Excretion system diseases

 

Glomerular Diseases

A variety of conditions may damage the kidney glomeruli, either directly or indirectly because of disease elsewhere in the body.

Typically, the filtration membrane sustains damage, and its permeability increases.

Glomerulonephritis (gloˉ-mer-uˉ-loˉ-ne-FRIˉ-tis) is an inflammation of the kidney that involves the glomeruli. One of the most common causes is an allergic reaction to the toxins produced by streptococcal

bacteria that have recently infected another part of the body, especially the throat. 

The glomeruli become so inflamed, swollen, and engorged with blood that the filtration membranes allow blood cells and plasma proteins to enter the filtrate. As a result, the urine contains many erythrocytes (hematuria) and a lot of protein. The glomeruli may be permanently damaged, leading to chronic renal failure.

Nephrotic syndrome 

(nef-ROT-ik) is a condition characterized by proteinuria (proˉ-teˉn-OO-reˉ-a), protein in the urine, and hyperlipidemia (hıˉ-per-lip-i-DEˉ-meˉ-a), high blood levels of cholesterol, phospholipids, and triglycerides. 

The proteinuria is due to an increased

permeability of the filtration membrane, which permits proteins,

especially albumin, to escape from blood into urine. Loss of albumin

results in hypoalbuminemia (hıˉ-poˉ-al-buˉ-mi-NEˉ-meˉ-a), low blood

albumin level, once liver production of albumin fails to meet increased

urinary losses. 

Edema, usually seen around the eyes, ankles, feet, and

abdomen, occurs in nephrotic syndrome because loss of albumin from the blood decreases blood colloid osmotic pressure. 

Nephrotic syndrome 

is associated with several glomerular diseases of unknown cause, as well as with systemic disorders such as diabetes mellitus, systemic lupus erythematosus (SLE), a variety of cancers, and AIDS.

Renal Failure

Renal failure is a decrease or cessation of glomerular filtration. In acute renal failure (ARF), the kidneys abruptly stop working entirely (or almost entirely). The main feature of ARF is the suppression of urine flow, usually characterized either by oliguria (ol-i-GUˉ-reˉ-a),daily urine output between 50 mL and 250 mL, or by anuria (an-Uˉ-reˉ-a),daily urine output less than 50 mL. Causes include low blood volume

(for example, due to hemorrhage), decreased cardiac output, damaged renal tubules, kidney stones, the dyes used to visualize blood vessels in angiograms, nonsteroidal antiinflammatory drugs, and some anti biotic drugs. It is also common in people who suffer a devastating illness or overwhelming traumatic injury; in such cases it may be related to a more general organ failure known as multiple organ

dysfunction syndrome (MODS).

Renal failure causes a multitude of problems. There is edema due to

salt and water retention and metabolic acidosis due to an inability of the

kidneys to excrete acidic substances. In the blood, urea builds up due to

impaired renal excretion of metabolic waste products and potassium

level rises, which can lead to cardiac arrest. Often, there is anemia because

the kidneys no longer produce enough erythropoietin for adequate red

blood cell production. Because the kidneys are no longer able to convert

vitamin D to calcitriol, which is needed for adequate calcium absorption

from the small intestine, osteomalacia also may occur.

Chronic renal failure (CRF) 

refers to a progressive and usually

irreversible decline in glomerular filtration rate (GFR). CRF may result

from chronic glomerulonephritis, pyelonephritis, polycystic kidney

disease, or traumatic loss of kidney tissue. CRF develops in three

stages. In the first stage, diminished renal reserve, nephrons are de-

stroyed until about 75% of the functioning nephrons are lost. At this

stage, a person may have no signs or symptoms because the remaining

nephrons enlarge and take over the function of those that have been lost. Once 75% of the nephrons are lost, the person enters the second stage, called renal insufficiency, characterized by a decrease in GFR and increased blood levels of nitrogen-containing wastes and creatinine. Also, the kidneys cannot effectively concentrate or dilute the

urine. The final stage, called end-stage renal failure, occurs when about 90% of the nephrons have been lost. At this stage, GFR diminishes to 10–15% of normal, oliguria is present, and blood levels of nitrogen-containing wastes and creatinine increase further. People

with end-stage renal failure need dialysis therapy and are possible

candidates for a kidney transplant operation.

Polycystic Kidney Disease

Polycystic kidney disease (PKD) (pol-eˉ-SIS-tik) is one of the most common inherited disorders. In PKD, the kidney tubules become riddled with hundreds or thousands of cysts (fluid-filled cavities). In addition, inappropriate apoptosis (programmed cell death) of cells in noncystic tubules leads to progressive impairment of renal function and eventually to end-stage renal failure.

People with PKD also may have cysts and apoptosis in the liver,pancreas, spleen, and gonads; increased risk of cerebral aneurysms;heart valve defects; and diverticula in the colon. Typically, symptoms are not noticed until adulthood, when patients may have back pain,urinary tract infections, blood in the urine, hypertension, and large

abdominal masses. Using drugs to restore normal blood pressure,

restricting protein and salt in the diet, and controlling urinary tract infections may slow progression to renal failure.

Urinary Bladder Cancer

Each year, nearly 12,000 Americans die from urinary bladder cancer.

It generally strikes people over 50 years of age and is three times more likely to develop in males than females. The disease is typically painless as it develops, but in most cases blood in the urine is a primary sign of the disease. Less often, people experience painful and/or frequent urination.

As long as the disease is identified early and treated promptly,the prognosis is favorable. Fortunately, about 75% of urinary bladder vancers are confined to the epithelium of the urinary bladder and are easily removed by surgery. The lesions tend to be low-grade, meaning that they have only a small potential for metastasis.

Urinary bladder cancer is frequently the result of a carcinogen.About half of all cases occur in people who smoke or have at some time smoked cigarettes. The cancer also tends to develop in people who are exposed to chemicals called aromatic amines. Workers in the

leather, dye, rubber, and aluminum industries, as well as painters,Are often exposed to these chemicals.

Kidney Transplant

A kidney transplant is the transfer of a kidney from a donor to a recipient whose kidneys no longer function. In the procedure, the donor kidney is placed in the pelvis of the recipient through an abdominal incision. The renal artery and vein of the transplanted kidney are attached to a nearby artery or vein in the pelvis of the

recipient and the ureter of the transplanted kidney is then attached

to the urinary bladder. During a kidney transplant, the patient receives only one donor kidney, since only one kidney is needed to maintain sufficient renal function. The nonfunctioning diseased kidneys are usually left in place. As with all organ transplants, kidney transplant recipients must be ever vigilant for signs of infection or organ rejections The transplant recipient will take immunosuppressive drugs forthe rest of his or her life to avoid rejection of the “foreign” organ.

Cystoscopy

Cystoscopy (sis-TOS-koˉ-peˉ; cysto- -

 bladder; -scopy - to examine) is

a very important procedure for direct examination of the mucosa of thee urethra and urinary bladder and prostate in males. In the procedure, a cystoscope (a flexible narrow tube with a light) is inserted intothe urethra to examine the structures through which it passes.With special attachments, tissue samples can be removed for examination (biopsy) and small stones can be removed. Cystoscopy is useful

for evaluating urinary bladder problems such as cancer and infections. It can also evaluate the degree of obstruction resulting from an enlarged prostate.