use of stents seems to be a preferable alternative. Unfortunately, the high costs associated with the purchase of stents and the lack of a guarantee that it will not move or be expelled, so far does not favour the use of this method for treatment of pets (Tan et al. 2018).
The most common endoscopic method for managing the oesophageal stricture is using dilatating balloons. It is important to note that balloon dilation is considered more effective in some cases due to the better control of the dilating segment of the oesophagus. On the other hand, cons of this method are mostly its high costs in some countries, the difficulties in properly matching the right size of the balloon and the need to use appropriate pressure during the procedure. Moreover, ideally, the use of the dilating balloons should be performed with additional imaging techniques like fluoroscopy. There are only few reports regarding the use of Savary-Gilliard dilators in similar cases in cat patients (Bissett et al. 2009). Nevertheless, the bougienage technique with Savary-Gilliard dilators seemed to be an effective method of treatment of oesophageal strictures in cats (Bissett et al. 2009), which is also confirmed by the case described above. Pros of the bougienage technique are first of all its low costs (the equipment is reusable) and high availability in some countries. It should however be pointed out, that for the proper use of this method a presence of well experienced endoscopist is essential.