Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein, less than 150 mg/day; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become foamy. Severe proteinuria can cause nephrotic syndrome in which there is worsening swelling of the body.
The nephron is the minute or microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and a cup-shaped structure called Bowman's capsule. The renal tubule extends from the capsule. The capsule and tubule are connected and are composed of epithelial cells with a lumen. A healthy adult has 1 to 1.5 million nephrons in each kidney. Blood is filtered as it passes through three layers: the endothelial cells of the capillary wall, its basement membrane, and between the foot processes of the podocytes of the lining of the capsule. The tubule has adjacent peritubular capillaries that run between the descending and ascending portions of the tubule. As the fluid from the capsule flows down into the tubule, it is processed by the epithelial cells lining the tubule: water is reabsorbed and substances are exchanged ; first with the interstitial fluid outside the tubules, and then into the plasma in the adjacent peritubular capillaries through the endothelial cells lining that capillary. This process regulates the volume of body fluid as well as levels of many body substances. At the end of the tubule, the remaining fluid—urine—exits: it is composed of water, metabolic waste, and toxins.
Nephrotic syndrome is a collection of symptoms due to kidney damage. This includes protein in the urine, low blood albumin levels, high blood lipids, and significant swelling. Other symptoms may include weight gain, feeling tired, and foamy urine. Complications may include blood clots, infections, and high blood pressure.
Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibodies. Often, no symptoms are noticed initially. As it progresses, bone pain, anemia, kidney dysfunction, and infections may occur. Complications may include hypercalcemia and amyloidosis.
Nephrosis is any of various forms of kidney disease (nephropathy). In an old and broad sense of the term, it is any nephropathy, but in current usage the term is usually restricted to a narrower sense of nephropathy without inflammation or neoplasia, in which sense it is distinguished from nephritis, which involves inflammation. It is also defined as any purely degenerative disease of the renal tubules. Nephrosis is characterized by a set of signs called the nephrotic syndrome. Nephrosis can be a primary disorder or can be secondary to another disorder. Nephrotic complications of another disorder can coexist with nephritic complications. In other words, nephrosis and nephritis can be pathophysiologically contradistinguished, but that does not mean that they cannot occur simultaneously. Types of nephrosis include amyloid nephrosis and osmotic nephrosis.
The proximal tubule is the segment of the nephron in kidneys which begins from the renal pole of the Bowman's capsule to the beginning of loop of Henle. At this location, the glomerular parietal epithelial cells (PECs) lining bowman’s capsule abruptly transition to proximal tubule epithelial cells (PTECs). The proximal tubule can be further classified into the proximal convoluted tubule (PCT) and the proximal straight tubule (PST).
Glomerulonephritis (GN) is a term used to refer to several kidney diseases. Many of the diseases are characterised by inflammation either of the glomeruli or of the small blood vessels in the kidneys, hence the name, but not all diseases necessarily have an inflammatory component.
Hypertensive kidney disease is a medical condition referring to damage to the kidney due to chronic high blood pressure. It manifests as hypertensive nephrosclerosis. It should be distinguished from renovascular hypertension, which is a form of secondary hypertension, and thus has opposite direction of causation.
Acute tubular necrosis (ATN) is a medical condition involving the death of tubular epithelial cells that form the renal tubules of the kidneys. Because necrosis is often not present, the term acute tubular injury (ATI) is preferred by pathologists over the older name acute tubular necrosis (ATN). ATN presents with acute kidney injury (AKI) and is one of the most common causes of AKI. Common causes of ATN include low blood pressure and use of nephrotoxic drugs. The presence of "muddy brown casts" of epithelial cells found in the urine during urinalysis is pathognomonic for ATN. Management relies on aggressive treatment of the factors that precipitated ATN. Because the tubular cells continually replace themselves, the overall prognosis for ATN is quite good if the underlying cause is corrected, and recovery is likely within 7 to 21 days.
Bence Jones protein is a monoclonal globulin protein or immunoglobulin light chain found in the urine, with a molecular weight of 22–24 kDa. Detection of Bence Jones protein may be suggestive of multiple myeloma, or Waldenström's macroglobulinemia.
Acute uric acid nephropathy is a rapidly worsening (decreasing) kidney function that is caused by high levels of uric acid in the urine (hyperuricosuria).
Phosphate nephropathy or nephrocalcinosis is an adverse renal condition that arises with a formation of phosphate crystals within the kidney's tubules. This renal insufficiency is associated with the use of oral sodium phosphate (OSP) such as C.B. Fleet's Phospho soda and Salix's Visocol, for bowel cleansing prior to a colonoscopy.
