Henoch–Schönlein purpura (HSP) - Often considered a systemic form of IgA nephropathy, Henoch–Schönlein purpura (HSP) is a systemic small-vessel vasculitis that is characterized by deposition of IgA antibody immune complexes in different key areas throughout the body. Most often, the condition presents in children with palpable purpura, abdominal pain, and arthritis. When the kidneys are affected, the IgA immune complexes deposit in the glomerulus very similarly to IgA nephropathy and will present in a similar way. Hemolytic uremic syndrome - Most cases occur immediately following infectious diarrhea caused by a specific type of E. coli (O157:H7). The bacteria produces a toxin that causes widespread inflammation and numerous blood clots in small blood vessels (thrombotic microangiopathy). When the inflammation reaches the kidney, or the by-products of systemic inflammation build up in the kidney, the patient will begin showing signs of nephritic syndrome or potentially acute kidney failure (elevated creatinine, BUN, etc.). Adults
Goodpasture syndrome - This is a rare autoimmune disease where autoantibodies are produced that target the glomerular basement membrane in both the lungs and the kidneys. The damage to the basement membrane causes bleeding, and the disease often presents in patients as hematuria and haemoptysis (coughing up blood). If not treated promptly with plasmapharesis to remove the autoantibodies, it can lead to permanent damage in the lungs/kidneys. Systemic Lupus Erythematosus (SLE) - Better known as simply "Lupus", this autoimmune disease can affect nearly every major system in the human body and the kidneys are no exception.
The kidney is responsible for excreting nitrogenous substances in the urine, so an elevated BUN usually indicates that the kidney is not functioning appropriately. Urine Analysis (Urinalysis) - After the patient provides a urine specimen, it is sent to the lab for analysis using a variety of methods including urine dipstick testing and microscopic examination. Because the kidney is responsible for making urine, analyzing the urine directly can provide crucial data that can help the physician diagnose nephritic syndrome. Some findings on urinalysis that are consistent with nephritic syndrome include red blood cells (hematuria), red blood cell casts, proteinuria, and possibly white blood cells (pyuria).If nephritic syndrome is identified and diagnosed, then it is important for the physician to determine the underlying cause. To do this, he/she may order any of a large variety of relevant lab tests, some of which are included here:

Blood culture - This is the process where a sample of the patients blood is sent to the microbiology lab to attempt to isolate and grow any bacteria that may be circulating in the blood, in order to identify the pathogen. This is helpful if the physician suspects infection as the underlying cause of the nephritic syndrome. Antinuclear antibody (ANA) titer - ANA is commonly positive in patients who have an underlying autoimmune disease, so this test is useful if the physician suspects an underlying autoimmune disease (refer to the Causes section above for examples) as the cause of the presenting nephritic syndrome.