Renal Disorders PDF

RENAL DISORDERS KIDNEY STRUCTURE Each kidney contains about 1.2 million nephrons. The nephron is the functional unit of the kidney, meaning it is the smallest structure within the kidney that can carry out the functions of the organ. The nephron carries ou...

RENAL DISORDERS KIDNEY STRUCTURE Each kidney contains about 1.2 million nephrons. The nephron is the functional unit of the kidney, meaning it is the smallest structure within the kidney that can carry out the functions of the organ. The nephron carries out the following functions: o Filters plasma o Reabsorbs and secretes o Forms a protein-free fluid filtrate o Regulates the filtrate to maintain fluid volume, electrolytes, and pH There are three types of nephrons: o Cortical nephrons o Midcortical nephrons o Juxtamedullary nephrons The glomerulus is a network of capillaries located within the nephron. The glomerulus filters plasma, which is the fluid component of blood. The fluid that is filtered out of the blood by the glomerulus is called the filtrate. The filtrate enters the proximal convoluted tubule (PCT) of the nephron. The glomerular filtration rate (GFR) is a measure of how much plasma is filtered by the glomeruli per unit of time. A normal GFR is 90–120 mL/min. The glomerular membrane is freely permeable to water but impermeable to large molecules such as the protein albumin. This means that water can pass through the membrane easily, but large molecules cannot. The juxtaglomerular apparatus helps to regulate blood pressure and the filtration rate of the glomerulus. Kidneys receive 1000 to 1200 ml of blood per minute. About 99% of the filtrate is reabsorbed back into the bloodstream. The remaining 1% is excreted as urine. The kidneys produce several hormones, including: o Renin o Angiotensin o Aldosterone o Natriuretic peptides o Urodilantin  o Renalase o Erythropoietin o Vitamin D The kidneys also play a role in regulating the body's acid-base balance by excreting hydrogen ions (H+) and reabsorbing bicarbonate ions (HCO3-). RENAL FUNCTION The kidneys perform many vital functions, including: o Filtering waste products from the blood o Regulating blood pressure o Producing hormones o Maintaining electrolyte balance o Maintaining acid-base balance Nephrons are the functional units of the kidneys. Each nephron is composed of a glomerulus and a tubule. o The glomerulus is a network of capillaries that filters blood. o The tubule is a long, coiled structure that reabsorbs needed substances from the filtrate and secretes waste products into the filtrate. The process of urine formation begins with glomerular filtration. Blood flows into the glomerulus, and the high pressure forces water and small molecules out of the blood and into the Bowman's capsule, forming the filtrate. o The glomerular filtration rate (GFR) is a measure of how much blood is filtered by the glomeruli per unit of time. A normal GFR is 90–120 mL/min. The GFR provides the best estimate of functioning renal tissue. The filtrate then flows through the tubule, where it is modified by reabsorption and secretion. o Reabsorption is the process of moving substances from the filtrate back into the blood. This process is important for conserving water and electrolytes. About 99% of the filtrate is reabsorbed. o Secretion is the process of moving substances from the blood into the filtrate. This process is important for removing waste products from the body. The final product of urine formation is urine, which is excreted from the body. The kidneys play a role in regulating blood pressure through the renin-angiotensin- aldosterone system (RAAS). When blood pressure drops, the kidneys release renin, an enzyme that converts angiotensinogen to angiotensin I. Angiotensin I is then converted to angiotensin II, a powerful vasoconstrictor that raises blood pressure. Angiotensin II also stimulates the release of aldosterone from the adrenal glands. Aldosterone causes the kidneys to reabsorb more sodium and water, which also increases blood pressure. The kidneys also produce hormones that help to regulate red blood cell production (erythropoietin), calcium absorption (vitamin D), and blood pressure (natriuretic peptides).  