Filtration and Fluid Balance

Filtration and Fluid Balance
Chapter 16 The Urinary System: Filtration and Fluid Balance

Multimedia Directory Slide 13 Urinary System Animation
Slide 25 Kidney Animation Slide 35 Kidney Anatomy Exercise Slide 48 Kidney Stones Video Slide 59 Urinalysis Video Slide 60 Dipstick Urinalysis Video Slide 68 Hypovolemic Shock Animation Slide 104 Renal Failure Video Slide 108 Dialysis Video Slide 121 Urinary Bladder Exercise Slide 162 Ultrasound Technicians Video 2

Introduction Urinary system acts as purification plant, cleaning blood of waste materials Liver does some purification, but urinary system controls electrolyte and fluid balances for body Kidneys filter blood, reabsorb and secrete ions, and produce urine Without this important function you would die in a few days 3

Learning Objectives Present an overview of the organs and functions of the urinary system Describe the internal and external anatomy and physiology of the kidneys Discuss the importance of renal blood flow Describe the process of urine formation 4

Learning Objectives (cont’d)
Trace the pathway of reabsorption or secretion of vital substances List and discuss the importance of hormones for proper kidney function Describe the anatomy and physiology of the bladder and urination Discuss several common disorders of the urinary system 5

Pronunciation Guide Afferent arterioles Aldosterone
Click on the megaphone icon before each item to hear the pronunciation. Afferent arterioles Aldosterone Antidiuretic hormone (ADH) Atrial natriuretic peptide Calyx, calyces Cortical nephron Efferent arterioles External urethral sphincter (AFF er ent ahr TEE ree ohlz) (al DOSS ter ohn) (AN tye dye yoo RET ik) (AY tree al nay tree your RET ick PEP tide) (KEY licks, KAY leh seez ) (CORE tih cull NEFF rahn) (EFF erent ahr TEE ree ohlz) (EKS ter nal yoo REE thral SFINK ter) 6

Pronunciation Guide (cont’d)
Click on the megaphone icon before each item to hear the pronunciation. Glomerulus Glomerular capsule Glomerulonephritis Glomerulosclerosis Hematuria Juxtaglomedullary nephron Juxtaglomerular cells (gloh MAIR yoo luss) (gloh MAIR you CAP sell) (gloh MAIR you loh neh FRY tis) (gloh MAIR you loh sklee ROW sis) (HE mah TOO ree ah) (JUX ta glo MED DULL lair ee NEFF rahn) (JUX ta gla MARE you ler) 7

Pronunciation Guide (cont’d)
Click on the megaphone icon before each item to hear the pronunciation. Lithotripsy Nephropathy Renal hilum Renal medulla Renin-angiotensin- aldosterone Urea Uremia Ureter Urethra (LITH oh TRIP see) (neh FROP ah thee) (REE nal HIGH lum) (REE nal meh DULL lah) (REE nen-an gee oh TEN sen-al DOSS ter ohn) (you REE ah) (you REEM ee ah) (yoo REE ter) (yoo REE thrah) 8

System Overview Urinary system consists of two kidneys, bean shaped organs located in superior dorsal abdominal cavity that filter blood and make urine, and accessory structures Ureter is tube that carries urine from each kidney to single urinary bladder, located in inferior ventral pelvic cavity Urinary bladder is basically expandable sac that holds urine 9

System Overview (cont’d)
Urethra is tube that transports urine from bladder to outside of body Job of urinary system is to make urine, thus controlling body’s fluid and electrolyte balance and eliminating waste products To make urine, three processes necessary: Filtration Reabsorption Secretion 10

System Overview (cont’d)
Filtration Involves filtering blood to filtrate (that which is allowed to pass through filter), contains various substances that can either be reabsorbed or eliminated Part of filtrate is reabsorbed and sent back into blood stream, some is eliminated in urine 11

Figure 16-1 Anatomy of the urinary system.
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Urinary System Animation
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External Anatomy of the Kidney
Kidney covered by fibrous layer of connective tissue called renal capsule Indentation that gives kidney bean shape called renal hilum At hilum, renal arteries bring blood to kidneys to be filtered and renal veins take filtered blood away from kidney Ureter also attached at hilum to transport urine from kidney to bladder 14

Internal Anatomy of the Kidney
Kidney can be divided into three layers: Renal cortex: outer layer, grainy in appearance, has little obvious structure to naked eye; where blood filtration occurs Renal medulla: middle layer Renal pelvis: inner layer 15

Internal Anatomy of the Kidney (cont’d)
Renal medulla Contains number of triangle-shaped, striped areas called renal pyramids Renal pyramids composed of collecting tubules for urine that is formed in kidney Adjacent pyramids separated by narrow renal columns, extensions of cortical tissue 16

