Diagnosis and treatment of mesenteric volvulus in a red kangaroo (Macropus rufus)

• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 244, Nº. 7, 2014, págs. 844-850
• Idioma: inglés
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• Resumen

  • Case Description�An 8-year-old male red kangaroo (Macropus rufus) was evaluated with a 2-week history of vomiting and anorexia. Four days prior, the patient became refractory to medical management. The kangaroo was admitted for diagnostic testing and treatment including whole body CT, blood work, and emergency laparotomy.

    Clinical Findings�CT findings of a severely enlarged stomach, splenic displacement, and a whirl sign were indicative of mesenteric volvulus with gastric dilatation-volvulus (GDV). Contrast enhancement of abdominal viscera suggested intact arterial blood supply; however, compression of the caudal vena cava and portal vein indicated venous obstruction. Results of preoperative blood work suggested biliary stasis without evidence of inflammation. Additionally, a tooth root abscess was diagnosed on the basis of results of CT.

    Treatment and Outcome�Exploratory laparotomy confirmed the diagnosis of mesenteric volvulus and GDV. The volvuli were corrected by clockwise derotation, and a gastropexy was performed. Tissue samples were obtained from the spleen and liver for evaluation. The kangaroo recovered from surgery, and the abscessed tooth was extracted 6 days later. Eight days after initial evaluation, the kangaroo was discharged.

    Clinical Relevance�In the present report, the CT whirl sign was used to diagnose volvulus of the abdominal viscera, which suggests that this diagnostic indicator has utility in veterinary patients. Mesenteric volvulus with GDV was successfully treated in a nondomestic species. The tooth root abscess, a common condition in macropods, may explain the historic episodes of anorexia reported by the owner and may have contributed to the development of mesenteric volvulus and GDV in this kangaroo.

    An 8-year-old male red kangaroo (Macropus rufus) from a small private zoo was evaluated because of vomiting and anorexia. Clinical signs had been noticed for at least 2 weeks prior, with a reported initial frequency of vomiting 1 to 4 times/d. The severity and frequency of the vomiting had increased over the 4 days prior to initial evaluation to 6 to 10 times/d. The kangaroo's clinical signs had become refractory to treatment with flunixin meglumine and sucralfate administered by the owner at unknown doses. A complete medical history revealed that the kangaroo had a similar vomiting episode a year before, which resolved with medical management under the care of a local veterinarian. Furthermore, there was a history of intermittent vomiting over the past year with several 1- to 2-day periods of malaise and inappetence. This kangaroo lived in a large box stall that connected to a pasture shared with 1 female kangaroo. It had no other known medical history.

