Protein-Losing Enteropathy Associated With Cystic Mucoid Changes in the Intestinal Crypts of Two Dogs
Two dogs were emaciated and hypoalbuminemic due to protein-losing enteropathy associated with a severe, focal, mucoid, cryptal ectasia of the duodenum and marked villus atrophy. In one case, diseased portions of the duodenum were obvious endoscopically and were limited to discrete, focal areas in the small intestine, with apparently more undiseased tissue than diseased tissue being present. The signs and lesions in one dog resolved after initiating combination dietary and pharmacological therapy.
Introduction
Canine protein-losing enteropathy (PLE) is an important syndrome reported to be associated with a variety of intestinal diseases, including lymphangiectasia,1–4 immunoproliferative enteropathy,5 inflammatory bowel disease such as lymphocytic-plasmacytic enteritis,367 food hypersensitivity,8 histoplasmosis,9 intussusception,610 small intestinal bacterial problems,11 neoplasia,12 and dilated small intestinal crypts filled with proteinaceous material.13 The list of documented causes of PLE in humans includes a wide range of diseases, such as parasites, intestinal ulceration/erosion, viral enteritis, sprue, intestinal bacterial overgrowth,14 chemotherapy/radiation therapy,15 increased activation of tissue plasminogen activator,16 hypoalbuminemia causing mucosal edema,17 vascular lesions in the intestinal mucosa,18 and systemic lupus erythematosus.19–21 Some of these seem to be obvious causes of PLE in dogs, even though they are not well documented in the literature.
Apart from parvoviral enteritis, diseases causing major changes in the intestinal crypts have been scantily described in veterinary medicine. Although lesions of the intestinal crypts have been mentioned in several publications,22–24 there have only been two reports that have focused on cases characterized primarily by disease that centered upon this segment of the mucosa.1325 In both of these reports, PLE was associated with the presence of crypt lesions. This report describes two more patients with crypt lesions different from those reported in the most recent series13 but similar to one case reported a decade ago.25 The authors’ purpose in reporting these two cases is to further characterize this lesion as well as the clinical course that is associated with it.
Case Reports
Case No. 1
A 10-year-old, male German shepherd dog was referred to the Texas Veterinary Medical Center (TVMC) because of a suspected PLE. The dog was first noted to be losing weight 14 months prior to referral. The dog developed a poor appetite and loose stools 3 months prior to referral. Two weeks before referral, the referring veterinarian performed an exploratory laparotomy and biopsied the stomach, duodenum, jejunum, liver, and mesenteric lymph nodes. These tissues were reported as having histopathologically insignificant lesions. At admission, the dog weighed 11.8 kg, had a grade IV/VI systolic heart murmur that was loudest on the left side at the base of the heart, and had a lack of muscle mass. There was no evidence of ascites on physical examination.
Pertinent clinical pathology abnormalities included anemia (packed cell volume [PCV], 12%; reference range, 35% to 55%) that was nonregenerative (corrected reticulocyte count, 0.26%) with 2+ hypochromasia, neutrophilic leukocytosis (neutrophils, 47.0 × 103/μL; reference range, 3.0 to 11.5 × 103/μL), panhypoproteinemia (albumin, 1.0 gm/dL; reference range, 2.4 to 3.6 gm/dL; total protein, 2.7 gm/dL; reference range, 5.7 to 7.0 gm/dL), and hypocholesterolemia (56 gm/dL; reference range, 120 to 247 gm/dL). The urinalysis showed no evidence of a protein-losing nephropathy (negative protein in 1.064 specific gravity urine). Serum trypsin-like immunoreactivity (TLI), cobalamin, folate, and gastrin concentrations were within reference ranges. Abdominocentesis retrieved a clear fluid that was a pure transudate. Salmonella spp. was cultured from the feces. Gastroduodenoscopy and colonileoscopy were performed, at which time the duodenum appeared diffusely roughened, hemorrhagic, and eroded. The duodenum, colon, and ileum were biopsied. Histopathological description of the duodenal samples is given later.