Renal pelvis Funnel, divided into two or three large collecting cups called major calyces Each major calyx divided into several minor calyces, forming cup-shaped areas around tips of pyramids to collect urine that continually drains through pyramids 17

Renal pelvis Kidney is essentially combination of filtration and collection system Blood filtered by millions of tiny filters in cortex, and filtrate flows through tiny tubules in medulla and collects in renal pelvis (enlarged proximal portion of ureter) which empties into ureter tube where urine is carried to bladder 18

Figure 16-2 The internal and external anatomy of the kidney.
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Blood Vessels Good blood supply to kidney essential to allow it to function properly There is network of blood vessels throughout kidney tissue Single renal artery enters each kidney at hilum, branching into five segmental arteries Segmental arteries branch into lobar arteries in renal sinus 20

Blood Vessels Lobar arteries branch into interlobar arteries which pass through renal columns Arcuate arteries originate from interlobar arteries and arch around pyramids in renal medulla Arcuate arteries give rise to interlobular arteries which give rise to afferent arterioles Each afferent arteriole leads to ball of capillaries called glomerulus 21

Blood Vessels (cont’d)
Efferent arterioles leave from glomerulus and travel to specialized series of capillaries called peritubular capillaries and vasa recta (straight collecting tubes) that are part of renal nephron, functional unit of kidney Peritubular capillaries wrap around collecting tubules of nephron, allowing efficient movement of ions between blood and fluid in nephron 22

Blood Vessels (cont’d)
From each set of peritubular capillaries, blood flows out interlobular veins From there, blood flows out series of veins that are direct reverse of arteries with exception that there are no segmental veins Blood finally leaves kidney via renal vein 23

Figure 16-3 Renal blood vessels and the pathway of blood through the renal system.
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The Nephron Functional unit of kidney, consisting of millions of microscopic funnels and tubules Divided into two distinct parts: Renal corpuscle: a filter Renal tubule: where reabsorption and secretion take place 26

The Nephron (cont’d) Blood enters renal corpuscle via glomerulus, ball of capillaries Surrounding glomerulus is double-layered membrane called glomerular capsule, or Bowman’s capsule Layers of glomerular capsule similar to layers of serous membrane 27

The Nephron (cont’d) Inner layer of glomerular capsule, visceral layer, surrounds glomerular capillaries and is made of specialized squamous epithelial cells called podocytes; makes for very efficient filter Outer layer, or parietal layer, of glomerular capsule is simple squamous epithelium and completes filter 28

The Nephron (cont’d) Blood flows into glomerulus and everything BUT blood cells and few large molecules, mainly protein, pushed from capillaries across filter and into glomerular capsule Material filtered from blood into glomerular capsule called glomerular filtrate If blood or protein leaks into urine can indicate kidney filtration problem 29

Figure The nephron. 30

The Nephron (cont’d) Rest of nephron is series of tubes known as renal tubules Glomerular filtrate travels from glomerular capsule into first part of renal tubule, proximal tubule Wall of proximal tubule made of cuboidal epithelium with microvilli 31

The Nephron (cont’d) From proximal tubule, glomerular filtrate flows into nephron loop (or Loop of Henle) Nephron loop consists of descending loop (similar in structure to proximal tubule) and ascending loop (simple cuboidal epithelium) Glomerular filtrate travels from nephron loop to distal tubule 32

The Nephron (cont’d) Wall of distal tubule is like that of ascending branch of nephron loop From distal tubule, glomerular filtrate flows into one of several collecting ducts, made of cuboidal epithelium Collecting ducts lead to minor calyces, then to major calyces, renal pelvis, and ureter At this point, glomerular filtrate is urine 33

Figure 16-5 The renal tubule.
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Kidney Anatomy Exercise
Click here to view complete an interactive labeling activity of the kidney. Back to Directory 35

The Nephron (cont’d) Blood vessels are in close proximity to nephrons because certain substances within filtrate must be brought back into blood stream Blood approaches nephron via afferent arteriole Blood flows from afferent arteriole into glomerulus 36

The Nephron (cont’d) Blood flows from glomerulus via efferent arteriole into peritubular capillaries and vasa recta, series of blood vessels surrounding renal tubule Surrounding blood vessels allow for reabsorption back into blood stream from filtrate that is within tubular system Blood leaves nephron via interlobular veins 37

Pathology Connection: Kidney Stones
Substances in urine crystallize in renal tubule Often because concentration of molecule is higher than normal Stones can be due to Excess calcium (70% of stones) Excess uric acid (10% of stones) Kidney infections 38

Pathology Connection: Kidney Stones
Some stones pass unnoticed; larger or irregularly shaped stones may lodge in tubule, obstructing flow and irritating nearby tissues 39

Pathology Connection: Kidney Stones (cont’d)
Symptoms may include: Blood in urine Severe flank pain Urinary urgency Fever Nausea 40

