Pathophysiology/Complications ORIGINAL ARTICLE Acanthocytes in the Urine Useful tool to differentiate diabetic nephropathy from glomerulonephritis? GUNNAR H. HEINE, MD MATTHIAS GIRNDT, MD of patients who are most likely to have a URBAN SESTER, MD HANS K¨OHLER, MD nondiabetic glomerulopathy and to selec- tively perform renal biopsy in this sub- group of patients. Urinary erythrocyte morphology ex- amined by phase-contrast microscopy al- OBJECTIVE — The presence of hematuria has been suggested to indicate nondiabetic ne- lows to differentiation of glomerular and phropathy in diabetic patients with proteinuria. However, hematuria is frequently found in patients with biopsy-proven diabetic glomerulosclerosis without nondiabetic nephropathy. nonglomerular bleeding (10). Glomeru- Urine microscopy allows discrimination of glomerular hematuria, which is defined as acantho- lar bleeding is indicated by urinary excre- cyturia (urinary excretion of acanthocytes, which are dysmorphic erythrocytes with vesicle-like tion of acanthocytes. Acanthocytes are protrusions), from nonglomerular hematuria. We hypothesized that acanthocyturia is an un- characteristic ring-formed erythrocytes common finding in diabetic nephropathy, which suggests the presence of a nondiabetic ne- with vesicle-shaped protrusions (Fig. 1) phropathy in diabetic patients with proteinuria. (11,12) that have been described previ- ously in the peripheral blood of patients RESEARCH DESIGN AND METHODS — Urine samples of patients with the clinical diagnosis of diabetic nephropathy (n ϭ 68), of patients with biopsy-proven glomerulonephritis suffering from certain hereditary neuro- (n ϭ 43), and of age-matched healthy control subjects (n ϭ 20) were examined by phase-contrast logical disorders (abetalipoproteinemia, microscopy for the presence of hematuria (Ն8 erythrocytes/␮l) and acanthocyturia. Acantho- chorea-acanthocytosis, and McLeod syn- cyturia of Ն5% (5 acanthocytes among 100 excreted erythrocytes) was classified as glomerular drome) (13). When urine sediments of hematuria; acanthocyturia of 2–4% was classified as suspected glomerular hematuria. patients with biopsy-proven glomerulo- nephritis and patients with nonglomeru- RESULTS — Hematuria was found in 62% of patients with the clinical diagnosis of diabetic lar kidney diseases, urolithiasis, cystitis, nephropathy, in 84% of patients with glomerulonephritis, and in 20% of the healthy control subjects upon a single urine examination. In contrast, glomerular hematuria occurred in 4% of urethritis, and tumors are compared, ac- patients with diabetic nephropathy and in 40% of patients with glomerulonephritis (P Ͻ 0.001). anthocytes are an excellent predictive marker of glomerular bleeding (11). CONCLUSIONS — In contrast to hematuria, acanthocyturia is uncommon in patients with Acanthocyte formation in glomerulo- the clinical diagnosis of diabetic nephropathy. In diabetic patients with proteinuria, the finding nephritis has been explained by a possible of acanthocyturia points to nondiabetic glomerulopathies, and renal biopsy should be mechanical influence of the impaired glo- considered. merular basement membrane on the Diabetes Care 27:190–194, 2004 spectrin backbone of the erythrocyte that passes the glomerular barrier. Compared with glomerulonephritis, diabetic ne- phropathy is characterized by a different he prevalence of microscopic hema- tion of renal tissue from diabetic patients pattern of glomerular lesions, which may turia in diabetic patients with mac- with hematuria fairly often only demon- result in a different type of hematuria. It roalbuminuria may range between strates diabetic nephropathy without evi- T has been suggested that hematuria in di- 12.5% (1) and 67–73% (2,3), depending dence of nondiabetic glomerulonephritis on the population of diabetic patients (isolated diabetic nephropathy) (1,4–7). abetic nephropathy might result from studied and the definition of hematuria. In addition, it was recently reported that areas of aneurysmal dilatation in glomer- The finding of microscopic hematuria in the prevalence of hematuria in diabetic ular capillaries with subsequent rupture diabetic patients has been suggested to in- patients with histologic evidence of non- and with little mechanical damage to dicate nondiabetic glomerulopathy, diabetic nephropathy is only slightly (6) erythrocytes. which would demand further nephrologi- or not at all (8,9) increased when com- We studied the prevalence of hema- cal examination, including renal biopsy pared with patients with biopsy-proven turia and acanthocyturia in patients with (1). However, renal biopsy is an invasive isolated diabetic nephropathy. Therefore, clinically diagnosed diabetic nephropa- procedure with potentially severe