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A 25-year-old woman presents with nausea and vomiting of 2 days duration. She is not on any medications and was previously well until now. Her physical examination is normal except for a postural drop in her blood pressure from 110/80 mm Hg supine to 90/80 mm Hg standing. Her serum electrolytes are sodium 130 mEq/L, potassium 3 mEq/L, chloride 90 mEq/L, bicarbonate 30 mEq/L, urea 50 mg/dL, and creatinine 0.8 mg/dL. Which of the following electrolytes is most likely to be filtered through the glomerulus but unaffected by tubular secretion?
Urea is filtered at the glomerulus, and thereafter, any movement in or out of tubules is a passive process depending on gradients, not secretion. Reabsorption of urea in the distal tubule and collecting duct, when urine flow is reduced, results in the disproportionate elevation of urea nitrogen over creatinine in prerenal azotemia.
Ten days after a kidney transplant, a 32-yearold man develops allograft enlargement, fever, oliguria, and hypertension. Which of the following is the most likely diagnosis?
Renal scans initially show a reduction in excretion with cortical retention. This is the most common type of rejection. Most acute rejections will respond to immunosuppressive agents if diagnosed early. In contrast, immediate nonfunction of a graft can be caused by damage to the kidney during procurement and storage. Such problems are becoming less frequent. Obstruction, vascular compression, and ureteral compression are other causes of primary nonfunction of a renal graft.
A 19-year-old man presents with malaise, nausea, and decreased urine output. He was previously well, and his physical examination is normal except for an elevated jugular venous pressure (JVP) and a pericardial rub. His electrolytes reveal acute renal failure (ARF). Which of the following findings on the urinalysis is most likely in keeping with acute glomerulonephritis (GN)?
Both granular and erythrocyte casts are present, but the latter indicate bleeding from the glomerulus and are most characteristically seen. Red cells reach the urine probably via capillary wall “gaps” and form casts as they become embedded in concentrated tubular fluid with high protein content. Proteinuria is invariably present but is not as specific.
A 24-year-old woman presents with nausea, vomiting, anorexia, and gross hematuria. She had a sore throat 2 weeks ago that resolved on its own. On examination, her blood pressure is 160/90 mm Hg, pulse 90/min, JVP is 7 cm, heart sounds are normal, there is 1+ pedal edema, and the lungs are clear. She has a renal biopsy. Which of the following electron microscopy findings on the renal biopsy is most likely in keeping with poststreptococcal GN?
These humps are discrete, electron-dense nodules that persist for about 8 weeks and are highly characteristic of the disease. Light microscopy reveals diffuse proliferation, and immunofluorescence reveals granular immunoglobulin G (IgG) and C3. Most patients will recover spontaneously
A 74-year-old man is brought to hospital because of urinary retention. He has a Foley catheter inserted to relieve the obstruction, and 1500 cc of urine is emptied from his bladder. Over the next few hours, he has 200cc/h of urine output. Which of the following urine electrolyte values is most likely in keeping with his diagnosis?
The urine contains large amounts of potassium, magnesium, and sodium. The large volume is often appropriate for preexisting volume expansion, but careful attention to fluid and electrolytes is important to prevent hypokalemia, hypomagnesemia, hyponatremia or hypernatremia, and volume depletion.
A 68-year-old woman has used large amounts of analgesic for years to relieve severe headaches and arthritis. She now has an elevated urea and creatinine consistent with chronic renal failure. Which of the following changes in the kidney is most likely seen with her diagnosis?
She has analgesic nephropathy, and chronic analgesic ingestion may lead to papillary necrosis and tubulointerstitial inflammation. Complete understanding of the pathogenesis is lacking, and may vary with different analgesics. Depletion of reducing equivalents such as glutathione may also play a role.
A 64-year-old woman develops severe diarrhea 2 weeks after finishing antibiotics for pneumonia. She has also noticed decreased urine output despite drinking lots of fluids. On examination, she has a postural drop in her blood pressure, the JVP is low, and the abdomen is soft but diffusely tender. Despite giving 4 L of normal saline, her urine output remains low. The urinalysis is positive for heme-granular casts and the urine sodium is 42 mEq/L. Which of the following medications should be held during the recovery phase of this woman’s ARF?
Although all drugs should be reassessed at this time, and if appropriate, the dosage adjusted, drugs with known nephrotoxicity, such as ACE inhibitors and NSAIDs, should be stopped.
A 64-year-old woman has metabolic alkalosis and the bicarbonate level is 34 mEq/L. Which of the following is the most likely cause?
Diuretics are a common cause for metabolic alkalosis since many patients take these medications for hypertension or CHF. Diarrhea causes a nonanion gap metabolic acidosis, and mineralocorticoid excess leads to metabolic alkalosis, primarily because of renal bicarbonate generation. Other major mechanisms for metabolic alkalosis include extracellular fluid (ECF) volume contraction, potassium depletion, and increased distal salt delivery. Less common causes are Liddle syndrome, bicarbonate loading (posthypercapnic alkalosis), and delayed conversion of administered organic acids.
A 32-year-old man with sickle cell anemia is seen for routine follow-up. He feels well at the present time, but in the past he has had many sickle cell crises, which have resulted in kidney injury. Which of the following renal abnormalities is most likely to be seen in him?
In sickle cell anemia, the kidney is characterized by an inability to concentrate the urine because of functional tubule defects that occur as a result of ischemic injury. Papillary necrosis may also occur in patients with homozygous sickle cell disease or sickle cell trait during a sickle crisis. Some patients can develop glomerular injury (focal and segmental glomerular sclerosis) after many years from the anemia-induced hyperfiltration that occurs.