Diagnosis History and exam Urinalysis Ultrasound Imaging studies Metabolic analysis Capture and analysis of stone 41

Treatment Depends on number, size, location, and composition of stones Some stones may move on their own Patients treated for pain and sent home with instructions to drink lots of fluids, filter their urine to collect any stones that pass Medications may be given to increase chance of passing stones (corticosteroids or alpha blockers) 42

Procedures that can be helpful include Extracorporeal shock wave lithotripsy: shock waves applied outside body to break stone into small pieces more easily passed Ureteroscopy: fiberoptic endoscope is threaded up urethra, through bladder, and into ureter; attached instrument shatters stone and captures pieces Percutaneous nephrolithotomy: endoscope and small incision used to remove large stones 43

Figure 16-6 Three methods of lithotripsy
Figure Three methods of lithotripsy. a) Percutaneous ultrasonic lithrotripsy. A nephro-scope is inserted into the renal pelvis, and ultrasound waves are used to fragment the stones. The fragments are then removed through the nephroscope. 44

Figure Three methods of lithotripsy. b) Dornier Compact Delta® lithrotripsy system. Acoustic shock waves generated by the shock-wave generator travel through soft tissue to shatter the renal stone into fragments, which are then eliminated in the urine (source: Courtesy Dornier Medical Products, Inc.) 45

Figure Three methods of lithotripsy. c) Water immersion lithotripsy procedure. 46

Recurrence is often a problem (50% of patients will have recurrence) Long-term treatment focuses on prevention of future stones by Adhering to diet designed to prevent patient’s particular type of stone Prescribing medication that decreases likelihood of recurrence 47

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Pathology Connection: Polycystic Kidney Disease (PKD)
Genetic disorder where large cysts form in kidneys One form is so serious patients die in infancy More common form is adult-onset disorder characterized by decreasing kidney function as normal nephrons are destroyed by cysts As more cysts develop, kidneys get very large, one is recorded to have weighed 22 pounds Patients also at risk for aneurysms and heart abnormalities 49

Pathology Connection: Polycystic Kidney Disease (PKD) (cont’d)
Symptoms vary, but may include Hypertension Impaired renal function Urinary tract infection Dilute urine Liver cysts Cerebral hemorrhage Decreased kidney perfusion Pain Hematuria Hormone abnormalities (increased erythropoietin and increased activity of renin-angiotensin-aldosterone system) 50

Pathology Connection: Polycystic Kidney Disease (PKD) (cont’d)
Diagnosis: ultrasound, genetic testing Course of disease and treatment No cure except transplantation of kidney Patients generally progress to renal failure in their late 40s, 50s or early 60s Patients treated for complications of kidney disease Patients who develop end stage renal disease require kidney dialysis or kidney transplant 51

Urine Formation Kidney controls fluid and electrolyte balance by controlling urine volume and composition In order to form urine, nephron must perform three processes: Glomerular filtration Tubular reabsorption Tubular secretion 52

Urine Formation (cont’d)
During glomerular filtration, fluid and molecules pass from glomerular capillaries into glomerular capsule, across filter composed of walls of capillaries and podocytes of glomerular capsule Filtrate flows into renal tubule where composition of filtrate is controlled by reabsorption and secretion 53

Substances that are reabsorbed pass from renal tubule into peritubular capillaries and return to blood stream Substances that are secreted pass through peritubular capillaries into renal tubule and eventually leave body as urine 54

Filtration moves fluid and chemicals into nephron from blood Reabsorption and secretion control concentration of chemicals and volume of urine Glomerular filtrate is chemically similar to blood, while urine is chemically different 55

Some substances, like glucose, are completely reabsorbed while substances like metabolic waste products (urea and creatinine) are almost completely secreted as urine 56

Figure 16-7 The processes involved in urine formation.
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Table 16-1 Kidney Fluid Chemistry
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Dipstick Urinalysis Video
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Control of Filtration Filtration controlled by several factors:
Filter size: determines what gets through filter Pressure: higher pressure on one side of filter allows chemicals to be pushed though filter Podocytes and capillary walls of renal corpuscle create filter with fixed openings 61

Control of Filtration Plasma, and many of substances dissolved in plasma, pass through filter, but blood cells, platelets, and large molecules can’t get through healthy kidney; thus they remain in bloodstream 62

Figure 16-8 Filter selectivity.
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Figure 16-9 Comparison of damaged and healthy kidneys.
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Filtration Rate Can be controlled by changing pressure difference across filter Higher blood pressure in glomerular capillaries increases filtration, while lower pressure decreases filtration Minor changes in systolic blood pressure do not change glomerular pressure because it is protected by mechanism called autoregulation 65

