Week 13: Urinalysis
Reabsorption and secretion take place along the different segments of the nephron. Reabsorption in the distal convoluted tubule is controlled by which hormones? Select all that apply.
-Aldosterone -Antidiuretic hormone
In addition to urinalysis, blood analysis is also important when diagnosing renal disease. Which of the following would be suggestive of renal disease or renal failure if present in the blood at higher than normal levels?
-Creatinine -blood K+ -BUN (blood urea nitrogen)
Filtration, reabsorption, and secretion are the three physiological processes that occur within the nephrons of the kidneys to produce urine. Which of the following statements are FALSE regarding the production of urine? Select all that apply. -The amount of fluids ingested affects the volume of the urine excreted. -The composition of urine can change daily. -If materials do not leave blood at the glomerulus, it can never be part of the filtrate. -Urine always has a pHpH of 6.0. -About 180 liters of filtrate are formed by the glomeruli per day.
-If materials do not leave blood at the glomerulus, it can never be part of the filtrate. -Urine always has a pH of 6.0.
The kidneys filter the blood plasma to maintain the chemical balance of body fluids. Which of the following are normal components of urine? Select all that apply.
-Water -Urea -Creatinine
Drag and drop the abnormal urinary condition at the left to match the appropriate description at the right. Drag the terms on the left to the appropriate blanks on the right to complete the sentences.
1. This indicates the presence of red blood cells in the urine: Hematuria 2. This condition could indicate a problem with glomerular filtration: Albuminuria 3. This condition could occur temporarily after a high-carbohydrate meal: Glucosuria 4. This condition could indicate liver disease: Bilirubinuria 5. This condition could occur during a period of starvation: Ketonuria 6. This indicates the presence of leukocytes and pus in the urine: Pyuria
Using the image below, identify the specific gravity of the sample in the urinometer.
1.017 In this figure, the lower meniscus is between 1.010- 1.020 and accurately near 1.017
Which of the following is the net filtration pressure (NFP) in the kidney if the glomerular hydrostatic pressure (GHP) = 45 mm Hg, the blood colloid osmotic pressure (BCOP) = 20 mm Hg, and the capsular hydrostatic pressure (CsHP) = 10 mm Hg?
15 mm Hg GHP - (BCOP + CsHP)
Let's review the functional anatomy of the nephron. Select the correct function for each segment of the nephron
A : Site of filtration; materials enter the filtrate of the nephron from the blood E : Functions to eliminate urine from the nephron; important site for water reabsorption when ADH is released C : Important in countercurrent mechanism to establish an osmotic gradient in the interstitial fluid of the medulla of the kidney B : Main site of reabsorption; most materials enter the blood from the filtrate D : Final site of processing (reabsorption and secretion) before filtrate enters the collecting duct.
Antidiuretic hormone (ADH) regulates the formation of concentrated or dilute urine. In which time period is Max's body secreting its highest amount of ADH? Explain your answer.
ADH is going to be highest when the body is most dehydrated. In Max's case, this is right after his 2-hour run. During his run, Max loses water via sweat and exhalation, and doesn't effectively replace it. The osmolality of his blood increases, signaling the posterior pituitary to release ADH. ADH targets the principle cells in the collecting ducts of the kidney tubules, causing them to increase reabsorption of water from the filtrate. This negative feedback mechanism attempts to conserve water in order to decrease blood osmolality and restore body fluid homeostasis.
Which of the following conditions is most likely to result in a urine sample with a specific gravity of 1.005?
Adequate hydration Adequate hydration results in lighter colored urine with a low specific gravity.
Urinalysis can also provide information regarding renal function. Which urinalysis would suggest possible renal damage or failure (it would be in the urine if the kidneys were not functioning normally)?
Albuminuria
An easy and inexpensive test used to assess kidney function is a urinalysis. A urine sample is taken from the patient and examined for any abnormal components. Match each abnormal component with its clinical term.
Albuminuria : The presence of albumin, or protein, in the urine Hematuria : The presence of blood in the urine Pyuria : The presence of white blood cells and pus in the urine Ketonuria : The presence of ketones in the urine Glycosuria : The presence of glucose (sugar) in the urine
Complete the sentences on the right with the terms on the left.
At the glomerulus, blood pressure forces water, ions, and other solutes out of the blood and into the capsular space in a process called filtration. Cells in the renal tubule reclaim materials needed by the body in a process called reabsorption. Unneeded materials that were not removed at the glomerulus leave the blood in a process called secretion. You are examining a urine sample that is amber in color. The color is due to urochrome. A patient, with undiagnosed diabetes mellitus and exhibiting signs of ketosis, submits a urine sample. You would expect to find ketones in the urine. Glucosuria is indicated by high levels of glucose in the urine. A patient with high blood pressure submits a urine sample with high levels of albumin. This condition is called albuminuria. Hematuria is usually an indication of bleeding possibly caused by inflammation or urinary tract infection. Urobilinogen in the urine is called urobilinogenuria. Pyuria is indicated when leukocytes are in the urine.
