• View in gallery

    Photographs of bearded dragons (Pogona vitticeps) positioned for coelioscopy. A—A bearded dragon positioned in dorsal recumbency. Notice the location of the skin incision for the ventral approach to coelioscopy just to the left of the midline and caudal to the umbilicus (black line) and the skin incision for the left lateral approach through an intercostal space (white line). B—A bearded dragon in right lateral recumbency. Notice the location for the skin incision for the left lateral approach to coelioscopy (white line). C—An endoscopist inserting the endoscope with the ventral approach. The head of the bearded dragon is to the right of the photograph.

  • View in gallery

    Anatomic illustration of a male bearded dragon positioned in dorsal recumbency indicating the insertion points for an endoscopic telescope in a ventral approach and left lateral approach to coelioscopy and the approximate position of coelomic structures. The yellow-shaded area indicates the light field for the endoscope. Ce = Cecum. Cl = Cloaca. Co = Colon. F = Gastric fundus. FB = Fat body. G = Gallbladder. H = Heart. Hp = Hemipenis. K = Kidney. L = Lung. Li = Liver. P = Pylorus. T = Testis. (Adapted from Bucy DS, Sanchez-Migallon Guzman D, Zwingenberger AL. Ultrasonographic anatomy of bearded dragons (Pogona vitticeps). J Am Vet Med Assoc 2015;246:868–876. Reprinted with permission.)

  • View in gallery

    Endoscopic images of the coelomic cavity obtained with a left lateral approach (A, C, D, E, F, I, K, and L) or ventral approach (B, G, H, and J) to coelioscopy performed in male (A, B, C, D, E, H, J, K, and L) and female (F, G, and I) bearded dragons. A—Heart (1) and hypoinflated left lung (2). B—Caudal vena cava (1) and deflated right lung (2). C—Deflated left lung adjacent to the left lobe of the liver. D—Inflated left lung. E—Ventral aspect of the left lobe of the liver. F—Stomach (1), liver (2), deflated left lung (3), and fat body (4). G—Gallbladder (1) between the right and left lobes of the liver (2) and the colon (3). H—Close-up view of the gallbladder between lobes of the liver. I—Pancreas (1), large follicles (2), and liver (3). J—Pancreas (1), small intestine (2), and left testis (3). K—Spleen (1), stomach (2), and colon (3). L—Left adrenal gland (1), testis (2), vas deferens (3), and pigmented coelomic membrane (4).

  • View in gallery

    Endoscopic images of the coelomic cavity obtained with a left lateral approach (A, B, C, D, E, J, K, and L) or ventral approach (F, G, H, and I) to coelioscopy performed in male (A, B, H, I, J, K, and L) and female (C, D, E, F, and G) bearded dragons. A—Left testis (1). B—Cranial pole of the left kidney (1), which is adjacent to the vas deferens (2). C—Cranial pole of the left kidney (1) and oviduct (2). D—Left kidney (1), oviduct (2), and mesosalpinx (3) with small follicles. E—Left ovary with small follicles in the same female as in panel D. F—Large preovulatory follicles (1), fat body (2), and liver (3). G—Multiple eggs in the oviduct of a gravid female. H—Small intestines (1) and liver (2). I—Small intestines (1), gallbladder (2), and right fat body (3). J—Colon (1) and vas deferens (2). K—Lightly pigmented coelomic membrane (1). L—Darkly pigmented coelomic membrane (1).

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Evaluation of a ventral and a left lateral approach to coelioscopy in bearded dragons (Pogona vitticeps)

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  • 1 1William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.
  • | 2 2Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.
  • | 3 3Department of Population Health and Reproduction, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.
  • | 4 4Department of Surgical and Radiological Science, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

Abstract

OBJECTIVE

To compare a ventral and a left lateral endoscopic approach to coelioscopy in bearded dragons (Pogona vitticeps).

ANIMALS

18 adult bearded dragons.

PROCEDURES

In a randomized crossover design involving 2 surgical approaches, anesthetized bearded dragons first underwent coelioscopy with a ventral approach (left lateral of midline next to the umbilicus; animal positioned in dorsal recumbency) or left lateral approach (intercostal; animal positioned in right lateral recumbency) and then with the alternate approach. A 2.7-mm × 18-cm, 30° oblique telescope with a 4.8-mm operating sheath and CO2 insufflation at 2 to 5 mm Hg were used. Ease of entry into the coelom and ease of visual examination of visceral structures were scored.