Filtration Rate (cont’d)
As systemic BP increases, afferent arterioles leading into glomerulus constrict, decreasing amount of blood getting into glomerulus Autoregulation can be overridden Since kidney regulates fluid volume, kidney can work with cardiovascular system to regulate blood pressure 66

Filtration Rate (cont’d)
Glomerular filtration can decrease to conserve fluid when blood pressure falls, or increase filtration if blood pressure rises Sympathetic nervous system can control urine production through adrenal medulla; secretion of epinephrine or norepinephrine causes vasoconstriction of afferent arteriole, decreasing glomerular filtration; thus urine output decreases during fight or flight responses 67

Hypovolemic Shock Animation
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Pathology Connection: Nephropathy
General term for kidney disease; particularly applies in cases where there is damage to filtering apparatus of nephrons Several types including diabetic and drug-induced Symptoms may include: proteinuria, hematuria, hypertension Diagnosis: based on urinalysis, blood tests 69

Pathology Connection: Nephropathy (cont’d)
Course of disease: generally progressive, but some types can be reversed if treated in early stages Treatments Cortocosteroids Immunosuppressants Blood pressure medications Diet Kidney replacement (in cases of end-stage renal disease) 70

Diabetic Nephropathy Diabetes mellitus (DM): characterized by high glucose levels in blood; caused by abnormalities in insulin production or response High glucose levels disrupt osmotic balance of blood Kidneys work hard to remove excess glucose, and urine output is high Over time, kidney is damaged: begins with thickening of filter surface of glomerular capsule, eventually leads to breakdown of kidney tissue, destroying filtering ability 71

Diabetic Nephropathy Signs and symptoms Substances that would normally not pass through filter begin to appear in urine (like proteins and blood cells) Treatment If caught in early stages (when only microalbuminuria), patients can reverse damage through use of strict glycemic control, ACE inhibitor medications (used even if blood pressure is normal) Symptoms and signs of diabetic nephropathy 72

Diabetic Nephropathy Diabetics can prevent onset of kidney damage by controlling blood sugar levels, preventing high blood pressure, and reducing blood cholesterol levels Epidemiology Diabetic nephropathy is leading cause of kidney disease in America 40% of diabetics will develop it 1/3 of patients on dialysis have diabetes mellitus 73

Diabetic Nephropathy Prognosis: Once large amounts of protein begin to show up in urine (macroalbuminuria), patients typically live 5-10 years Drug-induced nephropathy (nephrotoxic drugs) Mechanisms of damage may include: Direct toxicity Allergy-induced damage Crystallization in kidney 74

Drugs that can cause damage include Analgesics (analgesic nephropathy): drugs in this class include pain relievers, particularly nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen; drugs can be particularly problematic in patients who already have renal disease or other risk factors Antibiotics: problems with antibiotics are usually related to allergic reactions Immunosupressants: this class includes drugs used after kidney transplant 75

Contrast dye Used during some types of imaging studies Can cause severe vasospasm in afferent arterioles, resulting in nephropathy People at higher risk for developing contrast-related nephropathy include patients With diabetes mellitus, kidney disease, or congestive heart failure Who are dehydrated or take diuretic medicine As many as 30% of patients who develop this type are left with permanent kidney damage 76

Glomerulonephritis: inflammation of glomerulus Glomerulosclerosis: scarring of glomerulus Both cause damage to delicate filter apparatus When filter is damaged, blood cells and blood proteins enter filtrate and eventually appear in urine Removal of waste products is decreased and electrolyte balance usually abnormal due to change in urine chemistry 77

Glomerulosclerosis: scarring of glomerulus Many causes, including bacterial infection, diabetic nephropathy, systemic lupus erythematous (SLE), and genetic disorders such as Alport's syndrome and Goodpasture’s syndrome 78

Control of Tubular Reabsorption and Secretion
Glomerular filtration controls speed of filtration and, ultimately, amount of urine produced Tubular reabsorption and secretion control chemistry and volume of urine Substances that are reabsorbed move from tubule back to blood stream via peritubular capillaries and stay in body Substances that are secreted stay in tubule and eventually leave body via urine 79

Control of Tubular Reabsorption and Secretion (cont’d)
Anything that affects reabsorption and secretion affects urine chemistry First thing that affects tubular reabsorption and secretion is tubule permeability Each section of tubule can reabsorb and secrete different substances Molecules move across membranes through several different methods 80

Diffusion: movement of molecules across semipermeable membrane; some move by being carried across by proteins (active transport) Differences in tubular permeability result in dramatic differences in what molecules are reabsorbed or secreted in each part of tubule 81

Table 16-2 Individual Tubule Functions
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Also affecting tubular reabsorption and secretion is special type of circulation around nephron loop, called counter-current circulation Ions move across cell membranes from higher to lower areas of concentration 83

Fluid more concentrated moves across membrane, while solute in higher concentration on other side of membrane will move to join water Attempt to maintain homeostasis 84

