Acute Renal Failure 

Acute renal failure (ARF), or acute kidney injury (AKI), as it is now referred to in the literature, is defined as an abrupt or rapid decline in renal filtration function. This condition is usually marked by a rise in serum creatinine concentration or by azotemia (a rise in blood urea nitrogen [BUN] concentration).^[1] (See Etiology and Prognosis.)

However, immediately after a kidney injury, BUN or creatinine levels may be normal, and the only sign of a kidney injury may be decreased urine production. (See History.)

A rise in the creatinine level can result from medications (eg, cimetidine, trimethoprim) that inhibit the kidney’s tubular secretion. A rise in the BUN level can occur without renal injury, resulting instead from such sources as GI or mucosal bleeding, steroid use, or protein loading, so a careful inventory must be taken before determining if a kidney injury is present. (See Etiology and History.)

See Chronic Kidney Disease and Acute Tubular Necrosis for complete information on these topics.

An example of AKI, apparently the result of acute tubular necrosis (ATN), is seen in the image below.

Categories of AKI

AKI may be classified into 3 general categories, as follows:

• Prerenal - as an adaptive response to severe volume depletion and hypotension, with structurally intact nephrons
• Intrinsic - in response to cytotoxic, ischemic, or inflammatory insults to the kidney, with structural and functional damage
• Postrenal - from obstruction to the passage of urine

While this classification is useful in establishing a differential diagnosis, many pathophysiologic features are shared among the different categories. (See Etiology.)

Oliguric and nonoliguric patients with AKI

Patients who develop AKI can be oliguric or nonoliguric, have a rapid or slow rise in creatinine levels, and may have qualitative differences in urine solute concentrations and cellular content. (Approximately 50-60% of all causes of AKI are nonoliguric.)

This lack of a uniform clinical presentation reflects the variable nature of the injury.

Classifying AKI as oliguric or nonoliguric based on daily urine excretion has prognostic value. Oliguria is defined as a daily urine volume of less than 400 mL/d and has a worse prognosis, except in prerenal failure.

Anuria is defined as a urine output of less than 100 mL/d and, if abrupt in onset, suggests bilateral obstruction or catastrophic injury to both kidneys. Stratification of renal failure along these lines helps in diagnosis and decision-making (eg, timing of dialysis) and can be an important criterion for patient response to therapy.

The RIFLE system

In 2004, the Acute Dialysis Quality Initiative work group set forth a definition and classification system for acute renal failure, described by the acronym RIFLE (Risk of renal dysfunction, Injury to the kidney, Failure or Loss of kidney function, and End-stage kidney disease; see the table, below).^[2] Investigators have since applied the RIFLE system to the clinical evaluation of AKI, although it was not originally intended for that purpose. AKI research increasingly uses RIFLE.

Table 1. RIFLE Classification System for Acute Kidney Injury (Open Table in a new window)

When the failure classification is achieved by UO criteria, the designation of RIFLE-F_O is used to denote oliguria. The initial stage, risk, has high sensitivity; more patients will be classified in this mild category, including some who do not actually have renal failure. Progression through the increasingly severe stages of RIFLE is marked by decreasing sensitivity and increasing specificity.

A vast array of fluid and electrolyte abnormalities can be seen with acute kidney injury (AKI).

Cardiovascular complications

Cardiovascular complications (eg, congestive heart failure [CHF], myocardial infarction, arrhythmias, cardiac arrest) have been observed in as many as 35% of patients with AKI. Fluid overload secondary to oliguric AKI is a particular risk for elderly patients with little cardiac reserve.

Pericarditis is a relatively rare complication of AKI. When pericarditis complicates AKI, consider additional diagnoses, such as systemic lupus erythematosus (SLE) and hepatorenal syndrome.

