Transcript Answer - Lecom

Acute Renal Failure
Darren Dreyfus, D.O.
Associates In Nephrology, P.C.
St. Vincent’s Health System
Question 1
Question 1
A previously healthy 74-year-old man is hospitalized
with cough and chest pain. On physical
examination, the blood pressure is 148/92 mm Hg,
heart rate is 74/min, respiration rate is 18/min,
and temperature is 37.8 oC (100 oF). The left lower
lung field has scattered basilar crackles. The
hematocrit is 34% and leukocytosis is present.
The serum creatinine concentration is 2.3 mg/dL.
Urinalysis shows a pH of 6.0, 1+ proteinuria, and
no hematuria or ketonuria.
Question 1
Which of the following is most useful in
distinguishing acute from chronic renal failure in
this patient?
(A)
(B)
(C)
(D)
(E)
A previous hematocrit
A previous serum creatinine concentration
Blood urea nitrogen to creatinine ratio
Microscopic urinalysis
Renal ultrasonography
Answer
Question 1 - Answer
Answer: B
Although many evaluations remain to be performed
to establish a diagnosis in this patient with a
decreased glomerular filtration rate, the first step
must be to determine whether he has a history of
renal insufficiency.
This allows the clinician to distinguish between acute
and chronic renal failure
A previously elevated serum creatinine concentration
can establish the diagnosis of chronic renal
disease.
Question 1 - Answer
Ultrasonography provides information on size and symmetry
of the kidneys and evidence for obstruction including
hydronephrosis; however, renal ultrasonography may be
normal in the presence of mild chronic renal disease.
The ratio of blood urea nitrogen to creatinine is not diagnostic
of renal disease but when elevated suggests the possibility
of pre-renal azotemia.
The previous hematocrit may suggest chronic renal disease,
but it is also not diagnostic.
The urinalysis may be helpful in establishing the nature of the
renal insufficiency but not its chronicity.
Question 2
Question 2
A 62-year-old man with a nonhealing diabetic
ulcer is evaluated for preoperative
clearance. He has a 10-year history of
diabetes, hypertension, and severe
peripheral vascular disease. He received
insulin, amlodipine, and aspirin.
On physical examination, blood pressure is
140/90 mm Hg. No cardiopulmonary
abnormality or volume overload is detected.
Question 2
Which of the following is the most appropriate
method to evaluate this patient’s renal
function?
(A) A 24-hour urine collection for creatinine
and volume
(B) Estimate creatinine clearance with a
creatinine-based formula
(C) Measure the fractional excretion of sodium
(D) Measure the serum creatinine
Answer
Question 2 - Answer
The staging of chronic kidney disease is based on
the glomerular filtration rate. The estimated
glomerular filtration rate is therefore paramount
for correct diagnosis and treatment.
To minimize error and ensure widespread availability,
the National Kidney Foundation suggests using
creatinine-based formulae to estimate the
glomerular filtration rate, such as the CockcroftGault formula or the formula derived from the
Modification of Diet in Renal Disease (MDRD)
study.
Question 2 - Answer
Answer: B
The serum creatinine concentration alone is not
recommended for estimation of the glomerular filtration
rate, but is a useful tool to monitor progression of chronic
renal failure.
This concentration represents the balance between
production of creatinine, which is relatively constant, and
elimination through glomerular filtration, tubular secretion,
and nonrenal pathways (usually negligible in healthy
persons).
Muscle mass; comorbid conditions, such as malnutrition; and
amputations can cause the serum creatinine concentration
and the glomerular filtration rate to lower than expected
for the degree of actual renal insufficiency.
Question 2 - Answer
A 24-hour urine collection by itself is not useful but
when used to calculate a creatinine clearance can
provide an acceptable estimate of glomerular
function; however, daily and diurnal variation in
creatinine excretion and problems with collection
can cause error in the estimate of glomerular
filtration rate.
