WHAT DO WE KNOW ABOUT ALIMENTARY TRACT DUPLICATIONS IN CATS?

O presente trabalho trata-se de uma revisão de escopo de duplicações de trato gastrointestinal em gatos. Os critérios de inclusão foram determinados pela revisão de relatos de caso de duplicações gastrointestinais confirmadas por exame histopatológico, incluindo-se também neste trabalho um caso de um felino diagnosticado com duplicação cística duodenal em nossa instituição. Treze casos de duplicações gastrointestinais foram analisados, sendo que um animal possuía uma duplicação bifocal, totalizando, portanto, quatorze duplicações. As variáveis consideradas foram idade, sexo, raça, sintomatologia, localização anatômica, morfologia, presença de comunicação luminal, progressão para malignidade e recorrência. Aproximadamente 62% (n=8/13) dos gatos afetados apresentavam entre 4 meses a 2 anos de idade. Não foi observada predisposição quanto ao sexo, enquanto raça e sintomatologia variaram. Duplicações duodenais corresponderam a 36% (n=5/14). Duplicações císticas sem comunicação luminal 93% (n=13/14). Uma duplicação evoluiu para neoplasia e a recorrência de duplicações gastrointestinais entre os gatos foi de 15% (n=2/13). Evolução para obstrução, hemorragias e malignidade já foram descritas em humanos e gatos como consequência de duplicações gastrointestinais. Considerando a importância e o desafio diagnóstico desta afecção, conclui-se que o clínico veterinário de pequenos animais deve considerar as duplicações de aparelho digestivo no diagnóstico diferencial de gatos jovens com vômitos crônicos e massas císticas intestinais.


INTRODUCTION
Alimentary tract duplications are uncommon congenital disorder that can occur in variable anatomic sites and demand for treatment complete excision whenever possible (Radlinsky et al., 2005). Even though duplications are considered benign lesions, malignant transformation has been reported in cats (Hobbs et al., 2015).
In veterinary literature, reports of alimentary tract duplications are scarce. Herein, we aimed to construct a scoping review of data collected from the published literature of feline gastrointestinal duplications cases, adding one case of a duodenal duplication cyst diagnosed at our institution, the first Latin America case description, to overview the occurrence of this affection in cats.

Presentation
A 2-year-old male spayed shorthair cat, negative for FIV and FeLV, weighing 4.0kg, was presented to primary veterinary care with a one-week history of daily emesis.
History and presenting signs A previous abdominal ultrasound had been performed due to emesis history, revealing a cystic-like mass adhered to the duodenum. Symptomatic treatment was prescribed on attempt to reduce emesis clinical sign, consisting of oral administration of antiemetic drugs (ondansetron 0.5mg/kg TID 5 days) and proton pump inhibitors (omeprazole 1.0mg/kg BID 5 days). Despite complete remission of clinical signs, the animal was referred to the Veterinary Teaching Hospital (HUVET) of Universidade Federal Fluminense for further diagnostic investigation and resolution.

Physical and lab evaluation
On presentation at HUVET, physical examination revealed no abnormality except for mild epigastric pain. Complete blood count and a serum biochemical profile did not evidence alterations.

Other diagnostic assessments
A second abdominal ultrasound demonstrated a round cystic structure with 1.02cm (length) x 1.00cm (width) x 1.17cm (height) dimensions in the antimesenteric border of descending duodenum, near the cranial flexure. Cystic wall was thick and double-wall sign was present, with hyperechoic inner layer and an outer hypoechoic layer. Also, the cyst had anechoic content ( Figure 1a). The architecture of intestinal wall layers was preserved and there were no signs of cyst communication with the intestinal lumen. Furthermore, there was near mesenteric fat tissue alteration. Cranial to the mass, a well-defined hyperechoic area was observed containing small tubular formations.
Altogether, ultrasound diagnostic was compatible with duplication cyst and differential diagnosis considered were type I choledochal cyst; abscess; and pancreatic pseudocyst.
Thirteen gastrointestinal duplication cases in cats were analyzed and one animal had a bi-focal duplication, totalizing fourteen duplications. Variables considered were as follows:

