History
A 14-year-old 20-kg (44-lb) spayed female mixed-breed hound-type dog was admitted to the teaching hospital because of a 2-day history of lethargy, vomiting, and hematuria. The vaccination status and parasitic prophylaxis of the dog were current, with no history of ingestion of foreign material.
On physical examination, the dog was quiet, alert, and responsive. On abdominal palpation, a firm but not clearly defined structure on the left side of the abdomen was appreciated.
Findings on plasma biochemical analysis were unremarkable. Findings on CBC included a mild thrombocytopenia (184 × 103 platelets/μL; reference range, 220 × 103 platelets/μL to 600 × 103 platelets/μL) and a mild increase in the mean platelet volume (14.0 fL; reference range, 8.0 to 12.5 fL). Urine analysis revealed hematuria and a urine specific gravity of 1.032. No abnormalities were detected on thoracic radiography. Three-view abdominal radiography was performed (Figure 1).
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 14-year-old 20-kg (44-lb) spayed female mixed-breed hound-type dog that was evaluated because of a 2-day history of lethargy, vomiting, and hematuria.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 14-year-old 20-kg (44-lb) spayed female mixed-breed hound-type dog that was evaluated because of a 2-day history of lethargy, vomiting, and hematuria.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 14-year-old 20-kg (44-lb) spayed female mixed-breed hound-type dog that was evaluated because of a 2-day history of lethargy, vomiting, and hematuria.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
On radiographic evaluation, mild loss of abdominal serosal detail is noted (Figure 2). A large (21-cm-long), well-defined, smoothly marginated, oval soft tissue mass is present in the left side of the retroperitoneal space. Because of the mass, there is ventral displacement of the colon and urinary bladder and cranioventral and right-sided displacement of the small intestines. The right kidney is caudally displaced.
Same radiographic images as in Figure 1. Mild loss of abdominal serosal detail is noted in the ventral aspect of the midabdomen. A large (21-cm-long), well-defined, smoothly marginated, oval soft tissue mass is present in the left side of the retroperitoneal space (arrows), causing ventral displacement of the colon (star) and urinary bladder and cranioventral and right-sided displacement of the small intestines. The right kidney is caudally displaced.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Same radiographic images as in Figure 1. Mild loss of abdominal serosal detail is noted in the ventral aspect of the midabdomen. A large (21-cm-long), well-defined, smoothly marginated, oval soft tissue mass is present in the left side of the retroperitoneal space (arrows), causing ventral displacement of the colon (star) and urinary bladder and cranioventral and right-sided displacement of the small intestines. The right kidney is caudally displaced.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Same radiographic images as in Figure 1. Mild loss of abdominal serosal detail is noted in the ventral aspect of the midabdomen. A large (21-cm-long), well-defined, smoothly marginated, oval soft tissue mass is present in the left side of the retroperitoneal space (arrows), causing ventral displacement of the colon (star) and urinary bladder and cranioventral and right-sided displacement of the small intestines. The right kidney is caudally displaced.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
On abdominal ultrasonographic evaluation, a minimal amount of anechoic free abdominal fluid is noted (Figure 3). In the region of the left kidney, a well-defined oval, mixed echoic, partially cavitary mass is present; no normal renal architecture is apparent. The size of the mass as measured on ultrasonographic evaluation is approximately the same size as defined radiographically. Hyperechoic gravity-dependent sediment is present in the urinary bladder.
Longitudinal ultrasonographic image of the left kidney region of the dog in Figure 1. A well-defined oval, mixed echoic, partially cavitary mass is present; no normal renal architecture is apparent. The image was obtained with a 8- to 11-MHz micro convex transducer.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Longitudinal ultrasonographic image of the left kidney region of the dog in Figure 1. A well-defined oval, mixed echoic, partially cavitary mass is present; no normal renal architecture is apparent. The image was obtained with a 8- to 11-MHz micro convex transducer.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Longitudinal ultrasonographic image of the left kidney region of the dog in Figure 1. A well-defined oval, mixed echoic, partially cavitary mass is present; no normal renal architecture is apparent. The image was obtained with a 8- to 11-MHz micro convex transducer.
Citation: Journal of the American Veterinary Medical Association 252, 11; 10.2460/javma.252.11.1345
Diagnostic imaging findings were indicative of neoplasia of the left kidney with abdominal effusion; differential diagnoses included renal carcinoma, histiocytic sarcoma, and lymphoma. Nephroblastoma was considered less likely because of the advanced age of the patient. Differential diagnoses for the abdominal effusion included paraneoplastic effusion and hemorrhage. Sediment in the urinary bladder was likely the result of hemorrhage from the renal mass and consistent with the history of hematuria.
