Böbrekler, sıvı-elektrolit ve asit-baz dengesinde, sistemik kan basıncının düzenlenmesinde, kemik mineral metabolizmasında ve eritropoezde merkezi rol oynar. Böbreğin bu fonksiyonlarının değerlendirilmesinde laboratuvar tetkikleri önemli bir yer alır. Bu tetkikler, böbreğin glomerüler ve tübüler fonksiyonlarını değerlendiren testler olarak 2'ye ayrılır. Çocuklarda glomerüler fonksiyonları değerlendirmek için çok sayıda yöntem kullanılmıştır. Bununla birlikte, glomerüler filtrasyon hızı (GFH), hâlen glomerüler fonksiyonunun en iyi göstergesidir. GFH'yi belirlemede en yaygın yöntem ekzojen ve endojen ajanların kullanıldığı klirens ölçüm yöntemidir. Klirens ölçümü için kullanılacak olan ideal bir madde dolaşımda serbestçe bulunmalı, glomerüler bazal membrandan serbestçe filtre olmalı, nefron boyunca sekrete edilmemeli ve geri emilmemeli, sabit hızda endojen üretilmeli ve kolaylıkla ölçülebilir olmalıdır. Klinik uygulamada endojen ajanlar kullanılarak, çeşitli matematiksel yöntemler ile tahmini GFH hesaplamaları da bulunmaktadır. Tübüler fonksiyonların değerlendirilmesi, glomerüler fonksiyonun değerlendirmesinden daha karmaşıktır. İdrar dansitesi, ozmolalitesi ve pH değeri tübüler fonksiyonlar hakkında fikir veren ve rutin olarak kullanılan başlıca laboratuvar parametreleridir. Tübüler fonksiyonların ayrıntılı incelemesi rutin olarak yapılmaz. Renal fosfat kaybı, idrar asidifikasyon defekti veya idrar konsantrasyon yeteneğinde azalma olan durumlarda renal tübüler fonksiyonlar ayrıntılı olarak araştırılır. İlgili tübülün farklı segmentlerine göre farklı fonksiyonlar etkilenebilir. Tübüler fonksiyonların değerlendirilmesi glukoz, fosfat, bikarbonat ve amino asitlerin geri emilimini, solütlerin fraksiyonel atılımını, konsantrasyon ve dilüsyon kapasitesini değerlendiren testleri içerir.
Anahtar Kelimeler: Böbrek hastalıkları; laboratuvar; glomerüler fonksiyonlar; tübüler fonksiyonlar
The kidneys play a central role in the maintenance fluid-electrolyte and acid-base balance, systemic blood pressure, bone and mineral metabolism and erythropoiesis. Laboratory tests are important in evaluating these functions of the kidney. Laboratory tests can be categorized into tests for glomerular and tubular functions. Broad sets of evaluation tools have been used to judge glomerular function in children. Glomerular filtration rate (GFR) is still the best indicator of renal function. The most common measurement method of GFR is clearance methodology, using exogenous and endogenous markers. The ideal substance for the measurement of clearance should be free in the circulation, freely filterable from through the glomerular basement membrane, not secreted and not reabsorbed along the nephron, generated endogenously at a steady rate and easily measurable. An estimation of GFR from endogenous biomarkers by various mathematical equations is also available for clinical use. Assessment of tubular function is more complicated than the measurement of glomerular function. Urine specific gravity, osmolality and pH are main laboratory parameters that are routinely used for evaluation of tubular functions. Detailed evaluation of tubular functions is not routinely performed. Tubular functions are assessed in detail in case of renal phosphate wasting, urine acidification defect or decrease concentration ability. Different functions may be affected with respect to the different segments of tubule involved. Evaluation of tubular functions include tests evaluating reabsorption of glucose, phosphate, bicarbonate and amino acids, fractional excretion of solutes, concentrating and diluting capacity.
Keywords: Kidney diseases; laboratory; glomerular functions; tubular functions
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