Protein-Losing Enteropathies in Dogs.

WHAT IS YOUR DIAGNOSIS? An eight-year-old male neutered Labrador was presented to the R(D)SVS Internal Medicine Service for investigation of diarrhoea and vomiting. Diarrhoea had developed 10 days previously, and was described as being watery and of large volume, occurring 2-3 times a day. Melaena had also been observed. During this period the dog had also vomited occasionally, producing mainly a clear colourless liquid with bile, but no blood. The dog’s appetite had progressively decreased in the last 2 weeks, and a weight loss of 2 kg had been noted since the last weight check, one month previously. The dog had been in the owner’s possession since the age of 8 weeks, had no significant prior medical history, and had not travelled outside the UK. Routine vaccination and anthelmintic treatments were up to date, and there was no history of tick exposure. The dog was being fed a supermarket brand complete dry dog food, with occasional table scraps as treats. The dog was on no medication at the time of referral. On presentation the dog was quiet, but alert and responsive. Bodyweight was 36.1kg, with BCS 6/9. The dog was estimated to be around 5% dehydrated, based on tacky mucous membranes but no skin tent. The dog appeared to resent abdominal palpation, but no specific abnormalities were detected; there was no evidence of organomegaly, abdominal effusion, or abdominal masses upon palpation. The remainder of the examination was unremarkable, including rectal examination. 1. Where is the most likely site of disease, given this dog’s clinical signs? The clinical signs are diarrhoea, vomiting, melaena, a decreased appetite and weight loss. The presence of melaena, the history of weight loss, and the description of the diarrhoea (large volume, normal frequency, with no tenesmus, mucous or urgency) are most consistent with pathology affecting the small intestine. Haematology and biochemistry profiles were submitted. Results are shown below: page 1 of 7 : Parameter WBC Neutrophils (segmented) Neutrophils (non segmented) Lymphocytes Monocytes Eosinophils Basophils RBC PCV Hb MCV MCHC Platelets (automated count) Result 13.7 11.234 0 1.37 0.959 0.137 0 5.21 0.384 12.5 73.7 32.7 358 Range 6-15 3.6-12 0 0.7-4.8 0-1.5 0-1 0-0.2 5.5-8.5 0.39-0.55 12-18 60-77 32-36 200-500 Unit x 109/l x 109/l x 109/l x 109/l x 109/l x 109/l x 109/l x 1012/l l/l g/dl fl % x 109/l Result 18.6 27 26 0.7 0.7 1.94 111 2.2 79 13.5 1.52 5.0 32.1 145 0.58 2.9 3.6 Range 26-35 21-102 20-60 0-7 0-6.8 2.3-3 99-115 3.8-7 40-132 18-37 0.9-2.0 3.6-5.6 58-73 139-154 0.57-1.14 1.7-7.4 3-5 Unit g/l U/l U/l umol/l umol/l mmol/l mmol/l mmol/l umol/l g/l mmol/l mmol/l g/l mmol/l mmol/l mmol/l mmol/l Biochemistry: Parameter Albumin ALT AP Bile acids Bilirubin Calcium Chloride Cholesterol Creatinine Globulin Inorganic phosphate Potassium Protein (total) Sodium Triglyceride Urea Glucose 2. What are the differentials for hypoalbuminaemia? How can this dog’s clinical signs and the remainder of the haematology/biochemistry results help narrow the diagnosis? page 2 of 7 Hypoalbuminaemia can result from: 1) Decreased synthesis (hepatic failure, or acute phase response*) 2) Increased catabolism (e.g. prolonged starvation*) 3) Increased loss: - Renal (protein losing nephropathy, PLN) - Gastrointestinal (protein losing enteropathy, PLE) - Exudative loss (e.g. cutaneous losses due to burns, or repeat drainage of exudative effusion e.g. pyothorax/septic abdomen) - Haemorrhage 4) Redistribution: - Haemodilution - Increased capillary permeability (leakage into the interstitium) * Unlikely to be severe The dog presented with clinical signs consistent with small intestinal disease, making PLE the primary differential. Concurrent hypoglobulinaemia also suggested PLE, which typically causes panhypoproteinaemia (exceptions are hyperglobulinaemia found in histoplasmosis and Basenji enteropathy). The low cholesterol levels in this dog were also consistent with PLE. Hypocholesterolaemia in PLE is attributed to gastrointestinal loss and lipid malabsorption. Concurrent hypocholesterolaemia and hypoalbuminaemia can also be seen with hepatic dysfunction; however liver enzymes and function tests (bile acids, glucose, bilirubin) were normal in this dog, making significant hepatic pathology less likely. PLN was considered less likely at this stage, based on the low globulin and cholesterol levels (typically normal, or increased in PLN). Low total calcium levels are frequently recorded in PLE, and may reflect a combination of low protein-bound and ionised calcium fractions. The remainder of the differentials (starvation, haemodilution, exudative losses, haemorrhage) were considered less likely based on the dog’s history. The mild normocytic normochromic anaemia present was consistent with chronic disease. 