Abstract
CASE DESCRIPTION A 13-year-old female green iguana (Iguana iguana) was examined because of a 6-day history of vomiting, anorexia, and lethargy and a 4-day history of decreased fecal and urate output.
CLINICAL FINDINGS Physical examination revealed a distended abdomen, signs of depression, pallor, tachycardia, harsh lung sounds, and vomiting. Abdominal radiographs revealed gas distention of the stomach and small intestine with fluid lines evident on the lateral view. Plasma biochemical analysis indicated hypochloremic metabolic alkalosis, hyperglycemia, and hyperuricemia.
TREATMENT AND OUTCOME Exploratory laparotomy confirmed a diagnosis of small intestinal entrapment and 170° volvulus involving approximately 80% (20 to 30 cm) of the small intestine. The portion of the small intestine extending from the middle portion of the duodenum to the caudal extent of the ileum was resected, and end-to-end anastomosis of the remaining small intestine was performed. The iguana recovered without apparent complications and was reportedly doing well 1 year after surgery.
CLINICAL RELEVANCE Findings suggested that iguanas, as hindgut fermenters, may tolerate > 70% resection of the small intestine with a good outcome and no clinical evidence of residual gastrointestinal dysfunction.
A 13-year-old female green iguana (Iguana iguana) was examined by the Avian and Exotic Medicine Service of the Ontario Veterinary College companion animal hospital (OVC Health Sciences Centre) because of a 6-day history of vomiting, anorexia, and lethargy and a 4-day history of decreased urate and fecal output. There was no other medical history of note. The owner had acquired the iguana 12 years ago. The iguana was allowed to roam freely in a dedicated room equipped with large branches for climbing and basking, ceramic heating bulbs, and a UVB fluorescent bulb that was changed every 6 months. The ambient temperature was 24° to 35°C (75° to 95°F). Humidity was not monitored; however, a humidifier was provided in the room during the winter. The iguana was soaked in lukewarm water (30°C [85°F]) for 15 minutes once weekly. It received a diet comprised of commercial iguana pellets and a mix of fruits, vegetables, and dark leafy greens (eg, collard greens, zucchini, peppers, bananas, oranges, grapes, carrots, and broccoli). A powdered calcium supplement was also administered daily. Water was provided ad libitum and changed daily.
The iguana had been evaluated by the primary care veterinarian 3 days previously. Because of an apparently distended abdomen, an orogastric tube was placed, which yielded approximately 100 mL of green liquid. Plasma biochemical analyses were also performed, which indicated hyperuricemia (uric acid concentration, 1,482 μmol/L; reference interval, 0 to 487 μmol/L);1 plasma chloride concentration was not measured. Abdominal radiographs (lateral and ventrodorsal views) were obtained and revealed mild gas distension of the stomach and intestines. The iguana was then given oral barium sulfate prior to discharge; however, no additional radiographs were obtained.
At the time of initial examination at our hospital, the iguana appeared depressed, with pale mucous membranes, mild tachycardia (heart rate, 72 beats/min; reference mean ± SD heart rate, 52 ± 16 beats/min),2 and harsh lung sounds on thoracic auscultation. It weighed 4 kg (8.8 lb) and was estimated to be approximately 10% clinically dehydrated. The coelomic cavity was distended, and the iguana showed signs of pain on palpation. The iguana vomited approximately 50 mL of green fluid during the physical examination. A blood sample was collected from the ventral tail vein. Evaluation of venous blood gases and electrolyte concentrations revealed severe hypochloremia (65 mmol/L; reference interval, 102 to 130 mmol/L), normal pH (7.48; reference mean ± 2SD, 7.38 ± 0.12), high bicarbonate concentration (51.7 mmol/L; reference mean ± 2SD, 24 ± 8 mmol/L), high partial pressure of carbon dioxide in venous blood (pvco2; 69.7 mm Hg; reference mean ± 2SD, 42 ± 22 mm Hg), a base excess of 24.2 mmol/L (reference mean ± 2SD, −4 ± 12 mmol/L), normal plasma lactate concentration (10.5 mmol/L; reference mean ± 2SD, 4.2 ± 6.8 mmol/L), and hyperglycemia (glucose concentration, 33 mmol/L, reference interval, 9 to 16 mmol/L).1,2 The calculated apparent strong ion difference (sodium concentration – chloride concentration) was 80 mEq/L (reference value in mammals, 36 mEq/L) and the anion gap was 31.8 mEq/L (reference interval in dogs, 12 to 24 mEq/L).3 As noted, the plasma biochemical analysis performed 3 days prior to referral revealed hyperuricemia (1,482 μmol/L). Overall, these results suggested hypochloremic metabolic alkalosis and respiratory acidosis, likely caused by chronic vomiting and decreased ventilatory capacity secondary to the distended coelomic cavity.