    Initial physical examination revealed the kangaroo to be bright and alert with a thin body condition (body condition score, 3/9) and mild muscle wasting. The kangaroo weighed approximately 68 kg (150 lb) and stood hunched, appearing to guard a moderately distended abdomen. The patient was observed to vomit 3 times during visual examination. Attempts at cardiothoracic auscultation while the kangaroo was awake caused visible signs of stress, and a complete examination was delayed until the animal was sedated. Deep sedation was achieved after administration of ketamine hydrochloridea (5 mg/kg [2.3 mg/lb], IM, once) and butorphanol tartrateb (0.2 mg/kg [0.09 mg/lb], IM, once). A complete physical examination under sedation was normal except for marked abdominal distension. Blood was then collected from the lateral tail vein and submitted for hematologic evaluation and serum biochemical analysis. Hematologic evaluation demonstrated evidence of dehydration, with elevated PCV (53%; reference range, 46% to 51%)1 and elevated total protein concentration (9 g/dL; reference range, 6 to 6.8 g/dL). The results of the biochemistry profile demonstrated moderate hyponatremia (138 mEq/L; reference range, 146 to 152 mEq/L), mild hypokalemia (4.3 mEq/L; reference range, 4.6 to 5.6 mEq/L), moderately icteric plasma, mildly elevated aspartate aminotransferase activity (124 U/L; reference range, 36 to 43 U/L), and mildly elevated bilirubin concentration (4.5 mg/dL; reference range, 1 to 4 mg/dL). Blood lead concentration and Toxoplasma antibody titers were within reference limits. General anesthesia was induced and maintained with isofluranec in oxygen administered by facemask. Once the kangaroo was anesthetized, an IV catheter was placed in the left lateral saphenous vein. Given the extent of abdominal distention, large patient size, shorter examination times versus radiography or ultrasonography, and excellent cross-sectional and multiplanar detail with image reconstruction, it was determined that CT was the most suitable imaging modality. With the patient positioned in dorsal recumbency, whole body CTd scans before and after contrast media administration (iohexole, 700 mg/kg [318.2 mg/lb] IV, once) were performed. CT images were acquired in a volumetric fashion with contiguous transverse slices, and reconstructed in 1- to 4-mm transverse, sagittal and dorsal plane images, and volume-rendered maximum-intensity projection. The images were displayed in soft tissue, bone, lung, and soft tissue postcontrast windows, and viewed on a commercial picture archiving and communication system.f Evaluation of the results of CT revealed that the abdominal cavity was distended by a very large, sacculated, gas- and fluid-distended stomach2 (Figure 1). A moderately enlarged, gas- and fluid-filled esophagus was diagnosed as generalized megaesophagus. The dilated esophagus could be traced into the midcranial abdomen, where it tapered, and coursed slightly to the right into a whirl-like structure composed of swirling strands of alternating mesenteric soft tissue� and fat-attenuating tissue (whirl sign)3 around the celiac and cranial mesenteric arteries, with the esophagus at the center (Figure 2). The prehepatic caudal vena cava and portal vein were severely narrowed, particularly through the region of the whirl. The spleen was moderately to severely enlarged,4 had increased contrast enhancement in a speckled pattern, and was abnormally located in the right dorsal abdomen (Figure 3). The small and large intestinal segments were diffusely, mildly distended (up to 1.5 cm in diameter) with gas, fluid, and feces, with normal wall contrast enhancement. Unusually, the small intestine was divided into separate portions, with 1 part located in the left craniodorsal abdomen and the remainder in the caudal and right dorsal abdomen. The tributaries and branches of the portal vein and cranial mesenteric and celiac arteries, originating at the whirl at the root of the mesentery, were subsequently distributed throughout the abdomen toward these displaced viscera. The gallbladder was moderately enlarged and fluid distended. The bile duct was also enlarged and could be traced into the whirl, where it tapered until it was no longer visible. A small amount of fluid was dispersed throughout the peritoneal cavity. The liver was confined to the right cranial abdomen. No evidence of a tumor, foreign body, or other cause of gastrointestinal obstruction was observed. A tooth root abscess of the right lower first incisor was diagnosed on the basis of severe expansion and thinning of the alveolar bone surrounding this tooth with a large amount of periapical lucency.

    View larger version(71K) Figure 1� Sagittal plane CT reconstruction (slice thickness, 2 mm; soft tissue window) of the abdomen of an 8-year-old male red kangaroo (Macropus rufus) evaluated because of a 2-week history of progressive vomiting and anorexia. Patient is in dorsal recumbency. The sacculated stomach is severely enlarged, with gas and fluid distension. Horizontal gas-fluid interfaces (arrows) can been seen within various stomach compartments (the fluid is dependent). Cd = Caudal. Cr = Cranial. D = Dorsal. V = Ventral.

    View larger version(128K) Figure 2� Dorsal plane maximum-intensity projection CT reconstruction (slice thickness, 10 mm; soft tissue window images obtained after contrast administration) of the patient in Figure 1. The whirl sign, created by contrast-enhancing mesenteric blood vessels swirled with fat-attenuating mesentery, is evident in the cranial midabdomen (arrows), indicating mesenteric volvulus. L = Left. R = Right. See Figure 1 for remainder of key.

    View larger version(143K) Figure 3� Dorsal plane CT reconstruction (slice thickness, 2 mm; soft tissue window images obtained after contrast administration) of the patient in Figure 1. The spleen, which is enlarged and has increased contrast enhancement in a speckled pattern, is abnormally located in the right side of the abdomen (arrows). See Figures 1 and 2 for remainder of key.