RESULTS

Both approaches were straightforward, with the left lateral approach requiring significantly more time than the ventral approach. Scores for ease of visual examination for the heart, lungs, liver, stomach, intestines, pancreas, gallbladder, left kidney, gonads, and fat body were good to excellent. Visual examination of the spleen and adrenal glands was difficult in most animals via either approach. The left kidney, testis, and vas deferens were easier to see with the left lateral approach, whereas the pancreas in females and gallbladder in both sexes were easier to see with the ventral approach. All bearded dragons recovered without complications from the procedures, except for one with nephritis, renal gout, and hepatic necrosis.

CONCLUSIONS AND CLINICAL RELEVANCE

Both coelioscopy approaches could be safely and effectively used in bearded dragons. Choice of approach should be based on the coelomic structures requiring evaluation.

Bearded dragons (Pogona vitticeps) are one of the most common reptile companion animals in the United States, Europe, and Australia.1–3 Similar to many other reptiles, sick bearded dragons can become a diagnostic challenge because of nonspecific clinical signs, inconclusive results of clinicopathologic tests, and ambiguous diagnostic imaging findings.4 Particularly when diagnostic imaging is used, a clear understanding of the normal anatomy of a species is important. Descriptions of the normal anatomy of bearded dragons determined via ultrasonography,5 echocardiography,6 contrast radiography,7 and CT8,9 have been published.

Compared with conventional diagnostic imaging modalities, endoscopy offers the advantage of allowing direct visual examination of the internal structures by use of high-resolution imaging and simultaneously allows collection of samples for cytologic, histologic, microbiological, and molecular testing.10 The minimally invasive nature of coelioscopy for examination of internal structures is a major advantage over exploratory coeliotomy.10 Specific procedures have been evaluated in reptiles, including coelioscopy for liver and kidney biopsies in freshwater turtles11 and green iguanas,12 pulmonoscopy in ball pythons,13 and cystoscopy for sex identification in freshwater turtles14; these studies have helped to confirm the diagnostic value and safety of these procedures.

The use of coelioscopy has been evaluated in green iguanas.12,15 Endoscopy of the coelom in that species most often involves a left or right lateral approach with the animal positioned in lateral recumbency.4,10,16 In green iguanas, no substantial difference exists between these approaches in visibility of the lungs, liver, pancreas, small intestines, large intestines, ovaries, oviducts, testes, epididymides, vasa deferentia, bladder, fat body, or kidneys.4 For visual examination of the heart, stomach, and spleen, a left lateral approach is preferred, whereas the right lateral approach is preferred for visual examination of the gallbladder.12 In contrast to green iguanas, dorsoventrally compressed lizards such as bearded dragons are often positioned in dorsal recumbency for coelioscopy with a ventral approach.4 The authors are aware of only 1 case report17 in which a lateral approach was used in a bearded dragon for coelioscopy and pulmonoscopy. To our knowledge, no studies have been performed to describe the various endoscopic approaches to the coelom of bearded dragons or the endoscopic anatomy of coelomic structures in this species.

The purpose of the study reported here was to compare a left lateral and a ventral approach to coelioscopy in bearded dragons regarding the ease of entry into the coelomic cavity and ease of visual examination of coelomic structures in this species. We anticipated that the results could serve as a reference guide for use of the techniques and structure identification. We hypothesized that it would be easier to visually examine the left kidney and gonads via a left lateral approach but that the ventral approach would provide better access to the heart, lungs, liver, gallbladder, stomach, intestines, and spleen.

Materials and Methods

Animals

Eighteen captive adult bearded dragons (9 males and 9 females) were acquired from a private breeding facility in southern California. Mean ± SD body weight of the males and females was 412 ± 89 g (range, 310 to 588 g) and 377 ± 92 g (range, 222 to 508 g), respectively. Animals were deemed healthy on the basis of results of a physical examination, WBC estimate, and differential cell count and measurement of PCV and blood total protein concentration performed at the time of arrival at our facility. The bearded dragons were housed at our campus laboratory animal service facility and were allowed an acclimatization period of 3 to 6 days before endoscopic procedures were performed. All animals were housed individually in glass enclosures (60 × 45 × 45 cm) equipped with a UV-B light and heat lamp, which were set to a 12-hour light cycle. Room temperature was maintained between 25°C and 28°C. A basking spot in each glass enclosure was maintained at a temperature between 30°C and 35°C. Enclosures were cleaned daily, and a diet of dark leafy greens, crickets, and mealworms was offered. The study was approved by and conducted in accordance with requirements of the University of California-Davis Institutional Animal Care and Use Committee (protocol No. 20303).