Radiographs (standing lateral and dorsoventral views) acquired at the time of initial examination revealed a large gas-filled stomach, multiple loops of gas-distended intestines, and visible fluid lines on the standing lateral radiographic view (Figures 1 and 2). A large amount of the barium administered 3 days previously was still evident in the stomach, which suggested gastric stasis (normal gastric emptying time, approx 8 hours).4 The lung fields appeared compressed as a result of gastrointestinal distention. On the basis of the clinical signs, results of laboratory testing (ie, metabolic alkalosis), and radiographic findings, obstructive ileus was the presumptive diagnosis. Because of financial constraints, the owners elected to delay the recommended exploratory laparotomy until after the weekend (ie, 2 days), with supportive care provided in the interim.
Standing lateral radiographic view of a 13-year-old female green iguana (Iguana iguana) evaluated because of a 6-day history of vomiting, anorexia, and lethargy and a 4-day history of decreased urate and fecal output. On physical examination, the abdomen was distended and signs of pain were evident during abdominal palpation. Three days previously, abdominal radiographs were obtained by the primary care veterinarian and revealed mild gas distention of the stomach and intestines, and the iguana received barium sulfate PO at that time. Note the distention of the gastrointestinal system, the presence of gas, and the presence of fluid lines (arrows). Barium is still present in the stomach (asterisk) 3 days after administration.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1061
Dorsoventral radiographic view of the iguana in Figure 1. See Figure 1 for key.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1061
Treatment for dehydration and metabolic alkalosis was immediately instituted. An initial fluid bolus of saline (0.9% NaCl) solutiona (30 mL/kg [13.6 mL/lb]) was administered SC, and the iguana was placed in a warm water bath (30°C) for 15 minutes, during which time a large amount of feces and urates was passed. A fecal examination was not performed. Butorphanolb (0.05 mg/kg [0.023 mg/lb], IM, q 12 h) was prescribed for analgesia, with ceftazidimec administered for antimicrobial prophylaxis (40 mg/kg [18.2 mg/lb], IM, q 48 h), and the iguana was placed in a warm incubator with UVB lighting. The temperature was maintained at the higher end of the preferred optimal temperature range (29° to 38°C [84° to 100°F]) for this species.1 The iguana continued to receive boluses of saline solution (30 mL/kg, SC, q 8 to 12 h) throughout the weekend prior to the scheduled surgery. Handling was minimized because this resulted in stress-induced vomiting. The iguana's condition was otherwise stable over the weekend.
