Urinary system diseases are one of the leading causes of death and disability worldwide. In fact, kidney disease is the ninth leading cause of death in the United States. Basic knowledge of some of the more common disorders is thus of value. Common medical terms and their definitions are a good place to start.
Acute tubular necrosis (ATN) – Is a form of acute renal failure that develops in individuals with extreme conditions. It results from severe damage to cells of the renal tubules. The form of the damage is necrosis. The most common causes are ischemia and toxins. Other causes include shock, sepsis (the presence of pathogens or their toxins in the bloodstream), heatstroke, crush injuries and other forms of trauma.
Acute renal failure (ARF) – Is a decline in kidney function due to injury which occurs over a short period of time. The time frame from insult to the decline is usually hours to a few days. The condition is frequently reversible when promptly recognized and properly treated. It does have a fair amount of morbidity and mortality though.
Azotemia – Is an excess of nitrogenous waste products in the blood. It consists mainly of BUN and creatinine. But it also consists of other compounds that contain nitrogen. It results from the insufficient filtering of BUN and creatinine by the kidney, increased reabsorption of BUN by the kidney tubule, or a combination of both. It is not a synonym of uremia. But it is a part of the syndrome.
Prerenal azotemia is a state of excess of nitrogenous waste products in the blood in which the excess of urea is much greater than that of creatinine. By definition, it is when the ratio of the concentration of BUN to serum creatinine is greater than 10:1.
Benign prosthetic hyperplasia (BPH) – Is enlargement of the prostate gland which is not due to cancer. The increased size is due to a greater-than-normal number of prostate cells, not an increase in the size of the cells.
Chronic kidney disease (CKD) – Is an alternate term for chronic renal failure (CRF). In general, it is the progressive loss of kidney function over a period of months to years. More specifically, it is a glomerular filtration rate of less than 60 mL/m/1.73 mm² or evidence of kidney damage which has been present for 3 or more months. Albuminuria is often present and is the most common marker of kidney damage. The amount of albumin that defines CKD is an albumin-to-creatinine ratio of greater than 30 mg/g, measured in at least 2 of 3 spot urine tests. The ratio is the amount of albumin divided by the amount of creatinine in the same urine specimen. The concentration units of albumin and urine are mg/dl and g/dl respectively. There are five CKD stages.
There are many causes of CKD. The leading cause is diabetes mellitus. Hypertension is second. Glomerulonephritis is the third leading cause in the United States.
The inflammation and damage to the capillaries of the filtering units of the kidneys is not the direct result of infection, even in the case of acute poststreptococcal glomerulonephritis (APSGN) – a form of the disease that occurs following a throat or skin infection caused by a specific strain of streptococcus bacteria.
A full understanding of the pathogenesis of APSGN is unknown but there are two widely proposed theories. Both propose the combining of antibodies with parts of the bacteria to form complexes that damage the kidneys. According to one theory the complexes form in the kidneys. The other suggests that they form outside the kidneys but deposit in them. In either case the immune system seems to be involved, as is the case with many other forms of the acute and chronic disease.
Hydronephrosis – Is distention or swelling of a kidney(s) with dilation of the renal pelvis and calyces due to the blockage of the flow of urine. The obstruction can be in any part of the urinary tract. Hydroureter is swelling of a ureter(s) which usually accompanies it.
Nephritic syndrome is the classic signs and symptoms of acute glomerulonephritis. They are hematuria, signs and symptoms of renal failure and hypertension. Proteinuria might also be present but if so, it is usually < 3.5 grams per day.
Interstitial nephritis refers specifically to inflammation of the kidney interstitium.
Tubulointerstitial nephritis is inflammation involving the renal tubules and interstitial tissue.
Urolithiasis is an all-inclusive term. It refers to the presence of stones anywhere in the urinary tract.
Nephrotic syndrome – Is a syndrome in which there is the loss of large amounts of protein in the urine with resultant low albumin in the blood which leads to edema. The cause of the protein loss is leakiness of the basement membrane of glomeruli. It is a feature of certain forms of glomerulonephritis.
Overactive bladder – Is a disorder in which the bladder muscle contracts involuntarily causing the sudden urge to urinate. It is a cause of urge incontinence.
Polycystic kidney disease – Is a genetic disease in which the kidneys form multiple cysts. The cysts cause a decline in kidney function and lead to kidney failure. There are two modes of inheritance of the disease. One is autosomal dominant. The other is autosomal recessive.
Acute pyelonephritis is a primary infection of the kidney that usually results from the spread of an existing infection of the bladder. Unlike cystitis or infection in other parts of the lower urinary tract, it does not respond to antibiotics taken by mouth. Hence, treatment of it must take place in a hospital or other acute care setting.
Chronic pyelonephritis is chronic inflammation with or without scarring of the kidney tissue. It is the result of recurrent or persistent infections. If untreated, it can lead to CKD including stage 5 disease.
Renal artery stenosis – Is narrowing of the main artery to the kidney. It can be the result of atherosclerosis or thickening of the muscular wall of the vessel. It can cause a marked elevation in blood pressure.
Renal calculus (Renal stone) (Nephrolith) – Is a solid mass of crystals that forms in the kidneys or in the urinary tract from minerals present in the urine. There are different types based on their composition. Calcium is the most common component. Many contain uric acid. – Renal calculi – Pl – Renal stones – Pl – Nephroliths – Pl.
Renal cell carcinoma (Hypernephroma) – Is cancer of the kidney parenchyma. It forms from the lining cells (epithelium) of the renal tubules. Clear cell carcinoma is a synonym for it as well. It is the most common form of kidney cancer.
Renal cortical necrosis – As the name implies, is necrosis due to ischemia of the cortex of usually both kidneys. The pathogenesis is not totally clear, but it involves spasm of the arteries that feed the kidneys. Many of the same factors that lead to ATN can trigger it also. But it is rare. It has a high mortality. The renal failure it causes is usually not reversible.
Renal insufficiency – Is a reduced ability of the kidneys to filter and excrete nitrogenous waste products from the blood. It is more of a notation of the kidneys’ reduced state of function than it is a specific condition. It might be indicative of actual kidney injury or a state leading up to it. It can be either acute or chronic.
Renal tubular acidosis – Is a defect in the kidneys’ function of maintaining an acid–base balance in the body. It results in decreased net excretion of acid in the urine and a buildup of it in the blood. The defect can be in the proximal or distal renal tubules. There are different types based on the pathophysiology. In general though, when the defect is in the proximal tubules there is reduced bicarbonate reabsorption. When the defect is in the distal tubules there is a reduction of hydrogen ion secretion.
Uremia (Uremic syndrome) – Is a state of health resulting from the profound loss of kidney function. Because it is almost always associated with azotemia, the common presumed belief is that retained BUN and other nitrogenous end products of metabolism cause many of the signs and symptoms which characterize it. In reality though, this is a theory which lacks absolute proof; even though based on its origin the word uremia means urine in blood. Thus, the direct cause of many of the signs and symptoms of chronic renal failure is unknown, except for those in which there is proof of correlation with specific abnormalities of renal function. Uremia can be a feature of ARF or end-stage chronic kidney disease. It is more common with the latter though. – Uremic – adj.
Urinary tract infection (UTI) – Is infection of any portion of the urinary tract.
Vesicoureteral reflux – Is the abnormal backward flow of urine from the bladder into one or both ureters. It is due to a defect(s) of the bladder, ureter(s), or the valve between the two. It can be present from birth or acquired. The acquired form is usually the result of repeated infections of the urinary tract. Either type predisposes one to chronic or recurrent UTIs.