Renal Thrombotic Microangiopathy, Podocytopathy, and Chylous Ascites: A Hard-Nosed Diagnosis

A 67-year-old Sub-Saharan African man presented to an outside institution with progressive, painless abdominal distention, anorexia, leg swelling, and dyspnea on exertion. He had not seen a physician in many years. He denied alcohol use, intravenous drug use, or any recent surgery. He was referred to our institution for a second opinion. On physical examination, he was alert and orientated. His temperature, pulse, blood pressure, and room air oxygen saturation were 36.1°C, 82 beats per minute, 115/73 mm Hg, and 99%, respectively. He had no purpura and no stigmata of chronic liver disease. He had 3+ pitting edema to the hips and a distended nontense abdomen with shifting dullness.

Laboratory studies revealed hemoglobin of 13.9 g/dL (ref: 13.9-16.3 g/L), platelet count of 101 K/cu mm (ref: 150-350 K/cu mm), and creatinine of 6.8 mg/dL (ref: 0.6-1.3 mg/dL) (no prior baseline known) corresponding to an estimated glomerular filtration rate (eGFR) of 10 mL/min/1.73m2 and a serum albumin of 1.4 g/L (ref: 3.5-5.3g/dL). Urinalysis revealed 3+ protein. Urine microscopy demonstrated fatty casts, fine granular casts, and oval fat bodies, but no red or white cell casts. A 24-hour urine collection noted 16.1 g of proteinuria (ref: 0-100 mg/24 h). He had normal liver function tests and coagulation studies, except an elevated D-dimer of 5.10 mg/dL (ref: 0.17-0.88 mg/L). All further inflammatory and infectious studies were negative, including antinuclear antibodies, antinuclear cytoplasmic antibodies, cryoglobulins, hepatides panel, human immunodeficiency virus, filariasis antibodies, and kappa/lambda light chain ratio. C3, C4, and CH50 levels were normal. ADAMTS13 activity was 107% (ref: 70%-150%). Lactate dehydrogenase was elevated at 386 U/L (ref: 118-273 U/L) and haptoglobin was 97 mg/dL (ref: 36-195 mg/dL). A peripheral blood smear did not show a microangiopathic process. All bacterial, mycobacterial, and fungal blood cultures were negative.

The patient underwent a diagnostic and subsequent therapeutic paracentesis (Figure 1). The triglyceride content of the ascitic fluid (220 mg/dL) was consistent with chylous ascites; however, other features were unlike chylous ascites (low albumin content of 0.3 g/dL and low lactate dehydrogenase [LDH] level of 50 U/L) (Table 1). Cytologic findings were negative, as were bacterial, acid-fast, and fungal cultures. Echocardiography was unremarkable. Liver biopsy performed at an outside hospital revealed panlobular lymphocytic rich inflammation, but no fibrosis or fibrin thrombi. A kidney biopsy was performed when his eGFR was 9.0 mL/min per 1.73m2 (Figure 2). His renal biopsy demonstrated both focal segmental glomerular sclerosis and fibrin thrombi (Figure 2A). A few glomeruli (n = 5-6) showed periglomerular fibrosis and ischemic shrinking of the capillary tuft and capillary wall (Figure 2B). Immunofluorescence showed nonspecific staining for immunoglobulin G, immunoglobulin M, and C3. There was extensive podocyte foot process effacement overlying the wrinkled basement membranes (Figure 2C). There was expansion of the subendothelial space. There was segmental thickening and folding of the basement membranes. Focal double contours, with mesangial cell interposition, could be identified, but there were no signs of chronic thrombotic microangiopathy.