Study design

To minimize the number of animals used in the study, a complete crossover design was used in which all bearded dragons underwent coelioscopy via both a left lateral and a ventral approach in a single anesthetic event. Bearded dragons were randomly assigned to 2 groups by drawing numbers from a bag. Animals in one group (5 males and 4 females) underwent coelioscopy via a left lateral approach followed by coelioscopy via a ventral approach, whereas animals in the other group (4 males and 5 females) underwent coelioscopy via a left lateral approach followed by coelioscopy via a ventral approach.

To minimize the effect of the surgeon's learning experience, the order in which bearded dragons underwent the procedures was balanced so that an animal of one group was followed by an animal of the other group. Also, after coelioscopy was performed on a maximum of 2 consecutive animals of the same sex, an animal of the opposite sex was selected for the next procedure. Finally, to keep the duration of anesthesia to a minimum, only the reproductive organs on the left side were identified and evaluated.

Anesthesia

Food was withheld from each bearded dragon for 24 to 48 hours before anesthesia and endoscopy. Bearded dragons were weighed before these procedures began.

Anesthesia was induced in each animal by IM forelimb injection of hydromorphone hydrochloridea (0.5 mg/kg), dexmedetomidineb (0.075 to 0.2 mg/kg), and ketamine hydrochloridea (5.0 to 7.5 mg/kg). Animals were intubated with a 14-gauge catheter or 2-mm noncuffed endotracheal tube and ventilated by use of a pressure-driven ventilator.c Anesthesia was maintained with 1% to 3% isofluraned in oxygen (flow rate, 1 L/min). Anesthetic depth was monitored by evaluating muscle tone and reflexes. Heart rate was monitored via Doppler ultrasonography,e with the probe taped to the sternum. Respiratory rate and end-tidal partial pressure of CO2 were monitored via capnography. Heat support was provided with a circulating warm water blanket. After the procedures were completed, each bearded dragon received atipamezolef (0.75 to 1.5 mg/kg, IM) and was manually ventilated with room air by use of a manual resuscitator until spontaneous respiration resumed.

Coelioscopy

For the ventral approach to coelioscopy, bearded dragons were positioned in dorsal recumbency (Figure 1). The caudal aspect of the ventrum was aseptically prepared with alternating scrubs of chlorhexidine and sterile saline (0.9% NaCl) solution, and a craniocaudal skin incision (3 to 5 mm in length) was made with a No. 15 scalpel blade 5 mm to the left of the umbilicus. The coelomic membrane was bluntly perforated by use of a mosquito hemostat, and a 4.8-mm (14.5F) operating sheathg with a 2.7-mm × 18-cm, 30° rigid telescopeg was then inserted into the coelomic cavity in a cranial direction. The telescope was connected to a video camera,h monitor,i xenon light source,j and CO2 insufflator.k The CO2 insufflation was set to a rate of 0.5 L/min and pressure range of 2 to 5 mm Hg. During insertion of the telescope, assisted ventilation was discontinued to avoid puncturing the lungs.

Figure 1—
Figure 1—

Photographs of bearded dragons (Pogona vitticeps) positioned for coelioscopy. A—A bearded dragon positioned in dorsal recumbency. Notice the location of the skin incision for the ventral approach to coelioscopy just to the left of the midline and caudal to the umbilicus (black line) and the skin incision for the left lateral approach through an intercostal space (white line). B—A bearded dragon in right lateral recumbency. Notice the location for the skin incision for the left lateral approach to coelioscopy (white line). C—An endoscopist inserting the endoscope with the ventral approach. The head of the bearded dragon is to the right of the photograph.

Citation: American Journal of Veterinary Research 81, 3; 10.2460/ajvr.81.3.267

Ease of entry into the coelom was scored by the endoscopist using a previous published scale11,12 from 1 to 5 (1 = impossible [no success after trying for 15 minutes], 2 = difficult [requiring between 11 and 15 minutes], 3 = satisfactory [requiring between 6 and 10 minutes], 4 = good [requiring between 2 and 5 minutes], and 5 = excellent [requiring ≤ 2 minutes]). Ease of locating and visually examining the heart, lungs, liver, stomach, small intestines, colon, spleen, pancreas, adrenal glands, kidneys, and reproductive tract were scored (ie, the VES) by use of a previous published scale11,12 from 1 to 5 (1 = impossible, 2 = difficult [requiring an extensive search and substantial movement of viscera], 3 = satisfactory [requiring some searching and minor manipulation of viscera], 4 = good [easy to locate but requiring minor manipulation to see structures clearly], and 5 = excellent [obvious and clear visibility with minimal to no manipulation required]). After all structures were scored, the sheath and telescope were removed from the coelomic cavity, and the skin and muscles were closed by use of a single horizontal mattress suture of 4-0 poliglecaprone 25l and surgical glue.m