The dog was treated in the intensive care unit (ICU) for 15 days with total parenteral nutrition (TPN) (13 days) and two blood transfusions (each with 500 mL of fresh whole blood) because of the severe hypoalbuminemia and anemia. Sucralfate (1 gm per os [PO], q 6 to 8 hours), ferrous sulfate (22 mg/kg body weight, PO q 24 hours), and ranitidine (4.4 mg/kg body weight, intravenously [IV], q 8 to 12 hours) were administered because of the ulceration (see Histopathology section) and the anemia. Chlorpromazine (12 mg/kg body weight, IV q 12 hours) was administered to alleviate vomiting, and chloramphenicol (55 mg/kg body weight, IV, q 8 hours) was administered because of concerns about bacterial invasion via the eroded mucosa and the possibility of small intestinal bacterial overgrowth. Assorted other drugs were used for short (i.e., 24 to 48 hours) periods. The dog’s ideal weight was estimated to be 23 kg; therefore, TPN solution consisted of 20% lipid emulsion (285 mL), 8.5% amino acids (1.6 L), 50% dextrose in water (223 mL), 40 mL of TPN electrolyte solution, 10 mL of potassium phosphate solution, and 7 mL of multiple vitamin solution. This mixture was designed to provide 950 nonprotein calories and 138 grams of protein daily. It was administered by constant-rate infusion through a dedicated central venous catheter at 90 mL per hour. The dog’s serum albumin concentration increased to 1.5 gm/dL on the seventh day of TPN; however, the body weight did not change appreciably. As there was no evidence of meaningful clinical response after another 6 days of TPN, the dog was euthanized.
A partial necropsy was allowed. The abdomen was opened, and an acute, 8-cm intussusception was found in the small intestine. Multiple sections of small intestine (both adjacent to and far removed from the intussusception), pancreas, spleen, mesenteric lymph nodes, and liver were submitted for histopathology. The only significant histopathological changes were in the intestines (see Histopathology section).
Case No. 2
A 10-year-old, intact female Bedlington terrier was referred to the TVMC because of a suspected PLE. The dog started passing soft stools without blood, mucus, or melena 6 weeks prior to referral. Serum cobalamin and folate concentrations were decreased (cobalamin, 190 ng/L; reference range, 249 to 733 ng/L; folate, 6.4 ng/L; reference range, 6.5 to 11.5 ng/L). Weight loss was first noticed 3 weeks prior to referral, and 1 week later the appetite diminished markedly. By the time of referral, the dog had lost approximately 3.5 kg. At physical examination, the dog was very thin and weighed 7.3 kg.
Pertinent clinical pathology abnormalities included a neutrophilic leukocytosis (26.5 × 103/μL), panhypoproteinemia (albumin, 1.7 gm/dL; total protein, 4.1 gm/dL), and hypocholesterolemia (72 mg/dL). The urinalysis showed no evidence of a protein loss (1.014 specific gravity urine without evidence of protein by dipstick or sulfosalicylic acid precipitation). Abdominal ultrasonography demonstrated a thickened intestinal wall that had normal layering. Gastroduodenoscopy was performed, and large, multifocal lesions suggestive of erosions were noted [Figure 1]. Biopsies were obtained from both affected and non-affected portions of the duodenum. A histopathological description of the duodenal samples is given later.
After seeing the duodenal lesions, initial therapy consisted of feeding a commercial enteral dieta (600 kcal per day) plus white turkey meat and white potato (one part turkey to two parts potato), sucralfate (1 gm PO, q 12 hours), famotidine (1.25 mg/kg body weight, PO, q 12 hours), and cephalexin (22 mg/kg body weight, PO, q 12 hours). The latter three drugs were used because of the nature of the ulcerative lesions in the duodenum. After the crypt lesions were identified on histopathology, immunosuppressive therapy with metronidazole (10 mg/kg body weight, PO, q 12 hours), prednisolone (1.2 mg/kg body weight, PO, q 24 hours), cyclosporin (50 mg PO in the a.m.; 25 mg PO in the p.m.), and azathioprine (3 mg/kg body weight, PO, q 48 hours) was begun. Tetracycline (22 mg/kg body weight, PO, q 12 hours) was administered because of the concern for small intestinal bacterial overgrowth (antibiotic-responsive enteropathy). During this time, the serum albumin concentration dropped to 1.1 gm/dL, the body weight decreased to 6.9 kg, and the patient had a poor appetite. After the cyclosporin was stopped, the dog’s appetite immediately improved. The serum albumin concentration gradually increased to 1.7 gm/dL, while the body weight increased to approximately 7.3 kg (it varied from week to week). Eventually, the sucralfate and tetracycline were stopped, and commercial foods (prescription diets) were fed in addition to the enteral diet. The stools eventually became nearly normal in appearance, and the serum albumin concentration rose to 2.45 gm/dL. The cephalexin was discontinued, and the famotidine was decreased (1.25 mg/kg body weight, PO q 24 hours). The enteral diet was discontinued, and the dog was fed commercial dog food.b At 5 months postdiagnosis, the dog weighed 7.6 kg and had stool consistency that ranged from normal to pudding. One month later the dog was spayed, and the intestines were rebiopsied endoscopically; there was no visual or histopathological evidence of intestinal disease detected. Ten months after originally being presented to the TVMC, the dog was clinically well.