    From these CT findings, the kangaroo was suspected to have an anticlockwise mesenteric volvulus, a GDV = 180° with associated splenomegaly and 45° to 90° splenic displacement, and secondary megaesophagus. An underlying cause for these pathological changes was not detected. Even though contrast enhancement of the abdominal viscera indicated adequate arterial blood supply, venous obstruction was evident. Biliary obstruction was also considered as a differential diagnosis because of the presence of icteric plasma and elevated serum bilirubin concentration. At the time of the CT scan, not all imaging findings had been thoroughly evaluated. Therefore, the kangaroo was recovered from anesthesia pending a complete review of all diagnostic tests. On the basis of the imaging results, combined with hematologic and clinical findings, surgical exploration of the abdomen was elected.

    The kangaroo was again anesthetized approximately 4 hours later with midazolamg (0.2 mg/kg, IV, once) and dexmedetomidineh (0.1 mg/kg [0.045 mg/lb], IV, once), an endotracheal tube was placed, and inhalation anesthesia was maintained with sevofluranei in oxygen. The kangaroo was positioned in dorsal recumbency, and the abdomen was clipped of hair and prepared for surgery by means of standard aseptic technique. A routine ventral midline incision was made, and upon entry of the abdomen, the stomach was confirmed to be severely gas distended with omentum covering the ventral portion, similar to what is typically found in dogs affected with GDV. The proximal loops of small intestine were discolored (ie, dusky purple), appeared to be in an abnormal location, and at that time, were markedly distended (Figure 4). The spleen was not immediately identified upon entering the abdomen because it was dorsal to the distended stomach and small intestine. Once located, the spleen was an abnormal blue-gray color and displaced to the right dorsal abdomen. A small volume of serosanguinous fluid was present in the abdomen. The root of the mesentery was palpated and found to be thick and firm. The bowel was examined, and no perforations, foreign bodies, or masses were detected. The gallbladder was observed and found to be full and patent, although expressed with some difficulty. Neither a 1- or 0.75-cm-diameter orogastric tube could be passed into the stomach because of firm resistance at the cardia. The spleen was gently passed dorsally to the distended small bowel loops from right to left into its normal position. This movement was achieved with some resistance and tension, and it was observed that the remainder of the bowel began to change to a similar purple color as the more proximal small bowel loops. A 16-gauge catheter was placed into the stomach to allow gas decompression. Two liters of warm sterile saline (0.9% NaCl) solution was then poured into the abdomen, and the abdominal contents were allowed to float freely to aid in manipulation. Initial attempts to rotate the viscera counterclockwise only added tension to the attachments and exacerbated the dark discoloration of the bowel. Therefore, the intestines, spleen, and stomach were subsequently rotated (from the ventral aspect) in a clockwise direction. The viscera moved without tension and swiftly transitioned to a more normal coloration. The gastrointestinal tract was assessed as viable, and therefore, resection was not indicated. The root of the mesentery was palpated again and found to be relaxed with no suggestion of twisting within the tissue as observed previously. Biopsy samples were obtained from the spleen and liver to help identify any underlying disease that could have contributed to the clinical signs. A gastropexy was performed by scarification along a taenia band of the stomach. A 5-cm incision was made in the right ventrolateral aspect of the body wall, and scarification was performed adjacent to this site. Several simple interrupted No. 1 polypropylene sutures were placed between the sites of scarification, fixing the stomach to the body wall. A 0.75-cm orogastric tube could be passed successfully at this time. Closure of the incision and recovery from anesthesia were normal. Vitamin Ej (40 U/kg [18 U/lb], SC, once) was administered to help prevent stress or capture myopathy in this animal in light of recent confinement, travel, surgery, and hospitalization. Results of histologic evaluation of the spleen were normal; however, the liver showed evidence of biliary obstruction of undetermined chronicity.