For the left lateral approach, animals were positioned in right lateral recumbency with the ventrum facing the surgeon. The skin of the left lateral body wall was prepared aseptically. A craniocaudal skin incision (3 to 5 mm in length) was made with a No. 15 scalpel blade midway between the forelimbs and hind limbs at the level of the ninth intercostal space. The ninth rib was grasped with a forceps, and a mosquito hemostat was used to bluntly dissect the subcutaneous and muscular layers in a craniocaudal direction between the 9th and 10th ribs. After the coelomic cavity was entered, the operating sheath with the endoscope was placed in the coelomic cavity, and ease-of-entry scores and VESs were assigned for coelomic structures. Closure of the skin and muscle layer was the same as for the ventral approach.

Postoperative care

During recovery from anesthesia, all bearded dragons received lactated Ringer solution (30 mL/kg, SC), ceftiofur crystalline free acidn (30 mg/kg, SC), and meloxicamo (0.2 mg/kg, SC). The bearded dragons were returned to their enclosures and closely monitored for 14 days. All animals received tramadolp (10 mg/kg, PO) every 24 hours for 3 days and meloxicam (0.2 mg/kg, SC) every 24 hours for 5 days after coelioscopy. Sutures were removed 14 days after the procedures, and the bearded dragons were then returned to the breeding facility.

Statistical analysis

Statistical analysis was performed with statistical software.q Summary statistics are reported as median and range because the data were not normally distributed. The Wilcoxon signed rank test was used to compare ease-of-entry scores and VESs between the 2 approaches for males, females, and all bearded dragons. The Mann-Whitney U test was used to compare ease-of-entry scores and VESs between sexes. Values of P ≤ 0.05 were considered significant.

Results

Both coelioscopic procedures were performed in all bearded dragons with no intraoperative complications. All animals recovered from anesthesia without complications and began eating within 24 hours after the procedures, except for 1 bearded dragon that died 8 hours after the procedures. Necropsy of that animal revealed moderate granulomatous nephritis, renal gout, hepatic necrosis, and segmental colitis with atypical cryptosporidiosis. Gross lesions of the liver and kidneys were also evident during coelioscopy.

Scores for ease of entry into the coelom and visual examination of coelomic structures were summarized (Table 1). The ventral approach to the coelom could be performed significantly (P = 0.001) more rapidly than could the left lateral approach regardless of the sex of the bearded dragon. In 4 animals in which the coelomic membrane was not initially penetrated on the left lateral approach, insertion of the endoscope through the skin with insufflation resulted in CO2 accumulation in the subcutaneous space, which pushed the coelomic membrane even farther away from the incision. In these cases, the coelomic membrane had to be grasped with forceps and incised with a scalpel blade.

Table 1—

Median (range) scores for coelioscopy of bearded dragons (Pogona vitticeps) as performed with a left lateral and a ventral approach.

 Males (n = 9)Females (n = 9)All(n = 18)
VariableVentralLeft lateralVentralLeft lateralVentralLeft lateral
Ease of entry into coelom5 (5-5)4 (3-5)*5 (5-5)4 (2-5)*5 (5-5)4 (2-5)*
VES
  Heart5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)
  Lungs5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)
  Liver5 (5-5)5 (5-5)5 (5-5)5 (4-5)5 (5-5)5 (4-5)
  Gallbladder5 (4-5)4 (1-5)*5 (4-5)1 (l-5)*5 (4-5)1 (1-5)*
  Stomach5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)
  Small intestines5 (5-5)5 (4-5)5 (5-5)5 (4-5)5 (5-5)5 (4-5)
  Large intestines5 (4-5)4 (1-4)*5 (4-5)4(2-1)5 (4-5)4 (1-5)
  Spleen3 (1-1)4 (1-5)1 (1-4)1 (1-5)2 (1-4)4 (1-5)
  Pancreas5 (5-5)5 (1-5)5 (5-5)4(1-5)*5 (5-5)4 (1-5)*
  Adrenal glands3 (2-1)3 (1-5)1 (1-4)1 (1-5)2 (1-4)2.5 (1-5)
  Left testis or ovary4 (2-1)5 (4-5)*4(1-4)4 (1-5)4 (1-5)5 (1-5)
  Left vas deferens or oviduct4(3-1)5 (4-5)*4(4-4)5 (2-5)4 (3-5)5 (2-5)
  Left kidney4 (3-5)5 (4-5)*4(1-5)5 (4-5)*4 (1-5)5 (4-5)*
  Fat body5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)5 (5-5)