Histopathology
Histopathological lesions in the small intestines of both dogs were similar. The lesions were multifocal, with normal-appearing intestine interrupted by segments of affected intestine. Affected areas were characterized by markedly blunted villi that sometimes were collapsed and fused with adjacent villi [Figure 2]. Luminal epithelium was multifocally, superficially ulcerated, and at these sites neutrophils were present in the underlying lamina propria. Crypts of Lieberkuhn were frequently markedly dilated and filled with mucin, and sometimes they contained scattered macrophages with enlarged, foamy cytoplasms and degenerating polymorphonuclear cells. Occasionally the crypts were dilated by mucus to the point of rupture, and ruptured crypts were partially lined by flattened enterocytes. In the lamina propria around ruptured crypts, macrophages had phagocytosed mucus and had enlarged, vacuolated, and foamy cytoplasms. Multifocally, the enterocytes lining the crypts were beginning to regenerate and were lined by markedly hypertrophic enterocytes. Lacteals were minimally dilated and contained proteinaceous fluid. At the margins of affected areas, there was abrupt transition between affected and nonaffected mucosa. Unaffected areas were characterized by unremarkable villous architecture and only minimally increased numbers of lymphocytes and plasma cells in the lamina propria [Figure 3]. Immunohistochemical staining failed to reveal evidence of parvovirus antigen in the tissue sections. Histopathology of the intussusception in case no. 1 confirmed that it was an acute lesion.
Discussion
Protein-losing enteropathy is an important syndrome in the dog. In adult dogs, PLE is typically caused by intestinal lymphangiectasia, inflammatory bowel disease, and lymphoma, although many causes have been reported. Based upon anecdotal comments from clinicians, patients with severe PLE sometimes appear to be difficult to treat successfully, perhaps more so than dogs that have inflammatory bowel disease with normal serum albumin concentrations. Therefore, it seems valuable to diagnose these patients promptly because of the advantage of beginning appropriate therapy as soon as possible, before the serum albumin concentration becomes so low as to cause ascites, edema, or both. Furthermore, there is the concern that patients with severe PLE can develop pulmonary thromboembolism,13 possibly due to loss of antithrombin III into the intestinal lumen.
Possibly the most important aspect of this report revolves around the implications of the segmental nature of the lesions. Both of the patients of this report had segmental lesions interspersed in histopathologically normal-appearing mucosa. This multifocal distribution within a segment of intestine is why multiple biopsy samples (even of one segment of bowel) are needed to optimize the chance of finding clinically significant intestinal lesions. One cannot assume that just because the clinical signs of intestinal disease are severe, most or all of the intestines will be affected or that the lesions will be uniformly distributed within an affected section of bowel. The lesions described in this report were severe and yet very segmental.
The multifocal nature of these duodenal lesions also has implications for surgical biopsies obtained at laparotomy. Examination of the endoscopic image in Figure 1 reveals that there appeared to be more unaffected mucosa than affected mucosa. The authors have no reason to suspect that affected segments would have been visible from the serosal side of the intestine; therefore, if a single random biopsy was obtained from the duodenum (as is commonly the case at surgery), it is possible and perhaps likely that these lesions would have been missed.
Endoscopy allows direction of the biopsy forceps when sampling the duodenal mucosa. Apparently affected as well as apparently unaffected mucosa was sampled to make sure that tissue representative of everything in that section of bowel was obtained. Severe, focal lesions can be missed if only a few endoscopic samples are taken. However, it is also critical to note that the major histopathological lesion in these dogs was below the level of the villi, and if endoscopic tissue samples are superficial (i.e., pieces of tissue comprised almost entirely of villi), the true nature or severity of the lesions may not be recognized.