The fractional excretion of sodium is not useful in
estimating the glomerular filtration rate but is
useful in the diagnosis of pre-renal azotemia in an
oliguric patient.
Question 3
Question 3
A 65-year-old man is admitted to the hospital
because of fever and dysuria.
Laboratory studies show a leukocyte count of
12,000/uL, a blood urea nitrogen level of 24
mg/dL, a serum creatinine concentration of 1.4
mg/dL, and pyuria.
Empiric treatment with TMP is started. Three days
later, the pyuria and fever have resolved.
The leukocyte count is 10,000/uL, BUN is 24, and
serum creatinine is 1.8 mg/dL. Urinalysis shows
not leukocytes, casts, or crystals.
Question 3
Which of the following is most likely the
explanation for the rise in the serum
creatinine from 1.4 mg/dL to 1.8 mg/dL?
(A) Acute interstitial nephritis
(B) Acute phyelonephritis
(C) Acute tubular necrosis
(D) Obstructive uropathy
(E) Reduced creatinine excretion
Answer
Question 3 - Answer
Answer: E
Trimethoprim and other organic cations, such as
cimetidine, competitively inhibit creatinine
secretion in the distal tubule.
Although acute interstitial nephritis can occur
secondary to treatment with TMP, it takes several
days to evolve and is less commonly seen in the
absence of other systemic allergic symptoms, such
as eosinophils in the urine, rash, and fever.
Acute phyelonephritis is not likely, given that
systemic symptoms resolved.
Question 3 - Answer
Obstructive uropathy can occur; however, it causes
the glomerular filtration rate to decrease and,
therefore, the BUN level would be elevated.
Unlike aminoglycosides or amphotericin B, TMP has
not been associated with acute tubular necrosis
and there is no evidence of acute tubular necrosis
in the urinalysis such as muddy brown casts or
renal tubular epithelial cells.
Question 4
Question 4
A 49-year-old man is evaluated because of dyspnea
and hemoptysis of 3 days’ duration. He has had no
fever or chills. He takes no medications.
On examination, blood pressure is 155/88 mm Hg,
pulse rate is 90/min, respiratory rate is 18/min,
and temperature is 37 oC (98.6 oF). Pulmonary
examination reveals coarse crackles in the right
mid-lung field. The remainder of the examination
is normal.
Question 4
Leukocyte count – 9200/uL
Hemoglobin – 8.7 g/dL
Serum creatinine – 4.4 mg/dL (1.3 mg/dL 3
months ago)
24-hour urine protein – 3.5 g
Urinalysis – 4+ proteinuria, 3+
hemoglobinuria
Question 4
Urine microscopy shows 25 to 50
erythrocytes/hpf, 5 to 1 leukocytes/hpf,
dysmorphic erythrocytes, and erythrocyte
casts. Kidney biopsy reveals proliferative
glomerulonephritis with 50% of glomeruli
having crescents. Immunofluorescence
shows linear staining with IgG.
Question 4
Which of the following provides the best
description of his diagnosis?
(A) Acute interstitial nephritis
(B) Acute tubular necrosis
(C) Chronic renal failure
(D) Rapidly progressive glomerulonephritis
Answer
Question 4 - Answer
Answer: D
The patient’s renal presentation is rapidly
progressive glomerulonephritis which consists of
glomerulonephritis with nephritic urine sediment,
acute renal failure developing over a few days to
weeks, and glomerular crescents on renal biopsy.
In view of the immunoflourescence noted on renal
biopsy, the most likely diagnosis is Goodpasture’s
disease.
Question 4 - Answer
Acute interstitial nephritis is unlikely based upon the
apparent lack of an inciting agent, such as an
antibiotic, lack of fever and rash, and a biopsy
finding that clearly shows a glomerular injury.
The patient has acute renal failure, but acute tubular
necrosis would not produce a nephritic sediment.