On the day of surgery, plasma biochemical analysis revealed normal uric acid concentration, but persistent hypochloremia (69 mmol/L) and hyperglycemia (20 mmol/L). The iguana was sedated with butorphanol (0.03 mg/kg [0.014 mg/lb]) and midazolamd (1 mg/kg [0.45 mg/lb]) IM, and an IV catheter was placed in the ventral tail vein. An IV bolus of saline solution (10 mL/kg [4.5 mL/lb]) was administered, and the iguana then received a constant rate infusion of 10 mL/kg/h for 2 hours prior to anesthetic induction in an attempt to further correct fluid and electrolyte deficits. General anesthesia was then induced by means of administration of propofole (10 mg/kg, IV); however, during induction, the IV catheter in the ventral tail vein became dislodged by the movements of the tail. The iguana was intubated with a 3.5-mm uncuffed endotracheal tube, and induction of anesthesia continued with administration of 5% isoflurane in oxygen and manual ventilation. An intraosseous catheter was then placed in the right femur with a 1.5-inch, 22-g spinal needle; infusion of saline solution was continued throughout via this catheter at a rate of 10 mL/kg/h. An orogastric tube was passed to decompress the stomach and prevent vomiting and aspiration during anesthesia. On initial passage of the tube, approximately 100 to 150 mL of green fluid was aspirated from the stomach. Monitoring included heart rate (by means of Doppler ultrasonography), ECG, and end-tidal partial pressure of CO2 (Petco2, by means of capnography). Additionally, the iguana was placed on a warming blanket to help maintain body temperature at the upper end of the optimal temperature range for the species. Once the animal's condition was stable following anesthetic induction, instrumentation, and positioning, anesthesia was maintained throughout surgery with 2% isoflurane in oxygen and mechanical ventilation.
Surgery was performed with the patient in dorsal recumbency. After standard aseptic skin preparation and draping, an 8-cm ventral paramedian skin incision was created. On entry into the coelomic cavity, severe distention of the stomach and the small and large intestines was noted. Further exploration revealed an approximately 1-cm mesenteric tear through which almost the entire length (about 20 to 30 cm) of the small intestine had passed and become entrapped, resulting in an approximately 170° volvulus of the small intestine (Figure 3). Following reduction and correction of the volvulus, the serosal surface of the affected small intestine was dark red to black and assessed as nonviable (Figure 4). Therefore, resection was deemed necessary. After isolation of the affected intestine, the portion of the small intestine extending from the middle part of the duodenum, just caudal to the entrance of the bile duct, to the caudal extent of the ileum, approximately 1 cm orad to the ileo-cecal junction, was resected. It was estimated that approximately 80% (20 to 30 cm) of the small intestine was resected. The remaining duodenum and ileum were anastomosed in an end-to-end fashion by means of a simple interrupted pattern with 5-0 absorbable suture material.f After the anastomosis was leak tested, the coelomic cavity was explored, with no other abnormalities detected, and then copiously lavaged with warm (37°C [98.6°F]) saline solution. The body wall and subcutaneous tissue were closed in a routine manner by use of a simple continuous pattern with 4-0 absorbable suture,g and the skin was closed with 4-0 absorbable suture in an everting interrupted pattern. The iguana recovered from anesthesia and was breathing room air without apparent complications.
Photograph of the patient in Figure 1 obtained at the time of initial entry into the coelomic cavity during an exploratory laparotomy. Almost the entire small intestine (20 to 30 cm [held in gloved fingers]) was entrapped via a mesenteric rent (arrow). C = Colon. D = Duodenum.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1061
Photograph of the patient in Figure 1 obtained during exploratory laparotomy. The small intestine is depicted after enlargement of the mesenteric rent that was entrapping the involved intestinal segment and after reduction and detorsion of the 170° volvulus. The affected small intestine appears congested and devitalized. The portion of the small intestine extending from the midduodenum to the caudal extent of the ileum was resected, and end-to-end anastomosis was performed. C = Colon. D = Duodenum.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1061
Samples of the resected small intestine were sent for histologic examination, including samples from adjacent to the surgical margins and from the center of the resected segment. Tissue samples from the margins showed marked hemorrhage in all layers of the intestinal wall. Early fibroplasia with many plump fibroblasts and occasional mitotic figures was noted between the layers of the tunica muscularis. The intestinal epithelial cells appeared viable throughout 1 section; within another, there was frequent erosion, diapedesis, and frank hemorrhage at villous tips. The lamina propria of affected villi contained fibrin, and there was hyaline degeneration of arteriolar walls as well as venous thrombosis. In samples from the center of the resected segment, there were bacterial colonies covering the mucosal surface and frequent thrombosed blood vessels in the remnants of the lamina propria. Viable epithelial cells were present in the base of a small proportion of crypts. The submucosa was markedly edematous with a mild to moderate infiltration of heterophils, and there was hemorrhage between the layers of the tunica muscularis. Lesions in all samples examined were considered consistent with a diagnosis of venous infarction secondary to small intestinal volvulus and entrapment.