Scores for ease of entry were defined as 1 = impossible (no success after trying for 15 minutes), 2 = difficult (requiring between 11 and 15 minutes), 3 = satisfactory (requiring between 6 and 10 minutes), 4 = good (requiring between 2 and 5 minutes), and 5 = excellent (requiring ≤ 2 minutes). The VESs were defined as 1 = impossible, 2 = difficult (requiring an extensive search and substantial movement of viscera), 3 = satisfactory (requiring some searching and minor manipulation of viscera), 4 = good (easy to locate but requiring minor manipulation to see structures clearly), and 5 = excellent (obvious and clear visualization with minimal to no manipulation required).

Median value differs significantly (P ≤ 0.05; Wilcoxon signed rank test) from the value for the ventral approach.

Median value differs significantly (P ≤ 0.05; Mann-Whitney U test) from the value for males with the same approach.

The insertion point of the endoscope in relation to the position of the organs was important for visual examination (Figure 2). No obvious pulmonary, hepatic, or other serosal divisions were evident within the coelomic cavity. The VESs for the heart, lungs, liver, stomach, small intestines, and fat body (Figure 3) were excellent for both sexes and independent of the approach used (Table 1). The ventral approach allowed visual examination of both lungs. It was more difficult to visually examine the right lung with the left lateral approach because of shifting of the structures. To visually examine the right lung by use of the left lateral approach, the tip of the endoscope had to be pushed to the right side of the coelom and along the lateral surface of the right lobe of the liver. Almost the entire ventral surface and the most lateral aspects of the dorsal surface of the liver could be visually examined with the ventral approach, whereas visual examination of the right lobe of the liver was more challenging with the left lateral approach.

Figure 2—
Figure 2—

Anatomic illustration of a male bearded dragon positioned in dorsal recumbency indicating the insertion points for an endoscopic telescope in a ventral approach and left lateral approach to coelioscopy and the approximate position of coelomic structures. The yellow-shaded area indicates the light field for the endoscope. Ce = Cecum. Cl = Cloaca. Co = Colon. F = Gastric fundus. FB = Fat body. G = Gallbladder. H = Heart. Hp = Hemipenis. K = Kidney. L = Lung. Li = Liver. P = Pylorus. T = Testis. (Adapted from Bucy DS, Sanchez-Migallon Guzman D, Zwingenberger AL. Ultrasonographic anatomy of bearded dragons (Pogona vitticeps). J Am Vet Med Assoc 2015;246:868–876. Reprinted with permission.)

Citation: American Journal of Veterinary Research 81, 3; 10.2460/ajvr.81.3.267

Figure 3—
Figure 3—

Endoscopic images of the coelomic cavity obtained with a left lateral approach (A, C, D, E, F, I, K, and L) or ventral approach (B, G, H, and J) to coelioscopy performed in male (A, B, C, D, E, H, J, K, and L) and female (F, G, and I) bearded dragons. A—Heart (1) and hypoinflated left lung (2). B—Caudal vena cava (1) and deflated right lung (2). C—Deflated left lung adjacent to the left lobe of the liver. D—Inflated left lung. E—Ventral aspect of the left lobe of the liver. F—Stomach (1), liver (2), deflated left lung (3), and fat body (4). G—Gallbladder (1) between the right and left lobes of the liver (2) and the colon (3). H—Close-up view of the gallbladder between lobes of the liver. I—Pancreas (1), large follicles (2), and liver (3). J—Pancreas (1), small intestine (2), and left testis (3). K—Spleen (1), stomach (2), and colon (3). L—Left adrenal gland (1), testis (2), vas deferens (3), and pigmented coelomic membrane (4).

Citation: American Journal of Veterinary Research 81, 3; 10.2460/ajvr.81.3.267

Visual examination of the gallbladder was significantly (P < 0.001) easier with the ventral versus left lateral approach in all animals. Furthermore, it was significantly (P = 0.001) more difficult to access the gallbladder in females than in males with the left lateral approach. Males had significantly (P = 0.01) higher scores for the large intestines when the ventral approach was used. With both approaches, the spleen in females had low scores (median, 1), whereas scores for the spleen in males were low (median, 3) with the ventral approach but much higher (median, 4) with the left lateral approach. With the ventral approach, scores for the spleen differed significantly (P = 0.049) between males and females. The spleen was located adjacent to the stomach and small intestines on the left side of the coelom and could be found in a few animals by moving cranial to the left testis (or ovary) underneath loops of small intestines. The VESs for the pancreas were significantly higher with the ventral approach overall (P = 0.012) and for females (P = 0.017) but not males.