3. What are your differentials for protein losing enteropathy (PLE)? Differentials for PLE:  Inflammation (inflammatory bowel disease) - Lymphoplasmacytic, eosinophilic, granulomatous  Intestinal lymphangiectasia - Primary - Secondary e.g. venous hypertension (right-sided heart failure, cirrhosis)  Neoplasia - Alimentary lymphoma  Structural - Intussusception page 3 of 7  Infectious - Histoplasmosis, Phycomycosis, Parvovirus, Salmonellosis, Giardiasis  Gastrointestinal hemorrhage - Hemorrhagic gastroenteritis, neoplasia, ulceration Any disease causing gastrointestinal tract inflammation, infiltration, congestion, or bleeding can result in PLE, including intussusception (predominantly juvenile animals), endoparasitism (predominantly juvenile animals), and severe acute infections e.g. parvoviral infection. However, in the majority of cases, the clinical signs are chronic. An adult dog with no history of travel outside the UK is therefore most likely to be affected by inflammatory bowel disease, lymphangiectasia, or alimentary lymphoma. 4. How would you investigate this case further? a) Rule out other causes of hypoalbuminaemia:  Urinalysis and urine protein creatinine ratio, to rule out PLN.  Bile acid stimulation test, to rule out hepatic dysfunction. Urinalysis, including UPC (0.11, ref < 0.2) was unremarkable. A bile acid stimulation test was not consistent with hepatic dysfunction (pre prandial 0.3 umol/l, post prandial 0.5 umol/l). b) Investigate causes of gastrointestinal protein loss:  TLI, cobalamin and folate levels, to rule out exocrine pancreatic insufficiency (TLI), and to provide further evidence of small intestinal disease (cobalamin and folate) and establish the need for supplementation.  Basal cortisol as a screening test for hypoadrenocorticism (Bovens et al. 2014). A cortisol value of > 55 nmol/l can rule out hypoadrenocorticism, but a value below this level needs to be followed up with an ACTH stimulation test.  Faecal parasitology to rule out helminth and Giardia infections.  Abdominal ultrasound with a particular focus on the intestinal wall (especially wall thickness and layering) and associated lymph nodes.  Gastrointestinal biopsy (surgical or endoscopic) and histopathology to establish the underlying gastrointestinal pathology. In this case, faecal parasitology, Giardia SNAP® testing and culture were negative. Cobalamin (202 mg/l, ref > 275), and folate (4.4 ug/l, ref 8.2-13.5) were decreased, consistent with small intestinal disease. TLI was within normal limits (23.2 ug/l, ref 6.1-35). Basal cortisol (138 nmol/l) was sufficiently high to rule out hypoadrenocorticism. Abdominal ultrasound revealed hypomotility of the gastrointestinal tract and a corrugated duodenal wall, but no loss of intestinal wall layering. The jejunal lymph nodes were mildly enlarged, but fine needle aspiration was unsuccessful. A very small amount of anechoic abdominal effusion was present (too small to sample). page 4 of 7 Enlarged jejunal lymph node Small volume of free fluid in abdomen page 5 of 7 5. What could be the cause of the free abdominal fluid? Ascites, subcutaneous dependent edema, and pleural effusion are common in PLE patients. In most cases, fluid accumulates secondary to decreased colloid oncotic pressure from hypoalbuminemia. Effusions or edema may develop when serum albumin concentrations fall below 15 g/l; effusions in these situations are usually pure transudates (low protein content, and low nucleated cell count). However, pure transudates in abdominal effusion can sometimes be seen despite serum albumin concentrations higher than 15 g/l, as in this dog, suggesting the presence of other factors governing the formation of effusion e.g. increased hydrostatic pressure, lymphatic obstruction, or increased vascular permeability. Treatment was initiated with intravenous