Figure 16-10 Movement of solute (ions) and solvent (water) down their concentration gradient.
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Water and ions tend to move in opposite directions, making it impossible to remove both without special selection environment around nephron loop 86

Counter current circulation in nephron possible because of concentration gradient, with low ion concentration at beginning of descending loop and high concentration at tip of loop, as well as differences in permeability between descending loop (water) and ascending loop (ions) 87

Filtrate flows into descending loop, reabsorbing water and increasing concentration of ions; as filtrate enters ascending loop, fluid is concentrated because of water loss, membrane is permeable to only ions, and ions move across membrane 88

Figure 16-11 Sites of tubular reabsorption and secretion.
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Third factor that affects reabsorption and secretion is blood-pressure-regulating hormones Antidiuretic hormone (ADH): made by hypothalamus and secreted from posterior pituitary when BP decreases or ionic concentration increases Increases permeability of distal tubules and collecting duct; more water is reabsorbed, increasing blood volume, increasing blood pressure, and diluting ionic concentration 90

Third factor that affects reabsorption and secretion is blood-pressure-regulating hormones Antidiuretic hormone (ADH): made by hypothalamus and secreted from posterior pituitary when BP decreases or ionic concentration increases Less urine is produced Alcohol or caffeine inhibit ADH production, increasing urine production 91

Aldosterone: adrenocorticosteroid secreted by adrenal cortex Secreted when plasma sodium decreases or plasma potassium increases Increases reabsorption of sodium ions and secretion of potassium ions, increasing serum sodium levels and decreasing serum potassium levels by distal tubule and ascending limb of nephron loop As sodium is reabsorbed, water is also reabsorbed, decreasing urine volume 92

Renin-angiotensin-aldosterone system: series of chemical reactions that regulate blood pressure Decrease in blood flow to kidney causes special group of cells near glomerulus, juxtaglomerular apparatus, to secrete renin into bloodstream Liver secretes chemical called angiotensinogen Renin converts angiotensinogen into angiotensin 93

Atrial natriuretic peptide (ANP): secreted by atria of heart when blood volume increases Decreases sodium reabsorption and thus increases urination 94

Another enzyme made by lungs, angiotensin converting enzyme (ACE), converts angiotensin I to angiotensin II, increasing thirst, increasing ADH secretion, increasing aldosterone secretion, and causing vasoconstriction; these increase blood pressure by increasing fluid volume Notice how kidneys, lungs, and heart work together to regulate blood pressure 95

Pathology Connection: Uremia and Renal Failure
Condition where organic wastes accumulate in bloodstream Symptoms include: Fatigue Neuropathy Seizures Lack of appetites Cramps Mental confusion Metabolic disorders Itching Insulin resistance Hiccups Anemia Clotting abnormalities Systemic inflammation Decreased sense of smell and taste 96

Pathology Connection: Uremia and Renal Failure (cont’d)
Treatments Low-protein diet Kidney replacement therapy Dialysis: leads to partially treated uremia; prolongs life, but does not fully treat condition Kidney transplant: only effective treatment 97

Hemolytic uremic syndrome Disorder caused by infection with bacteria E. coli, typically from eating undercooked meat Bacterium infects digestive tract and releases toxins, which destroy RBCs Damaged RBCs lodge in blood vessels in kidney, blocking them and preventing blood flow to nephron Without treatment, permanent kidney damage may result 98

Figure 16-12 Placement of transplanted kidney.
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Renal failure: spectrum of disorders involving abnormal kidney function Risk factors include: injury, ischemia, nephrotoxic medications, hypovolemia, hypotension, hypertension, liver disease, diabetes mellitus, lupus, infections, urinary tract obstruction, immune system malfunctions, PKD, and cardiovascular disease Symptoms: decreased urine output, uremia, fluid retention, anorexia, fatigue, hiccups, nausea, mental confusion, clotting disorders, seizures 100

Chronic renal failure (CRF): ongoing, progressive disease of kidney (lasting 3 months or more) Common risk factors Diabetes mellitus (45%) Structural damage to kidneys Hypertension (20%) Cardiovascular disease Lupus Age Obesity Polycystic kidney disease Nephrotoxic drugs African American, Latino, or native American ethnicity 101

Progression may be controlled by treating underlying cause of damage or controlling BP and cholesterol Useful medications include: ACE inhibitors, angiotension receptor blockers, statin drugs Other important aspects of treatment: blood sugar control, smoking cessation 102

As disease progresses, patient may eventually need kidney replacement Can lead to end-stage renal disease (ESRD), final stage of renal failure, treatment is dialysis or transplantation Most patients never make it to ESRD; they die of cardiovascular disease 103