The VESs for the adrenal glands were low; however, scores for males with the ventral approach were significantly (P = 0.02) higher than were scores for females with the ventral approach. The left adrenal gland was located lateral to the left testis (or ovary) and was covered by the coelomic membrane. The left testis and vas deferens had significantly (P = 0.006 and P = 0.008, respectively) lower VESs for the ventral approach than for the left lateral approach. There was no significant difference in scores for the left ovary and oviduct in females for both approaches. One of 9 females had eggs in the left and right oviduct, which were laid approximately 7 days after the procedure. Large preovulatory follicles were present in 6 of 9 females, and small preovulatory follicles were found in 2 of 9 females.

The left kidney had significantly higher VESs with the left lateral approach in males (P = 0.01) and females (P = 0.028) than with the ventral approach. In 1 female and 2 males, the right kidney was visually identified via the ventral approach, but this required a few minutes of searching and moving the viscera and fat bodies (Figure 4). Because of concerns about prolongation of the anesthetic duration, the right kidney was not assessed in the remaining bearded dragons. Visual examination of the right kidney was not possible with the left lateral approach.

Figure 4—
Figure 4—

Endoscopic images of the coelomic cavity obtained with a left lateral approach (A, B, C, D, E, J, K, and L) or ventral approach (F, G, H, and I) to coelioscopy performed in male (A, B, H, I, J, K, and L) and female (C, D, E, F, and G) bearded dragons. A—Left testis (1). B—Cranial pole of the left kidney (1), which is adjacent to the vas deferens (2). C—Cranial pole of the left kidney (1) and oviduct (2). D—Left kidney (1), oviduct (2), and mesosalpinx (3) with small follicles. E—Left ovary with small follicles in the same female as in panel D. F—Large preovulatory follicles (1), fat body (2), and liver (3). G—Multiple eggs in the oviduct of a gravid female. H—Small intestines (1) and liver (2). I—Small intestines (1), gallbladder (2), and right fat body (3). J—Colon (1) and vas deferens (2). K—Lightly pigmented coelomic membrane (1). L—Darkly pigmented coelomic membrane (1).

Citation: American Journal of Veterinary Research 81, 3; 10.2460/ajvr.81.3.267

The injectable anesthetic protocol resulted in a surgical plane of anesthesia, although most bearded dragons required supplementation with isoflurane for maintenance of anesthesia. Obstruction of the lumen of the endotracheal tube or catheter with a mucous plug was encountered in several animals, and suction was required to maintain patency. The position of the head and neck also influenced the ability to ventilate the animals during anesthesia. On entry into the coelom and initiation of CO2 insufflation, the pressure used for positive ventilation had to be increased to overcome the increased pressure in the coelomic cavity. Insufflation of the lungs was visually assessed during the endoscopy procedure and adjusted accordingly.

Although skin closure was performed in a routine manner as for other small reptiles, the sutures were removed after only 2 weeks, which was earlier than usual. Because tissue glue was also used, no dehiscence was noted while the bearded dragons were at the campus facility or after they were returned to the breeding facility.

Discussion

The coelioscopic procedure described in the present report was safe and effective for the evaluation of visceral structures in the coelomic cavity of bearded dragons. Few differences were identified between approaches and between sexes of bearded dragons.

The ventral approach to coelioscopy was performed significantly more rapidly than was the left lateral approach. This observation was likely related to the greater difficulty of the left lateral approach, which was made between the ribs and involved more muscle tissue dissection. This entry site for the left lateral approach was chosen because the ribs in bearded dragons extend far more caudally than they do in lizards with a more rounded coelom, such as green iguanas. A lateral caudal approach in bearded dragons has been described17 whereby the entry point is caudal to the last rib rather than at an intercostal location. Maneuverability was excellent for the left lateral intercostal approach in the study reported here, and a more caudal approach, similar to that used in other lizards such as green iguanas, would likely not have resulted in an improvement in VESs for the kidneys and gonads because scores were already excellent with the intercostal approach. A more cranial lateral approach might be more difficult to use because the endoscopist must cross his or her hands to see structures in the caudal aspect of the coelom, which could adversely affect ergonomics.

