Canine Intestinal Lymphangiectasia Concomitant with Renal Cell Carcinoma


 The etiology of dilation of lymphatic vessels, termed as intestinal lymphangiectasia, remains unknown. In most cases, it occurs secondary to other pathologic conditions such as gastrointestinal neoplasms. However, only a few cases of canine intestinal lymphangiectasia concurrent with non-gastrointestinal neoplasms have been reported so far. Moreover, the correlation between intestinal lymphangiectasia and non-gastrointestinal neoplasms has not been discussed in any other literature. In this study, we report a rare case of intestinal lymphangiectasia concomitant with renal cell carcinoma in an 11 year old female mixed Maltese, suggesting that non-gastrointestinal neoplasms could be associated with the development of intestinal lymphangiectasia. On gross observation, the small intestine was irregularly swollen presenting an accordion like shape. Microscopic examination revealed prominent dilatation of the lymphatic vessels, especially, within the submucosa and muscularis layer. The lacteals within the villi were dilated and presented “club-shaped” tips. The carcinoma might trigger intestinal lymphangiectasia by compressing the main lymphatic vessels or the cisterna chyli, subsequently increasing the pressure of the lymphatic vessels in the gastrointestinal tract. Moreover, metastasis of the carcinoma to the gastrointestinal tract could induce intestinal lymphangiectasia. Thus, the occurrence of intestinal lymphangiectasia must be considered when an abdominal neoplasm is located around major lymphatic vessels.


INTRODUCTION
Intestinal lymphangiectasia (IL) refers to the dilation of lymphatic vessels in the gastrointestinal tract. It is often observed in Yorkshire Terriers, Scottish Terriers, Lundehunds, and soft-coated Wheaten Terriers [1][2][3][4]. IL leads to the loss of lymphatic fl uid, which is enriched with proteins, lipids, lymphocytes, immunoglobulins, and electrolytes and is often associated with protein-losing enteropathy. Thus, IL results in progressive weight loss, malnutrition, lethargy, immunodefi ciency, and organ malfunction [4,5].
IL represents clinicopathological abnormalities such as hypoalbuminemia, panhypoproteinemia, hypocalcemia, hypocholesterolemia, hypocobalaminemia, and lymphopenia. However, these abnormalities are not specifi c for IL because they are observed in other conditions, such as gastroenteritis, Crohn's disease, liver failure, hepatic cirrhosis, pericarditis, protein-losing nephropathy, and nephrotic syndrome [1,6,7]. Thus, the presence of these biochemical abnormalities indicates the need for further examinations in order to reach a defi nitive diagnosis. Ultrasonography and endoscopy are suggested as non-invasive diagnostic methods for IL. Dogs with IL present loss of layering, thickening, and edema of the intestinal wall on ultrasound imaging [8]. The endoscopic fi ndings of IL include white spots at the top of the villi, giving it a "snakeskin appearance" [9]. However, it represents only 68 % of the sensitivity and 48 % of the specifi city, suggesting that it could be used as a supportive diagnostic method for IL along with laboratory abnormalities [10].
Despite the advantages of the aforementioned diagnostic methods, which include non-invasiveness, low risk of complications after examination, and relatively low costs, histopathological observation of the full-thickness of the intestine has been the golden standard for the diagnosis of IL owing to its high sensitivity and specifi city. Microscopically, IL is characterized by a marked dilation of lymphatic vessels in the submucosa, muscularis, and serosa layers of the intestine, and the dilation of lacteals in the mucosa layer. Additionally, marked infi ltration of infl ammatory cells is observed adjacent to the lymphatic vessels. The infl ammatory cells are mainly composed of lymphocytes, plasmacytes, epitheloid and foamy macrophages, and neutrophils; multinucleated giant cells are occasionally observed [4].
Although the presence of IL has been associated with other pathological conditions, its etiology remains unknown. Primary IL is rarely reported in humans and dogs. It occurs during childhood, generally before 3 years of age, and in young adults. Genetic defects are thought to be associated with the development of primary IL, and gene expression levels associated with lymphangiogenesis, such as vascular endothelial growth factor receptor 3 (VEGFR3), VEGF-C, and D, are altered in humans with primary IL [11].
However, in most cases, IL occurs secondary to other pathological conditions. It is mainly associated with an increase in pressure in the lymphatic vessels of the gastrointestinal tract. Most pathological conditions that accompany an increase in lymphatic pressure induce IL. Infl ammation in the lymphatic vessels can trigger this disease. Additionally, portal hypertension due to hepatic cirrhosis, pericarditis, and right-sided heart failure increases the pressure in the lymphatic vessels and fi nally leads to IL. Similarly, gastrointestinal neoplasms obstruct lymphatic drainage in the gastrointestinal tracts thereby resulting in IL.
Neoplasms in the intestine or mesentery are known to cause IL [12][13][14]. However, only a few cases of IL associated with non-intestinal neoplasms have been reported so far [4]; moreover, to the best of our knowledge, the correlation between IL and non-intestinal neoplasms has not been discussed in the literature. In this study, we report a rare case of IL with renal cell carcinoma (RCC) in a dog, which indicated that non-intestinal abdominal neoplasms could be associated with the development of the disease.