AKI also can be a complication of cardiac diseases, such as endocarditis, decompensated CHF, or atrial fibrillation with emboli. Cardiac arrest in a patient with AKI always should arouse suspicion of hyperkalemia. Many authors, in emergency situations, recommend a trial of intravenous calcium chloride (or gluconate) in all patients with AKI who experience cardiac arrest.

Pulmonary complications

Pulmonary complications have been reported in approximately 54% of patients with AKI and are the single most significant risk factor for death in patients with AKI. Several diseases exist that commonly present with simultaneous pulmonary and renal involvement, including pulmonary/renal syndromes (eg, Goodpasture syndrome, Wegener granulomatosis, polyarteritis nodosa, cryoglobulinemia, sarcoidosis). Hypoxia commonly occurs during hemodialysis and can be particularly significant in the patient with pulmonary disease. This dialysis-related hypoxia is thought to occur secondary to white blood cell (WBC) lung sequestration and alveolar hypoventilation.

GI complications

GI symptoms of nausea, vomiting, and anorexia are frequent complications of AKI and represent one of the cardinal signs of uremia. GI bleeding occurs in approximately one third of patients with AKI. Most episodes are mild, but GI bleeding accounts for 3-8% of deaths in patients with AKI.

Mild hyperamylasemia commonly is seen in AKI (2-3 times controls). Elevation of baseline amylase can complicate diagnosis of pancreatitis in patients with AKI. Lipase, which commonly is not elevated in AKI, often is necessary to make the diagnosis of pancreatitis. Pancreatitis has been reported as a concurrent illness with AKI in patients with atheroemboli, vasculitis, and sepsis from ascending cholangitis.

Jaundice has been reported to complicate AKI in approximately 43% of cases. Etiologies of jaundice with AKI include hepatic congestion, blood transfusions, and sepsis.

Hepatitis occurring concurrently with AKI should prompt the differential diagnosis of common bile duct obstruction, fulminant hepatitis B, leptospirosis, acetaminophen toxicity, and Amanita phalloides toxin.

Infectious complications

Infections commonly complicate the course of AKI and have been reported to occur in as many as 33% of patients with AKI. Most common sites are pulmonary and urinary tracts. Infections are the leading cause of morbidity and death in patients with AKI. Various studies have reported mortality rates of 11-72% in infections complicating AKI.

Neurologic complications

Neurologic signs of uremia are a common complication of AKI and have been reported in approximately 38% of patients with AKI. Neurologic sequelae include lethargy, somnolence, reversal of the sleep-wake cycle, and cognitive or memory deficits. Focal neurologic deficits rarely are due solely to uremia and should remain a diagnosis of exclusion in patients with AKI.

The pathophysiology of neurologic symptoms is still unknown, but they do not correlate well to levels of BUN or creatinine.

A number of diseases express themselves with concurrent neurologic and renal manifestations (eg, SLE, thrombotic thrombocytopenic purpura [TTP], hemolytic uremic syndrome [HUS], endocarditis, malignant hypertension).

Also see Management of Acute Complications of Acute Renal Failure.

The driving force for glomerular filtration is the pressure gradient from the glomerulus to the Bowman space. Glomerular pressure is primarily dependent on renal blood flow (RBF) and is controlled by combined resistances of renal afferent and efferent arterioles. Regardless of the cause of acute kidney injury (AKI), reductions in RBF represent a common pathologic pathway for decreasing GFR. The etiology of AKI consists of 3 main mechanisms.

• Prerenal failure - Defined by conditions with normal tubular and glomerular function; GFR is depressed by compromised renal perfusion
• Intrinsic renal failure - Includes diseases of the kidney itself, predominantly affecting the glomerulus or tubule, which are associated with release of renal afferent vasoconstrictors; ischemic renal injury is the most common cause of intrinsic renal failure.
• Postobstructive renal failure - Initially causes an increase in tubular pressure, decreasing the filtration driving force; this pressure gradient soon equalizes, and maintenance of a depressed GFR is then dependent on renal efferent vasoconstriction

Patients with chronic renal failure may also present with superimposed AKI from any of the aforementioned etiologies.

