History
A 9-year-old spayed female Miniature Schnauzer was evaluated because of vomiting and lethargy of 1 week's duration. Abnormal physical examination findings included severe bilateral organomegaly on abdominal palpation suspected to be due to bilateral kidney enlargement and a grade 4/6 systolic heart murmur. Results of a CBC were unremarkable, but serum biochemical analysis revealed azotemia and hyperphosphatemia (SUN, 114 mg/dL [reference range, 7 to 32 mg/dL]; creatinine, 4.3 mg/dL [reference range, 0.5 to 1.5 mg/dL]; phosphorus, 9.4 mg/dL [reference range, 2.2 to 7.9 mg/dL]). Urine was minimally concentrated (specific gravity, 1.018) with proteinuria (2+; scale, negative to 4+). Radiographs of the abdomen were obtained (Figure 1).
Lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 9-year-old spayed female Miniature Schnauzer with abdominal organomegaly on abdominal palpation and acute renal failure.
Citation: Journal of the American Veterinary Medical Association 240, 7; 10.2460/javma.240.7.821
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
The kidneys are markedly enlarged, and the caudal pole of the left kidney is slightly irregular (Figure 2). There is also slight irregularity of the caudoventral margins of the liver, and rounding of the head and possibly the body of the spleen is present. Increased width and opacity in the region of the caudal mediastinum can also be seen. Based on these findings, multicentric lymphoma with infiltration of both kidneys and bilateral primary renal neoplasms (ie, tumors arising from the kidneys) with metastases were considered to be the most likely differential diagnoses. Differential diagnoses for the caudal mediastinal widening included a primary mediastinal mass, accessory lung lobe mass, or mediastinal lymph node mass; metastatic disease from the suspected renal neoplasia; or a dilated, fluid-filled esophagus.
Same radiographic images as in Figure 1. The kidneys (arrows) are markedly enlarged, and the caudal pole of the left kidney is slightly irregular. There is slight irregularity of the caudoventral margins of the liver, and rounding of the head and possibly the body of the spleen is present. Increased width and soft tissue opacity in the region of the caudal mediastinum can also be seen.
Citation: Journal of the American Veterinary Medical Association 240, 7; 10.2460/javma.240.7.821
Abdominal ultrasonography was performed to better characterize the renomegaly and to determine whether other abdominal organs were affected. Ultrasonography revealed multiple, variably sized hypoechoic nodules within both renal cortices and medullae, with distortion of the renal capsule. The large number of nodules in both kidneys resulted in loss of all typical kidney architecture (Figure 3). In addition, multiple hypoechoic nodules (up to approx 1.5 cm in diameter) were present within the liver, spleen, and pancreas; a 1.6-cm-diameter nodule was present in the region of the left adrenal gland; and there was enlargement of several intra-abdominal lymph nodes. Ultrasonography of the caudal aspect of the thorax and liver revealed an approximately 7 × 4-cm echogenic mass caudal to the heart, within either the caudal mediastinum or accessory lung lobe. Thoracic radiography confirmed widening of the caudal mediastinum due to a soft tissue opacity mass with associated lateral deviation of the mainstem bronchi; there was also a round, 3-cm-diameter soft tissue opacity in the right cranial lung lobe.
Transverse ultrasonographic image of the left kidney in the same dog as in Figure 1. There are multiple, variably sized hypoechoic nodules within the renal cortex and medulla that have resulted in loss of all typical kidney architecture. Vertical scale on right indicates distance in centimeters.
Citation: Journal of the American Veterinary Medical Association 240, 7; 10.2460/javma.240.7.821
Comments
Cytologic evaluation of an aspirate from the left kidney was performed; cells obtained had multiple criteria of malignancy and were most consistent with a histiocytic sarcoma. Azotemia did not improve despite aggressive supportive care, and the dog was euthanatized after 48 hours. Necropsy examination revealed disseminated histiocytic sarcoma (DHS) affecting the kidneys, liver, spleen, lymph node, lung, adrenal gland, pancreas, gastrointestinal tract, and cerebellum. Both kidneys were markedly enlarged, each weighing approximately 2% of the dog's total body weight (kidney weight is usually < 0.5% of body weight), with 80% to 90% of the typical parenchyma replaced by pale tan, roughly spherical masses; many of these pale tan masses were multilobular. The liver and spleen had fewer numbers of identical appearing masses on visceral and cut surfaces. The accessory lung lobe contained a 9-cm-diameter pale tan, firm mass with an associated enlarged mediastinal lymph node.
Disseminated histiocytic sarcoma is a subtype of 1 of 3 histiocytic proliferative diseases recognized in dogs. These 3 groups include cutaneous histiocytomas, reactive histiocytosis (cutaneous and systemic histiocytosis), and histiocytic sarcomas (localized and disseminated forms, the latter of which was formerly known as malignant histiocytosis).1 Malignant fibrous histiocytomas may be a form of localized histiocytic sarcoma and thus are no longer classified as separate tumors by many veterinary pathologists. The most common organs affected in dogs with DHS are the lung, hilar and mesenteric lymph nodes, liver, spleen, and bone marrow; the kidneys are an uncommon site of dissemination. Dogs with DHS often are in poor clinical condition and have rapid disease progression, as in the dog of the present report.
Identification of moderate to severe bilateral renomegaly in dogs on physical examination or diagnostic imaging is uncommon; causes include bilateral primary renal neoplasia, lymphoma, bilateral hydronephrosis due to obstruction of both ureters, and perirenal abscesses.2 Mild renomegaly in dogs is difficult to detect on the basis of physical examination because the kidneys are less mobile than in cats and are often inaccessible as a result of positioning below the vertebral transverse spinous processes and cranial to the last rib. When detected, mild renomegaly may be due to acute pyelonephritis, glomerulonephritis, or acute renal failure and may be associated with portosystemic shunts.2
Ultrasonographic abnormalities are most commonly detected in the spleen and liver of dogs with DHS.1,3 In 1 study3 that compared the ultrasonographic appearances of various types of histiocytic proliferative diseases in the abdominal organs of dogs, malignant fibrous histiocytoma was the only subtype that resulted in renal abnormalities. However, studies4,5 limited to dogs with DHS have reported that hypoechoic nodules may be present in the kidneys of 10% to 30% of patients, with deformation of normal renal shape secondary to nodule protrusion only occasionally noted. Severe, bilateral renomegaly due to DHS as was noted in the dog of this report has not been previously reported.
- 1.↑
Clifford CA, Skorupski KA. Histiocytic diseases. In: Withrow SJ, Vail DM, eds. Withrow and MacEwen's small animal clinical oncology. 4th ed. Philadelphia: Saunders Elsevier, 2006;649–659.
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Pressler BM. Cancer and the kidney. In: Bonagura JD, Twedt DC, eds. Kirk's current veterinary therapy XIV. St Louis: Saunders Elsevier, 2009;925–930.
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Cruz-Arámbulo R, Wrigley R, Powers B. Sonographic features of histiocytic neoplasms in the canine abdomen. Vet Radiol Ultrasound 2004; 45:554–558.
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Ramirez S, Douglass JP, Robertson ID. Ultrasonographic features of canine abdominal malignant histiocytosis. Vet Radiol Ultrasound 2002; 43:167–170.
- 5.
Skorupski KA, Clifford CA, Paoloni MC, et al. CCNU for the treatment of dogs with histiocytic sarcoma. J Vet Intern Med 2007; 21:121–126.