DISCUSSION
Although the aetiopathogenesis of gastrointestinal duplication cysts remains unclear, theories involving defects in embryogenesis have been postulated, such as the partial twinning theory (Ravitch 1953), the split notochord theory (Bremer 1944), the canalization defects theory (Bentley and Smith 1960) and the environmental factors theory (Favara et al., 1971). No single embryologic mechanism is likely to be considered accurate, since duplications present variable forms (Pant et al., 2012).
Archives of Veterinary Science, v.26, n.1, p. 104-114, 2021. Cerquetella and colleagues (2015) described recurrent constipation and abdominal pain as a result of a possible colonic duplication cyst in a five-year-old domestic shorthair cat. Considering that histopathology, in that case, was not conclusive; the report was not included in this scoping review.
Young cats affected by duplications accounted for approximately 62% (n= 8/13) with most cases occurring in kittens from zero to 6 months old (Parry-Smith et al., 2008;Bernardé et al., 2014;Fruehwald and Ellison 2020) and junior cats from 7 months to 2 years (Radlinsky et al., 2005;Kramer et al., 2007;Doran et al., 2015;Agut et al., 2017) which is compatible to the age of the cat in the current case (2 years old). Human reports have analogous results with duplications being mostly diagnosed in infants and children (Stern and Warner 2000;Seeliger et al., 2012). Only one case was a geriatric cat that presented malignant transformation of a duodenal duplication cyst (Hobbs et al., 2015), which has also been reported in humans (Seeliger et al., 2012).
Duodenal duplications are known to be rare in humans and account for approximately 5% of enteric duplications (Arbell et al., 2002). Meantime, it is one of the most common locations of duplications in cats (approximately 36%; n= 5/14) (Parry-Smith et al., 2008;Bernardé et al., 2014;Hobbs et al., 2015;Agut et al., 2017) and this work reports the fifth case known in literature thus far.
Multiple level enteric duplications are rather uncommon but have been reported to occur in humans, with oesophageal duplication associated with small bowel duplication being the most frequent combination (Hur et al., 2007). Interestingly, one cat report showed a comparable presentation (Bernardé et al., 2014). Thus, once the duplication is diagnosed, other duplications should be sought; therefore, imaging methods should be contemplated (Nebot et al., 2018).
Ultrasound evaluation is the most used imaging method for diagnosis (Nebot et al. 2018) since it shows inner hyperechoic and outer hypoechoic layers -double-wall sign or muscular rim sign -relatively specific of duplication cysts (Hur et al., 2007;Agut et al., 2017), which was present in our cat's ultrasound evaluations. The technique has limitations once it is operator and patient dependent and, occasionally, US alone is not able to determine the origin of the lesion and presence of lumen communication. Hence, contrast radiography and computed tomography (CT) may complement evaluation (Agut et al., 2017).
Moreover, some factors associated to size, location, type, mucosal pattern and presence of complications may lead to different imaging findings of duplication cysts. It is important to consider bowel obstruction, intramural haematoma, intramural tumours, abscess, pancreatic pseudocysts, choledochal cysts and neoplasia as differential diagnosis (Agut et al., 2017;Nebot et al., 2018).
Exploratory laparotomy with total excision of the enteric duplication cyst is the standard treatment (Hobbs et al., 2015;Turner et al., 2019) and it was suitable in the current case, since there were no signs of recurrence and the cat recovered well after procedure. Recurrence has been reported in two previous cases (Kramer et al., 2007;Hobbs et al., 2015). In humans, minimally invasive techniques -such as laparoscopy -are also proving to be effective on complete resection of intestinal duplications (Górecki et al., 2015).

CONCLUSION
To summarize, it is essential for the small animal practitioner not to overlook alimentary tract duplications in the differential diagnosis of young cats with chronic vomiting and cystic intestinal masses diagnosed by US evaluation. As far as we are concerned, this is the first scoping review about alimentary tract duplications in cats, as well as the first case description to occur in Latin America.