Depressed RBF eventually leads to ischemia and cell death. This may happen before frank systemic hypotension is present and is referred to as normotensive ischemic AKI. The initial ischemic insult triggers a cascade of events that includes production of oxygen free radicals, cytokines and enzymes, endothelial activation and leukocyte adhesion, activation of coagulation, and initiation of apoptosis. These events continue to cause cell injury even after restoration of RBF.

Tubular cellular damage results in disruption of tight junctions between cells, allowing back leak of glomerular filtrate and further depressing effective GFR. In addition, dying cells slough off into the tubules, forming obstructing casts, which further decrease GFR and lead to oliguria.

During this period of depressed RBF, the kidneys are particularly vulnerable to further insults. This is when iatrogenic renal injury is most common. The following are common iatrogenic combinations:

• Preexisting renal disease (elderly, diabetic patients, jaundiced patients) with radiocontrast agents, aminoglycosides, atheroembolism, or cardiovascular surgery
• Angiotensin-converting enzyme (ACE) inhibitors with diuretics, small- or large-vessel renal arterial disease
• Nonsteroidal anti-inflammatory drugs (NSAIDs) with congestive heart failure (CHF), hypertension (HTN), or renal artery stenosis
• Hypovolemia with aminoglycosides, amphotericin, heme pigments, or radiologic contrast agents

Restoration of renal blood flow and associated complications

Recovery from AKI is first dependent upon restoration of RBF. Early RBF normalization predicts better prognosis for recovery of renal function. In prerenal failure, restoration of circulating blood volume is usually sufficient. Rapid relief of urinary obstruction in postrenal failure results in a prompt decrease of vasoconstriction. With intrinsic renal failure, removal of tubular toxins and initiation of therapy for glomerular diseases decreases renal afferent vasoconstriction.

Once RBF is restored, the remaining functional nephrons increase their filtration and eventually hypertrophy. GFR recovery is dependent upon the size of this remnant nephron pool. If the number of remaining nephrons is below some critical value, continued hyperfiltration results in progressive glomerular sclerosis, eventually leading to increased nephron loss. A vicious cycle ensues; continued nephron loss causes more hyperfiltration until complete renal failure results. This has been termed the hyperfiltration theory of renal failure and explains the scenario in which progressive renal failure is frequently observed after apparent recovery from AKI.

Prerenal AKI

Prerenal AKI represents the most common form of kidney injury and often leads to intrinsic AKI if it is not promptly corrected. Volume loss from GI, renal, cutaneous (eg, burns), and internal or external hemorrhage can result in this syndrome. Prerenal AKI can also result from decreased renal perfusion in patients with heart failure or shock (eg, sepsis, anaphylaxis).

Special classes of medications that can induce prerenal AKI in volume-depleted states are angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), which are otherwise safely tolerated and beneficial in most patients with chronic kidney disease.

Arteriolar vasoconstriction leading to prerenal AKI can occur in hypercalcemic states, with the use of radiocontrast agents, NSAIDs, amphotericin, calcineurin inhibitors, norepinephrine, and other pressor agents.

The hepatorenal syndrome can also be considered a form of prerenal AKI, because functional renal failure develops from diffuse vasoconstriction in vessels supplying the kidney.

To summarize, volume depletion can be caused by the following:

• Renal losses (diuretics, polyuria)
• GI losses (vomiting, diarrhea)
• Cutaneous losses (burns, Stevens-Johnson syndrome)
• Hemorrhage
• Pancreatitis

Decreased cardiac output can be caused by the following:

• Heart failure
• Pulmonary embolus
• Acute myocardial infarction
• Severe valvular disease
• Abdominal compartment syndrome (tense ascites)

Systemic vasodilation can be caused by the following:

• Sepsis
• Anaphylaxis
• Anesthetics
• Drug overdose

Afferent arteriolar vasoconstriction can be caused by the following:

