A 62-year-old male presents to the hospital complaining of nonradiating back pain for the past 2 days. He has a past medical history of hypertension, hyperlipidemia, and chronic back pain for which he takes ibuprofen, atorvastatin, and hydrochlorothiazide. He mentions that he tried to take a few extra doses of analgesics which did not seem to help, and it seems like his regular water pill is not working either. His vitals are as follows:
and laboratory work as follows:
Which of the following etiologies for acute renal injury (AKI) should ALWAYS be excluded first?
Correct Answer: A
Renal blood flow constitutes 20% of cardiac output. A large part of the renal perfusion (80%-90%) goes to renal cortex where glomerular filtration occurs. Prerenal azotemia as a consequence of reduction in renal perfusion, accounts for approximately 70% of the community-acquired and 40% of hospital-acquired cases of AKI. As this is a reversible process, most of the time, once the underlying inciting process is addressed, prerenal etiology (eg, vomiting, dehydration, and hemorrhage) should be excluded in all cases of AKI.
The renin-angiotensin-aldosterone system (RAAS) becomes activated secondary to a decrease in renal blood flow with subsequent increase in sodium reabsorption at the level of the proximal and distal tubule induced by angiotension II and aldosterone, respectively. As a result, the urine sodium concentration is less than 20 mmol/L and fractional excretion of sodium (FENa ) is less than 1%. Medications like nonsteroidal antiinflammatory drugs (NSAIDs) or RAAS inhibitors which interfere with the renal autoregulatory mechanisms could worsen prerenal azotemia, which seems likely in this patient.
Patients with NSAID overdose typically present with a wide spectrum of gastrointestinal symptoms, altered mental status, and arterial blood gas consistent with an anion gap metabolic acidosis. C and D are unlikely due to lack of neurological symptoms and patient not being in shock, respectively. Prerenal etiology should be excluded in all cases of AKI due to its reversible nature in the majority of cases.
Reference:
A 35-year-old obese female with a past medical history of type 2 diabetes, chronic kidney disease (CKD) stage 3, chronic obstructive pulmonary disease (COPD), and deep vein thrombosis (DVT) is brought to the emergency room with acute-onset shortness of breath. She is on home oxygen for the COPD, warfarin, and subcutaneous insulin therapy. Her chest x-ray reveals hyperinflated lung fields, and CT angiogram did NOT reveal pulmonary embolism (PE). She was admitted and treated for COPD exacerbation. Serum creatinine is noticed to have increased to 2.6/dL from a baseline of 1.3 mg/dL with concern for contrast-induced acute kidney injury (CIAKI).
Which of the following strategies is MOST likely to prevent CI-AKI?
Correct Answer: C
CI-AKI is the most common iatrogenic cause of AKI. The incidence is reported to be as high as 20% to 30% in patients with preexisting renal dysfunction. The most effective method of preventing CI-AKI is avoidance of iodinated contrast unless absolutely indicated, especially in patients with compromised kidney function.
Reduction in renal blood flow, tubular cell damage, and tubular obstruction are implicated in the pathogenesis of CI-AKI. Therefore, volume expansion with normal saline has been used extensively with the goal of improving medullary blood flow, diluting the contrast agent in the tubule, and increasing urinary flow. Low-osmolality contrast agents are less toxic to the kidneys as compared to high-osmolality agents.
Although NAC has antioxidant and anti-inflammatory properties and proposed to have a beneficial role in the prevention of CI-AKI, the largest trial on this subject did not confirm this. The most effective method of preventing CI-AKI is avoiding studies requiring IV contrast administration.
References:
A healthy 24-year-old male is admitted to the intensive care unit (ICU) for AKI and hyperkalemia. History is remarkable for a recent episode of sinusitis for which amoxicillin-clavulanate therapy was initiated. Physical examination is notable for a temperature of 37.6°C, skin rashes, and joint pain. Urine microscopy shows a few RBC’s and eosinophils. Laboratory results are given below:
What is the MOST appropriate next step in the management of this patient?
Correct Answer: B
Acute interstitial nephritis (AIN) is an important cause of AKI characterized by inflammation of the renal interstitium and tubules. AIN results from a hypersensitivity reaction, most commonly induced by medications, infections, and autoimmune disorders. Common offending agents are antibiotics (penicillins, cephalosporins, sulfonamides, ciprofloxacin, and rifampin), anticonvulsants (phenytoin, carbamazepine, phenobarbital, valproate), diuretics (thiazides, loop diuretics, triamterene), NSAIDs, and proton pump inhibitors. Medications account for over twothirds of all the AIN cases. Patients with AIN could present with sterile pyuria, hematuria, eosinophilia, and fever. The majority of the patients have complete recovery of renal function.
It is important to differentiate AIN from acute tubular necrosis (ATN). The diagnosis of AIN is difficult as symptoms could mimic infection. Sterile pyuria and eosinophiluria could suggest the diagnosis.
Removal of the offending agent is the most important component of AIN treatment. Treatment is largely supportive with use of renal replacement therapy as needed. Corticosteroid therapy in these patients is controversial. Discontinuation of the inciting agent is the cornerstone of treatment of acute interstitial nephritis.
A 33-year-old muscular male is brought to emergency room after being rescued from under a collapsed concrete building. Physical examination reveals multiple lower extremity bone fractures and skin lacerations. CT scan is negative for traumatic brain injury. Vitals are as follows:
and laboratory parameters are as follows:
He has received a liter of lactated ringers so far. His urine output is dark brown and only 10 mL for the past hour.
Which of the following is the next BEST step in the management of this patient?
Patients with rhabdomyolysis-induced AKI present with an elevated CK and reddish brown urine with absent erythrocytes on microscopic examination. They could have associated electrolyte abnormalities including hyperkalemia, hyperphosphatemia, and hypocalcemia. Early aggressive intravascular volume expansion is the most important measure to prevent worsening AKI from rhabdomyolysis. The goal is to enhance renal perfusion and flush the renal tubules off obstructing casts.
Fluid repletion is continued until the plasma CK level is stable and maintained <5000 units/L. The Renal Disaster Relief Task Force (RDRTF) of the International Society of Nephrology (ISN) recommends use of isotonic solution due to its ready availability and equivalent efficacy at volume expansion compared to sodium bicarbonate. Despite the theoretical benefits of using sodium bicarbonate in severe rhabdomyolysis, there is no concrete evidence that suggests that alkaline diuresis is more effective than saline diuresis in preventing AKI.
Which of the following statements is MOST ACCURATE regarding the pathophysiology behind bilateral obstructive nephropathy?
Often renal sodium excretion increases after relief of the obstruction. Two mechanisms that could potentially contribute to this include the downregulation of the apical membrane transporters and an upregulation of atrial natriuretic peptide. In patients with obstructive uropathy, reduction in GFR occurs due to an increase in tubular hydrostatic pressure, which alters the balance between the glomerular capillaries and the renal tubules. The hyperkalemia and metabolic acidosis in these patients are most likely a reflection of a reduced GFR and renal function. Ultrasound is utilized as a good screening tool for patients with new-onset or unexplained AKI to rule out urinary tract obstruction as a potential etiology.
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