crystalloid and colloid fluid therapy for rehydration and maintenance of oncotic pressure respectively, metronidazole for management of possible underlying inflammatory bowel disease, omeprazole as an anti-acid, and maropitant for anti-emetic effects. A constant rate infusion of metoclopramide was added for pro-kinetic and further anti-emetic effects. Clopidogrel was prescribed for thromboprophylaxis, given the hypercoagulability identified in dogs with PLE (Goodwin et al. 2011). Parenteral cobalamin supplementation was also initiated. The dog was anaesthetised for upper and lower gastrointestinal endoscopy, and oesophageal tube placement to facilitate enteral nutrition. Endoscopic biopsy was chosen in preference to surgical biopsy as it is less invasive, less costly, and allows visualisation of the mucosa (and hence targeted biopsy of any lesions identified). Given the documented importance of obtaining both duodenal and ileal biopsies when investigating chronic gastrointestinal disease in dogs (Procoli et al. 2013), both upper and lower gastrointestinal endoscopy were performed. Endoscopy revealed a diffusely irregular duodenal mucosa, with a cobblestone-appearance, increased friability, and a tendency to haemorrhage. There were no other significant findings; the oesophagus, stomach, ileum and colon appeared unremarkable. The following day the dog developed peripheral oedema, likely reflecting the combination of low oncotic pressure (9.6 mmHg, ref 14-27 mm Hg), a relative increase in hydrostatic pressure (intravenous fluids received under anaesthesia), and possibly an element of vasculitis or lymphatic obstruction. A central line was placed for total parenteral nutrition, thus providing nutrition and oncotic support. Histopathology results revealed low-grade intestinal lymphoma affecting the duodenum and ileum. Immunohistochemistry (CD3 and PAX5) confirmed this to be T cell lymphoma (CD3 positive cells). Concurrent inflammation was reported, suggesting that the lymphoma in this case may have developed as a consequence of a longer-standing inflammatory condition within the intestinal tract. page 6 of 7 The dog was treated with a combination of chlorambucil and prednisolone, in addition to the medications already instigated. Despite a brief improvement, the dog deteriorated and euthanasia was elected. Discussion: Canine protein-losing enteropathy (PLE) is associated with severe gastrointestinal disorders and has a guarded to poor prognosis. A recent retrospective study (Equilino et al. 2015) evaluating dogs with PLE secondary to inflammatory intestinal disease (neoplastic causes of PLE excluded) reported a median survival time of 67 days. Another recent retrospective study evaluated 92 dogs with all-cause PLE (Nakashima et al. 2015); 37% of these dogs were diagnosed with chronic enteropathy, 30% with intestinal lymphangiectasia, and 33% with intestinal lymphoma. Analysis of prognostic factors for survival in this study revealed a significantly shorter survival time in the lymphoma group, compared with the chronic enteropathy/ lymphangiectasia groups, and survival in dogs with large cell lymphoma was significantly worse than survival in dogs with small cell lymphoma. Additional factors predicting outcome included canine inflammatory bowel disease activity index (CIBDAI), and response to treatment (normalization of CIBDAI and plasma albumin concentration within 50 days). References: Bovens C. et al. Basal serum cortisol concentration as a screening test for hypoadrenocorticism in dogs. J Vet Intern Med. 2014 Sep-Oct; 28(5): 1541-5. Dossin O. et al. Protein-losing enteropathies in dogs. Vet Clin North Am Small Anim Pract. 2011 Mar; 41(2): 399-418. Equilino M. et al. Evaluation of serum biochemical marker concentrations and survival time in dogs with protein-losing enteropathy. J Am Vet Med Assoc. 2015 Jan 1; 246(1): 91-9. Goodwin L. et al. Hypercoagulability in dogs with protein-losing enteropathy. J Vet Intern Med. 2011 Mar-Apr; 25(2): 273-7. Nakashima K. et al. Prognostic factors in dogs with protein-losing enteropathy. Vet J. 2015 May 6 (Epub, ahead of print). Procoli F. et al. Comparison of histopathologic findings in duodenal and ileal endoscopic biopsies in dogs with chronic small intestinal enteropathies. J Vet Intern Med. 2013 Mar-Apr; 27(2): 268-74. page 7 of 7