Clinical Scenario: The Nephron and Analysis of Common Kidney Disorders
Barry Wells is a 35-year-old male who has come to the emergency room complaining of an intermittent sharp pain in his lower right abdomen, which radiates to his right testicle. He is nauseated and noticed that his urine stream decreases while urinating. He also mentions that his urine has a pinkish color to it. Blood work and a urinalysis are ordered.
Drag and drop the correct terms on the left to complete the sentences. Words may be used once, more than once, or not at all.
During Tubular secretion substances are selectively moved from the blood into the filtrate. Solutes are returned to the blood during Tubular reabsorption. Small substances are passively moved from the blood to the filtrate in Glomerular filtration.
Max needs to drink more water before exercise to avoid dehydration.
False Max's urinalysis data indicate that his urine is already dilute (pale yellow with low specific gravity). If he drinks more water, the kidneys will simply eliminate it, further diluting the urine and possibly causing him to stop to urinate during the race.
Max is curious about the protein content of his urine. Which of these statements provides an accurate basis for Tracey's response, explaining normal conditions?
Few proteins are small enough to pass through the glomerular membrane, but the few that do are reabsorbed. So, proteins are not usually present in urine.
Tracey had been slightly concerned about the trace glucose that was found in Max's urine six hours after his exercise until she discovered that he had eaten an entire large pizza an hour before the urinalysis. Explain why glucose might show up in Max's urine after a particularly heavy meal.
Glucose passes easily through the glomerular filtration membrane, and normally 100% of it is reabsorbed in the proximal convoluted tubule (PCT). The reabsorption of glucose is accomplished by secondary active transport and requires a transport protein in the membrane to facilitate the movement of glucose across the membrane. Typically, there are more than enough of these transport proteins, but they do have an upper limit beyond which no more glucose can be transported. This is called the transport maximum (Tm) for glucose. Generally, the Tm for glucose is not reached until blood levels of glucose exceed 180 mg/dL, which is known as the renal threshold. The most common cause of hyperglycemia (high blood glucose) is diabetes mellitus. So, if the renal threshold is exceeded for glucose in the PCT, it will "spill" into the filtrate and be eliminated in urine. Without further testing, it's unknown whether Max has a lower-than-normal renal threshold for glucose, or has exceeded the normal renal threshold of 180 mg/dL with his heavy meal.
Which urinalysis result would be a positive indicator of a kidney stone?
Hematuria Kidney stones are due to the formation of crystal deposits in the kidney. When these deposits come in contact with the lining of the urinary tract, they can cut into it and bleeding occurs. Kidney stones are very painful, and they must be eliminated or they could obstruct urine excretion.
Match these vocabulary terms to their meanings.
Interstitial fluid makes up about 80% of extracellular fluid. Hyponatremia, a lower than normal sodium level, can cause dysfunction of the nervous system. Alkalosis is a condition in which blood pH has risen above 7.45. During hyperventilation, increased breathing rate and depth of breathing go beyond the body 19s need to remove carbon dioxide. Fluids inside cells make up the intracellular fluid fraction of total body water.
Clinical Case Study: Max's Maximum: A Case Study on the Urinary System
It took the diagnosis of high blood pressure (hypertension) at the age of 45 to shock Max into taking better care of himself. A former college football player, he had let himself go, eating too much junk food, drinking too much alcohol, sitting on his chubby bottom for the majority of the last two decades, and even indulging in the frequent habit of smoking cigars. Max's physician had to prescribe two different antihypertensive medications in order to get his blood pressure under control. She also prescribed regular exercise, a low-salt diet, modest alcohol intake, and smoking cessation. Max was scared, really scared. His father had hypertension at a young age as well, and ended up on dialysis before dying from complications of kidney failure. Fortunately for Max, he took his doctor's advice and began a dramatic lifestyle change that would bring him to his present-day situation. Now, at the age of 55, he was a master triathlon athlete who routinely placed among the top five tri-athletes of the same age group in the country. Max's competitive spirit had been ignited by this, but at the same time he wanted to be first among his peers. To that end, he hired Tracey, a Certified Clinical Exercise Specialist, to help him gain the edge he needed to win at the end of the race. His most immediate concern was that he was experiencing problems with dehydration and fatigue because he hadn't found an effective way to drink enough fluids while exercising. Tracey showed Max an impressive array of assessment tools for quantifying and analyzing his physiological state before, during, and after his workouts. One of the tools was urinalysis, which Max found a bit odd, but he dutifully supplied urine samples on a regular, prescribed basis. Tracey explained that Max's hydration status was tricky due to the medication he took to control his hypertension, and that renal status (as measured in the urinalysis) was one of the tools she could use to evaluate his physiological state. Tracey logs the following results of Max's urinalysis immediately after, and six hours after, a rigorous 2-hour run.