CASE PRESENTATION
An 11-year-old female mixed Maltese was brought to an animal hospital with symptoms of anorexia, vomiting, and weight loss. She had a history of pyometra and gallbladder myxoma. X-ray examination revealed the presence of a mass in the left kidney, which was surgically removed. During surgery, the small intestines were found to be fl accid and diffusely dilated. Parts of the dilated lesions and the mass collected from the kidney were submitted to the Laboratory of Veterinary Pathology at the Kyungpook National University. The tissues were routinely processed and embedded in paraffi n, cut into sections (thickness, 6 µm), and stained with hematoxylin and eosin. In the serum biochemistry analysis, the levels of most proteins, including albumin, calcium, and cholesterol, were within normal ranges. However, an increase in the level of gamma-glutamyl transferase (GGT; 42 U/L; reference range, 0-7 U/L) and decreases in the levels of total bilirubin (<0.1 mg/dl; reference range, 0-0.9 mg/dl) and amylase (413 U/L; reference range, 500-1500 U/L) were observed. The increase in GGT, in this case, might have been caused by the obstruction of the biliary ducts due to the myxoma in the gallbladder.
On gross observation, the small intestine was irregularly swollen and accordionshaped ( Figure 1A). On the cut surface, the wall of the small intestine was irregularly thickened and the lumen was narrow ( Figure 1B). Microscopic examination revealed dilatation of the lymphatic vessels within the submucosa and muscularis layer and the lacteals within the villi. Based on these fi ndings, the case was diagnosed as an IL. Among the intestinal layers, the dilation of lymph vessels was particularly remarkable in the muscularis layer. The dilated vessels were fi lled with eosinophilic protein-rich lymph.
According to the histopathological standards of gastrointestinal disease of the World Small Animal Veterinary Association (WSAVA), IL, so-called lymph dilation, is graded as mild, moderate, and marked lacteal dilation [15]. In mild lacteal dilation, the central lacteals form 50% of the width of villous lamina propria; moderate lacteal dilation indicates central lacteal ballooning which represents 75% of the width of the villous lamina propria; and in marked lacteal dilation, the central lacteals represent 100% of the width of the villous lamina propria [15]. Based on these standards, this dog was diagnosed with moderate lacteal dilation, and some villi presented "club-shaped" tips ( Figure 1C-1F). Hipogranulomatous lymphangitis or edema were not observed. Mild infi ltration of infl ammatory cells was observed, and the most infi ltrated cells were lymphocytes and plasmacytes.
The mass of the kidney was large enough to occupy most of the abdomen. It was located in the medulla and cortex of the kidney and protruded out toward the center of the abdomen. The tumor was not encapsulated, but well-circumscribed (Figure 2A). The neoplastic cells were arranged in a tubular pattern with a delicate collagen septum, whereas some areas of the tumor appeared as a solid mass. The mass was composed of epithelial cells with large and round nuclei and abundant eosinophilic cytoplasm. Mitotic fi gures were often observed ( Figure 2B). Based on these fi ndings, this tumor was diagnosed as a RCC. The dog was euthanized immediately after the surgery because of complications and poor prognosis.

DISCUSSION
The etiology of IL is not fully understood; however, it is known that IL is mainly caused by an increase in pressure in the lymphatic vessels, which may be attributed to conditions such as infl ammation, portal hypertension, and gastrointestinal neoplasia. In the current case study, IL was observed concurrently with RCC. Unlike gastrointestinal neoplasms, which directly obstruct intestinal lymphatic vessels, the RCC was physically distant from the IL lesion.
The etiology of IL can be complex and related to several pathological conditions at the same time. Therefore, the possible causes of IL were thoroughly considered in the present case study. Gastrointestinal infl ammation is one of the well-known causes of IL. The severe infi ltration of infl ammatory cells in lymphatic vessels disturbs the lymphatic fl ow. IL can occur secondary to infl ammation and be resolved after treating the infl ammation with corticosteroids [16]. Most of the IL lesions present with signs of infl ammation. In one study, 15 out of 17 dogs with IL presented with varying degrees of had infl ammation.
In the current case report, only a mild infi ltration of infl ammatory cells was observed in the lymphatic vessels and intestinal wall. Thus, the infl ammatory cells in the lesions were probably not suffi cient to disturb the lymphatic fl ows. It is diffi cult to discern the causative role of infl ammation in IL because it could occur as a result of the disease. Lymph fl uid could leak from the dilated lymphatic vessels following the development of IL. This could be followed by the infi ltration of infl ammatory cells around the IL lesion. The infi ltrated infl ammatory cells, including epithelioid cells and multinucleated giant cells, often form lipogranulomatous lymphangitis around the dilated lymphatic vessels, in response to the chronic leakage of lipid-laden chyle [17]. Therefore, it is diffi cult to determine the exact role of infl ammation in IL.
