Nephritic syndrome is a syndrome comprising signs of nephritis, which is kidney disease involving inflammation. It often occurs in the glomerulus, where it is called glomerulonephritis. Glomerulonephritis is characterized by inflammation and thinning of the glomerular basement membrane and the occurrence of small pores in the podocytes of the glomerulus. These pores become large enough to permit both proteins and red blood cells to pass into the urine (yielding proteinuria and hematuria, respectively). By contrast, nephrotic syndrome is characterized by proteinuria and a constellation of other symptoms that specifically do not include hematuria. Nephritic syndrome, like nephrotic syndrome, may involve low level of albumin in the blood due to the protein albumin moving from the blood to the urine. Signs and symptoms Historically, nephritic syndrome has been characterized by blood in the urine (hematuria), high blood pressure (hypertension), decreased urine output <400 ml/day (oliguria), red blood cell casts, pyuria, and mild to moderate proteinuria. If the condition is allowed to progress without treatment, it can eventually lead to azotemia and uremic symptoms. This constellation of symptoms contrasts with the classical presentation of nephrotic syndrome (excessive proteinuria >3.5 g/day, low plasma albumin levels (hypoalbuminemia) <3 g/L, generalized edema, and hyperlipidemia). Signs and symptoms that are consistent with nephritic syndrome include: Hematuria (red blood cells in the urine) Proteinuria (protein in the urine) ranging from sub-nephrotic (<3.5 g/day) to >10 g/day, although it is rarely above nephrotic range proteinuria levels. Hypertension resting blood pressure is persistently at or above 130/80 or 140/90 mmHg. Blurred vision Azotemia (increased plasma Urea and Creatinine) Oliguria (low urine output <400 ml/day) Red blood cell casts (seen with urinalysis and microscopy) Pyuria (white blood cells or pus in the urine) Causes Nephritic syndrome is caused by extensive inflammatory damage to the glomerulus capillaries, which is associated with a variety of medical conditions that we will discuss. Furthermore, the cause of this inflammation can be infectious, autoimmune, or thrombotic. The causative conditions can be divided conveniently between age groups as follows, though it is important to note that many of the conditions listed in children/adolescents can also occur in adults with lower frequency, and vice versa: Children/adolescents IgA nephropathy (Note: Contrast time of onset with Post-streptococcal Glomerulonephritis) - Most commonly diagnosed in children who recently had an upper respiratory tract infection (URI). Symptoms typically present within 1–2 days of a non-specific URI with severe flank/abdominal pain, gross hematuria