SECTION 10 Problems of Urinary Function
49
Assessment: Urinary System
Teresa Turnbull
http://evolve.elsevier.com/Lewis/medsurg/
CONCEPTUAL FOCUS
Elimination Fluids and Electrolytes
LEARNING OUTCOMES
1. Identify the anatomic location and functions of the kidneys, 5. Perform a physical assessment of the urinary system using
ureters, bladder, and urethra. appropriate techniques.
2. Explain the physiologic events involved in the formation 6. Distinguish normal from abnormal findings of a physical
and passage of urine from glomerular filtration to voiding. assessment of the urinary system.
3. Obtain significant subjective and objective data related to 7. Describe the purpose, significance of results, and nursing
the urinary system from a patient. responsibilities related to diagnostic studies of the urinary
4. Link the age-related changes of the urinary system to the system.
differences in assessment findings. 8. Evaluate findings of a urinalysis.
KEY TERMS
costovertebral angle (CVA) glomerulus
creatinine nephron
cystoscopy, Table 49.12 renal biopsy, Table 49.12
glomerular filtration rate (GFR) urinalysis
Adequate kidney function is essential to health. If a person has control BP, make erythropoietin, activate vitamin D, and regu-
complete kidney failure and treatment is not provided, death is late acid-base balance.
inevitable. This chapter discusses the structures and functions,
assessment, and diagnostic studies of the urinary system. Macrostructure
The paired kidneys are bean-shaped organs located retroperi-
STRUCTURES AND FUNCTIONS OF URINARY toneally (behind the peritoneum) on either side of the vertebral
column at about the level of the 12th thoracic (T12) vertebra
SYSTEM to the 3rd lumbar (L3) vertebra. Each kidney weighs 4 to 6 oz
The upper urinary system consists of 2 kidneys and 2 ureters. (113 to 170 g) and is about 5 in (12.5 cm) long. The right kidney,
The lower urinary system consists of a urinary bladder and ure- positioned at the level of the twelfth rib, is lower than the left.
thra (Fig. 49.1). Urine is formed in the kidneys, drains through An adrenal gland lies on top of each kidney.
the ureters to be stored in the bladder, and then passes out of the Each kidney is surrounded by a significant amount of fat and
body through the urethra. connective tissue that cushion, support, and help the kidney to
maintain its position. A thin, smooth layer of fibrous membrane
Kidneys called the capsule covers the surface of each kidney. The capsule
The kidneys are the principal organs of the urinary system. The protects the kidney and serves as a shock absorber if this area
primary functions of the kidneys are to (1) regulate the volume is traumatized from a sudden force or strike. The hilus on the
and composition of extracellular fluid (ECF) and (2) excrete medial side of the kidney serves as the entry site for the renal
waste products from the body. The kidneys also function to artery and nerves and as the exit site for the renal vein and ureter.
1177
,1178 SECTION 10 Problems of Urinary Function
Inferior
Diaphragm to the bladder. The renal pelvis can store a small volume of urine
vena cava Left adrenal (3 to 5 mL).
gland
Right
adrenal
Microstructure
gland Left renal The nephron is the functional unit of the kidney. Each kidney
artery
Right renal and vein
has around 1 million nephrons. Each nephron is composed of
artery the glomerulus, Bowman capsule, and a tubular system. The
and vein tubular system consists of the proximal convoluted tubule,
Right Left kidney
Aorta
loop of Henle, distal convoluted tubule, and collecting tubules
kidney
Left ureter (Fig. 49.3). The glomerulus, Bowman capsule, proximal tubule,
Right ureter and distal tubule are in the cortex of the kidney. The loop of
Left common
Psoas iliac artery Henle and collecting tubules are in the medulla. Several collect-
muscle and vein ing tubules join to form a single collecting duct. The collect-
ing ducts eventually merge into a pyramid that empties via the
Sigmoid papilla into a minor calyx.
colon
Urinary bladder
Urethra Blood Supply
A
Blood flow to the kidneys, around 1200 mL/min, accounts for
20% to 25% of the cardiac output. Blood reaches the kidneys
Male Female
via the renal artery, which arises from the aorta and enters the
kidney through the hilus. The renal artery divides into second-
ary branches and then into still smaller branches, each of which
forms an afferent arteriole. The afferent arteriole divides into a
capillary network, the glomerulus, which is a collection of up
to 50 capillaries (Fig. 49.3). The capillaries of the glomerulus
unite in the efferent arteriole. This efferent arteriole splits to
form a capillary network, the peritubular capillaries, which sur-
B C round the tubular system. All peritubular capillaries drain into
the venous system. The renal vein empties into the inferior vena
Fig. 49.1 Organs of the urinary system. (A) Upper urinary tract in rela- cava.
tion to other anatomic structures. (B) Male urethra in relation to other
pelvic structures. (C) Female urethra.