The location of the skin incision for the ventral approach was chosen to avoid the ventral abdominal vein and pelvic veins. The site where the pelvic veins join and continue as the ventral abdominal vein differs among reptile species, but it is approximately one-fourth the distance between the cranial aspect of the pubic bone and the umbilicus.18 Our examination of a bearded dragon cadaver revealed that the pelvic veins converge into the ventral abdominal vein just caudal to the umbilicus. Therefore, we did not encounter problems with the ventral approach that was used in the present study.

Antimicrobials are typically not warranted for a sterile procedure such as coelioscopy. However, they were administered in the present study because of concerns about breaches in sterility.

The VESs for the heart, lungs, liver, stomach, small intestines, and fat body did not differ significantly between approaches used or sexes of the bearded dragons of the present study. Although the overall ease of visual examination of these organs was not significantly different, not every part of these structures was visible with both approaches. The ventral surface of the liver, lungs, and fat body and the left and right side of the heart were visible with the ventral approach, whereas only the left organ or the left side of the respective organ could be visually examined with the left lateral approach, which was also the case in green iguanas.12 The ventral and dorsal surface of the left lobe of the liver could be evaluated with the left lateral approach. The approach used for evaluation of structures in the coelom should be selected on the basis of the side of the disease process, and other imaging modalities (eg, radiography and ultrasonography) can provide useful information prior to coelioscopy.

The gallbladder was easily seen with the ventral approach but was more difficult to assess with the left lateral approach, particularly in female bearded dragons. This likely was because structures (especially the stomach) shifted to the right side and because most females had large follicles, which decreased the available space for maneuvering the endoscope. The location of the gallbladder on the right side of the coelom could also have contributed to the lower scores with the left lateral approach. The gallbladder was located at the caudal margin of the liver slightly to the right side of the coelomic cavity. When the coelom was entered with the ventral approach, the gallbladder was best approached by moving the endoscope cranially to follow the abdominal vein and then directing the tip of the endoscope dorsally between the lobes of the liver. Evaluation of the gallbladder can be important because tumors and other disease processes of the gallbladder have been reported in bearded dragons.19,20 Collection of biopsy specimens from solid masses and aspiration of bile would best be performed via a ventral approach but might also be possible via a right lateral approach because the gallbladder can easily be visually examined with a right paralumbar approach in green iguanas.12

The pancreas was easier to see with a ventral approach in female bearded dragons owing to the same reasons as for the gallbladder. The pancreas of lizards is trilobed and is suspended in the mesentery between the stomach and duodenum.19 Overall, almost the entire pancreas could be seen with the ventral approach.

Visual examination and recognition of the spleen were difficult in most bearded dragons. The VESs for the spleen were significantly lower in females versus males because of large follicles in the coelom and impairment of the endoscopist's line of sight. The spleen was located on the left side of the coelom adjacent to the caudal part of the stomach. In some of the males, the spleen could be found by starting at the cranial pole of the left testis and directing the endoscope cranially and dorsally between the small intestines. Visual examination of the spleen with a right lateral approach may be even more difficult because of the location of the spleen within the left side of the coelomic cavity.

Visual examination of the adrenal glands was difficult to impossible in most bearded dragons. Particularly in gravid females, the adrenal glands were obscured by follicles, and manipulation of the follicles with the endoscope was not attempted. In males, the left adrenal gland was located between the left testis and vas deferens and covered by the coelomic membrane. The black pigmentation of the coelomic membrane in all bearded dragons also made it difficult to visually identify the adrenal glands.

In the male bearded dragons, the left testis, vas deferens, and kidney were more easily seen with the left lateral approach. This was mainly because these structures were covered by the large fat body, which needed to be pushed aside with the tip of the endoscope. Gravity caused the left fat body to move medially when the animals were positioned in lateral recumbency. The contralateral reproductive organs and kidney were not assessed in the present study to minimize the duration of anesthesia. Early attempts to locate the right kidney with the left lateral approach were unsuccessful because the large fat bodies and colon obstructed the view. At least in part, the more cranial midbody entry point of the left lateral approach might have affected the endoscopist's ability to move the endoscope caudally to view the contralateral side, compared with a traditional paralumbar approach. However, access to both gonads and both kidneys is only occasionally possible from both sides in green iguanas.12 With the bearded dragons positioned in dorsal recumbency, only the left gonad and kidney were evaluated, although it was possible to see the right gonad and kidney in some animals. Thus, we recommend the ventral approach when both sides of the coelom need to be assessed, but the endoscopist's position might need to be adjusted to facilitate visual examination of structures on the right side. Surgeon preference (ie, right handed vs left handed) must also be taken into consideration when performing coelioscopy in lizards because a left lateral approach would be easier for a right-handed surgeon and a right lateral approach for a left-handed person. Clinical examination, radiography, and ultrasonography would likely help to identify unilateral disease.