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Pathology Connection: Kidney Replacement Therapy
Dialysis: patient’s blood filtered by artificial or biological filter; partial treatment; does not work as well as functional kidneys Hemodialysis Blood removed from patient via IV, is passed through dialysis machine, where blood passes through semipermeable membrane (filter) that removes fluid, electrolytes and wastes Blood returned to patient through another IV; must be performed 2-3 times per week, usually at dialysis center, 2-4 hours per session 105

Dialysis: patient’s blood filtered by artificial or biological filter; partial treatment; does not work as well as functional kidneys Peritoneal dialysis Dialysis fluid pumped into peritoneal cavity, Waste from body fluids filters across peritoneum into dialysis fluid After several hours dialysis fluid is removed 106

Figure 16-13 Peritoneal dialysis and hemodialysis.
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Side effects of dialysis Low BP Nausea Cramps Headaches Fatigue Infection Fluid overload Clotting abnormalities 109

Kidney transplant: surgical replacement of damaged kidney with donor kidney Only real cure for end-stage renal disease Second most common organ transplant in US (only corneal transplants are more common) 3 types: cadaver transplants; living related donor transplants; living unrelated donor transplants 110

Success rate: 90% survival at 1-year; 80% survival at 3 years; 50% survival at 10 years Transplant recipients must take immunosuppressant drugs, usually for rest of their lives, to prevent organ rejection 111

The Urinary Bladder and Urination Reflex
Glomerular filtrate flows out collecting duct, into minor calyces, and then into major calyces, forming renal pelvis Once glomerular filtrate leaves collecting ducts, its concentration can’t be changed and it is urine Urine collects in renal pelvis and flows down ureters to urinary bladder, where it is stored 112

The Urinary Bladder and Urination Reflex (cont’d)
Urinary bladder: small hollow organ posterior to pubic symphysis, behind peritoneum Lined with transitional epithelium, only epithelium stretchy enough to expand as bladder fills Ability to stretch enhanced by series of pleats called rugae 113

Urinary bladder: small hollow organ posterior to pubic symphysis, behind peritoneum Has muscular wall consisting of several layers of circular and longitudinal smooth muscle, covered by connective tissue and parietal peritoneum 114

Figure 16-14 The urinary bladder.
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As urine accumulates, bladder fills and stretches Stretch triggers urinary reflex and need to void to empty bladder Urination had been thought to be spinal reflex, but new research indicates is controlled by brain 116

When bladder is full, signals sent from bladder to spinal cord to pons; pons sends parasympathetic signals down spinal cord, causing contraction of muscular walls of bladder, and bladder empties 117

Urine leaves bladder via urethra, thin muscular tube lined with several different types of epithelium along its length Part of brain can inhibit urination by controlling internal urethral sphincter, valve at junction of bladder and urethra, and external urethral sphincter, valve that is part of muscles of pelvic floor 118

Sympathetic stimulation of these sphincters prevents urine from leaving body Although you have little control over bladder contraction, you have good control over sphincters starting from age 2, or slightly later in boys 119

Figure 16-15 Control of urination.
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Urinary Bladder Exercise
Click here to view an interactive labeling exercise of the urinary bladder. Back to Directory 121

Pathology Connection: Incontinence / Overactive Bladder
Incontinence: inability to control urination; possible causes: overactive bladder, urinary tract infection, benign prostatic hypertrophy (BPH) Overactive bladder: common condition characterized by urinary urgency, nighttime urination, and urinary frequency (with or without incontinence) 122

Symptoms must occur in absence of pain or obvious urinary pathology such as UTI More common in women and people over age 40 Cause is unknown, but may be due to abnormalities of bladder muscles, nerves innervating bladder, or in stretch receptors in bladder wall Diagnosis: mainly by ruling out other disorders through history, exam, and urinalysis 123

Treatments may include Bladder training: decreases sensitivity of bladder to fullness, thereby increasing bladder control Medications: block parasympathetic stimulation or increase sympathetic activity 124

Prognosis Nearly 50% of patients not cured with treatment Many patients have to make lifestyle changes, such as: drinking fewer liquids, avoiding situations where frequent trips to restroom could be problematic 125

Pathology Connection: Urinary Tract Infection (UTI)
Caused by movement of fecal bacteria into urinary tract Symptoms: frequent, painful urination, hematuria (bloody urine), cloudy urine, and urine with unusual odor 126

Pathology Connection: Urinary Tract Infection (UTI)
People at higher risk Women (because urethra is shorter) Elderly, hospitalized patients Patients with catheters Patients with structural abnormalities of urinary tract Men with BPH 127

Pathology Connection: Urinary Tract Infection (UTI) (cont’d)
Diagnosis Urinalysis (looking for blood and bacteria in urine) Imaging Bacterial culture of urine Treatments: antibiotics and increased fluids 128

