Nephrology Flashcards
What are the symptoms and signs of acute renal failure?
Symptoms: Fatigue, nausea and vomiting, anorexia, shortness of breath, mental status changes.
Signs: Increased levels of blood urea nitrogen (BUN) and creatinine, metabolic acidosis, hyperkalemia,
tachypnea (caused by acidosis and hypervolemia), and hypervolemia (bilateral rales on lung
examination, elevated jugular venous pressure, dilutional hyponatremia).
What are the three broad categories of renal failure?
Prerenal, renal/intrarenal, and postrenal.
Define prerenal failure. What are the causes? How do you recognize it?
In prerenal failure, the kidney is not adequately perfused. The most common cause is hypovolemia
(dehydration, hemorrhage). Look for a BUN-to-creatinine ratio greater than 20 and signs of hypovolemia
(e.g., tachycardia, weak pulse, depressed fontanelle). Give intravenous fluids and/or blood. Other common
prerenal causes are sepsis (treat the sepsis and give intravenous fluids), heart failure (give digoxin
and diuretics), liver failure (hepatorenal syndrome; treat supportively), and renal artery stenosis (RAS).
Define postrenal failure. What causes it?
In postrenal failure, urine is blocked from being excreted at some point beyond the kidneys (ureters,
prostate, urethra). The most common cause is benign prostatic hypertrophy (BPH). Patients are men
older than age 50 with BPH symptoms (e.g., hesitancy, dribbling); ultrasound demonstrates bilateral
hydronephrosis. Treat with catheterization (suprapubic, if necessary) to relieve the obstruction and
prevent further renal damage. Then consider surgery (transurethral resection of the prostate). Other
causes are nephrolithiasis (but remember that stones generally have to be bilateral to cause renal
failure), retroperitoneal fibrosis (watch for a history of methysergide, bromocriptine, methyldopa, or
hydralazine use), and pelvic malignancies.
What is the most common cause of intrarenal failure?
Intrarenal failure, which results from a problem within the kidney itself, is most commonly caused by
acute tubular necrosis from various causes.
What do you need to know about intravenous contrast and renal failure?
Intravenous contrast can precipitate renal failure, usually in diabetic patients and patients with preexisting
renal disease. Avoid contrast in such patients if possible. If you must give intravenous contrast,
give lots of intravenous hydration before and after the contrast is given to decrease the chance of
renal failure. Also consider the use of oral acetylcysteine on the day before and the day of contrast
administration.
True or false: Muscle breakdown can cause renal failure
True. Myoglobinuria or rhabdomyolysis caused by strenuous exercise (e.g., marathon runners),
alcohol, burns, muscle trauma, muscle compression (e.g., prolonged immobilization after a fall),
heat stroke, and neuroleptic malignant syndrome may cause renal failure. The cellular debris that
results from muscle breakdown plugs the renal filtration system. Look for very high levels of creatine
phosphokinase (CPK). Treat with hydration and diuretics.
What medications commonly cause renal insufficiency or failure?
Chronic use of nonsteroidal antiinflammatory drugs (NSAIDs; may cause acute tubular necrosis or
papillary necrosis), cyclosporine, aminoglycosides, and methicillin.
Define Goodpasture syndrome. How does it present?
Goodpasture syndrome is caused by the presence of measurable antiglomerular basement membrane
antibodies, which cause a linear immunofluorescence pattern on renal biopsy. These antibodies
react with and damage both kidneys and lungs. Look for a young man with hemoptysis, dyspnea, and
renal failure. Treat with steroids and cyclophosphamide
Define Wegener granulomatosis. How does it present?
Wegener granulomatosis is a vasculitis that also affects the lungs and kidneys. Look for nasal
involvement (bloody nose, nasal perforation) or hemoptysis and pleurisy as presenting symptoms,
along with renal disease. Patients test positive for titers of antineutrophil cytoplasmic antibody
(ANCA). Treat with cyclophosphamide and glucocorticoids. Methotrexate is an alternative.
What is the prototypical cause of glomerulonephritis? How does it present?
Poststreptococcal glomerulonephritis is the classic example on board examinations. It usually affects
children with a history of upper respiratory infection or strep throat 1 to 3 weeks earlier. Presenting symptoms
include edema, hypervolemia, hypertension, hematuria, and oliguria. Red blood cell (RBC) casts
on urinalysis clinch the diagnosis. Treat supportively. Also watch for lupus erythematosus as a cause of
glomerulonephritis. Renal failure is a major cause of morbidity and mortality in patients with lupus
What are the indications for dialysis in patients with renal failure?
Whenever renal failure is present, first try to determine the cause and fix it, if possible, to correct the
renal failure. Indications for acute dialysis include uremic encephalopathy, pericarditis, severe metabolic
acidosis (roughly pH < 7.25), heart failure, and hyperkalemia severe enough to cause arrhythmia
Define nephrotic syndrome. What causes it? How is it diagnosed?
Nephrotic syndrome is defined by proteinuria (>3.5 g/day), hypoalbuminemia, edema (the classic
pattern is morning periorbital edema), and hyperlipidemia with lipiduria. In children it is usually
caused by minimal change disease (podocytes with missing ”feet” on electron microscopy), which
often follows an infection. Measure 24-hour urine protein or spot urine protein-to-creatinine ratio to
clinch the diagnosis. Treat with steroids. Causes in adults include diabetes, hepatitis B, amyloidosis,
lupus erythematosus, and drugs (e.g., gold, penicillamine, captopril).
Define nephritic syndrome. What is the classic cause? How is it treated?
Nephritic syndrome generally is defined as oliguria, azotemia (rising BUN/creatinine), hypertension,
and hematuria. The patient may have some degree of proteinuria, but not in the nephrotic range. The
classic cause is poststreptococcal glomerulonephritis. Treatment is supportive, including control of
hypertension and maintenance of urine output with intravenous fluids and diuretics
What causes chronic kidney disease (CKD)?
Any of the causes of acute renal failure can cause chronic renal failure if the insult is severe or
prolonged. Most cases of CKD are a result of diabetes mellitus (number one cause) or hypertension
(number two cause). A popular Step 2 cause is polycystic kidney disease. Watch for multiple cysts
in the kidney and a positive family history (usually autosomal dominant; autosomal recessive form
presents in children), hypertension, hematuria, palpable renal masses, berry aneurysms in the circle
of Willis, and cysts in liver (Fig. 22-1).
