Protein-Losing Nephropathy

WHAT IS YOUR DIAGNOSIS? An 5 year old, female neuter, English Springer spaniel was presented to the R(D)SVS Internal Medicine Service for investigation of ascites of four days duration. Her appetite was good and there was a mild increase in thirst and frequency of urination. The dog was still bright and alert and had good exercise tolerance. No coughing, sneezing or episodes of dyspnoea were noted. On clinical examination, the dog was bright, alert and responsive with a body weight of 17.2kg and a body condition score of 5/9. The mucous membranes were pink and moist, with a capillary refill time of one second. The heart rate was 140 beats/min but the dog was quite nervous. The dog was panting but no adventitious lung sounds were auscultated. A clear abdominal fluid thrill was detected but there were no other specific finding on palpation. The rectal temperature was normal at 38.9°C. Blood samples were taken for routine haematology and serum biochemistry. A free catch urine sample was also collected. Abdominocentesis was performed and a clear colourless fluid was collected. page 1 of 6 Haematology Parameter Result Reference Range RBC (x 10 /l) 4.64 5.5-8.5 PCV (%) 31.1 39-55 Hb (g/dl) 11.4 12-18 MCV (fl) 68.5 60-77 MCHC (%) 36 32-36 6.7 6-15 Neutrophils (x 10 /l) 5.56 3.6-12 9 0.87 0.7-4.8 0.27 0-1.5 9 0 0-1 Basophils (x 10 /l) 0 0-0.2 303 200-500 12 9 TWBC (x 10 /l) 9 Lymphocytes (x 10 /l) 9 Monocytes (x 10 /l) Eosinophils (x 10 /l) 9 9 Platelets (x 10 /l) Serum biochemistry Parameter Result Reference Range Total protein (g/l) 29.2 58-73 Albumin (g/l) 10.3 26-35 Globulin (g/l) 18.9 18-37 Bile acids (μmol/l) 0.7 0-7 Total bilirubin (μmol/l) 0.5 0-6.8 Urea (mmol/l) 10.2 1.7-7.4 Creatinine (μmol/l) 142 40-132 Glucose (mmol/l) 5.0 3-5 AP (iu/l) 22 20-60 ALT (iu/l) 49 21-102 Sodium (mmol/l) 146 139-154 Cholesterol (mmol/l) 12 3.8-7 Potassium (mmol/l) 4.7 3.6-5.6 I. phosphate (mmol/l) 1.7 0.9-2.0 Total calcium (mmol/l) 2.01 2.3-3.0 page 2 of 6 Urinalysis: Specific gravity 1.028, blood +++, protein ++++, sediment showed occasional red blood cell Abdominal fluid analysis: clear appearance, cell count 0.21 x 109/l, protein 0.5 g/l, specific gravity 1.008= true transudate 1) What are your differential diagnoses for hypoalbuminaemia in a dog? 2) How would you interpret these lab results and how would you investigate this case further? page 3 of 6 1. Causes of hypoalbuminaemia include: a) Liver dysfunction b) Protein-losing enteropathy e.g. severe IBD, lymphangectasia, lymphoma c) Protein-losing nephropathy e.g. glomerulonephritis, amyloidosis d) Third spacing e.g. lost into pleural or peritoneal effusions, into cellular interstitium in vasculitis e) Burns f) Severe malnutrition g) Acute phase shift i.e. mild non-pathological decrease in production in favour of globulins h) Anomalous e.g. hypoadrenocorticism, exocrine pancreatitic insufficiency (likely forms of PLE) 2. The presence of hypoalbuminaemia and a true transudate indicates that the hypoalbuminaemia is highly likely to be the cause of the ascites. The next step then is to work out the cause of the hypoalbuminaemia so that treatment can be targeted. Burns, severe malnutrition and an acute phase shift can be immediately ruled out. The normal liver parameters make liver dysfunction unlikely; this was confirmed with a normal bile acid stimulation test. The presence of protein on the urine dipstick suggested renal protein loss. A urine sample was submitted for urine protein:creatinine ratio (UPC) which was elevated 4.59 (ref <0.5), consistent with a protein-losing nephropathy. A urine sediment examination was performed at the same time to rule out lower urinary tract inflammation; a UPC is used to quantify renal protein loss as lower urinary tract inflammation would falsely elevate this result. The sediment was inactive in this case. Note that blood in the urine does not affect the UPC unless the sample is macroscopically haemorrhagic. The normocytic, normochromic anaemia was likely to be anaemia of chronic disease/inflammation. Specific investigation