There are several similarities between the two dogs of this report and those previously reported. The common clinical signs reported in these two dogs were decreased appetite, diarrhea, and weight loss, whereas those previously reported in the other two studies were anorexia, vomiting, diarrhea, and weight loss.1325 All of the previously reported dogs as well as these two patients were panhy-poproteinemic,1325 and both of the dogs of this report as well as three dogs in a prior report had hypocholesterolemia.13 Finally, all animals had histopathologically abnormal intestinal crypts. However, there are also differences in the histopathological changes seen in the two cases of this report, compared with the other reported cases. Some intestinal crypts in the previously reported dogs were filled with mucus, and some crypts contained proteinaceous material and necrotic cell debris.13 In the cases reported here, the crypts contained mucus; however, brightly eosinophilic proteinaceous material was not a feature. Furthermore, the degree of crypt distention in these two dogs was much more severe than the degree described in the two previous reports.1325 There were also differences between villi in this and previous reports. The previously reported dogs either had deep ulceration or villi that were normal in length and shape. The authors found no evidence of deep ulceration in multiple biopsies. However, the authors consistently found marked villous blunting, but only affecting the villi above the ectatic crypts. Interestingly, there was an obvious and abrupt transition from normal villi to blunted villi, which is consistent with the segmental nature of the lesions.
The histopathological lesions in the cases presented here had some features in common with canine parvovirus (CPV) infection. Histopathological lesions that can be seen in CPV-2 infections and that were seen in these two cases included villous collapse and fusion, the segmental nature of the histopathological lesions, and dilated, mucus-filled crypts sometimes lined by hypertrophic enterocytes. However, the history and clinical presentation of the cases presented here are not what would be expected with CPV-2 infection,26 and immunohistochemical staining for canine parvovirus antigen on the sections was negative.
Despite the severe histopathological changes, one of the patients in this study had a favorable response associated with aggressive medical and dietary therapy. Admittedly, the intestinal disease may have spontaneously resolved, although that seems unlikely in view of its progressive nature prior to coming to TVMC. Although the diarrhea in this dog never completely resolved, it diminished in intensity. More importantly, there was an increase in the body weight plus a major increase in the serum albumin concentration, both signs that the intestinal disease was being controlled or ameliorated. The other patient of this report was euthanized due to disease severity, and the major question is whether the intussusception found at necropsy was responsible for the decline in condition or if the intussusception was simply a preterminal event that occurred in addition to the patient’s intestinal disease. In a prior report,13 two of four patients that were treated aggressively with anti-inflammatory drugs plus either TPN or elemental diets had a remission of clinical signs. While not all patients with severe disease of the small intestinal crypts apparently respond to therapy, one can state that patients with intestinal lesions of the severity seen here can sometimes resolve their disease.
Conclusion
The authors report on a dramatic intestinal crypt lesion of unknown cause that is associated with PLE. Despite its severity (both histopathologically and clinically), the lesion is not necessarily fatal. Whether case no. 2 of this report improved because of the therapy or in spite of the therapy is unknown; however, evidently at least some animals with such lesions can improve, as seen by the increase in serum albumin concentration and stabilization of body weight. Therefore, it is important to obtain a diagnosis of intestinal disease in a timely fashion. Endoscopic biopsies may have some advantages over full-thickness biopsies taken at laparotomy, if the samples taken are of adequate quality and quantity to allow the pathologist to examine the full thickness of the mucosa, and if at least some of the biopsies are directed to those areas that appear to be diseased.
Vivonex TEN; Sandoz Nutrition Co., Minneapolis, MN
Canine Select Protein Diet; Waltham USA, Vernon, CA
Citation: Journal of the American Animal Hospital Association 39, 2; 10.5326/0390187
Citation: Journal of the American Animal Hospital Association 39, 2; 10.5326/0390187
Citation: Journal of the American Animal Hospital Association 39, 2; 10.5326/0390187
Endoscopic picture of the duodenum of case no. 2. Note the focal, erosive lesions (arrowheads); more unaffected duodenum than affected duodenum is seen in this location.
Photomicrograph of a section of duodenum from case no. 2. Villi are collapsed and fused to adjacent villi. Crypts of Lieberkuhn are dilated and filled with mucin and aggregates of foamy macrophages. Many crypts have ruptured, and macrophages in the surrounding lamina propria have phagocytosed mucus (Hematoxylin and eosin stain; bar=300 μm).
Contributor Notes
