History
A 12-year-old 3.4-kg (7.48-lb) vasectomized male ring-tailed lemur (Lemur catta) that appeared clinically normal and was kept at a zoological park was evaluated as part of a routine examination. The examination was performed while the lemur was under general anesthesia. On physical examination, a sperm granuloma was noted on the right testicle, which had remained unchanged since it was first identified 4 years earlier. No other abnormalities were detected on physical examination. Findings on CBC were within reference range. Serum biochemical analysis revealed mildly high alanine aminotransferase activity (which had been similarly high when measured 3 years earlier), mildly high γ-glutamyl transpeptidase activity, mildly high BUN concentration (which had been on the high end of the reference range during the past 7 years), and mild hypocalcemia. Abdominal radiography was performed (Figure 1).
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a clinically normal 12-year-old vasectomized male ring-tailed lemur (Lemur catta) that were obtained as part of a routine examination.
Citation: Journal of the American Veterinary Medical Association 246, 8; 10.2460/javma.246.8.839
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
On survey radiographs, a large, ovoid to tubular soft tissue opacity is evident in the central portion of the caudoventral aspect of the abdomen displacing viscera cranially (Figure 2). This structure is in the area of the urinary bladder; the urinary bladder is not identifiable in the survey radiographs.
Same radiographic images as in Figure 1. A large ovoid or tubular soft tissue opacity (arrows) in the caudoventral aspect of the abdomen in the area of the urinary bladder appears to displace the viscera cranially; the urinary bladder is not evident on these survey radiographs.
Citation: Journal of the American Veterinary Medical Association 246, 8; 10.2460/javma.246.8.839
Ultrasonographic examination of the caudal portion of the abdomen revealed an abnormal structure that was fine textured, homogeneous, and echogenic internally (Figure 3). No motion was detected in terms of the content of the structure. On a transverse ultrasonographic view of the middle portion of the abdomen, the abnormal structure had a J-shape such that 2 cylindrical structures were revealed as the structure bent back on itself. The structure appeared to be surrounded by a small amount of anechoic fluid. The bladder in the region of the structure was noted to be ultrasonographically normal and measured approximately 1 cm in diameter. Color flow Doppler ultrasonography revealed several pinpoint areas of color signal (2 to 3 points in cross section, each < 0.25 cm in diameter) in the internal area of the structure, not associated with the wall of the structure.
Sagittal (A) and transversel (B) ultrasonographic images of the caudal and middle aspect of the abdomen of the lemur in Figure 1. A—Notice the tubular structure (arrows) in the caudoventral portion of the abdomen; the abnormal abdominal structure appeared fine textured, homogenous, and echogenic internally (asterisk), with no detectable internal motion of the content. B—Transverse view of the midabdomen showing 2 adjacent circular echogenic structures (arrows) where the tubular structure doubles back on itself at its cranial termination, forming a J-shaped structure. The structure appears to be outlined by anechoic surroundings (asterisk), which may indicate a small amount of peritoneal effusion. Images were obtained via a transabdominal approach with a 5.0- to 8.0-MHz curved array transducer.
Citation: Journal of the American Veterinary Medical Association 246, 8; 10.2460/javma.246.8.839
On the basis of radiographic and ultrasonographic findings, differential diagnoses included prostatic or paraprostatic abscess, enlarged seminal vesicle, and neoplasia originating from the prostate, urinary bladder, or colon. Radiographically, a paraprostatic cyst could also have been considered; however, the echogenic contents of the structure did not appear cystic—a cyst would characteristically contain anechoic fluid. Peritonitis was also suspected because of the small amount of peritoneal effusion (anechoic region around the structure) that was detected ultrasonographically.
Contrast radiography with the lemur under general anesthesia was performed 6 weeks after the initial examination to further evaluate the structure. Twenty milliliters of diluted iohexol solution (300 mg/mL diluted 1:1 with sterile water to a concentration of 150 mg/mL) was injected transcutaneously with ultrasound guidance into the abnormal structure. Contrast images clearly outlined the size and shape of the structure, revealing a single elongated, smooth tubular structure in the caudal portion of the abdomen that curved back on itself at its cranial aspect (Figure 4). In addition, the injection of contrast material forced fluid out of the urethra, indicating communication of the structure with the urogenital system and making seminal vesicle disease the most likely diagnosis. Etiologies for seminal vesicle enlargement include a functional or partial mechanical outflow obstruction, inflammation, infection, neoplasia, or normal anatomic variation for this species.
