A 56-year-old man presents with hypertension and peripheral edema. He is otherwise healthy and takes no medications. Family history reveals that his father and a brother have kidney disease. His father was on hemo-dialysis before his death at age 68 of a stroke. Physical examination reveals BP 174/96 and AV nicking on funduscopic examination. He has a soft S4 gallop. Bilateral flank masses measuring 16 cm in length are palpable. Urinalysis shows 15 to 20 RBC/hpf and trace protein but is otherwisenormal; his serum creatinine is 2.4 mg/dL.
Which is the most likely long-term complication of his condition
This patient has adult polycystic kidney disease (APCKD), an autosomal dominant condition. It is the commonest genetic renal disease causing ESRD and often presents with hypertension, hematuria, and large palpable kidneys. Imaging studies would confirm the diagnosis by showing numerous bilateral renal cortical cysts. Cysts are often seen in the liver and pancreas but rarely cause symptoms. Most patients progress to end-stage renal disease despite meticulous blood pressure control with ACE inhibitors or angiotensin receptor blockers.
About 10% of patients with adult PCK disease harbor berry aneurysms in the circle of Willis; a ruptured berry aneurysm may have accounted for his father’s stroke. APCKD patients also have an increased incidence of abdominal and thoracic aneurysms as well as diverticulosis. The abnormal gene, on chromosome 16 in 85% of patients, appears to encode a structural protein that helps keep the renal tubules open and unobstructed. This same protein provides strength to the walls of arteries and other epithelial structures (pancreatic ductules, bile ductules, colon). Malignancy and dementia are not seen with increased incidence in APCKD patients.
A 73-year-old woman with arthritis presents with confusion. Neurologic examination is nonfocal, and CT of the head is normal. Laboratory data include
What is the acid-base disturbance?
This patient’s normal pH would initially suggest a normal acid-base status. However, the P CO2 is significantly low, indicating a respiratory alkalosis. If the pH is normal, there must be a superimposed metabolic acidosis; that is, metabolic compensation would not return the pH all the way back to 7.4. Indeed the serum bicarbonate is too low for a compensatory response (metabolic compensation for respiratory alkalosis rarely drops the HCO3 below 17 mEq/L) and the anion gap is elevated at 21. The only cause of a substantially elevated anion gap is metabolic acidosis (the AG can be elevated to 16 or 17 in alkalosis). Therefore, this patient has a combined (mixed) disturbance, that is, combined respiratory alkalosis and metabolic acidosis. This is the classic acid-base disturbance associated with salicylate intoxication. Aspirin stimulates central respiratory drive; in addition, several metabolic substances (salicylic acid and lactic acid due to suppression of oxidative phosphorylation, among others) build up to widen the anion gap. Choices a, b, and e are wrong because compensation never normalizes the pH.
A 17-year-old woman presents with peripheral and periorbital edema. She has previously been healthy and takes no medications. Her blood pressure is 146/92; she is afebrile. The patient has mild basilar dullness on lung examination; her cardiac examination is normal. She has periorbital edema and soft, doughy 3+ edema in her legs. Her serum creatinine is 0.6 mg/dL and her serum albumin is 2.1 g/L. Urinalysis shows 3+ protein, no RBC or WBC, and some oval fat bodies.
What is the next best step to take in evaluating this patient?
This patient almost surely has the nephrotic syndrome, which is characterized by sufficient albuminuria to cause hypoalbuminemia and its complications (edema, hyperlipidemia, and hypertension). The degree of albuminuria required to cause the clinical syndrome is 3.5 g per 24 hours or greater and this can be confirmed by the 24-hour urine collection. The urine dipstick shows 3+ (300 mg/dL) or 4+ (1000 mg/dL) proteinuria. Proteinuria can be approximated on a spot urine specimen by measuring the urine albumin/creatinine ratio (> 3.5 mg/g). The occasional patient with this degree of proteinuria but without the clinical manifestations of the nephrotic syndrome is said to have nephrotic-range proteinuria. Remember that other proteins (eg, Bence-Jones proteins, myoglobin) can cause severe proteinuria, but, since they do not cause albumin loss in the urine, they do not cause the nephrotic syndrome. These proteins often do not show up on the urine dipstick, which is relatively albumin specific.
Once the diagnosis of the nephrotic syndrome is made, an underlying cause should be sought. In the absence of diabetes (overwhelmingly the most common cause of nephrotic range proteinuria in adults), most cases will be associated with primary glomerular diseases. Systemic lupus, amyloidosis, and several infectious diseases can cause the nephrotic syndrome but are usually associated with systemic manifestations that point to the proper diagnosis. Kidney biopsy is usually carried out in adults, but in children and adolescents, where minimal change disease is the most common cause, a trial of corticosteroids usually precedes renal biopsy. Serum and urine protein electrophoresis would help diagnose multiple myeloma, but this would be a very rare condition in a young patient. Plasma aldosterone and renin levels are useful in ruling out hyperaldosteronism as a cause of hypertension but play no role in the evaluation of proteinuria or the nephrotic syndrome. Nuclear medicine renal scans are typically used to evaluate individual kidney function in asymmetric disease, vascular supply to kidneys after trauma, or to determine morphology and function in patients allergic to contrast agents. There is no role for these scans in the evaluation of the patient with nephrotic syndrome.
A 63-year-old man alcoholic with a 50-pack-year history of smoking presents to the emergency room with fatigue and confusion. Physical examination reveals a blood pressure of 110/70 with no orthostatic change. Heart, lung, and abdominal examinations are normal and there is no pedal edema. Laboratory data are as follows:
Which of the following is the most likely diagnosis?
Inappropriate secretion of antidiuretic hormone is suggested in a patient without clinical evidence of volume depletion or an edematous (ie, salt-retaining) condition. This syndrome may be idiopathic, associated with certain pulmonary and intracranial pathologies, resulting from endocrine disorders (eg, hypothyroidism), or drug-induced (eg, many psychotropic agents). Volume depletion is unlikely in the absence of orthostatic hypotension. Psychogenic polydipsia requires the ingestion of huge quantities of water to overcome the kidneys’ ability to excrete a free-water load and would be associated with a very dilute urine (ie, urine specific gravity of 1.001 or 1.002). Cirrhosis is unlikely in the absence of ascites and edema. Congestive heart failure can cause hyponatremia but would be associated with edema and evidence of venous congestion.
A 65-year-old diabetic man with a creatinine of 1.6 was started on an angiotensin-converting enzyme inhibitor for hypertension and presents to the emergency room with weakness. His other medications include atorvastatin for hypercholesterolemia, metoprolol and spironolactone for congestive heart failure, insulin for diabetes, and aspirin. Laboratory studies include
Which of the following is the most likely cause of hyperkalemia in this patient?
The syndrome of hyporeninemic hypoaldosteronism occurs in older diabetic patients, particularly males with congestive heart failure. The syndrome often presents when aggravating drugs are added. Beta-blockers impair renin secretion; ACE inhibitors decrease aldosterone levels; and spironolactone competes for the aldosterone receptor. Combined with diabetes and mild renal insufficiency, the result may be life-threatening hyperkalemia. Moderate renal insufficiency per se is unlikely to cause such severe hyperkalemia. Hypertonicity caused by hyperglycemia could aggravate hyperkalemia, but a blood glucose of 250 mg/dL should not cause severe hyperkalemia. Statin drugs may cause muscle injury and rhabdomyolysis, but a CK of 400 IU/L is a modest elevation (probably caused by the renal insufficiency) and would not cause severe hyperkalemia. A high-potassium diet may contribute modestly to hyperkalemia but is rarely a major factor by itself.
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