The present study had some limitations. More than half of the female bearded dragons had large follicles, and 1 female had eggs within the coelomic cavity that displaced some of the structures and hindered visual examination. This likely had an influence on scores for the gallbladder, adrenal glands, and pancreas in females. The VESs for the 2 sexes would have been likely more similar if juvenile (immature) females had been used instead of mature females. Careful palpation and radiographic or ultrasonographic imaging are recommended for adult females to determine their reproductive status prior to coelioscopy.

Furthermore, the bearded dragons used in the present study were presumed to be healthy on the basis of results of a physical examination and CBC. Considering that 1 animal died, these results may not have reflected the true health status of the bearded dragons. In that bearded dragon, physical examination revealed a mildly low body condition score as the single abnormal finding, and CBC results were unremarkable. Nevertheless, no gross abnormalities other than mild changes in the color of the liver were observed in any of the other bearded dragons.

Another limitation of the study reported here was that biopsy specimens were not collected during the endoscopic procedures. Tissue samples of the kidneys and liver collected from iguanas and sliders by use of a 1.7-mm (5F) endoscopic biopsy forceps were evaluated in previous studies11,15 and revealed severe crush artifacts in 77.3% of liver biopsy specimens but only 4.8% of kidney biopsy specimens.11 In bearded dragons, biopsy specimens can be collected from the liver with a ventral and a left lateral approach, although different parts of the liver are visible via either approach, which should be taken into consideration in animals with localized disease. Collection of biopsy specimens from the kidneys should ideally be performed with a lateral approach.

Finally, the endoscopist of the present study had limited experience performing coelioscopy in lizards. This might have had a minor effect on some of the VESs (eg, spleen or adrenal glands), particularly when compared with the higher scores for these structures in green iguanas,12 but differences in anatomy and body conformation between bearded dragons and green iguanas might be a more likely explanation for this difference between species.

Results of the present study indicated that both coelioscopic approaches could be performed safely and effectively in bearded dragons. Choice of approach should be made on the basis of the coelomic structures to be evaluated and surgeon preference. For evaluation of the left kidney, gonad, and spleen, a left lateral approach would be preferable, whereas the gallbladder and pancreas should be evaluated with a ventral approach. A larger surface area of most structures was visible with the ventral approach, and the ventral approach would potentially allow visual examination of both parts of paired structures (eg, left and right lung).

Acknowledgments

The authors thank Tracy Drazenovich for technical assistance and Bob Mailloux for providing the animals for the study.

ABBREVIATIONS

VES

Visual examination score

Footnotes

a.

Hospira Inc, Lake Forest, Ill.

b.

Dexdomitor, Pfizer Animal Health, New York, NY.

c.

Small animal ventilator VT-5000, BASi Vetronics, West Lafayette, Ind.

d.

Piramal Critical Care Inc, Bethlehem, Pa.

e.

Model 811 Doppler ultrasonic flow detector, Parks Medical Electronics, Las Vegas, Nev.

f.

Antisedan, Pfizer Animal Health, New York, NY.

g.

Karl Storz Veterinary Endoscopy America Inc, Goleta, Calif.

h.

Image 1 H3-Z camera head, Karl Storz Veterinary Endoscopy America Inc, Goleta, Calif.

i.

26-inch HD LED monitor, Karl Storz Veterinary Endoscopy America Inc, Goleta, Calif.

j.

SCB xenon 300 light source, Karl Storz Veterinary Endoscopy America Inc, Goleta, Calif.

k.

Endoflator, Karl Storz Veterinary Endoscopy America Inc, Goleta, Calif.

l.

Monocryl, Ethicon US LLC, Bridgewater, NJ.

m.

Formulated cyanoacrylate, MWI, Meridian, Idaho.

n.

Excede for swine, Pfizer Animal Health, New York, NY.

o.

Metacam, Boehringer Ingelheim, St Joseph, Mo.

p.

Spectrum Chemical Manufacturing Corp, Newbrunswick, NJ.

q.

Stata/IC, version 15.0, StataCorp, College Station, Tex.

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Contributor Notes

Dr. Frei's present address is Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.

Address correspondence to Dr. Sanchez-Migallon Guzman (guzman@ucdavis.edu).