The iguana was hospitalized for 3 days after surgery. Intraosseous fluid therapy (saline solution, 2 mL/kg/h [0.9 mL/lb/h]) was continued until postoperative day 2, at which time increased activity necessitated catheter removal. The iguana also received ceftazidime (40 mg/kg, IM, q 48 h), sucralfateh (200 mg/kg [90.9 mg/lb], PO, q 24 h), and hydromorphonei (0.05 mg/kg, IM, q 24 h) until hospital discharge 3 days after surgery. It was also syringe-fed approximately 10 mL of a premium recovery food for herbivoresj twice daily. Venous blood gases evaluated 1 day after surgery were mostly within reference ranges (chloride concentration, 93 mmol/L; bicarbonate concentration, 43.2 mmol/L; lactate concentration, 3.2 mmol/L; modified strong ion difference, 56 mEq/L; and anion gap; 16 mEq/L). By day 2 after surgery, the iguana was eating salad and pellets and was passing feces and urates. Ceftazidime administration (40 mg/kg, IM, q 12 h) was continued at home for an additional 10 days as well as meloxicam (0.2 mg/kg [0.09], PO, q 24 h) for an additional 3 days.
Follow-up continued for 1 year postoperatively, during which time the iguana appeared healthy with an apparently normal appetite. At the time of last follow-up, the owners were very satisfied with the outcome and reported that defecation was normal, with no diarrhea noted. The iguana appeared in good condition, maintaining its presurgical weight of 4 kg.
Discussion
This report documents the diagnosis and successful resolution of severe intestinal entrapment and volvulus in a green iguana by means of radical enterectomy and proximal duodenoileal anastomosis. The cause of the intestinal entrapment and volvulus was not determined in the patient of this report; however, gastrointestinal obstruction is relatively common in reptiles and frequently caused by the ingestion of foreign materials such as sand, gravel, and cotton.5–9 Other reported causes include intestinal neoplasia, impaction with parasites, and intussusception.8–12 Management typically requires prompt diagnosis and emergency surgical intervention. In the case described in the present report, the typical electrolyte abnormalities (ie, hypochloremic metabolic alkalosis), severe vomiting, and radiographic findings of gastrointestinal distention with delayed transit time of orally administered barium were highly suggestive of a gastrointestinal obstruction.
The iguana of this report did not undergo surgery until 8 days after the initial onset of clinical signs. It is possible that with earlier diagnosis and surgical treatment, the extensive enterectomy may have been avoided. In mammals, delayed surgical intervention is correlated with a negative outcome.13 For instance, in dogs with gastric dilatation and volvulus, the presence of clinical signs for > 6 hours prior to examination was associated with a decreased survival rate and increased rate of postoperative complications.13 In this iguana, most of the small intestine (about 20 to 30 cm) was severely congested with areas of necrosis by the time surgery was performed. Nonetheless, near complete small intestinal resection, including most of the duodenum, the entire jejunum, and most of the ileum, resulted in a favorable outcome for this patient. Length of intestine removed at surgery has also been correlated with a negative outcome in domestic mammals such as horses14; however, it is possible that this association may not apply to herbivorous reptiles. Our experience in treating the iguana of this report (which apparently recovered well, eating 1 day after surgery, and in apparent good health 1 year later, without notable weight loss or diarrhea) suggested that extensive small intestinal resection is feasible in green iguanas.