Physiology of Urine Formation
Urine formation is the outcome of a complex, multistep pro-
Renal column cess of filtration, reabsorption, secretion, and excretion of water,
Fibrous electrolytes, and metabolic waste products. Although urine for-
capsule mation is the result of this process, the primary functions of the
Renal
Calyx pyramid kidneys are to filter the blood and maintain the body’s internal
homeostasis.
Renal
pelvis
Renal artery Glomerular function. Urine formation begins at the glome
rulus, where blood is filtered. The glomerulus is a semipermeable
Renal
papilla membrane that allows filtration (Fig. 49.3). The hydrostatic
pressure of the blood within the glomerular capillaries causes
Medulla
a portion of blood to be filtered across the semipermeable
Renal vein membrane into Bowman capsule. There, the filtered portion
Cortex
of the blood (glomerular filtrate) begins to pass down to the
Ureter
tubule. Filtration is more rapid in the glomerulus than in
ordinary tissue capillaries because the glomerular membrane
Fig. 49.2 Longitudinal section of the kidney. is porous. The glomerular filtrate is similar in composition to
blood except that it lacks blood cells, platelets, and large plasma
The parenchyma is the actual tissue of the kidney (Fig. 49.2). proteins. Under normal conditions, capillary pores are too small
The outer layer of the parenchyma is the cortex. The inner layer is to allow the loss of these large blood components. However, in
the medulla. The medulla consists of a number of pyramids. The many kidney diseases, capillary permeability increases, which
apices (tops) of these pyramids are the papillae, through which allows plasma proteins and blood cells to pass into the urine.
urine passes to enter the calyces. The minor calyces widen and The amount of blood filtered each minute by the glomer-
merge to form major calyces, which form a funnel-shaped sac uli is the glomerular filtration rate (GFR). The normal GFR
called the renal pelvis. The minor and major calyces transport is about 125 mL/min. The peritubular capillary network reab-
urine to the renal pelvis, from there it drains through the ureter sorbs most of the glomerular filtrate before it reaches the end
, CHAPTER 49 Assessment: Urinary System 1179
Renal Glomerulus
corpuscle Bowman
capsule
Proximal
convoluted Distal
tubule convoluted
tubule
Descending
limb of Henle Cortex
Renal
tubule Medulla
Thick ascending
limb of Henle
Collecting
Henle loop duct
Thin ascending
limb of Henle
Papillary
duct
Fig. 49.3 The nephron is the basic functional unit of the kidney. This illustration of a single nephron unit
shows the surrounding blood vessels. (Modified from Thibodeau GA, Patton KT: The human body in health
and disease, ed 4, St Louis, 2005, Mosby.)
In the proximal convoluted tubule, about 80% of the electro-
TABLE 49.1 Functions of Nephron
lytes are reabsorbed. Normally, this includes all glucose, amino
Segments
acids, and small proteins. As reabsorption continues in the loop
Segment Function of Henle, water is conserved, which is important for concentrat-
Glomerulus Selective filtration ing the filtrate. The descending loop is permeable to water and
Proximal tubule Reabsorption of 80% of electrolytes and water, glucose, moderately permeable to sodium, urea, and other solutes. In
amino acids, HCO3− the ascending limb, chloride ions (Cl−) are actively reabsorbed,
Secretion of H+ and creatinine
followed by passive reabsorption of sodium ions (Na+). About
Loop of Henle Concentration of filtrate
Reabsorption of Na+ and Cl− in ascending limb and water
25% of the filtered sodium is reabsorbed in the ascending limb.
in descending loop Two key functions of the distal convoluted tubules are final
Distal tubule Reabsorption of water (regulated by ADH) and HCO3− regulation of water balance and acid-base balance. Antidiuretic
Regulation of Ca2+ and PO42—by parathyroid hormone hormone (ADH) is needed for water reabsorption in the kid-
Regulation of Na+ and K+ by aldosterone ney. It is important in water balance. ADH makes the distal con-
Secretion of K+, H+, ammonia voluted tubules and collecting ducts permeable to water. This
Collecting duct Reabsorption of water (requires ADH) allows water to be reabsorbed into the peritubular capillaries
and eventually returned to the circulation.