Common Disorders of the Urinary System
Kidney stones Etiology: increased urine concentration, infection, kidney disease; made of calcium and uric acid crystals; get larger and can block ureters Signs and symptoms: severe pain, hematuria, fever, chills, nausea, urinary urgency 129

Common Disorders of the Urinary System (cont’d)
Kidney stones Diagnosis: symptom, imaging, urinalysis, patient history Treatment: pain relief, extracorporeal shock wave lithotripsy, ureteroscopy, percutaneous nephrolithotomy 130

Polycystic kidney disease Etiology: genetic disorder causes large cycts to form in kidney Signs and symptoms: enlarged, cystic kidneys, hypertension, UTI, dilute urine, liver cysts, pain, hematuria, aneurysm Diagnosis: imaging, genetic tests Treatment: medication, kidney replacement, no cure 131

Ischemic nephropathy Etiology: decrease blood flow to kidneys Signs and symptoms: kidney failure, uremia, hypertension or hypotension, decreased urine output, increase serum creatinine and urea Diagnosis: urinalysis, blood tests Treatment: treat underlying cause and symptoms, kidney replacement if needed 132

Diabetic nephropathy Etiology: diabetes mellitus Signs and symptoms: early stages: increased glomerular filtration, protein in urine, later: uremia, hypertension, etc. Diagnosis: blood tests, urinalysis Treatment: tight glycemic control, blood pressure medications, lipid control, diet, kidney replacement 133

Drug induced nephropathy Etiology: drugs toxic to kidney tissue, especially contrast dye and NSAIDs Signs and symptoms: early stages: increased glomerular filtration, protein in urine, later: uremia, hypertension, etc. Diagnosis: blood tests, urinalysis Treatment: stop drugs, do not use contrast dyes for patients with known risk factors, keep patients well hydrated when using contrast dyes. 134

Glomerulonephritis and glomerulosclerosis Etiology: inflammation and scarring of glomerulus Signs and symptoms: early stages: increased glomerular filtration, protein in urine, later: uremia, hypertension, etc. Diagnosis: blood tests, urinalysis Treatment depends on cause: treating underlying cause may decrease progression 135

Uremia Etiology: build up of organic waste products in blood due to renal insufficiency Signs and symptoms: fatigue, neuropathy, seizures, lack of appetite, decreased smell and taste, mental confusion, insulin resistance, itching, inflammation, clotting etc. Diagnosis: blood tests Treatment, difficult: dialysis only partial treatment; transplant only cure 136

Diabetes insipidus Etiology: ADH deficiency Signs and symptoms: copious, dilute urine Diagnosis: rule out diabetes mellitus, ADH levels Treatment: tumor removal, pre-and post-operative medication 137

Renal failure (kidney disease) Etiology: either acute or progressive damage to kidneys from many different causes Signs and symptoms: decreased urine output, uremia, fluid retention, loss of appetite, fatigue, hiccups, nausea, mental confusion, clotting disorder, seizures 138

Renal failure (kidney disease) Diagnosis: blood test, urinalysis, imaging Treatment: blood pressure medication, glucose control, diet, treatment of underlying condition, prevention of cardiovascular disease, kidney replacement when progresses to end stage disease 139

Urinary tract infection (UTI) Etiology: bacterial infection of urinary tract, usually bladder Signs and symptoms: painful urination, urinary frequency, nighttime urination, foul smell, cloudy urine Diagnosis: urinalysis Treatment: antibiotics, prevention of recurrence is difficult 140

Overactive bladder Etiology: unknown, may be abnormalities in nervous or muscle control of bladder Signs and symptoms: frequent urination without pain or infection Diagnosis: rule out UTI Treatment: bladder training, sympathetic drugs Overactive Bladder 141

Hemolytic uremic syndrome Etiology: bacterial infection with certain strains of E. coli, toxins damage kidneys Signs and symptoms: fever, abdominal pain, pallor, fatigue, bruising, decreased urination, swelling Diagnosis: blood tests, history Treatment: blood transfusion, kidney dialysis 142

Pharmacology Corner Blood pressure medications High blood pressure
Diuretics Mechanism of action: decreases blood volume by decreasing body water; example: Lasix (decreases body water by preventing sodium reabsorption) causes more sodium, and water, to be excreted in urine Angiotensin-Converting Enzyme (ACE) inhibitors Mechanism of action: decrease blood levels of angiotensin II; leads to systemic vasodilation which results in decreased blood pressure 143

Pharmacology Corner (cont’d)
Blood pressure medications Severely low blood pressure (cardiac and septic shock) Dopamine: given to restore renal blood flow (prevents renal damage); very dosage dependent; low doses must be given to achieve desired effect on kidneys Immunosuppressant drugs can be used to prevent rejection in kidney transplant 144