Chronic renal failure is not likely based upon a
normal creatinine 3 months ago.
Question 5
Question 5
A 43-year-old man is evaluated because of
hemoptysis for 3 days’ duration. On
examination, blood pressure is 155/72
mmHg, pulse rate is 90/min, respiration rate
is 18/min, temperature is 37 oC (98.6 oF).
Pulmonary examination reveals coarse
crackles in the right mid-lung field. The
remainder of the examination is normal.
Question 5
Leukocyte count – 9200/uL
Hemoglobin – 8.7 g/dL
Serum creatinine – 4.4 mg/dL (1.0 mg/dL 1
month ago)
24-hour urine protein – 3.5 g
Urinalysis – 4+ proteinuria, 3+
hemoglobinuria, and erythrocyte casts
Question 5
Which of the following tests would most likely
confirm the diagnosis of Goodpasture’s disease?
(A) Antinuclear antibody
(B) c-ANCA
(C) p-ANCA
(D) Circulating antiglomerular basement antibody
(E) Serum C3 and C4 levels
Answer
Question 5 - Answer
Answer: D
The syndrome of hemoptysis and rapidly progressive
renal failure due to a glomerulonephritis makes
Goodpasture’s syndrome the most likely diagnosis.
In the differential diagnosis of rapidly progressive
glomerulonephritis are lupus nephritis, Wegener’s
granulomatosis, and infection-associated
glomerulonephritis.
However, only Goodpasture’s disease is associated
with circulating antiglomerular basement
membrane.
Question 5 - Answer
Therefore, finding a circulating antibody against
glomerular basement membrane in serum is most
consistent with Goodpasture’s syndrome and
makes the diagnosis almost certain.
A positive ANA and low serum complement support
the diagnosis of systemic lupus erythematosus
whereas c-ANCA correlates best with Wegener’s
granulomatosis and p-ANCA with microscopic
polyangiitis and Churg-Strauss syndrome.
Question 6
Question 6
A 71-year-old man with a 4-month history of nonHodgkin’s lymphoma is evaluated in the
emergency department because of polyuria,
weakness, and lassitude of 3 days’ duration. His
cancer was treated with rituximab,
cyclosphosphamide, prednisone, vincristine, and
doxorubicin, followed by radiation therapy.
On physical examination, blood pressure is 124/78
mm Hg, with no orthostatic changes, pulse rate is
96/min, respiration rate is 18/min, and
temperature is 36.8 oC (98.2 oF). The remainder of
the examination is unremarkable.
Question 6
The serum creatinine concentraion, previously
normal, is now 2.4 mg/dL. Urinalysis shows
a pH of 6.0 and 1+ proteinuria, but no
hematuria or ketonuria. No formed elements
appear on microscopic examination.
Question 6
Which of the following should be done next to
determine the cause of this patient’s renal
insufficiency?
(A) Calculate the ratio of blood urea nitrogen to
creatinine
(B) Radioisotope renal scan
(C) Renal biopsy
(D) Renal ultrasonography
(E) Volume repletion with .5 L of normal saline,
intravenously
Answer
Question 6 - Answer
Answer: D
There are several potential causes of acute renal failure
associated with cancer and its treatment.
The differential diagnosis in this case includes urinary tract
obstruction and radiation nephritis.
Urinary tract obstruction must be ruled out, especially in
patients with cancer of the genitourinary tract or pelvic
organs.
Lymphoma may involve the prostate and abdominal lymph or
pelvic lymphadenopathy may obstruct the outflow of the
bladder.
The ratio of blood urea nitrogen to creatinine is not a
sufficiently sensitive measure on which to base clinical
decision making in this case.
Question 6 - Answer
Renal scanning is most useful in evaluating
asymmetric blood flow and yields valuable
information in selected patients with evidence of
renal arterial disease, which is not a consideration
in this case.
There is no evidence of volume depletion, so
intravenous normal saline is not indicated.
