Chronic glomerulonephritis can be caused by various intrinsic glomerular diseases (primarily of autoimmune origin) and by numerous systemic disorders that target the glomeruli. Two main clinical entities arise - nephritic syndrome and nephrotic syndrome, mainly distinguished by the presence of hematuria in the former and larger quantities of protein loss (>3.5 g/day) in the latter, respectively. A comprehensive laboratory workup, including determination of the glomerular filtration rate (GFR), is necessary to determine the severity of kidney disease and confirm the underlying cause.
Chronic glomerulonephritis denotes a progressive deterioration of kidney function and is one of the main factors involved in the pathogenesis of chronic kidney disease (CKD)  . It may be defined as a persistent and long-lasting inflammatory disorder of the glomeruli and is almost universally a complication of acute glomerulonephritis, distinguished by a slower progression and a milder clinical presentation . A broad classification of ailments that cause glomerulonephritis can be mainly based on the two clinical syndromes produced by these etiologies     :
The diagnosis of chronic glomerulonephritis may be difficult to make in its initial stages due to an asymptomatic or milder clinical course , which is why a thorough workup is imperative. The physician must obtain a detailed patient history that will address the appearance of macroscopic hematuria, hypertension, or peripheral edema. History of drug use is essential during the interview since non-steroidal anti-inflammatory drugs (NSAIDs), oral contraceptives, and penicillamine (a chelating agent) have been listed as iatrogenic causes of glomerulonephritis . Infections are an important etiology of glomerulonephritis as well, such as viral hepatitis (B and C), human immunodeficiency virus (HIV) infection, and many other bacterial/viral/fungal pathogens  , which is why the presence of additional symptoms must be assessed. Laboratory studies, however, are crucial for diagnosing chronic glomerulonephritis. Evaluation of serum electrolytes and creatinine, together with urinalysis for hematuria and protein content are key steps for identifying renal function abnormalities  . The role of urinalysis is further strengthened by the fact that a significant number of patients are asymptomatic when microscopic hematuria is detected . The glomerular filtration rate (GFR), considered to be the main indicator of renal function, can be calculated based on either serum creatinine levels (together with other components required for the calculation, such as age and gender)  . A full immunological workup (antinuclear antibody test, antineutrophil cytoplasmic antibodies test, anti-double-stranded DNA test, complement component 3 exam), ultrasonography, and eventually a renal biopsy might be necessary in order to confirm the underlying cause of chronic glomerulonephritis  .