Green iguanas, like horses and lagomorphs, are hind-gut fermenting herbivores.15 Iguanas have a complex fermentation system in the colon and cecum where most nutrient extraction is in the form of volatile fatty acids.16–19 Furthermore, it has been previously reported17 that only approximately 20% of total volatile fatty acid production in green iguanas occurs in the small intestine.17 As such, because the bile duct and pancreatic duct were left intact and the cecum and colon were unaffected, we suggest that this iguana was able to adjust and function adequately. The provision of high-quality food ad libitum in captivity may also potentially decrease the need to maximize nutrient extraction. However, some important macro- and micronutrients may require a functional small intestine for absorption.17 Protein digestion occurs almost entirely in the small intestine, whereas fiber is processed by the large intestine.17 The outcome at 12 months for the iguana of this report indicated that this patient apparently adapted well to its presumed decreased digestive function.
The iguana described in the present report also illustrated the severe acid-base and electrolyte abnormalities associated with chronic gastrointestinal obstruction in this species. In particular, hypochloremia was remarkably severe and, with the extremely high bicarbonate concentration and strong ion difference, was highly suggestive of ileus associated with mechanical obstruction, with third spacing of fluids in the stomach (as evident on the preoperative lateral radiographic view and by the frequent vomiting of liquid). The expected alkalosis was apparently balanced by respiratory acidosis, decreased renal perfusion, and increased lactate concentration secondary to decreased tissue oxygen delivery, resulting in a normal pH. Green iguanas have been reported to develop respiratory compensation for fluctuations in blood pH.20 In the iguana of this report, we suggest that the respiratory acidosis resulted from respiratory compensation or decreased ventilation because of gastrointestinal distention compressing the lungs, which, in Iguanidae, are not separated from the coelomic cavity by a postpulmonary septum (vs Varanidae, chelonians, and crocodilians). Additionally, blood pH in reptilians is reportedly more labile than in mammals and will change with environmental temperature and physiologic conditions.20,21 Thus, values considered extreme according to mammalian standards may be physiologic in reptiles, indicating that reptiles may tolerate a greater range of pH.20,21
Therefore, whereas the same overall approach to acid-base imbalance interpretation can be applied to reptilian and mammalian patients, this case suggested that reptiles can tolerate more severe changes and for a longer duration. In addition, it is our clinical experience that acid-base imbalance in reptiles may correct relatively slowly (ie, over several days) even with appropriate treatment. The marked hyperglycemia in the iguana of this report was also suggestive of gastrointestinal obstruction. Although an association between hyperglycemia, gastrointestinal obstruction, and survival has not been demonstrated in reptiles, it is recognized in other herbivorous mammals such as horses and rabbits.22,23 The lactate concentration (10.5 mmol/L) appeared high in this iguana when applying mammalian criteria, but was within the reference interval reported for reptiles.1 Reptiles have a greater capacity for anaerobic metabolism, compared with mammals, and high lactate values may also occur with a variety of physiologic and pathological conditions.21 Furthermore, the plasmabuffering system and bicarbonate concentrations in some active or aquatic reptilian species are greater than in mammals, likely to compensate for the lactic acidosis induced by anaerobic metabolism.20 As such, the association between plasma lactate concentration and tissue perfusion status may be difficult to determine in reptilian patients.
Acknowledgments
Presented in abstract form at the 21st Annual Association of Reptilian and Amphibian Veterinarians Conference, Orlando, Fla, October 2014.
Footnotes
Baxter, Mississauga, ON, Canada.
Torbugesic, Zoetis Canada Inc, Kirkland, QC, Canada.
Fortaz, GlaxoSmithKline, Research Triangle Park, NC.
Pharmaceutical Partners of Canada, Manotick, ON, Canada.
Pharmascience Inc, Montreal, QC, Canada.
PDS (polydioxanone) taper needle, Ethicon US LLC, Somerville, NJ.
PDS (polydioxanone) cutting needle, Ethicon US LLC, Somerville, NJ.
Aptalis Pharma Canada, Mont-Saint-Hilaire, QC, Canada.
Sandoz Canada Inc, Boucherville, QC, Canada.
Critical Care, Oxbow Animal Health, Murdock, Neb.
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