    View larger version(146K) Figure 4� Intraoperative photograph of the patient in Figure 1, during emergency laparotomy via a ventral midline approach. A�Notice the distended, twisted stomach with tightly wrapped omentum ventrally (large arrow) and distended, twisted loops of small intestines (small arrow). The spleen is not visible. B�Following repositioning of the viscera, the decompressed, normally located stomach (large arrow), relaxed loops of small intestines (small arrow), and the spleen are visible in the left side of the abdomen (arrowhead). See Figures 1 and 2 for remainder of key.

    The kangaroo was treated with crystalloid fluidsk (3 mL/kg/h, [1.4 mL/lb/h], IV, continuous rate infusion) supplemented with 2.5% dextrosel and potassium chloridem (15 mEq/L), buprenoprhinen (0.01 mg/kg [0.005 mg/lb], IV, q 8 h), flunixin meglumineo (0.5 mg/kg [0.23 mg/lb], IV, q 12 h), famotidinep (0.5 mg/kg, IV, q 24 h), and penicillin G procaineq (20,000 U/kg [9,000 U/lb], SC, q 24 h). The first day after surgery, the kangaroo was quiet and alert but had not shown any interest in food and had not defecated. Serosanguinous fluid was observed to be oozing from the incision site focally, but there were no signs of dehiscence. In the evening, the kangaroo was sedated with midazolamg (0.2 mg/kg, IV, once) to facilitate cleaning and bandaging of the incision site. Mirtazapiner (0.4 mg/kg [0.18 mg/lb], PO, q 24 h), an appetite stimulant frequently administered in small animals, was administered, and the kangaroo was observed eating hay shortly thereafter. The next morning, the abdominal incision continued to accumulate fresh blood at the same site, and an IV catheter placed 48 hours previously was still slowly oozing blood from the venous cut-down site. Given the increased activity of hepatic enzymes prior to surgery, and the potential for a protein-losing enteropathy following correction of the volvulus, there was concern that the kangaroo might have developed a coagulopathy. Blood was collected for a coagulation panel, which was suggestive of a mildly prolonged (Russell's viper venom) clotting time (27 seconds; canine range, 19 to 25 seconds) and normal D dimer concentration for a postoperative patient (404 ng/mL). Vitamin Ks (3 mg/kg, SC, once) was administered and the incision bandaged. Over the next 5 days in the hospital, the kangaroo steadily appeared brighter and became more active, suggesting its comfort level was improving. The incision site appeared clean and dry. The kangaroo was maintained on all previously described treatments and defecated normally starting 3 days after surgery.

    Six days after surgery, the kangaroo was anesthetized to address the tooth root abscess. A buccal alveolectomy and extraction of the right mandibular first incisor were completed. A full-thickness triangular mucogingival flap was used to cover the defect. A sample for anaerobic and aerobic bacterial cultures was taken from the periapical lesion, and the tooth was submitted for histologic evaluation. Aerobic bacterial culture grew an Aeromonas sp and an Enterococcus sp, whereas the anaerobic bacterial culture grew a Bacteroides sp and a Fusobacterum-like species. Histopathologic findings on evaluation of the tooth confirmed marked periodontitis with cellular infiltrates in the periodontal ligament and a mixed population of bacteria consistent with a tooth root abscess.

    The following day, it was observed that no feces had been produced since the previous morning. Gastrointestinal sounds were also decreased, and there was concern that the repeated anesthetic episodes may have caused generalized ileus. Abdominal radiographs were obtained and showed diffuse gas distension of the stomach and colon, consistent with ileus. Metoclopramidet (0.2 mg/kg, SC, q 12 h) was administered, and treatment with mirtazipine, famotidine, and flunixin meglumine was continued. By the following day, the kangaroo had an improved appetite but still had not produced feces. The kangaroo was discharged from the hospital to the care of the owners with hopes that returning to a normal environment would help to decrease stress, increase appetite and activity, and stimulate gastrointestinal motility. During the 3 weeks following discharge from the hospital, the owners reported that the kangaroo's appetite and fecal output steadily returned to normal. The kangaroo subsequently developed progressive anemia secondary to presumed gastric ulceration and was euthanized at home by the primary veterinarian 3 months after discharge. No necropsy was performed.