Left lateral (A) and ventrodorsal (B) contrast radiographic images of the abdomen of the same lemur as in Figure 1. Contrast radiography with the lemur under general anesthesia was performed 6 weeks after the initial examination. Contrast medium was injected transcutaneously with ultrasound guidance into the previously detected abnormal structure. Notice how clearly a single tubular structure in the caudal portion of the abdomen is delineated.
Citation: Journal of the American Veterinary Medical Association 246, 8; 10.2460/javma.246.8.839
Treatment and Outcome
Surgery was elected for removal of the abdominal structure. Laparotomy revealed an enlarged left seminal vesicle with several adhesions to the bladder. It is possible that these adhesions could have been secondary to peritonitis, given the small amount of peritoneal fluid outlining the structure in the ultrasonographic images. The vesicle was dissected and completely resected, sparing the apparently unaffected right seminal vesicle. The abnormal seminal vesicle was approximately 6 cm long, whereas the unaffected seminal vesicle was approximately 1.5 cm long. During surgery, biopsy specimens of the liver were also obtained for histologic evaluation and iron storage analysis, which revealed diffuse mild hemosiderosis. Following surgery, the lemur recovered well. At a physical examination 6 months after treatment, the lemur continued to be free of any related clinical problems.
Comments
The present report demonstrates the clinical value of including diagnostic imaging as part of routine physical examination; in this lemur, diagnostic imaging detected a serious subclinical abnormality that may have led to complications such as rupture if left unaddressed. Imaging is an especially important component of routine examinations in a zoological collection, where anesthesia is often required for hands-on assessments in many species.
As found in the lemur of the present report, ultrasonography as well as survey and contrast radiography are useful tools in the evaluation of nonhuman primates with suspected seminal vesicle disease. The use of a contrast technique better delineated the affected structure with its characteristic J-shape than did standard radiography alone. Abdominal ultrasonography and transabdominal contrast injection were used instead of transrectal approaches (as is often done in humans) because of available equipment, the lemur's size, and the size of the enlarged seminal vesicle. In humans, CT and MRI of seminal vesicles are also used, which could be useful in the evaluation of the nonhuman primate urogenital tract as well. Contrast agents can also be used exclusively with ultrasonography. As described in 1 report,1 IV administration of an injectable contrast agent that alters visibility of blood vessels in Doppler ultrasonography was used to differentiate structures and detect abnormalities in marmoset ovaries; authors of that report1 concluded that contrast-enhanced ultrasonography has much potential in nonhuman primate medicine.
A basic premise of diagnostic imaging is that, when 2-D image modalities are used, it is important to compare more than 1 image plane to determine the shape of 3-D structures. In the case of this lemur, viewing the transverse plane alone on ultrasonographic evaluation would have led to an incomplete description of the structure, whereas comparing the transverse plane with the sagittal plane revealed the J-shape of the structure.
In ring-tailed lemurs, seminal vesicles are elongated and curve back at their cranial termination, as seen in the lemur of the present report. Seminal vesicles are relatively large in lemurs, compared with other species, and can be considerably enlarged during the breeding season.2 In such instances, the seminal vesicles have been bilaterally and symmetrically enlarged (unlike the findings in the lemur of the present report), and therefore, enlargement has been attributed to possible seasonal influences of the reproductive cycle.a,b
In the lemur of the present report, the fact that imaging and surgical findings included enlargement of only the left seminal vesicle suggested an abnormal condition. The chronically high liver enzyme activities, which remained essentially unchanged after surgery other than a moderate decrease in alanine aminotransferase activity, were presumably unrelated. Possible etiologies for the enlargement could include chronic infection or historical trauma leading to mechanical obstruction.
Schopler RL, The Duke Lemur Center, Durham, NC: Personal communication, 2013.
Williams C, The Duke Lemur Center, Durham, NC: Personal communication, 2013.
1. Hastings JM, Morris KD, Allan D, et al. Contrast imaging ultrasound detects abnormalities in the marmoset ovary. Am J Primatol 2012; 74: 1088–1096.
2. Petter-Rousseaux A. Reproductive physiology and behavior of the Lemuroidea. In: Buettner-Janusch J, ed. Evolutionary and genetic biology of primates. New York: Academic Press, 1964; 91–132.