• Hypercalcemia
• Drugs (NSAIDs, amphotericin B, calcineurin inhibitors, norepinephrine, radiocontrast agents)
• Hepatorenal syndrome

Diseases that compromise renal perfusion include the following:

• Decreased effective arterial blood volume - Hypovolemia, CHF, liver failure, sepsis
• Renal arterial disease - Renal arterial stenosis (atherosclerotic, fibromuscular dysplasia), embolic disease (septic, cholesterol)

Intrinsic AKI

Structural injury in the kidney is the hallmark of intrinsic AKI, and the most common form is ATN, either ischemic or cytotoxic. Frank necrosis is not prominent in most human cases of ATN and tends to be patchy. Less obvious injury includes loss of brush borders, flattening of the epithelium, detachment of cells, formation of intratubular casts, and dilatation of the lumen (see the images below). Although these changes are observed predominantly in proximal tubules, injury to the distal nephron can also be demonstrated. In addition, the distal nephron may become obstructed by desquamated cells and cellular debris.

In contrast to necrosis, the principal site of apoptotic cell death is the distal nephron. During the initial phase of ischemic injury, loss of integrity of the actin cytoskeleton leads to flattening of the epithelium, with loss of the brush border, loss of focal cell contacts, and subsequent disengagement of the cell from the underlying substratum.

Many endogenous growth factors that participate in the process of regeneration have not been identified; however, administration of growth factors exogenously has been shown to ameliorate and hasten recovery from AKI. Depletion of neutrophils and blockage of neutrophil adhesion reduce renal injury following ischemia, indicating that the inflammatory response is responsible, in part, for some features of ATN, especially in postischemic injury after transplant.

Intrarenal vasoconstriction is the dominant mechanism for the reduced glomerular filtration rate (GFR) in patients with ATN. The mediators of this vasoconstriction are unknown, but tubular injury seems to be an important concomitant finding. Urine backflow and intratubular obstruction (from sloughed cells and debris) are causes of reduced net ultrafiltration (see the image below). The importance of this mechanism is highlighted by the improvement in renal function that follows relief of such intratubular obstruction.

In addition, when obstruction is prolonged, intrarenal vasoconstriction is prominent in part due to the tubuloglomerular feedback mechanism, which is thought to be mediated by adenosine and activated when there is proximal tubular damage and the macula densa is presented with increased chloride load.

Apart from the increase in basal renal vascular tone, the stressed renal microvasculature is more sensitive to potentially vasoconstrictive drugs and otherwise-tolerated changes in systemic blood pressure. The vasculature of the injured kidney has an impaired vasodilatory response and loses its autoregulatory behavior. This latter phenomenon has important clinical relevance because the frequent reduction in systemic pressure during intermittent hemodialysis may provoke additional damage that can delay recovery from ATN. Often, injury results in atubular glomeruli, where the glomerular function is preserved, but the lack of tubular outflow precludes its function.

A physiologic hallmark of ATN is a failure to maximally dilute or concentrate urine (isosthenuria). This defect is not responsive to pharmacologic doses of vasopressin. The injured kidney fails to generate and maintain a high medullary solute gradient, because the accumulation of solute in the medulla depends on normal distal nephron function. (Failure to excrete concentrated urine even in the presence of oliguria is a helpful diagnostic clue in distinguishing prerenal from intrinsic renal disease; in prerenal azotemia, urine osmolality is typically more than 500 mOsm/kg, whereas in intrinsic renal disease, urine osmolality is less than 300 mOsm/kg.)

Glomerulonephritis can be a cause of AKI and usually falls into a class referred to as rapidly progressive glomerulonephritis (RPGN). Glomerular crescents (glomerular injury) are found in RPGN on biopsy; if more than 50% of glomeruli contain crescents, this usually results in a significant decline in renal function. Although comparatively rare, acute glomerulonephritides should be part of the diagnostic consideration in cases of AKI.