A woman with diabetes mellitus has been dieting for several months and has lost more than 25 lbslbs. At her annual medical checkup, a urinalysis is performed. What would you expect to find in her urine?
Ketones
Lactic acid accumulation can be a consequence of intense exercise. Tracey notes that Max's kidneys are working to defend his body against acidosis. How can she tell? Describe this mechanism.
Max's pH is more acidic right after his run. This is evidence of a higher hydrogen concentration in urine. When pH drops, the tubule cells secrete hydrogen into the filtrate, allowing it to be lost in urine. They also reabsorb bicarbonate (a base) to help buffer the body fluids. The result is a restoration of normal pH.
What does the color of Max's urine tell Tracey about how concentrated or dilute it is? How does Max's urine color/concentration compare to the urine specific gravity at the same time?
Max's pale urine tells Tracey that his urine is diluted. The yellow urine is more concentrated, and the dark yellow urine is super concentrated. Specific gravity is the ratio of the density of a substance compared to the density of an equal volume of distilled water. Urine, with its various solutes, has a greater specific gravity than water which is (1.001-1.035), and depending on the concentration of the solute it can vary. The more concentrated the urine, the darker the color will be and specific gravity will be higher.
Based on Max's urinalysis data, should he drink more water prior to exercise to ensure that he doesn't dehydrate during intense activity? Explain your answer.
Max's urine is already extremely dilute before exercise, indicating he is probably well hydrated. If he were to drink more, then he would simply end up with a full bladder during his run (the kidneys would eliminate the excess water). Better advice would be to drink more strategically during his run. For instance, when he is doing his training runs, Max could take a drink every 15 minutes (more if he is sweating heavily) and practice different drinking regimens when he trains until he finds one that keeps him hydrated but does not require him to stop to urinate during his run.
Given the correlation between urine color and urine concentration, which of the following statements is true about Max's urine?
Max's urine is most dilute before exercise. The pale yellow urine and low specific gravity before exercise indicate that the kidneys are producing larger quantities of dilute urine.
Drag and drop the terms at the left to match the appropriate descriptions at the right.
Molecule from breakdown of hemoglobin: Bilirubin Yellow pigment in urine: Urochrome Excess albumin in urine: Albuminuria Leukocytes in urine: Pyuria Glucose in urine: Glucosuria Addition of materials to filtrate: Secretion Kidney stones: Renal calculi Blood in urine: Hematuria
How will the filtration rate in the renal corpuscles be affected if a kidney stone creates a blockage of the urinary tract?
Net filtration rate will decrease as capsular hydrostatic pressure increases.
Urinalysis revealed that a patient's urine had a pH of 4.0 and contained numerous casts and albumin. Which of the following is a likely recommendation from a doctor?
Patient should reduce protein intake.
Determine whether the following tests were positive or negative for the indicated substances on the pictured combination dipstick.
Positive: protein, ketone, leukocyte Negative: Glucose, blood
Tracey explains to Max that his transiently elevated blood glucose leads to "spilling" of glucose into his urine. Why does this happen?
Reabsorption of glucose is limited by transport proteins. Glucose passes freely through the glomerular filter and is usually 100% reabsorbed in the proximal convoluted tubules via transport proteins. However, the transporters have a set cumulative transport maximum beyond which they cannot reabsorb glucose. So, when blood glucose levels are high, too much glucose enters the tubules and some remains in the filtrate to be eliminated in urine.
Drag and drop the terms at the left to match the appropriate descriptions at the right.
Removal of materials from blood: Filtration Returning of materials from filtrate to blood: Reabsorption Product of bilirubin breakdown: Urobilinogen Fluid in the minor calyx of kidney: Urine Fluid passing through nephron tubules: Filtrate Removal of ammonia from amino acid: Deamination Product of fat metabolism: Ketone
A patient arrives at the Emergency Room with severe abdominal pain. The attending physician sends her for an ultrasound. The results indicate that she has a blockage in her left ureter and she is sent home with pain medication and advised to see a urologist if the pain continues. The pain does continue and the urologist schedules the patient for lithotripsy. What is the problem with the patient?
Renal calculi Renal calculi, also known as kidney stones, are solid pebbles of urinary salts containing calcium, magnesium, or uric acid. These calculi can occur in the kidneys, ureters, bladder, or urethra and may cause severe pain. If the calculi completely blocks the urinary tract and can't pass on its own, it must be removed either by surgery or lithotripsy.
What characteristic of urine is measured with the specific gravity test?
