Prevention
This complication can be minimized by awareness of the risk of it occurring during gastroscopy and upper airway endoscopy. The person passing the endoscopy controls the forward motion. This person should be careful when advancing the endoscope until confident in its location. Once seated in the esophagus, the person advancing the scope should make sure that there is aboral advancement of the scope synchronous with advancement of the endoscope into the nasal cavity. Alternatively, a larger diameter hollow tube can be positioned through the nasal cavity and into the esophagus [1]. The gastroscope is then passed through this tube, which prevents any resistance to passage and retroflexion of the endoscope in the nasopharynx [1]. Oral speculums must be used for any oral endoscopy procedures and the scope should be protected by a rigid sheath when in the mouth, if possible.
Figure 4.1 Photograph showing large segment (spanning the 160 cm to 205 cm gradations) of crushing and damage to a 3‐meter gastroscope after a segment of the midbody of the endoscope retroflexed into the oral cavity, where it was chewed by the patient.
Source: Julie E. Dechant.
Insufflation‐related complications
Definition
Insufflation is the directed administration of air through the endoscope to provide distension and visualization of collapsible hollow organs and can result in small intestinal volvulus or rupture of a hollow viscus.
Risk factors
None identified
Inattention during procedure
Pathogenesis
These complications are likely the result of the effective creation of a one‐way valve when performing endoscopy in long, narrow, tubular organs, whereby there is no means for the insufflated air to escape and depressurize the system.
Segmental jejunal volvulus has been described as a complication after gastroscopy [2]. The incidence of jejunal volvulus is low, with only 1–2 cases per year per institution included in their study (0.3–3.2%/year) [2]. All of the horses had gas distension of the affected small intestine, which was presumed to be related to the gas insufflation associated with gastroscopy. In the report of jejunal volvulus, there was no apparent association with duration of gastroscopy, duration of feed withholding, or use of duodenoscopy.
Although bladder rupture has not been directly described as a complication of cystoscopy in the literature, this author has observed a case in which prolonged urethroscopy and insufflation was used in an attempt to endoscopically remove a urethrolith [3]. The procedure resulted in retropulsion of the urethrolith into the bladder. Subsequently, a perineal urethrotomy was performed to ensure patency of the urinary tract, but bladder rupture and uroperitoneum was diagnosed 12 hours later. It cannot be proven that the urethroscopy caused the bladder rupture, but this was seen as a potential cause for the complication.
Gastric rupture has not been described in the equine literature as a sequella of gastroscopy; however, gastric rupture has been described in a human patient during diagnostic upper gastrointestinal endoscopy [4]. While this complication would be unlikely in most normal‐sized horses, it may be a potential complication in small patients.
Prevention
The authors of the jejunal volvulus case series concluded that it is advisable to minimize the duration and amount of air insufflated into the duodenum, reduce the amount of sedatives administered, and to use suction to decompress the stomach after gastroscopy is completed [2]. Bladder rupture and hypothetical gastric rupture are presumed to be exceptionally rare occurrences. Therefore, it is difficult to identify preventative measures. It may be prudent to avoid prolonged cystoscopy, especially if the urethra is partially obstructed.
Diagnosis
Jejunal volvulus was diagnosed as the presence of severe colic signs requiring colic surgery within a few hours of the gastroscopy procedure. Gastric rupture (hypothetical) or bladder rupture could be identified as the loss of distension at the time of the endoscopic examination. In the proposed clinical case, bladder rupture was identified as signs of uroperitoneum several hours later.
Treatment
All of these complications require emergency exploratory celiotomy to diagnose and correct the problem. Non‐surgical methods to manage bladder rupture have been described and may be a consideration in certain cases.
Expected outcome
If treated promptly, the outcome following jejunal volvulus and bladder rupture would be expected to be good. If intestinal ischemia or peritonitis occurs, the prognosis is much more guarded. Gastric rupture is a hypothetical risk, but if it occurred, the outcome would be poor due to difficulty in accessing the stomach for repair of the rupture and the spillage of gastric contents and subsequent peritonitis.
Air Embolism
Definition
One or more air bubbles get access to the circulatory system, causing blockade of one or multiple blood vessels.
Risk factors (attributed to presumptive venous air embolism)
Dorsal location of the urinary tract relative to the right ventricle
Presence of denuded epithelium
Pathogenesi
Urinary tract endoscopy was proposed to cause venous air embolism in two cases reported in the literature [5–7]. Please refer to the vascular air embolism section in Chapter 3: Complications of Intravascular Injection and Catheterization. Air was noted to be present within the renal pelvis during ultrasonographic examination performed 24 hours after the endoscopic procedure, which may suggest that air was absorbed through the renal vasculature [6]. The dorsal location of the urinary tract relative to the right ventricle is suggested to create a pressure gradient that favors the movement of air into the vasculature [7]. This may be additionally facilitated by the presence of denuded epithelium, which could increase the risk of air entering the bloodstream [5–7].
Prevention
Prevention of venous air embolism during urinary tract endoscopy would include use of alternative means to distend the urethra and bladder, such as saline solution or carbon dioxide gas, pre‐oxygenation with 100% oxygen, and anticoagulant therapy; however, the mucoid and crystalline nature of equine urine makes the use of saline to distend the bladder impractical [6, 7]. These precautions may be warranted in cases thought to be at higher risk for venous air embolism, such as cases presenting for hematuria or severe cystitis cases with denuded mucosa [7].
Diagnosis
Refer to Chapter 3: Complications of Intravascular Injection and Catheterization.
Treatment
The clinical signs and treatment of vascular air embolism are described in detail