Tests of renal function can be used to assess how well the kidneys are working. These tests include: o Blood tests, such as plasma creatinine concentration and blood urea nitrogen (BUN) o Urinalysis o Clearance tests, such as inulin clearance, cystatin C clearance, and creatinine clearance o Urine specific gravity Many factors can affect renal function, including age, disease, and medications. o In children, renal blood flow and GFR are lower than in adults. The number of nephrons decreases due to renal vascular and perfusion changes. Children also have an altered sodium and water balance, a delayed response to acid- base changes, and an increased risk for medication toxicity. o As people age, the number of nephrons decreases, and the GFR declines. Older adults also have a decreased ability to remove excess water and solutes, a decreased concentrating ability, a narrow margin for fluid and electrolyte balance, and an increased risk of medication toxicity. URINARY TRACT Here is a discussion about the urinary tract: The urinary tract is the body's drainage system for removing urine, which is composed of wastes and extra water. The urinary tract includes the kidneys, ureters, bladder, and urethra. Urine is made in the kidneys and travels down the ureters to the bladder. The bladder stores urine until it is full and then empties through the urethra. Urinary tract obstruction is an interference with the flow of urine at any site along the urinary tract. Obstruction can be caused by an anatomical or functional defect. o The severity of the obstruction depends on:  Location  Completeness  Involvement of the ureters and kidneys  Duration  Cause Upper Urinary Tract Obstruction Hydroureter is an accumulation of urine in the ureter. Hydronephrosis is an enlargement of the renal pelvis and calyces. Ureterohydronephrosis is the dilation of both the ureter and the pelvicaliceal system. Increased pressure in the glomerulus due to obstruction can lead to decreased kidney function and filtration. Tubulointerstitial fibrosis, or scarring of the kidney, can occur within 7 days of the obstruction.  After 14–28 days, the glomeruli can be damaged, and the renal cortex and medulla can thin. The ability to concentrate urine decreases, causing an increase in urine volume and decreased sodium, bicarbonate, and water, and excretion of H+ and K+, which can lead to metabolic acidosis and dehydration. Kidney stones are a common cause of upper urinary tract obstruction. They are masses of crystals, protein, or other substances that form within and may obstruct the urinary tract. o Kidney stones are classified according to the minerals that make up the stone. o The size of the stone determines whether it will pass through the urinary system. Recovery from upper urinary tract obstruction depends on the severity and duration of the obstruction. Compensatory hypertrophy and hyperfunction can occur in the kidney after obstruction. This means that the remaining nephrons grow larger and work harder to compensate for the lost nephrons. However, there is no replacement of nephrons. Postobstructive diuresis, or the production of large amounts of urine after the obstruction is relieved, can occur. This can lead to nephrogenic diabetes insipidus, a condition in which the kidneys are unable to concentrate urine. Lower Urinary Tract Obstruction Neurogenic bladder is a dysfunction of the urinary bladder due to disease or injury of the central nervous system or peripheral nerves involved in the control of urination. o This can cause dyssynergia, which is a loss of coordinated neuromuscular contraction.  Detrusor hyper-reflexia refers to an overactive bladder.  Detrusor areflexia refers to an underactive bladder. Overactive bladder syndrome (OBS) is a condition that causes a frequent and sudden urge to urinate that may be difficult to control. Individuals with OBS often experience frequency, urgency, and nocturia. Obstruction of the lower urinary tract can be caused by: o Urethral stricture o Prostate enlargement o Pelvic organ prolapse Partial obstruction of the bladder outlet or urethra can lead to low bladder wall compliance. Urinary Tract Infection (UTI) A UTI is an inflammation of the urinary epithelium caused by bacteria from gut flora. UTIs can occur anywhere along the urinary tract, including: o Acute cystitis (inflammation of the bladder) o Painful bladder syndrome/interstitial cystitis o Acute and chronic pyelonephritis (inflammation of the kidney and renal pelvis) Escherichia coli is the most common pathogen that causes UTIs.  