would be indicated if this progressed. The total hypocalcaemia was an expected finding due to the presence of hypoalbuminaemic since 40% of total blood calcium is normally complexed to calcium. Azotaemia was present and although there is some renal concentrating ability, it would be expected to be >1.030 in the face of azotaemia, indicating some possible renal compromise. Increased serum cholesterol is seen in 79-86% of dogs with protein-losing nephropathies. page 4 of 6 3) What would you do next to complete your investigation? Our investigations were consistent with a diagnosis of protein-losing nephropathy (PLN). The next step would be to investigate for the underlying cause and for the complications of PLN. An in-house ELISA for heartworm, Lyme disease, Anaplasma phagocytophilum and Erlichia canis was negative, as was urine PCR testing for Leptospira. Thoracic radiographs and abdominal ultrasound were performed to detect a potential neoplastic, infectious or inflammatory focus as a trigger for a PLN. All results were within normal limits except for the presence of ascites. A coagulation profile (PT, APTT, fibrinogen) was performed to test adequate clotting ability prior to renal biopsy. Ultrasound-guided percutaneous renal biopsy was performed and the samples submitted for routine haematoxylin & eosin histopathology, immunofluorescence and electron microscopy. The final diagnosis was Membranous Glomerulonephropathy. Systolic blood pressure was high normal at 156 mmHg. Retinal examination was unremarkable. Management While the biopsy results were pending, standard therapy for canine glomerular disease was commenced. Treatment included a reduced protein commercial renal diet, benazepril 0.5mg/kg PO q24hrs (to reduce proteinuria), aspirin 1 mg/kg PO q24hrs (to prevent thromboembolism as dogs with a PLN are hypercoagulable) and an omega 3 fatty acid supplement. Spironolactone 2mg/kg PO q24hrs was also added to help reduce the ascites. Despite increasing both benazepril and spironolactone doses, there was no improvement in UPC, hypoalbuminaemia or ascites. Once the renal biopsy results were received, immunosuppressive therapy with prednisolone 1mg/kg PO q12hrs and azathioprine 2mg/kg PO q24hrs was commenced. Within two weeks, serum albumin levels had increased to 18.4 g/l and ascites had resolved. Discussion Protein-losing nephropathies can be grouped into glomerulonephritides and amyloidosis. Glomerulonephritis can be further subdivided into several disease entities: membranoproliferative glomerulonephritis, membranous glomerulonephropathy, proliferative glomerulonephritis, hereditary nephritis, minimal change disease and glomerulosclerosis. Gaining a definitive diagnosis based on renal biopsy is the crux to successful management because immunosuppressive therapy is indicated in some diseases (such as membranous glomerulonephropathy, as in this case) while in others it can worsen the disease. In all cases, it is also important to try to identify and treat underlying disease elsewhere in the body. Since ongoing proteinuria is potentially damaging to the kidney in its own right, treatment with angiotensin-converting enzyme inhibitor and/or angiotensin-receptor blockers is vital. page 5 of 6 Complications of glomerular disease include oedema/effusions, hypertension, thromboembolism and hyperlipidaemia, which must all be managed to ensure the best outcome. References Brown S, Elliot J, Francey T, Polzin D, Vaden S. Consensus recommendations for standard therapy of glomerular diseases in dogs. Journal of Veterinary Internal Medicine 2013; 27: S27-S43 Segev G, Cowgill LD, Heine R, Labato MA, Polzin DJ. Consensus recommendations for immunosuppressive treatment of dogs with glomerular disease based on established pathology. Journal of Veterinary Internal Medicine 2013; 27: S44-S54 Vaden SL. Glomerular disease. In: Textbook of Veterinary Internal Medicine. Eds Ettinger SJ, Feldman EC. Elsevier Saunders, St. Louis, Missouri. pp 2021-2036 The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. www.ed.ac.uk/vet/hfsa-int-med page 6 of 6