Renal biopsy, even with its relatively low risk, is an
invasive procedure and is best deferred until later
in the course following a non-invasive evaluation.
Question 7
Question 7
A 56-year-old man is evaluated for anorexia
and a rash on his legs of 7 days’ duration.
One week ago he was hospitalized and
treated with intravenous penicillin for
pneumococcal pneumonia. He did well and
was sent home on the second day with a
prescription for a 10-day course of oral
penicillin. Serum creatinine concentration
was 0.9 mg/dL
Question 7
On physical examination today, his blood pressure is 130/90
mm Hg, with no orthostatic changes, pulse rate is 80/min,
respiration rate is 12/min, and temperature is 39.0 oC
(102.2 oF). A diffuse erythematous macular rash is found
on the lower extremities from the ankles to the thighs. The
remainder of the examination is normal.
Leukocyte count – 16,300/uL
BUN – 46 mg/dL
Serum creatinine – 3.4 mg/dL
Urinalysis – pH 6.0 specific gravity 1.014, 1+ proteinuria,
trace hematuria, no ketoneuria, 30 to 40 leukocytes/hpf
Question 7
Which of the following is the most likely
diagnosis?
(A) Acute interstitial nephritis
(B) Acute pyelonephritis
(C) Medium size-vessel vasculitits
(D) Membranous glomerulonephritis
(E) Rapidly progressive glomerulonephritis
Question 7 - Answer
Answer: A
The clinical course of new renal insufficiency with
pyuria after treatment with antibiotics is most
consistent with a diagnosis of acute interstitial
nephritis.
In many cases, renal dysfunction improves when the
offending agent is discontinued.
Vasculitis or rapidly progressive glomerulonephritis
might be considered a possibility but lacks
supporting evidence in finding no red blood cells
or casts in the urine.
Question 7 - Answer
Acute pyelonephritis does not usually cause
acute renal failure, particularly in the
absence of symptoms such as fever and
flank pain.
Membranous glomerulonephritis commonly
presents as the nephrotic syndrome, for
which there is no supporting evidence.
Question 8
Question 8
A 43-year-old woman with a 2-year history of HIV
infection is evaluated because of back pain and new
onset renal insufficiency of 30 hours’ duration.
Her HIV medications include zidovudine, lamivudine, and
indinavir.
Six months ago, she developed type 2 diabetes and
hypercholesterolemia and began treatment with
rosiglitazone and atorvastatin.
On physical examination, blood pressure is 130/85 mm
Hg, pulse rate is 88/min with no orthostatic changes,
and temperature is 37.8 oF (100 oF). Other than 2+
lower pedal edema, the remainder of the examination
is unremarkable.
Question 8
BUN – 22 mg/dL
Serum creatinine – 3.2 mg/dL (0.7 mg/dL 1
month ago)
Serum uric acid – 9.0 mg/dL
Microscopic and dipstick urinalysis – 3+ blood,
1+ protein by dipstick. Muddy brown casts
and tubular epithelial cells, but no
erythrocytes, leukocytes or crystalluria
Question 8
Which of the following is the most likely
diagnosis?
(A)
(B)
(C)
(D)
Diabetic nephropathy
HIV-associated nephropathy
Nephrolithiasis
Rhabdomyolysis
Answer
Question 8 - Answer
Answer: D
The hematuria on dipstick and lack of erythrocytes on
microscopy support a diagnosis of rhabdomyolysis.
The absences of urine crystals and erythrocytes argues
against indinavir crystal nephrolithiasis.
The absence of proteinuria argues against HIVassociated nephropathy and diabetic nephropathy.
In addition, the short history of diabetes is inconsistent
with a diagnosis of diabetic nephropathy which
typically complicates diabetes of more than 10 years’
duration.