Drugs for UTIs Antibiotics (Bactrim, Cipro) Drugs for incontinence Anticholinergic drugs (Block parasympathetic stimulation to empty bladder) 145

Some drugs can damage kidneys Examples: NSAIDS (if overused), antibiotics, others Mechanism of damage may include direct toxicity, allergy-induced damage, or crystallization in kidney 146

Snapshots from the Journey
Urinary system consists of paired kidneys, and paired ureters that carry urine to single urinary bladder; urethra transports urine from bladder to outside of body Function of urinary system is control of fluid and electrolyte balance and elimination of nitrogen containing waste 147

Snapshots from the Journey (cont’d)
Kidney is bean shaped, covered in capsule; has indentation known as renal hilum and interior cavity known as renal sinus; can be divided into 3 layers: renal cortex, renal medulla, and renal pelvis Renal pelvis is funnel divided into large pipes, major calyces; each major calyces divided into several minor calyces; renal pelvis empties into ureter 148

Kidneys very well vascularized; blood is supplied to each by renal artery; blood vessel splits into smaller and smaller branches until there are millions of arterioles, afferent arterioles Afferent arterioles supply millions of nephrons, functional unit of kidney, with blood; blood leaves kidney by series of veins and ultimately returns to circulation via renal vein 149

Nephron is functional unit of kidney; there are millions of nephrons in each kidney; nephron divided into two parts: renal corpuscle (consisting of glomerulus) and glomerular capsule which filters blood and produces glomerular filtrate 150

Renal tubule, consisting of proximal tubule, nephron loop, distal tubule, and collecting ducts control concentration and volume of urine by reabsorbing and secreting water, electrolytes, and other molecules 151

Walls of nephron made of epithelium; type of epithelium changes depending on specific function of each part of nephron Urine formed a combination of 3 processes: glomerular filtration, tubular reabsorption, and tubular secretion; selectivity of glomerular filter determined by size of openings in filter and differences between blood pressure of glomerulus and pressure in glomerular capsule 152

Size of filter does not change unless glomerulus is damaged; protein, for example, cannot pass through filter; however, filtration rate will change if pressure in glomerulus changes; most of time, autoregulation, control of diameter of afferent arteriole, keeps glomerular pressure and glomerular filtration rate constant 153

Sympathetic stimulation can regulate (decrease) glomerular filtration and urine output due to constriction of afferent arterioles 154

Tubular reabsorption and secretion controlled by differences in tubular permeability; proximal tubule is most versatile, reabsorbing dozens of different molecules Nephron loop is part of elaborate counter-current mechanism, with descending loop permeable to water and ascending loop permeable to ions 155

Distal tubule and collecting ducts reabsorb water; permeability of renal tubule can be regulated by number of hormones which control blood pressure Hormones, aldosterone, ADH, natriuretic peptide, and others, regulate BP by regulating urine volume and ion secretion; changes in urine volume change total body fluid volume and thus change BP 156

Urinary bladder is collecting and storage device for urine located in pelvic cavity; has muscular wall Contractions of muscle result in voiding (urination), emptying bladder; urination is reflex controlled by parasympathetic neurons in pons 157

Signals from full bladder reach pons; neurons in pons send signals for bladder to contract; sympathetic neurons control 2 valves, internal and external urethral sphincters, which allow significant conscious control of urination reflex 158

Symptoms of renal disease common no matter what cause of kidney dysfunction; include blood in urine, decreased removal of wastes from blood (increased BUN and serum creatinine), and hypertension

Treatment of kidney disease involves treating underlying cause of disorder, by decreasing blood pressure, tightening blood sugar control, changing lifestyle, and decreasing cardiovascular disease risk factors

Most people with kidney disease do not die from uremia caused by end stage renal failure, but from cardiovascular disease caused in part by kidney dysfunction; only cure for kidney disease is kidney transplant but many patients can be helped by dialysis

Ultrasound Technicians Video
Click here to view a video on ultrasound technicians. Back to Directory 162

Case Study: Maria’s Story
During a recent trip to the doctor's office, Maria had a standard urinalysis. The results worry her doctor. In her urine there was a tiny amount of protein. The doctor orders more extensive tests Why is Maria's doctor concerned? It's only a little protein What other tests should the doctor order? 163

Case Study: Maria’s Story
During a recent trip to the doctor's office, Maria had a standard urinalysis. The results worry her doctor. In her urine there was a tiny amount of protein. The doctor orders more extensive tests When the tests come back, the doctor tells Maria she needs to go on an ACE inhibitor even though her blood pressure is normal. What is the diagnosis? 164

Case Study: Ray’s Story
Ray, paralyzed from the neck down after a swimming pool accident has been doing pretty well except for one thing. He keeps having urinary tract infections Why is Ray so susceptible to urinary tract infections? 165

Filtration and Fluid Balance

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Filtration and Fluid Balance

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