Intermittent Colic and Intussusception Due to a Cecal Polyp in a Rabbit

Intermittent Colic and Intussusception Due to a Cecal Polyp in a Rabbit

AEMV Forum Intermittent Colic and Intussusception Due to a Cecal Polyp in a Rabbit Romain Pizzi, BVSc, MSc, DZooMed, FRES MACVSc(Surg), MRCVS, Regina...

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Intermittent Colic and Intussusception Due to a Cecal Polyp in a Rabbit Romain Pizzi, BVSc, MSc, DZooMed, FRES MACVSc(Surg), MRCVS, Regina Ursula Hagen, DrMedVet, CertVR, MRCVS, and Anna Louise Meredith, MA, VetMB, DZooMed, CertLAS, MRCVS

Abstract A 9-year-old male rabbit was presented for chronic intermittent anorexia and colic. A small abdominal mass was evident on palpation, and ultrasonography demonstrated a luminal mass and small intussusception in the distal cecum. Surgical resection of the distal third of the cecum was performed and histologic examination yielded a diagnosis of an inflammatory fibroid polyp. Although reported as causing intussusception in humans and other animals, the authors are unaware of any reports in pet or laboratory rabbits. The etiology and histogenesis of inflammatory fibroid polyps are still unclear. Copyright 2007 Elsevier Inc. All rights reserved. Key words: anorexia; cecum; intussusception; polyp; rabbit

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9-year-old intact male pet rabbit presented with scant dry droppings after having eaten small quantities of fresh, leafy greens for the previous 3 days. The rabbit presented in good body condition, weighed 2.7 kg, and was alert but quieter than usual. The owner reported the rabbit having several similar periods of reduced appetite or anorexia lasting a few days over the past 3 months. On examination, the only abnormality found was a firm, nodular mass, approximately 2 cm in length, palpated in the midcranial abdomen. The rabbit showed intermittent signs of colic, which was defined as acute abdominal discomfort. No feces were passed in the next 24 hours despite supportive syringe feeding (Critical care formula for small herbivores; Oxbow, Murdock, NE USA), so the rabbit was administered Cisapride (0.5 mg/kg orally every 8 hours, Prepulsid; Janssen Pharmaceutica, Titusville, NJ USA),1 Metoclopramide (0.5 mg/kg subcutaneously every 8 hours, Metocloperamide hydrochloride 5mg/5 mL; Sandoz, Princeton, NJ USA),2 and meloxicam (6 mg/kg orally once a day, Metacam; Boehringer-Ingelheim Ltd., St. Joseph, MO USA).3

The rabbit was anesthetized with medetomidine (0.1 mg/kg, Domitor; Pfizer Ltd., New York, NY USA), ketamine (5 mg/kg, Vetalar V; Pfizer Ltd.), and butorphanol (0.5 mg/kg, Torbugesic; Fort Dodge Co., Fort Dodge, IA USA), administered intramuscularly as a cocktail.4 Oral examination was unremarkable. The rabbit was then intubated with a blind technique and maintained on isoflurane (Isoba; Schering-Plough Animal Health, Harefield, UK). Ultrasonography with a 12-MHz probe (Logic 9; General Electric, Giles, UK) demonstrated a clearly visible intussusception (Fig 1). A mass could be seen extending into the cecal lumen, which was at the time of scanning interpreted as degenerating intestinal wall (Figs 2, 3). Intravenous adFrom the Royal (Dick) School of Veterinary Studies, Edinburgh University, Midlothian, United Kingdom. Address correspondence to: Romain Pizzi, Zoological Medicine Ltd, 37 Easter Bush, Roslin, Midlothian, EH25 9RE, United Kingdom. E-mail: [email protected] © 2007 Elsevier Inc. All rights reserved. 1557-5063/07/1602-$30.00 doi:10.1053/j.jepm.2007.03.007

Journal of Exotic Pet Medicine, Vol 16, No 2 (April), 2007: pp 113-117

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Figure 1. Longitudinal view of the intussusception imaged with a 12-MHz linear transducer. To the right of the image is the proximal part of the lesion, to the left the distal part.

ministration of isotonic crystalloid solution (Aqupharm No. 11; Animalcare Ltd., Thetford, Norfolk, UK) was initiated at 5 mL/kg/h. A midline exploratory coeliotomy revealed a pedunculated intraluminal mural mass proximal to a small intussusception of the distal quarter of the cecum (Figs 4, 5). Fluids were increased to 10 mL/kg/h and enrofloxacin (20 mg/kg subcutaneous, Baytril 2.5%, Bayer, Newbury, UK) was administered.5 The distal third of the cecum was removed, with 2-cm margins from the base of the mass. Hemostasis of the vessels was achieved as close to the serosa as possible with bipolar electrosurgery (Ellman Inc., Oceanside, NY USA). The remaining cecal mucosa and serosa appeared normal. The cecum was closed with simple interrupted sutures using 0.3-mm (2/0 United States Pharmacopeia) monofilament polydioxanone (PDS II, Ethicon; Johnson & Johnson, Somerville, NJ USA). Omental fat was sutured to the serosa to cover the wound. After copious abdominal

lavage with sterile isotonic fluid (Aqupharm No. 11, Animalcare Ltd.) warmed to 35°C, the abdomen was closed routinely by means of a simple continuous pattern with 0.3-mm (2/0 USP) polydioxanone (PDS II, Ethicon) in the linea alba. The surface epithelium was closed with 0.15-mm (4/0 USP) monofilament proliglecaprone 25 (Monocryl, Ethicon) with a simple, continuous, subcuticular pattern. Atipamezole (0.1 mg/kg intramuscularly, Antisedan; Pfizer Ltd.) was administered after surgery. After recovery from anesthesia, the rabbit was continued on intravenous fluids, antibiotics, gastrointestinal motility agents (as before), syringe feeding, meloxicam, and buprenorphine (0.05 mg/kg subcutaneously every 8 hours, Vetergesic; Alstoe Animal Health Ltd., York UK).6,7 The following morning, the rabbit was still depressed and only accepting small quantities of food when syringe fed. No feces had been produced overnight. Conscious dorsoventral and lateral abdominal