Osmoreceptors in the anterior hypothalamus detect
decreases in plasma osmolality. These osmoreceptors send neu-
of the collecting duct. Therefore only 1 mL/min (on average) is ral input to superoptic nuclei cells in the hypothalamus. These
excreted as urine. superoptic nuclei cells have neuronal axons that end in the
Tubular function. The tubules and collecting ducts are posterior pituitary gland and act to inhibit ADH secretion. In
responsible for the reabsorption of essential materials and the absence of ADH, the tubules are essentially impermeable to
excretion of nonessential ones (Table 49.1). They carry out these water. Thus, any water in the tubules leaves the body as urine.
functions by reabsorption and secretion. Reabsorption is the Aldosterone (released from the adrenal cortex) acts on
passage of a substance from the lumen of the tubules through the distal tubule to cause reabsorption of Na+ and water. In
the tubule cells and into the capillaries. This process involves exchange for Na+, potassium ions (K+) are excreted. Circulating
both active and passive transport mechanisms. Tubular secretion blood volume and plasma concentrations of Na+ and K+ influ-
is the passage of a substance from the capillaries through ence aldosterone secretion.
the tubular cells into the lumen of the tubule. Reabsorption Acid-base regulation involves reabsorbing and conserving
and secretion cause many changes in the composition of the most of the bicarbonate (HCO3−) and secreting excess hydrogen
glomerular filtrate as it moves through the entire length of the ions (H+). The distal tubule has different ways to keep the pH of
tubule. ECF within a range of 7.35 to 7.45 (see Chapter 17).
49
Assessment: Urinary System
Teresa Turnbull
http://evolve.elsevier.com/Lewis/medsurg/
CONCEPTUAL FOCUS
Elimination Fluids and Electrolytes
LEARNING OUTCOMES
1. Identify the anatomic location and functions of the kidneys, 5. Perform a physical assessment of the urinary system using
ureters, bladder, and urethra. appropriate techniques.
2. Explain the physiologic events involved in the formation 6. Distinguish normal from abnormal findings of a physical
and passage of urine from glomerular filtration to voiding. assessment of the urinary system.
3. Obtain significant subjective and objective data related to 7. Describe the purpose, significance of results, and nursing
the urinary system from a patient. responsibilities related to diagnostic studies of the urinary
4. Link the age-related changes of the urinary system to the system.
differences in assessment findings. 8. Evaluate findings of a urinalysis.
KEY TERMS
costovertebral angle (CVA) glomerulus
creatinine nephron
cystoscopy, Table 49.12 renal biopsy, Table 49.12
glomerular filtration rate (GFR) urinalysis
Adequate kidney function is essential to health. If a person has control BP, make erythropoietin, activate vitamin D, and regu-
complete kidney failure and treatment is not provided, death is late acid-base balance.
inevitable. This chapter discusses the structures and functions,
assessment, and diagnostic studies of the urinary system. Macrostructure
The paired kidneys are bean-shaped organs located retroperi-
STRUCTURES AND FUNCTIONS OF URINARY toneally (behind the peritoneum) on either side of the vertebral
column at about the level of the 12th thoracic (T12) vertebra
SYSTEM to the 3rd lumbar (L3) vertebra. Each kidney weighs 4 to 6 oz
The upper urinary system consists of 2 kidneys and 2 ureters. (113 to 170 g) and is about 5 in (12.5 cm) long. The right kidney,
The lower urinary system consists of a urinary bladder and ure- positioned at the level of the twelfth rib, is lower than the left.
thra (Fig. 49.1). Urine is formed in the kidneys, drains through An adrenal gland lies on top of each kidney.