Question 9
Question 9
A 58-year-old woman is evaluated because of
lethargy, mild nausea, and weakness for the
past 2 weeks. Three months ago, the
patient began taking oral calcium
(1500mg/d) and 25-hydroxyvitamin D as
treatment for osteoporosis. She has chronic
hypertension controlled with metoprolol and
asymptomatic pulmonary sarcoidosis.
Question 9
On examination, the blood pressure is 140/80 mm Hg, pulse
rate is 80/min, and temperature is 37 oC (98.6 oF). The
remainder of the physical examination is normal.
Hematocrit – 38%
BUN – 34 mg/dL
Serum creatinine – 2.2 mg/dL (1.0 mg/dL 3 months ago)
Serum calcium – 12.8 mg/dL
Serum phosphorus – 3.5 mg/dL
Urinalysis – pH 5.5; specific gravity 1.010; no protein, cells, or
casts
 Serum protein electrophoresis – Normal
 Urine immunoelectrophoresis - Normal






Answer
Question 9 - Answer
Answer: D
Hypercalcemia can cause acute renal failure by
interfering with renal concentrating function, leading
to volume depletion; calcium deposition in the renal
parenchyma, causing fibrosis and by direct
hemodynamic effects, causing afferent arterial
constriction.
In this patient, the latter cause is most likely.
Elevated levels of Vitamin D lead to hypercalcemia by
increasing calcium absorption of calcium from the gut.
This probably was exacerbated by her recent high
calcium and vitamin D dietary modifications.
Question 9 - Answer
Acute renal failure due to meyloma kidney is
always associated with abnormal light
chains and anemia would be expected.
The negative urinalysis excludes acute
interstitial nephritis and glomerular disease.
In the absence of hypertension, severe
bilateral renal arterial stenosis is unlikely.
Question 10
Question 10
A 35-year-old man with HIV infection
diagnosed 2 months ago is evaluated
because of fever and confusion for 1 day.
He is on no medications.
On physical examination, he is afebrile, blood
pressure is 110/70 mm Hg and pulse rate is
100/min. Other than confusion and bilateral
lower extremity edema, the remainder of
the examination is normal.
Question 10
Hemoglobin – 7.8 g/dL
Leukocyte count – 10,200/uL
Platelet count – 19,000/uL
BUN – 37 mg/dL
Serum creatinine – 2.7 mg/dL (1.0 mg/dL 2 months
ago)
Urinalysis – Specific gravity 1.030; 3+ hematuria,
trace proteinuria, trace ketonuria, no glucosuria.
Urine microscopy is normal.
Peripheral blood smear shows many schistocytes.
Question 10
Which of the following is the most likely cause
of his renal failure?
(A)
(B)
(C)
(D)
Acute tubular necrosis
HIV-associated nephropathy
Pyelonephritis
Thrombotic thrombocytopenic purpura
Answer
Question 10 - Answer
Answer: D
The course and laboratory findings are consistent
with thrombotic thrombocytopenic purpura, which
can be a complication of HIV infection.
A case series from France suggest that thrombotic
thrombocytopenic purpura is a common cause of
acute renal failure in HIV infected patients.
Plasma exchange is indicated, but a recent case
report suggests an important role for concurrent
administration of antiretroviral therapy to achieve
desired therapeutic outcomes.
Question 10 - Answer
Classic HIV-associated nephropathy is unlikely
in the absence of significant proteinuria.
The urinalysis is incompatible with acute
tubular necrosis or pyelonephritis.
None of these conditions are associated with
a microangiopathic hemolytic anemia or
thrombocytopenia.
Question 11
Question 11
A 70-year-old woman is evaluated because of
malaise and anorexia for 1 week. She has
hypertension treated with hydrochlorothiazide.
On physical examination, the supine blood pressure
is 150/95 mm Hg, pulse rate is 80/min, respiration
rate is 20/min, and temperature is 37.4 oC (99.3
oF). The blood pressure is 125/80 mm Hg and the
pulse rate 96/min while standing. The remainder
of the examination is unremarkable.