Solute concentration
Tracey knows that proteinuria (protein in the urine) after intense exercise is physiological (normal). However, protein is typically not present in urine. Why is that?
The glomerulus is a passive filter that acts as a barrier to larger molecules, such as most plasma proteins. Also, because most proteins carry a net negative charge, they are repelled by the membrane, thereby hindering their passage. However, some smaller proteins can and do pass through the filtration membrane. Most of them are reabsorbed in the proximal convoluted tubule by endocytosis and then broken down into amino acids to be returned to the blood in the peritubular capillaries. The mechanism of exercise-induced proteinuria is unclear, but it is typically a transient occurrence. Any kidney disease can render the glomerulus dysfunctional, leading to a more sustained proteinuria. In fact, Max's hypertension, if left unchecked, could damage the filtration membrane of the glomerulus. The proteinuria will increase the specific gravity of his urine (along with his relative dehydration).
Tracey knows that the large pizza Max consumed just prior to collecting his third urine sample caused a transient increase in his blood glucose levels. What can be accurately said about the relationship between glucose in the blood and the amount of glucose filtered through the glomerular membrane?
The higher the blood glucose concentration, the more glucose is filtered through the glomerular membrane.
Mike and Fred have been hiking in the desert all afternoon. While on the trail, Fred drinks much more water than Mike. If urine samples were collected from both men, what differences in specific gravity of the samples would you expect to measure?
The sample from Fred will have a lower specific gravity.
Match these prefixes and suffixes to their meanings.
The word root hypo- means under, beneath, or less than normal. The word root inter- means occurring between, among, or reciprocal. The word root -osis means action, process, or condition. The word root hyper- means over, above, or excessive. The word root intra- means within, during, or internal.
Why is urinalysis a useful diagnostic tool for identifying certain diseases and infections?
There are many parameters of urine that can be quickly and easily tested.
Which of the following is NOT an abnormal component of urine? -Glucose -White blood cells -Albumin -Urea
Urea
Which of the following is a likely cause for above-normal amount of crystals in the urine?
Urinary tract infection
Which of the following is most likely to cause renal tubular alkalosis?
Urinary tract infection
Why is it important to follow strict safety procedures (e.g., universal precautions) when handling a urine sample?
Urine is a body fluid and might contain pathogens.
Based on the urine color and specific gravity, what might Tracey conclude about the hydration status of Max's body at the three different times?
When Max's urine is pale with a low specific gravity, his body is likely to be well hydrated; the kidneys are reabsorbing less water, allowing it to be eliminated in urine. When his urine is dark yellow with a higher specific gravity, his kidneys are concentrating urine and reabsorbing more water in an attempt to maintain body fluid homeostasis (defend plasma osmolality). Dehydration will trigger this response. The yellow urine signals euhydration; the corresponding high-normal specific gravity is likely due to the small amount of glucose in the urine.
Antidiuretic hormone (ADH), which regulates urine concentration and dilution, is __________.
lowest before Max exercises ADH is secreted in response to dehydration, as signaled by high blood osmolality. Max's data indicate that his body is well hydrated before exercise, so ADH secretion is lowest at that time.
During strenuous exercise, Max's body produces lactic acid and his blood pH begins to decline. His kidneys go to work to preserve acid-base balance by doing all of the following EXCEPT __________. -generating new bicarbonate -reabsorbing hydrogen -secreting hydrogen -reabsorbing bicarbonate
reabsorbing hydrogen
Max's regular exercise regimen has reduced his high blood pressure, allowing him to achieve normal blood pressure on a single antihypertensive medication. The medication he takes is called an angiotensin converting enzyme inhibitor, or ACE inhibitor, which blocks the activation of angiotensin II. Describe at least two mechanisms by which angiotensin II targets the kidneys to increase extracellular fluid volume and, therefore, increase blood pressure.
• Angiotensin II directly signals the renal tubules to reabsorb sodium. Where sodium goes, water follows by osmosis, causing blood volume and pressure to increase. • Angiotensin II signals the release of ADH from the posterior pituitary. ADH acts on the principle cells of the collecting ducts to cause reabsorption of water from the filtrate into the blood. Blood volume and pressure are increased. • Angiotensin II is a potent vasoconstrictor, which leads to a decline in peritubular capillary hydrostatic pressure and more fluid reabsorption. Blood volume and pressure are increased. • Angiotensin II prompts the release of aldosterone from the adrenal medulla. Aldosterone stimulates renal tubules to reabsorb sodium (with water following) and this leads to an increase in blood volume and pressure. • Angiotensin II stimulates the glomerular mesangial cells to contract and reduce glomerular filtration rates. Less filtrate is produced, less fluid is lost in urine, and blood volume and pressure are increased. • Angiotensin II triggers thirst by acting at the hypothalamus. This increases blood volume and blood pressure.