Figure 2. Longitudinal view of the intussusception at the level of the ileocecal junction. The polyp that was found protruding into the cecal lumen is labeled with an arrow.

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Figure 3. (A and B) Transverse image of the intussusception, imaged with a 12-MHz linear transducer showing the classical sonographic appearance of an intussusception with too many layers and lack of a visible lumen.

radiographs did not show any abdominal abnormalities. The rabbit did produce a small quantity of normal-appearing, moist feces later that same morning, but died in the early afternoon.

Postmortem Examination

Figure 4. Intraoperative view of the intussusception of the distal cecum.

Figure 5. View of the pedunculated cecal polyp and neighboring cecal mucosa after resection.

On gross postmortem examination, no other abnormalities were evident. Histological examination of

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Figure 6. Hematoxylin and eosin–stained section of the base of the fibroid polyp and neighboring cecal mucosa. A focal surface ulceration and associated degenerate neutrophils and necrotic debris are present. The fibrovascular nature is evident, and a small focal accumulation of lymphocytes is present (25⫻ magnification).

hematoxylin and eosin–stained sections of heart, lung, liver, kidney, and intestine revealed no other abnormalities. The cause of death could not be determined. Histology of the mass revealed a welldemarcated area at the level of the pedunculated mass, with well-differentiated mucosal epithelium, contiguous with a fibrovascular stroma (Fig 6). Fibroblasts were arranged in concentric rings around the arterioles and there was an associated infiltrate of eosinophilic granulocytes, with some focal nodular accumulations of lymphocytes and plasma cells (Fig 7). There were focal surface ulcerations, associated with large numbers of degenerate neutrophils, necrotic debris, and scattered bacterial colonies. In some regions, the neighboring cecal mucosa showed a high number of goblet cells, with some increased prominence of the lymphoid aggregates in the lamina propria. There was mild edema of the muscularis and serosa in areas of the associated cecum. These findings were judged to be consistent with an inflammatory fibroid polyp.

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reported.10-14 In contrast to intestinal obstruction, in which rabbits typically become rapidly anorexic and severely depressed, rabbits with cecal obstructions or impactions often remain bright and alert, but have a reduced appetite and fecal pellet production.10,11,15 They may show intermittent abdominal pain and a hunched posture. Affected rabbits may pick at food, eat a little, and drop the rest uneaten, and owners may not immediately be aware of the reduced food intake.15 Meloxicam was used in this case at a higher dose than reported by many authors, but a recent study demonstrated that a once-daily by mouth dosage of 0.3 mg/kg in rabbits did not provide therapeutic levels. The 0.3-mg/kg dose had an elimination halflife of only 8 hours, leading the authors to conclude that administration at 0.3 mg/kg by mouth once daily would be unlikely to provide effective analgesia over a 24-hour period.10,16,17 Although the cause of death could not be determined from the gross and histological postmortem examination findings, an electrolyte imbalance may have contributed to this animal’s demise. Preoperative and postoperative electrolyte determination may have been beneficial in the management of this patient. Ultrasonography is useful for identifying intestinal lesions if they are not obscured by gas. In some cases, and especially if a significant volume of intestinal or cecal gas is present, repeated examinations may be necessary. In this case, the lesion was correctly identified as an intussusception with ultrasonography, whereas the polyp was diagnosed at surgery.

Discussion Jenkins reported that the need for surgical interventions of the large bowel in the rabbit was uncommon and generally related to foreign body obstructions at the fusi coil because of the species’ unique gastrointestinal anatomy.8,9 Although dental disease and associated pain is the most common presenting cause for reduced appetite and decreased fecal production in rabbits, a variety of primary gastrointestinal disorders causing reduced appetite or anorexia are also

Figure 7. Hematoxylin and eosin–stained section of the inflammatory fibroid polyp, demonstrating fibroblasts in concentric rings around the arterioles, with an associated infiltrate of eosinophilic granulocytes and small mononuclear inflammatory cells (100⫻ magnification).

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Inflammatory fibroid polyps are reported as causing intussusception in humans and other animals, but the authors are unaware of any reports in pet or laboratory rabbits.18-20 Jabar reported a polyp in the cecum having a retrograde ball-valve like effect, contributing to chronic diarrhea and intussusception in an adult human.21 Jass and Savargaonkar et al reported that the etiology and histogenesis of inflammatory fibroid polyps still remain unclear.22,23

7. 8. 9.

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Conclusion

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This case illustrates the need for clinicians to fully evaluate anorexic rabbits clinically and carefully consider nondental causes. Owners must be attentive to changes in food intake and fecal pellet production to properly monitor their pet rabbits.

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Acknowledgments The authors thank Michelle Ward for helpful advice and Charlotte Routh for her initial management of the case.

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14. 15. 16. 17.

References 18. 1. 2.

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