A 63-year-old man with an 8-year history of recurrent severe arthritis in his large toes has an elevated creatinine level. Which of the following mechanisms is the most likely explanation for his renal impairment?
The typical renal lesions in gout are urate crystals in the medulla or pyramids, with surrounding mononuclear and giant cell reaction. The degree of renal impairment, however, does not correlate with hyperuricemia, and the decline in renal function correlates with aging, hypertension, renal calculi, or unrelated nephropathy.
A 67-year-old man presents with symptoms of renal colic. Plain x-rays of the abdomen reveal no obvious stone. An intravenous pyelogram (IVP) is ordered to confirm the clinical diagnosis. Which of the following coexisting medical conditions increases the risk of contrast-induced nephropathy?
The danger of ARF after IVP has led to caution, especially in patients with multiple myeloma. The patient should not be dehydrated if IVP is necessary. The risk is also increased in patients with diabetes mellitus or chronic renal failure.
A 64-year-old man presents with weight gain, shortness of breath, easy bruising, and leg swelling. On examination, his blood pressure is 140/80 mm Hg, pulse 100/min, JVP 4 cm, heart sounds normal, and lungs are clear. There is a 3+ pedal and some periorbital edema. Investigations include a normal chest x-ray (CXR), electrocardiogram (ECG) with low voltages, anemia, high urea and creatinine, and 4 g/day of protein in the urine. A renal biopsy, which shows nodular deposits that have an apple-green birefringence under polarized light when stained with Congo red. Which of the following is the most likely diagnosis?
Renal amyloidosis can be primary (AL) or secondary amyloidosis (AA). The hallmark finding, nephrotic syndrome, is present in 25% of patients at presentation and probably develops ultimately in over 50%. The apple-green birefringence deposits under polarized light are diagnostic of amyloidosis, and not seen in any other renal disease.
A 74-year-old man presents with fatigue, shortness of breath on exertion, and back and rib pain, which is made worse with movement. Investigations reveal he is anemic, calcium, urea, and creatinine are elevated. X-rays reveal multiple lytic lesions in the long bones and ribs, and protein electrophoresis is positive for an immunoglobulin G (IgG) paraprotein. Which of the following is the most likely mechanism for the renal injury?
In multiple myeloma, tubular damage by light chains is almost always present. The injury is a direct toxic effect of the light chains or indirectly from the inflammatory response. Infiltration by plasma cells and glomerular injury is rare. Hypercalcemia may produce transient or irreversible renal damage as do amyloid and myeloma cell infiltrates.
A 77-year-old man with a mass in the lung develops asymptomatic hyponatremia. His JVP is 4 cm, heart sounds are normal, and the lungs are clear. The urine sodium is 64 mEq/L and osmolality 550 mOsm/kg. Which of the following is the most likely diagnosis?
The urine osmolality in patients with SIADH need not be hypertonic to plasma, but only inappropriately high compared with serum. The major characteristics of SIADH include hyponatremia, volume expansion without edema, natriuresis, hypouricemia, and normal or reduced serum creatinine level, with normal thyroid and adrenal function.
A 69-year-old man has lost a friend to prostate cancer, and would like to be evaluated for the disease. He has no urinary symptoms. Which of the following tests is most likely indicated to screen him for prostate cancer?
Although an elevated PSA (>4) has the best positive predictive value, combining it with DRE is probably the most effective screening process.
A 63-year-old woman has Type II diabetes mellitus, which is well-controlled. Her physical examination is positive for peripheral neuropathy in the feet and nonproliferative retinopathy. A urinalysis is positive for proteinuria. Which of the following treatments is most likely to attenuate the course of renal disease?
It is very likely that control of hypertension and excellent glucose control will slow the development and course of renal disease in Type II diabetes mellitus. ACE inhibitors seem to decrease proteinuria and slow progression of renal disease. As renal function deteriorates, limiting dietary protein intake can also be beneficial. Calcium channel blockers have no extra effect beyond their antihypertensive effect.
A 32-year-old man has trace proteinuria on dipstick urinalysis. A 24-hour urine collection reveals 380 mg/day of protein excretion in the urine. Which of the following statements concerning this degree of proteinuria is correct?
Persistent proteinuria should always be investigated and, if no cause can be found, yearly follow-up instituted. Mild proteinuria has significant prognostic value in diabetes. Mild proteinuria can be caused by glomerular or tubular causes. Functional causes of proteinuria such as fever, orthostasis, exercise, and heart failure are usually reversible.
A 56-year-old man is involved in a severe motor vehicle accident. He develops ARF after admission to hospital. One of the possibilities for his ARF is posttraumatic renal vein thrombosis. Which of the following findings is most likely to suggest renal vein thrombosis?
Renal vein thrombosis is associated with heavy proteinuria and hematuria. Flank pain and pulmonary embolism can also occur.
A 69-year-old woman presents with left flank pain and hematuria. Physical examination suggests a left-sided abdominal mass. Computerized tomography (CT) scan of the abdomen reveals a 5-cm mass in the left kidney. Which of the following laboratory abnormalities might also be present?
This patient likely has hypernephroma (renal cell carcinoma). Polycythemia is caused by the production of erythropoietin-like factors. There is no relationship to hypertension. The tumor frequently presents as metastatic disease.
A 60-year-old woman with heart failure and normal renal function is started on furosemide (Lasix) 80 mg/day. She notices a good diuretic response every time she takes the medication. A few weeks later, she is feeling unwell because of fatigue and muscle weakness, but her heart failure symptoms are better. Which of the following is the most likely explanation for her muscle weakness?
Hypokalemia can result in paralytic ileus, rhabdomyolysis, weakness, and cardiac repolarization abnormalities. It is a common complication along with hyponatremia of starting patients on diuretics.
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