In one study, 15 out of 17 dogs with IL presented with mild to severe infl ammation, while the remaining 2 dogs did not have any infl ammation; 4 out of 15 dogs with severe infl ammation had mild IL, whereas 1 out of the 2 dogs without infl ammation had severe IL [4]. IL induced by infl ammation would be expected to be associated with severe infl ammation, which is required to disturb or block lymphatic vessels. On the other hand, ILs that are attributed to pathological conditions other than infl ammation might be associated with varying degrees of infl ammation, depending on the amount and duration of lymph leakage around the lymphatic vessels. Thus, the severity of infl ammation is not correlated to or predictive of the severity of IL.
Neoplasms can be found in the lymphatic vessels or intestinal walls of the gastrointestinal tract. Those occurring in the lymphatic vessels of the mesentery are known to induce IL [12]. In addition, a variety of gastrointestinal tumors, including gastric adenocarcinoma, lymphoma, and gastric neuroendocrine carcinoma, are concurrent with IL [13,14]. IL was reported to be resolved after resection of the primary mesenteric angiosarcoma [18]. Furthermore, chemotherapy, used to treat malignant lymphoma, was found to relieve gastrointestinal protein loss in a patient with IL [19]. These fi ndings indicate that IL can occur secondary to the physical obstruction of lymph vessels by gastrointestinal neoplasms and be resolved by getting rid of the primary cause. The lymphatic vessels tend to be focally dilated in cases where gastrointestinal or mesentery tumors are the main cause of lymphatic obstruction. IL is usually located within close range of a concurrent tumor. However, it was diffi cult to fi nd any neoplasms in the mesentery or gastrointestinal tract during exploratory laparotomy, X-ray imaging, and abdominal sonography in the current case study. To the best of our knowledge, correlations between IL and neoplasms that are physically distant from the impacted lymphatic vessels have not been reported. One study reported that 3 out of 23 dogs with IL presented with non-gastrointestinal neoplasms, including mammary ductal carcinoma, malignant fi brous histiocytoma, and adrenal adenoma; however, the correlation between these neoplasms and IL was not been addressed [4]. Moreover, two out of the three dogs presented with non-abdominal tumors, which might not have been associated with the IL. Though it is uncommon, the RCC is associated with the development of intestinal lymphangiectasia when considering the facts that it was hard to fi nd the general etiology of IL, such as severe infl ammation and gastrointestinal tumors. The possibilities that RCC is associated with the development of IL are as follow.
First, physical compression of RCC on the intestinal trunk and cisterna chyli might increase the lymphatic pressure in the intestine. In the present case study, the RCC was located near the cisterna chyli and intestinal trunk. The cisterna chyli receives lymph from the lower part of the body, including the abdomen, pelvis through the intestinal trunk, and lumbar trunks. The size of the RCC was suffi cient to obstruct the major lymphatic vessel. Second, the RCC might have metastasized and formed an embolus in the lymphatic vessels. It is known that approximately 69% of canine carcinomas of the kidney metastasize to other organs via the lymphatic or blood vessels [20]. Though RCC does not have a propensity for gastrointestinal metastasis, there are several reports of its metastasis to the gastrointestinal tracts in humans [21,22].Third, apart from physical compression or embolus formation from metastasis, RCCs may attribute to the incidence of IL, which is associated with either the functional alteration of kidney or pathological conditions due to the RCC itself. Albeit uncommon, it has been reported that RCC can be associated to gastrointestinal diseases [23]. RCC is associated with gastrointestinal symptoms such as pain, gastritis, and hiatus hernia [23]. Additionally, other renal diseases such as hemolytic uremic syndrome have been associated with the incidence of IL [24]. Though the mechanism involved remains unclear, renal diseases might be directly or indirectly involved in the occurrence of IL. Large portions of the medulla and cortex in the kidney were replaced by the RCC in the current case study (Figure 2A), which may have led to the malfunctioning of the kidney. Renal dysfunction triggers a decrease in protein reabsorption, which subsequently leads to a decrease in total protein levels in the plasma and lymph.
Sample collection through endoscopy is attempted because it is relatively less invasive than that via exploratory laparotomy. However, the critical limitation is that the endoscopic sample collection is confi ned to the mucosa layer. As shown in the present case report, the dilation of lymphatic vessels is often remarkable in the muscularis layer, but it is too deep to collect the sample by endoscopy; therefore, the lesion could be missed. In addition, a few samples from endoscopy might be of inadequate quality, which could affect the diagnosis [25]. The present case emphasizes the importance of full-thickness intestine sampling [26].
The limitation of this study is that it was impossible to know whether the resection of RCC resulted in the mitigation of IL, as shown in some other cases of IL with gastrointestinal tumor [18]. The dog was euthanized immediately after the surgery due to complications. If the IL had been relieved after the surgery, we might have been able to confi rm that the IL was caused by the non-gastrointestinal tumor.
The treatments of IL are confi ned to dietary fat restriction, as supportive treatment, apart from the elimination of the primary cause. Therefore, fi nding out the primary cause of IL is critical. The present case study suggests the possibility that a nongastrointestinal tumor can cause IL. Additionally, it indicates that IL should be considered when an abdominal mass ismetastatic or located near the major lymphatic vessels in the abdomen.