the ureters to be stored in the bladder, and then passes out of the Each kidney is surrounded by a significant amount of fat and
body through the urethra. connective tissue that cushion, support, and help the kidney to
maintain its position. A thin, smooth layer of fibrous membrane
Kidneys called the capsule covers the surface of each kidney. The capsule
The kidneys are the principal organs of the urinary system. The protects the kidney and serves as a shock absorber if this area
primary functions of the kidneys are to (1) regulate the volume is traumatized from a sudden force or strike. The hilus on the
and composition of extracellular fluid (ECF) and (2) excrete medial side of the kidney serves as the entry site for the renal
waste products from the body. The kidneys also function to artery and nerves and as the exit site for the renal vein and ureter.
1177
,1178 SECTION 10 Problems of Urinary Function
Inferior
Diaphragm to the bladder. The renal pelvis can store a small volume of urine
vena cava Left adrenal (3 to 5 mL).
gland
Right
adrenal
Microstructure
gland Left renal The nephron is the functional unit of the kidney. Each kidney
artery
Right renal and vein
has around 1 million nephrons. Each nephron is composed of
artery the glomerulus, Bowman capsule, and a tubular system. The
and vein tubular system consists of the proximal convoluted tubule,
Right Left kidney
Aorta
loop of Henle, distal convoluted tubule, and collecting tubules
kidney
Left ureter (Fig. 49.3). The glomerulus, Bowman capsule, proximal tubule,
Right ureter and distal tubule are in the cortex of the kidney. The loop of
Left common
Psoas iliac artery Henle and collecting tubules are in the medulla. Several collect-
muscle and vein ing tubules join to form a single collecting duct. The collect-
ing ducts eventually merge into a pyramid that empties via the
Sigmoid papilla into a minor calyx.
colon
Urinary bladder
Urethra Blood Supply
A
Blood flow to the kidneys, around 1200 mL/min, accounts for
20% to 25% of the cardiac output. Blood reaches the kidneys
Male Female
via the renal artery, which arises from the aorta and enters the
kidney through the hilus. The renal artery divides into second-
ary branches and then into still smaller branches, each of which
forms an afferent arteriole. The afferent arteriole divides into a
capillary network, the glomerulus, which is a collection of up
to 50 capillaries (Fig. 49.3). The capillaries of the glomerulus
unite in the efferent arteriole. This efferent arteriole splits to
form a capillary network, the peritubular capillaries, which sur-
B C round the tubular system. All peritubular capillaries drain into
the venous system. The renal vein empties into the inferior vena
Fig. 49.1 Organs of the urinary system. (A) Upper urinary tract in rela- cava.
tion to other anatomic structures. (B) Male urethra in relation to other
pelvic structures. (C) Female urethra.
Physiology of Urine Formation
Urine formation is the outcome of a complex, multistep pro-
Renal column cess of filtration, reabsorption, secretion, and excretion of water,
Fibrous electrolytes, and metabolic waste products. Although urine for-
capsule mation is the result of this process, the primary functions of the
Renal
Calyx pyramid kidneys are to filter the blood and maintain the body’s internal
homeostasis.
Renal
pelvis
Renal artery Glomerular function. Urine formation begins at the glome
rulus, where blood is filtered. The glomerulus is a semipermeable
Renal
papilla membrane that allows filtration (Fig. 49.3). The hydrostatic
pressure of the blood within the glomerular capillaries causes
Medulla
a portion of blood to be filtered across the semipermeable
Renal vein membrane into Bowman capsule. There, the filtered portion
Cortex
of the blood (glomerular filtrate) begins to pass down to the
Ureter
tubule. Filtration is more rapid in the glomerulus than in
ordinary tissue capillaries because the glomerular membrane
Fig. 49.2 Longitudinal section of the kidney. is porous. The glomerular filtrate is similar in composition to
blood except that it lacks blood cells, platelets, and large plasma
The parenchyma is the actual tissue of the kidney (Fig. 49.2). proteins. Under normal conditions, capillary pores are too small
The outer layer of the parenchyma is the cortex. The inner layer is to allow the loss of these large blood components. However, in
the medulla. The medulla consists of a number of pyramids. The many kidney diseases, capillary permeability increases, which
apices (tops) of these pyramids are the papillae, through which allows plasma proteins and blood cells to pass into the urine.
