Evaluation of light microscopy to localise the site of haematuria

Waxy casts in the urinary sediment of patients with different types of glomerular diseases: results of a prospective study

BACKGROUND

Casts are well known components of the urinary sediment. For most casts, the clinical associations are known and demonstrated, while for waxy casts they are totally unknown.

METHODS

Prospective study for the search and count of waxy casts in the urinary sediment of patients with different types of glomerular diseases.

RESULTS

Waxy casts were found in 39 out of 287 patients (13.6%), mostly in low number (1 to 9 out of 100 casts evaluated/sample). They were frequent in postinfectious glomerulonephritis and renal amyloidosis (5/9 patients, 44.5%, p=0.02 for each condition), while they were rare in membranous nephropathy (4/67 patients, 6.0%, 0.04) and absent in focal segmental glomerulosclerosis (0/23 patients, p=0.05). Waxy casts were associated significantly with higher serum creatinine levels (p<0.0001), with the presence of >1 leukocyte/HPF, granular casts and leukocytic casts (p=0.001 to 0.008) and with higher numbers of erythrocytes, leukocytes, renal tubular epithelial cells, granular casts, epithelial casts, and leukocytic casts (p<0.0001 to=0.03).

CONCLUSIONS

Waxy casts are uncommon and few in patients with glomerular diseases and are associated with impaired renal function and with several other structures of the urinary sediment.

Clinical Use and Pathogenetic Basis of Laboratory Tests for the Evaluation of Primary Arterial Hypertension

This review focuses on the laboratory biochemical tests that are useful in the diagnostic approach to the hypertensive patient. A "minimal" diagnostic laboratory work-up, including a small number of tests that are simple and relatively inexpensive, is first described. Because these tests provide basic information on the presence of major cardiovascular (CV) risk factors and target organ damage, and might give some clues to the presence of a secondary form of hypertension (HT), they should be performed on all patients presenting with HT. Other tests that are aimed at assessing the overall CV risk, a major determinant of prognosis that dictates the therapeutic strategy in the individual HT patient, are then discussed. They allow identification of major CV risk factors and associated clinical conditions which, if present, lead to a substantial change of therapeutic strategy. The role of C-reactive protein as a marker of atherosclerosis and its predictive value for CV events are also discussed. Finally, a section is devoted to tests that are currently confined to research purposes, such as markers of endothelial function including endothelin-1, homocysteine and genetic analysis.

Urine erythrocyte morphology in patients with microscopic haematuria caused by a glomerulopathy

The evaluation of urinary erythrocyte morphology (UEM) has been proposed for patients with isolated microscopic haematuria (IMH) to early orientate the diagnosis towards a glomerular or a nonglomerular disease. However, to date, the role of this test in patients with IMH has very rarely been investigated. Sixteen patients (ten children, six adults) with persistent IMH classified as glomerular on the basis of repeated UEM evaluations (55 urine samples, two to eight per patient) were submitted to renal biopsy. This showed a glomerular disease in 14/16 patients (87.5%) (nine thin basement membrane disease; three Alport syndrome; two other), whereas in two patients, no abnormalities were found. Of four microscopic criteria investigated to define a IMH as glomerular, >80% dysmorphic erythrocytes were not found in any sample, >or=40% dysmorphic erythrocytes alone were seen in seven samples (12.7%), >or=5% acanthocytes alone in 15 samples (27.3%) and erythrocytic casts in six samples (10.9%). There was >or=40% dysmorphic erythrocytes associated with >or=5% acanthocytes in 25 samples (45.5%). Sensitivity and positive predictive values in diagnosing a glomerular haematuria were 59.2% and 90.6%, respectively, for >or=40% dysmorphic erythrocytes, 69.4% and 85% for >or=5% acanthocytes/G1 cells and 12.2% and 100% for erythrocytic casts. Our findings demonstrate that the evaluation of UEM is useful to identify patients with an IMH of glomerular origin.

Urinary microscopy as seen by nephrologists

Urinary microscopy is a diagnostic tool which is largely used by nephrologists. In the opinion of the authors the best results can be achieved when all the aspects concerning this test are properly taken into account. Thus, from the methodological point of view, proper patient guidance, proper urine collection and handling, adequate microscopic equipment, and knowledge of the factors which can influence the results are all necessary. All the elements of clinical importance have to be known, namely, erythrocytes (with their morphological subtypes), leukocytes, tubular cells, uroepithelial cells (both superficial and deep), lipids, casts, crystals, and microorganisms. Then, the urinary findings have to be interpreted and, whenever possible, also combined into urinary profiles (e.g., the nephritic sediment, the nephrotic sediment). This, combined with other laboratory tests, the pathologic findings, and the clinical data, allows for the definition and management of urinary tract diseases.

What makes red cells dysmorphic in glomerular haematuria?

Although red cell morphology has been used to localise the site of haematuria in the urinary tract, the cause of red cell deformity is still speculative. We have conducted experiments in vitro using venous red cells which indicate that hypochromia depends mainly upon sodium concentration and occurs when this falls below 75 mmol/l. We simulated the passage of red cells through the renal tubule by sequentially treating them with fluids of composition similar to those in different tubular segments, and produced anisocytosis and hypochromia but not the typical "bizarre deformity"--the hallmark of glomerular haematuria. We conclude that dual injury is required to produce the "typical" dysmorphic red cells in glomerular haematuria. First, mechanical damage caused by passage of red blood cells through the glomerular basement membrane followed by a second, osmotic, injury sustained by red cells during passage through the hypotonic tubular segment.