Endoscopy has evolved from a procedure that was almost exclusively taught in academia to a service that an increasing number of large animal practices are offering as the cost of purchasing an endoscopic kit (Figure 1) is reducing. There are numerous advantages associated with the exploratory and curative applications of endoscopy: it is a minimally intrusive procedure and leads to quick patient recovery, it reduces need for the post-operative use of antimicrobials and it allows for clear visualisation of the area of interest, to name but a few. The various applications of endoscopy are named after the body regions observed: laparoscopy for the abdominal cavity, thoracoscopy for the thorax and theloscopy for the teat canal.
The etymology of the word endoscopy stems from the Greek “endo”, which means internal, and the word “skopein”, which means to observe. The main principle of endoscopy requires the insertion of a lens inside a hollow organ or region of the body. The tip of the lens has to be surrounded by gas; otherwise, the area of interest cannot be visualised, as is the case when the surrounding tissue collapses around the visceral tip of the endoscope or when the cavity is filled with liquid.
We insert our instruments through the body wall by incising the skin and placing a cannula in situ, thereby creating a portal. The portal through which the endoscope is inserted is called the “optical portal”. The portals through which instruments auxiliary to the surgical procedure are inserted are called the “working portals”.
Every corrective endoscopic procedure always starts as an exploration. This initial exploration allows the surgeon to verify the presence of a pathological condition and ascertain the level of collateral damage, such as the presence of adhesions (indicating acute or chronic infection) or the presence of tissue haemorrhages (indicating a traumatic or toxic effect). Based on the findings of this initial step, it is possible to establish the likelihood of a positive outcome in terms of commercial value and animal welfare.
Occasionally, the findings of an exploration can come as a surprise. On one occasion, I embarked on what seemed to be the endoscopic correction of a left displacement of the abomasum (LDA), only to find that along with the displaced organ, there was a displaced spleen, hence describing the first documented case of splenoptosis in cattle (Karvountzis, 2020). Once the displaced abomasum was reduced, the spleen was returned to its normal location by utilising a set of crocodile forceps. These forceps were inserted through the working portal while under observation with the endoscope. The forceps then gripped the dorso-caudal edge of the folded section of the dislodged spleen and the organ was unfolded in a medio-dorsal motion back to its normal position.
Corrections of left displacement of the abomasum
This is the most common application of endoscopy and it can be carried out while the patient is standing throughout the surgery, or standing initially and lying in dorsal recumbency at the completing stages of the procedure.
For a standing procedure, two portals are set up either side of the last rib at approximately a hand’s-width distance ventrally from the transverse processes (Figure 2). The optical portal lies on the paralumbar fossa and is approximately 1.0cm long, while the working portal that lies in the intercostal space is approximately 1.5cm long. If necessary, each skin incision can be extended in order to achieve the desired length and, more importantly, the desired fit around the relevant cannula.
The 10mm magnetic trocar and cannula are used to complete the optical portal. They are first inserted through the incised skin site at the paralumbar fossa and then progress through the remaining abdominal wall with a short, sharp, stab-like motion. The instruments are directed medio-cranio-dorsally in order to avoid inadvertently perforating any other organs. For the same reason, as soon as the trocar and cannula are in situ, the trocar needs to be removed.
At the working portal, we use the 13mm magnetic trocar and cannula. They are inserted through the incised skin site at the intercostal space, but the surgeon is trained to constantly observe its insertion through the intercostal muscle layers and the peritoneum with the endoscope. Like with the optical portal, once this instrument is in situ
the trocar is removed.
Correction of the LDA takes place according to the one-step endoscopic technique (Karvountzis, 2016, 2020; Christiansen, 2004). While looking down the endoscope, the following sequence of events takes place through the working portal: abomasal paracentesis, toggle insertion in the abomasum, passive deflation of the abomasum, passive repositioning of the abomasum and finally fixation of the abomasum caudo-laterally in relation to the xiphoid process on the ventral right side of the abdomen (Figures 3 and 4).
Should we elect to complete the LDA correction with the two-step procedure, all above steps remain the same, except the fixation of the abomasum (Christiansen, 2004). This can only take place once lateral recumbency has been achieved and two further portals set up: the optical portal that lies a hand’s width caudally to the xiphoid process on the right side of the patient, and the working portal that lies a hand’s width cranially to the navel on the right side also. With this approach, we fix the abomasum closer to the navel rather than the xiphoid process.
Corrections of right displacement of the abomasum
Endoscopy can also be used to explore and correct right displacement of the abomasum (RDA). The technique is similar to the two-step LDA correction and it depends on whether the RDA is volvulated or not.
In RDA cases that are not accompanied by volvulus, the procedure starts with the animal standing, setting up one portal on the left flank for abdominal insufflation, followed by casting of the patient to dorsal recumbency, setting up the optical and working portals as per two-step LDA correction, abomasal paracentesis, toggle insertion in the abomasum, passive deflation of the abomasum and finally abomasopexy at a hand’s width cranially to the navel on the right side of the abdomen.
The key determining factor in correcting an RDA endoscopically is the location of the pylorus. In un-volvulated cases this part of the abomasum faces caudally. When volvulation occurs, the pylorus faces cranially and the surgeon is advised to complete the RDA correction in two parts. The first part is identical to the un-volvulated RDA correction described above, repeating those steps until passive deflation of the abomasum has been achieved, but not its fixation. Abomasopexy will take place as part of a second operation, but not until the patient receives large volumes of oral rehydration therapy (ORT), which will assist the passive alleviation of the volvulus. Once the ORT is completed and approximately 12 hours following the first operation, we are then ready for the second two-step endoscopic procedure that is aimed at carrying out the abomasopexy.
Endoscopy presents an advantageous diagnostic tool when examining the thorax. There are numerous considerations attached to the decision on whether to carry out a thoracoscopy. The obvious instrument to use first would be ultrasound, but there are two limitations: firstly, the pulmonary content consists primarily of air, a substance that ultrasound devices cannot interpret well. Secondly, the best portable ultrasound sector probe would have a penetration of 22cm, whereas an endoscope can observe up to depths of 35 to 45cm, depending on the manufacturer. The main concern when carrying out thoracoscopy is the risk of pneumothorax, therefore the surgeon needs to have a clear plan on how to prevent this from occurring.
Theloscopy, or teat endoscopy (Figures 5 and 6), is an endoscopic procedure of huge prognostic value that can be carried out for exploratory or therapeutic reasons. We consider theloscopy for stenosis of the teat orifice, obstruction of the teat cistern and trauma of the teat wall (Ebner, 2009). Theloscopy allows us to handle teat problems with minimal invasion, while helping us to restore the flow of milk (Geishauser, 2004). Following the procedure, treated patients are likely to experience a transient and small increase of somatic cell count in that quarter.
The most salient learning points in relation to endoscopic procedures are:
- The target area can be fully visualised through 1.0–1.5 cm incisions
- No antibiosis is required for LDA corrections, unless they are complicated
- There is evidence that LDA corrected by endoscopy is associated with quicker clinical recovery (Seeger et al., 2006)
- There is strong evidence that cattle with LDA corrected endoscopically produce more milk during the first six weeks post-operatively than their cohorts that were laparotomically corrected (Seeger et al., 2006)