The virulence of uropathogens, or the ability of bacteria to cause disease, as well as host defense mechanisms, play a role in the development of UTIs. Tumors Renal tumors, or kidney tumors, can be either benign or malignant. o Types of renal tumors include:  Renal adenomas  Renal cell carcinoma (RCC)  Risk factors for RCC include cigarette smoking, obesity, and uncontrolled hypertension. Bladder tumors are most commonly transitional cell carcinoma. o Gross, painless hematuria is a common symptom. o Bladder tumors are most common in males older than 60 years KIDNEY STONES Kidney stones, also known as renal calculi or urinary stones, are masses of crystals, protein, or other substances that form within and may obstruct the urinary tract. Kidney stones are classified according to the minerals that make up the stone. The size of the stone determines whether it will pass through the urinary system. Several factors can increase the risk of developing kidney stones: o Gender and age o Race o Geographical location o Seasonal factors o Fluid intake o Diet o Occupation Kidney stones form when: o One or more salts in the urine become supersaturated. Supersaturation occurs when a salt is present in a higher concentration than the volume is able to dissolve. o A salt precipitates from a liquid to a solid state.  Temperature and pH can affect precipitation. o The precipitated salt grows into a stone through crystallization or aggregation. Kidney stones can cause renal colic, which is a type of pain that occurs when a stone blocks the flow of urine. Kidney stones are evaluated using imaging studies and 24-hour urinalysis. Treatments for kidney stones include: o Managing pain o Increasing fluid intake o Adjusting the pH of the urine. For example, potassium can make the urine more alkaline.  o Decreasing dietary intake of stone-forming substances o Removing the stone.  Stones can be removed using the following methods:  Percutaneous nephrolithotomy  Ureteroscopy  Ultrasonic or laser lithotripsy GLOMERULAR DISORDER Glomerulonephritis is an inflammation of the glomerulus, which is the network of tiny blood vessels in the kidney that filters blood. Glomerulonephritis causes damage to the glomerular membrane, which can lead to blood and protein in the urine. o Glomerular disorders can have several causes:  Immunologic abnormalities (most common)  Medications  Toxins  Vascular disorders  Systemic diseases  Viruses o The onset of glomerulonephritis can be sudden or insidious, meaning it can develop gradually. Immune responses involved in glomerulonephritis can be caused by several mechanisms: o Deposition of circulating soluble antigen-antibody complexes, often with complement fragments (type III hypersensitivity). This type of glomerulonephritis can occur after infection with Group A or B streptococcus or staphylococcus. o Antibodies reacting in situ against planted antigens within the glomerulus (type II hypersensitivity–cytotoxic). o Nonimmune causes, such as medications, toxins, ischemia, and diabetes. Individuals with severe glomerulonephritis may experience two major symptoms: o Hematuria, which is blood in the urine, with red blood cell casts. o Proteinuria exceeding 3 to 5 g/day with albumin (macroalbuminuria) as the major protein. Other manifestations of glomerulonephritis include: o Oliguria, or low urine output. o Hypertension, or high blood pressure. o Edema, or swelling. o Nephrotic sediment, which is a type of urine sediment that contains a lot of protein. o Nephritic sediment, which is a type of urine sediment that contains red blood cells and white blood cells. Nephrotic syndrome is a kidney disorder that is characterized by the excretion of 3.5 grams or more of protein in the urine per day. o Protein excretion is caused by glomerular injury. o Individuals with nephrotic syndrome may have the following findings:  Hypoproteinemia, or low blood protein levels.   Proteinuria.  Edema.  Dyslipidemia and lipiduria, or high levels of lipids in the blood and urine.  Vitamin D deficiency.  Hypothyroidism. Here is a discussion on CKD and AKI based on the provided sources: Chronic Kidney Disease (CKD) CKD is a progressive loss of renal function that affects nearly all organ systems. CKD is associated with hypertension, diabetes, systemic lupus erythematosus, and intrinsic kidney disease. CKD is classified into five stages: o Normal (GFR >90 mL/min) o Mild (GFR 60 to 89 mL/min) o Moderate (GFR 30 to 59 mL/min) o Severe (GFR 15 to 29 mL/min) o End stage (GFR