Question 11
Hematocrit – 29%
BUN – 62 mg/dL
Serum creatinine – 4.6 mg/dL
Serum sodium – 134 meq/L
Serum postassium – 5.0 meq/L
Serum chloride – 114 meq/L
Serum bicarbonate – 15 meq/L
Serum calcium – 12.5 mg/dL
Serum inorganic phosphate – 8.5 mg/dL
Urinalysis – Specific gravity 1.007; trace proteinuria; no
glycosuria or keonuria
Question 11
Which of the following is the most likely
diagnosis?
(A)
(B)
(C)
(D)
Hypercalcemia secondary to
hydrochlorothiazide therapy
Milk-alkali syndrome
Multiple myeloma
Primary hyperparathyroidism
Answer
Question 11 - Answer
Answer: C
The decreased anion gap in the presence of anemia,
proteinuria, and hypercalcemia, and acute renal failure
suggest multiple myeloma.
Acute renal failure is the initial presentation in as many as
one half of patients with multiple myeloma.
Except in multiple myeloma, hypercalcemia in the presence of
acute renal failure is relatively unusual because
hyperphosphatemia and a decrease in renal 1-alpha
hydroxylation of 25-hydroxycholecalciferol both act to
predispose to hypocalcemia.
Question 11 - Answer
Hypercalcemia may cause renal insufficiency through
several mechanisms, including hemodynamic
effects of vasoconstriction that mediate renal
sodium and water retention, and direct effects on
renal tubular sodium and water handling, resulting
in prerenal azotemia secondary to volume
depletion.
The hypercalcemia that characterizes the milk-alkali
syndrome is not associated with anemia or
proteinuria and is usually associated with
metabolic alkalosis.
Question 11 - Answer
Primary hyperparathyroidism should be
associated with hypophsphatemia and not
anemia or proteinuria.
Although hydrochlorothiazide toxicity can
present with volume depletion and prerenal
azotemia, the presence of hematologic and
metabolic complications makes this less
likely as a unifying diagnosis.
Question 12
Question 12
A 23-year-old previously healthy woman is
evaluated in the office because of 4 days of
fatigue, swelling of the feet and lower legs,
and red-brown urine.
She takes no medications.
On physical examination, her blood pressure
is 160/98 mm Hg, pulse is 92/min,
respiration rate is 12/min, and temperature
is 37.0 oC (98.6 oF).
Question 12
The only positive findings on physical
examination are her generally ill
appearance, periorbital edema and pitting
edema of the legs to just below the knee.
Laboratory testing reveals a serum creatinine
of 3.8 mg/dL.
The urine dipstick examination is positive for
blood.
Question 12
Which of the following is the most likely
diagnosis?
(A)
(B)
(C)
(D)
Acute
Acute
Acute
Acute
glomerulonephritis
interstitial nephritis
pyelonephritis
tubular necrosis
Answer
Question 12 - Answer
Answer: A
The urinalysis shows a red blood cell cast.
Casts are formed within the renal tubules and are
characteristically cylindrical with regular margins.
Red blood cell casts are red to brown in color and
contain uniformly small, round red blood cells.
Red blood cell casts are found almost exclusively in
the urine of patients with glomerulonephritis or
vasculitis.
Question 12 - Answer
Acute interstitial nephritis or pyelonephritis can be
associated with white blood cell casts.
Like red blood cell cats, leukocyte casts are
cylindrical with smooth margins but they are
composed of leukocytes rather than red blood
cells.
Leukocytes are larger than red blood cells, are not
red or brown in color, and have a granular
appearance.
Question 12 - Answer
Acute tubular necrosis can be associated with
muddy brown granular and epithelial casts.
These casts are pigmented and contain
granules or tubular epithelial cells which are
larger than leukocytes and contain a single,
centrally located, large nucleus.
End of Lecture
Thank you for your attendance.