urine passes to enter the calyces. The minor calyces widen and The amount of blood filtered each minute by the glomer-
merge to form major calyces, which form a funnel-shaped sac uli is the glomerular filtration rate (GFR). The normal GFR
called the renal pelvis. The minor and major calyces transport is about 125 mL/min. The peritubular capillary network reab-
urine to the renal pelvis, from there it drains through the ureter sorbs most of the glomerular filtrate before it reaches the end
, CHAPTER 49 Assessment: Urinary System 1179
Renal Glomerulus
corpuscle Bowman
capsule
Proximal
convoluted Distal
tubule convoluted
tubule
Descending
limb of Henle Cortex
Renal
tubule Medulla
Thick ascending
limb of Henle
Collecting
Henle loop duct
Thin ascending
limb of Henle
Papillary
duct
Fig. 49.3 The nephron is the basic functional unit of the kidney. This illustration of a single nephron unit
shows the surrounding blood vessels. (Modified from Thibodeau GA, Patton KT: The human body in health
and disease, ed 4, St Louis, 2005, Mosby.)
In the proximal convoluted tubule, about 80% of the electro-
TABLE 49.1 Functions of Nephron
lytes are reabsorbed. Normally, this includes all glucose, amino
Segments
acids, and small proteins. As reabsorption continues in the loop
Segment Function of Henle, water is conserved, which is important for concentrat-
Glomerulus Selective filtration ing the filtrate. The descending loop is permeable to water and
Proximal tubule Reabsorption of 80% of electrolytes and water, glucose, moderately permeable to sodium, urea, and other solutes. In
amino acids, HCO3− the ascending limb, chloride ions (Cl−) are actively reabsorbed,
Secretion of H+ and creatinine
followed by passive reabsorption of sodium ions (Na+). About
Loop of Henle Concentration of filtrate
Reabsorption of Na+ and Cl− in ascending limb and water
25% of the filtered sodium is reabsorbed in the ascending limb.
in descending loop Two key functions of the distal convoluted tubules are final
Distal tubule Reabsorption of water (regulated by ADH) and HCO3− regulation of water balance and acid-base balance. Antidiuretic
Regulation of Ca2+ and PO42—by parathyroid hormone hormone (ADH) is needed for water reabsorption in the kid-
Regulation of Na+ and K+ by aldosterone ney. It is important in water balance. ADH makes the distal con-
Secretion of K+, H+, ammonia voluted tubules and collecting ducts permeable to water. This
Collecting duct Reabsorption of water (requires ADH) allows water to be reabsorbed into the peritubular capillaries
and eventually returned to the circulation.
Osmoreceptors in the anterior hypothalamus detect
decreases in plasma osmolality. These osmoreceptors send neu-
of the collecting duct. Therefore only 1 mL/min (on average) is ral input to superoptic nuclei cells in the hypothalamus. These
excreted as urine. superoptic nuclei cells have neuronal axons that end in the
Tubular function. The tubules and collecting ducts are posterior pituitary gland and act to inhibit ADH secretion. In
responsible for the reabsorption of essential materials and the absence of ADH, the tubules are essentially impermeable to
excretion of nonessential ones (Table 49.1). They carry out these water. Thus, any water in the tubules leaves the body as urine.
functions by reabsorption and secretion. Reabsorption is the Aldosterone (released from the adrenal cortex) acts on
passage of a substance from the lumen of the tubules through the distal tubule to cause reabsorption of Na+ and water. In
the tubule cells and into the capillaries. This process involves exchange for Na+, potassium ions (K+) are excreted. Circulating
both active and passive transport mechanisms. Tubular secretion blood volume and plasma concentrations of Na+ and K+ influ-
is the passage of a substance from the capillaries through ence aldosterone secretion.
the tubular cells into the lumen of the tubule. Reabsorption Acid-base regulation involves reabsorbing and conserving
and secretion cause many changes in the composition of the most of the bicarbonate (HCO3−) and secreting excess hydrogen
glomerular filtrate as it moves through the entire length of the ions (H+). The distal tubule has different ways to keep the pH of
tubule. ECF within a range of 7.35 to 7.45 (see Chapter 17).