Treatment and Outcome
Ultrasound-guided fine-needle aspiration of the mass was performed. Cytologic evaluation of the aspirate revealed RBCs and leukocytes that included rare macrophages; no overtly atypical cells or infectious organisms were seen. Overall, the number of nucleated cells was not enough for further cytologic interpretation.
An exploratory laparotomy confirmed the presence of a large (21 × 10 × 13-cm) mass replacing the left kidney and displacing abdominal contents to the right side of the abdomen. Surgical removal of the renal mass and left ureter was performed. On microscopic evaluation of the mass, a histopathologic diagnosis of myxoma or myxosarcoma of the kidney was made.
The patient recovered from anesthesia without complication; postoperative recovery continued with hospitalization for 3 days while IV fluids and analgesics were administered.
Comments
Primary renal tumors are rarely found in dogs, typically affecting older animals. Carcinomas1,2 of epithelial cell origin are the most commonly reported, followed by sarcomas, arising from the renal mesenchyme, with nephroblastoma, originating from embryonal tissue of mixed origin, being most common in younger animals.1 Myxomas and myxosarcomas are tumors originating from fibroblasts and are rarely described in the veterinary literature. Reported sites of myxoma and myxosarcoma in dogs include skin, heart,3–5 joint,6 and periodontal ligament.7 Myxoma as a primary renal tumor is a rare finding in humans, and to our knowledge, a myxoma renal tumor has not been previously reported for a dog.
Clinical signs and CBC abnormalities of the dog of the present report were nonspecific and were in accordance with what has been reported in previous reports of primary renal tumors in dogs. Hematuria is a common clinical sign in dogs with renal tumors, with a prevalence of 32%,1 but is nonspecific for tumor type. Additionally, hematuria may also be a major complaint with other renal diseases such as nephritis, urinary tract infection, or uroliths. A palpable abdominal mass and signs of flank pain are not necessarily present in dogs with renal tumors (found in 20% of the cases).1 In the dog of the present report, the mass was palpated; however, because of its large size, it was not possible to associate the mass with an abdominal organ. On palpation, the dog of the present report did not show any signs of pain in the flank area. Other reported clinical signs associated with renal tumors include polydipsia and polyuria (10%), inappetence (27%), lethargy (26%), weight loss (20%), vomiting (13%), and behavioral changes (5%).1 In the dog of the present report, lethargy and vomiting were observed for only 2 days prior to hospital admission.
Survey abdominal radiography is most commonly used as the primary screening technique in veterinary medicine when an abdominal mass is palpated. In the case described in the present report, a left-sided retroperitoneal mass effect was present, making the organ of origin most likely the left kidney; however, an adrenal gland tumor with hemorrhage could not be ruled out. Abdominal ultrasonography is commonly used to identify the organ of origin when a mass effect is detected on radiographs. Computed tomography is considered the criterion standard of imaging modalities in cases where the organ of origin cannot be identified by radiography or ultrasonography. Computed tomographic images are also ideal for surgical planning. If CT is unavailable, excretory urography would be a further diagnostic tool to aid in the differentiation between renal versus nonrenal origin of a retroperitoneal mass. For the dog of the present report, tumor origin was determined on the basis of abdominal radiographic and ultrasonographic findings.
References
1. Bryan JN, Henry CJ, Turnquist SE, et al. Primary renal neoplasia of dogs. J Vet Intern Med 2006;20:1155–1160.
2. Baskin GB, De Paoli A. Primary renal neoplasms of the dog. Vet Pathol 1977;14:591–605.
3. Roberts SR. Myxoma of the heart in a dog. J Am Vet Med Assoc 1959;134:185–188.
4. Machida N, Hoshi K, Kobayashi M, et al. Cardiac myxoma of the tricuspid valve in a dog. J Comp Pathol 2003; 129:320–324.
5. Akkoc A, Ozyigit MO, Cangul IT. Valvular cardiac myxoma in a dog. J Vet Med A Physiol Pathol Clin Med 2007;54:356–358.
6. Berrocal A, Millan Y, Ordas J, et al. A joint myxoma in a dog. J Comp Pathol 2001;124:223–226.
7. Gupta K, Singh A, Sood N, et al. A rare case of odontogenic myxoma in a dog. J Vet Med A Physiol Pathol Clin Med 2005;52:401–402.
