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Micro-albuminuria is the earliest markers for chronic parenchymal kidney diseases
- Professor Pranab Kumar Bhattacharya, BhattacharyaRupak,Bsc(cal), Msc(JU) 7/51Purbapalli Sodepur Kol-110, Bhattacharya Upasana, DasguptaJayantaDM(cal)Gastro-Asso.Prof,Gastro, Chakraborty Anindya ,Ghosh Sukumar DM(cardio) ICVS, Prof. Anup Kundu MS,Mch(Uro) cal,Prof. Urosurgery IPGMERKol-20,W.B (17 October 2008)
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Professor Pranab Kumar Bhattacharya, Professor of Pathology, Incharge of Histopathology, Cytogenetics,Blood Bank &VCTC Institute of Post Graduate Medical Education & Research,244a AJC Bose Road, Kolkata-20, W.B , India, BhattacharyaRupak,Bsc(cal), Msc(JU) 7/51Purbapalli Sodepur Kol-110, Bhattacharya Upasana, DasguptaJayantaDM(cal)Gastro-Asso.Prof,Gastro, Chakraborty Anindya ,Ghosh Sukumar DM(cardio) ICVS, Prof. Anup Kundu MS,Mch(Uro) cal,Prof. Urosurgery IPGMERKol-20,W.B
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Because patients in the very early stages of chronic kidney diseases exhibit very few signs and symptoms, laboratory tests for screening and earliest diagnosis are critical. Chronic kidney diseases (CKD) most often present before nephrologists with nonspecific complains or remain asymptomatic or because of either abnormal blood or urine findings. After proper history taking, especially in regard to patient’s suffering from diabetes (Type1 &Type2), or hypertension, or both, SLE, drug history (commonly Lithium, analgesics, anti psychotics) and physical examinations like blood pressure, any dermatological findings (uremic pruritus, petichial hemorrhagic spots, vitilego, shallow appearance of skin etc) funduscopic examinations (for micro aneurism, proliferative retinopathy, Arterio venus nicking, arteriolar narrowing etc) senso-neural hearing loss (in alprot syndrome), assessment of cardiovascular diseases, looking for nasal & oropharyngial ulceration (for SLE) perforated nasal septum (for wegner granulomatosis), a palpable mass in loin, laboratory tests usually prescribed by a nephrologists are urine analysis for proteinurea, hematuria, casts, crystals, pus cells etc, USG. USG is of one of the sensitive tests for establishing CKD. Finding of a small kidney is consistent with CKD. However it is also important that kidney size is variable from individual to individual. So fallacies may remain. The best tests to detect early abnormalities in the kidney parenchymal functions is estimation of GFR. Urine analysis, USG, GFR measurement and kidney biopsy serve main role in detection & diagnosis of early kidney lesions. However there are major limitations for doing a kidney biopsy and those includes many risks, in connivance of the procedure as well as needs costly immunofluorescence stains with panel of antibodies & many other special stains for interpretation of biopsy material & a histopathological diagnosis, and sampling error. GFR is measured by renal clearance of a particular substance or a marker substance from plasma divided by the average plasma concentration over time measurement and calculated as GFR= uXv/pXt, where u= urine concentration; v= volume of urine (in 24 hours); p= average plasma concentration of the marker substance; t=time of urine collection. For convenience & cost effectiveness, in Kolkata metropolis based laboratories creatinine clearance is taken as a marker of GFR, though costly and the tests are not available in subdivisions and in rural villages. But as there is tubular secretion of creatinine, accuracies of creatinine clearance tests is done by blocking creatinine secretion with Histamine 2 receptor blocking drugs like cimetidine. As GFR by creatinine clearance is not available everywhere, proteinurea is consistent with most kidney parenchymal diseases. So all patients must include testing of proteinurea particularly microalbuminurea- if the negative urine protein is found by dipstick or by Albustix. Proteinurea can be accepted as screening tests for Chronic kidney diseases in both diabetic and non diabetic individuals. For patients in whom there is +ve dipstick results quantization of proteinurea is the next step by esbach albuminometer. One problem is that charged immunoglobulins light chain will escape the dipstick or albustix methods even if when present in large amount in urine. Other fallacies are- a very high pH >7.0 can give also false positive result or when contamination occurs with blood as in hematuria urine. The lower limit of detection of dipstick is 10-20mg/dl and at this level major constituent is tam horss fall protein and positive result may not reflect kidney diseases. In Albustix ( Bayer diagnostic) trace reaction indicate urine albumin concentration between a wide range of 50-200mg/l and thus mere positive reaction can be used to indicate albumin concentration than those generally found in patients with micro albuminurea. Proteinurea specially microalbuminurea is thus an accepted marker for a CKD and progression of diseases. Even in patients with controlled essential hypertension and type 2 diabetes mellitus and in whom no evidence of renal diseases, acceleration of renal disease progression correlates with baseline proteinurea. So proteinurea and Microalbumiurea may be accepted as a marker for future decline of normal renal function even in non-diabetic individuals. Microalbuminurea can not be detected by dipstick or albustix method. Microalbuminurea is defined as albumin excretion rate of more than 300mg per gram of creatinine. Microalbuinurea is measured by immunometric dipstick micral test (bhoringer) or by Microbuminest (ames) using reagent tablet. Microalbuinurea is marker for progression for kidney diseases(nephropathy) in patients with both Type-1 and Type-2 DM and for increased risk of cardiovascular death in them. It is also an independent risk factor for both stroke and acute myocardial infraction Competing interests: None declared |
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