compli- it would be helpful to define a pattern of thy and in patients with biopsy-proven cations, and careful histologic examina- hematuria that characterizes a subgroup glomerulonephritis to examine whether ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● acanthocyturia occurs with both glomer- From the Department of Nephrology, University of Homburg, Homburg, Germany. ular lesions or whether it is specific for Address correspondence and reprint requests to Gunnar Heine, MD, Department of Nephrology, Uni- glomerulonephritis. In the latter case, the versity of Homburg, 66421 Homburg, Germany. E-mail: [email protected]. finding of acanthocyturia in a diabetic pa- Received for publication 1 July 2003 and accepted in revised form 17 September 2003. tient might point to nondiabetic, poten- A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion factors for many substances. tially treatable glomerulopathy, in which © 2004 by the American Diabetes Association. renal biopsy may be indicated. 190 DIABETES CARE, VOLUME 27, NUMBER 1, JANUARY 2004 Heine and Associates nephropathy (10 patients), mesangial- proliferative glomerulonephritis (8 pa- tients), membranous glomerulonephritis (5 patients), focal glomerulosclerosis (3 patients), crescentic glomerulonephritis (2 patients), and other forms/mixed forms of glomerulonephritis (5 patients). Urinalysis Urinalysis within 4 hours after voiding was performed by an observer who was blinded for the clinical diagnosis and who was experienced in urinalysis (perform- ing Ͼ100 urinary examinations per month). Whenever possible, three urine samples from three separate days were an- alyzed; this procedure is known to in- crease sensitivity to detect glomerular bleeding (11). The urine samples were analyzed by phase-contrast microscopy. Cell numbers of urinary erythrocytes and leukocytes were counted in a Fuchs-Rosenthal Figure 1—Glomerular hematuria characterized by the presence of Ն5% acanthocytes (ring- counting chamber without prior centrifu- formed erythrocytes with vesicle-shaped protrusions) among all erythrocytes excreted (phase- gation (unspun urine). contrast microscopy). For patients with erythrocyte counts Ն8 red cells/␮l urine (defined as hematu- ria), red cell morphology was assessed in a RESEARCH DESIGN AND diagnosis of diabetic nephropathy was spun urine specimen. A total of 10 ml of METHODS — Between April 1999 confirmed by an experienced nephrologi- urine was centrifuged at 2,000 rpm for 5 and August 2001, we examined urine cal consultant. min. The sediment was resuspended with samples of all patients who presented to Patients with diabetic nephropathy 0.5 ml of urine. Aliquots of 20 ␮lofthe our Department of Nephrology with the and nondiabetic control subjects were suspension were analyzed by phase- clinical diagnosis of diabetic nephropathy older than patients with glomerulone- contrast microscopy to examine at least (n ϭ 68) or with biopsy-proven glomer- phritis, and renal function was more se- 100 erythrocytes. ulonephritis (n ϭ 43). Patients with glo- verely impaired in patients with diabetic Acanthocytes were defined as a ring- merulonephritis were only included if nephropathy than in those with glomeru- form of erythrocytes with vesicle-shaped urinalysis was performed before initiation lonephritis (Table 1). protrusions (Fig. 1) (11). Acanthocyturia of immunosuppressive treatment of the Results of renal biopsy in patients of Ն5% (5 acanthocytes among 100 ex- underlying renal disease. For a control with glomerulonephritis included mi- creted red cells) was classified as glomer- group, urine samples were obtained from nimal-change disease (10 patients), IgA ular hematuria; acanthocyturia of 2–4% 20 volunteers who were matched in age to the patients with the clinical diagnosis of diabetic nephropathy and who had nei- Table 1—Biometric data and serum creatinine levels of patients with diabetic nephropathy ther symptomatic nephrological or uro- and patients with glomerulonephritis; biometric data of control subjects logical diseases nor diabetes. Diabetic nephropathy was diagnosed Serum Serum in patients treated for type 1 diabetes (n ϭ ϭ Sex (male/ creatinine creatinine 4) or type 2 diabetes (n 64) who were female) Age (years) Ն130 ␮mol/l mean (␮mol/l) on insulin therapy and who had mi- croalbuminuria (30–300 mg albumin/ Diabetic nephropathy (n ϭ 68) 35/33 64.6 Ϯ 11.7 84% (57/68) 329.9 Ϯ 213.9 day; n ϭ 5) or overt proteinuria (Ͼ300 Glomerulonephritis (n ϭ 43) 27/16 49.2 Ϯ 16.7 47% (20/43) 165.1 Ϯ 130.4 mg protein/day; n ϭ 63). Diabetic ne- Control subjects (n ϭ 20) 7/13 56.8 Ϯ 23.3 —— phropathy was not diagnosed in patients Diabetic nephropathy vs. NS P Ͻ 0.001 P Ͻ 0.001 P Ͻ 0.001 in whom case history, renal ultrasonogra- glomerulonephritis