Uromodulin (UMOD), also known as Tamm–Horsfall protein (THP), is a zona pellucida-like domain-containing glycoprotein that in humans is encoded by the UMOD gene. Uromodulin is the most abundant protein excreted in ordinary urine.
A myeloma protein is an abnormal antibody (immunoglobulin) or a fragment thereof, such as an immunoglobulin light chain, that is produced in excess by an abnormal monoclonal proliferation of plasma cells, typically in multiple myeloma or Monoclonal gammopathy of undetermined significance. Other terms for such a protein are monoclonal protein, M protein, M component, M spike, spike protein, or paraprotein. This proliferation of the myeloma protein has several deleterious effects on the body, including impaired immune function, abnormally high blood viscosity, and kidney damage.
In hematology, plasma cell dyscrasias are a spectrum of progressively more severe monoclonal gammopathies in which a clone or multiple clones of pre-malignant or malignant plasma cells over-produce and secrete into the blood stream a myeloma protein, i.e. an abnormal monoclonal antibody or portion thereof. The exception to this rule is the disorder termed non-secretory multiple myeloma; this disorder is a form of plasma cell dyscrasia in which no myeloma protein is detected in serum or urine of individuals who have clear evidence of an increase in clonal bone marrow plasma cells and/or evidence of clonal plasma cell-mediated tissue injury. Here, a clone of plasma cells refers to group of plasma cells that are abnormal in that they have an identical genetic identity and therefore are descendants of a single genetically distinct ancestor cell.
Sickle cell nephropathy is a type of nephropathy associated with sickle cell disease which causes kidney complications as a result of sickling of red blood cells in the small blood vessels. The hypertonic and relatively hypoxic environment of the renal medulla, coupled with the slow blood flow in the vasa recta, favors sickling of red blood cells, with resultant local infarction. Functional tubule defects in patients with sickle cell disease are likely the result of partial ischemic injury to the renal tubules.
Free light chains (FLCs) are immunoglobulin light chains that are found in the serum (blood) in an unbound (free) state. In recent decades, measuring the amount of free light chains (FLCs) in the blood has become a practical clinical test. FLC tests can be used to diagnose and monitor diseases like multiple myeloma and amyloidosis.
Light chain deposition disease (LCDD) is a rare blood cell disease which is characterized by deposition of fragments of infection-fighting immunoglobulins, called light chains (LCs), in the body. LCs are normally cleared by the kidneys, but in LCDD, these light chain deposits damage organs and cause disease. The kidneys are almost always affected and this often leads to kidney failure. About half of people with light chain deposition disease also have a plasma cell dyscrasia, a spectrum of diseases that includes multiple myeloma, Waldenström's macroglobulinemia, and the monoclonal gammopathy of undetermined significance premalignant stages of these two diseases. Unlike in AL amyloidosis, in which light chains are laid down in characteristic amyloid deposits, in LCDD, light chains are deposited in non-amyloid granules.
Onconephrology is a specialty in nephrology that deals with the study of kidney diseases in cancer patients. A nephrologist who takes care of patients with cancer and kidney disease is called an onconephrologist. This branch of nephrology encompasses nephrotoxicity associated with existing and novel chemotherapeutics, kidney disease as it pertains to stem cell transplant, paraneoplastic kidney disorders, paraproteinemias, electrolyte disorders associated with cancer, and more as discussed below.
Monoclonal gammopathy of renal significance (MGRS) are a group of kidney disorders that present with kidney damage due to nephrotoxic monoclonal immunoglobulins secreted by clonal plasma cells or B cells. By definition, people with MGRS do not meet criteria for multiple myeloma or other hematologic malignancies. The term MGRS was introduced in 2012 by the International Kidney and Monoclonal Gammopathy Research Group (IKMG). MGRS is associated with monoclonal gammopathy of undetermined significance (MGUS). People with MGUS have a monoclonal gammopathy but does not meet the criteria for the clonal burden nor the presence of end organ damage seen in hematologic malignancies. In a population based study based on the NHANES III health survey; 6% of patients with MGUS were subsequently classified as having MGRS. The prevalence and incidence of MGRS in the general population or in specific populations is not known but it is more prevalent in those over the age of 50 as there is a monoclonal protein (M-protein) present in 3% of those 50 and years older and 5% of those 70 years and older, placing those 50 and older at increased risk of MGRS.