To summarize, vascular (large and small vessel) causes of intrinsic AKI include the following:

• Renal artery obstruction (thrombosis, emboli, dissection, vasculitis)
• Renal vein obstruction (thrombosis)
• Microangiopathy (TTP, HUS, disseminated intravascular coagulation [DIC], preeclampsia)
• Malignant hypertension
• Scleroderma renal crisis
• Transplant rejection
• Atheroembolic disease

Glomerular causes include the following:

• Anti-glomerular basement membrane (GBM) disease (Goodpasture syndrome)
• Anti-neutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA-associated GN) (Wegener granulomatosis, Churg-Strauss syndrome, microscopic polyangiitis)
• Immune complex GN (lupus, postinfectious, cryoglobulinemia, primary membranoproliferative glomerulonephritis)

Tubular etiologies may include ischemia or cytotoxicity. Cytotoxic etiologies include the following:

• Heme pigment (rhabdomyolysis, intravascular hemolysis)
• Crystals (tumor lysis syndrome, seizures, ethylene glycol poisoning, megadose vitamin C, acyclovir, indinavir, methotrexate)
• Drugs (aminoglycosides, lithium, amphotericin B, pentamidine, cisplatin, ifosfamide, radiocontrast agents)

Interstitial causes include the following:

• Drugs (penicillins, cephalosporins, NSAIDs, proton-pump inhibitors, allopurinol, rifampin, indinavir, mesalamine, sulfonamides)
• Infection (pyelonephritis, viral nephritides)
• Systemic disease (Sjögren syndrome, sarcoid, lupus, lymphoma, leukemia, tubulonephritis, uveitis)

Postrenal AKI

Mechanical obstruction of the urinary collecting system, including the renal pelvis, ureters, bladder, or urethra, results in obstructive uropathy or postrenal AKI.

If the site of obstruction is unilateral, then a rise in the serum creatinine level may not be apparent due to contralateral renal function. Although the serum creatinine level may remain low with unilateral obstruction, a significant loss of GFR occurs, and patients with partial obstruction may develop progressive loss of GFR if the obstruction is not relieved. Causes of obstruction include stone disease; stricture; and intraluminal, extraluminal, or intramural tumors.

Bilateral obstruction is usually a result of prostate enlargement or tumors in men and urologic or gynecologic tumors in women.

Patients who develop anuria typically have obstruction at the level of the bladder or downstream to it.

To summarize, causes of postrenal AKI include the following:

• Ureteric obstruction (stone disease, tumor, fibrosis, ligation during pelvic surgery)
• Bladder neck obstruction (benign prostatic hypertrophy [BPH], cancer of the prostate [CA prostate or prostatic CA], neurogenic bladder, tricyclic antidepressants, ganglion blockers, bladder tumor, stone disease, hemorrhage/clot)
• Urethral obstruction (strictures, tumor, phimosis)
• Intra-abdominal hypertension (tense ascites)
• Renal vein thrombosis

Diseases causing urinary obstruction from the level of the renal tubules to the urethra include the following:

• Tubular obstruction from crystals (eg, uric acid, calcium oxalate, acyclovir, sulfonamide, methotrexate, myeloma light chains)
• Ureteral obstruction - Retroperitoneal tumor, retroperitoneal fibrosis (methysergide, propranolol, hydralazine), urolithiasis, or papillary necrosis
• Urethral obstruction - Benign prostatic hypertrophy; prostate, cervical, bladder, colorectal carcinoma; bladder hematoma; bladder stone; obstructed Foley catheter; neurogenic bladder; or stricture

The patient's age has significant implications for the differential diagnosis of AKI.

Newborns and infants

In newborns and infants, causes of prerenal AKI include the following:

• Perinatal hemorrhage - Twin-twin transfusion, complications of amniocentesis, abruptio placenta, birth trauma
• Neonatal hemorrhage - Severe intraventricular hemorrhage, adrenal hemorrhage
• Perinatal asphyxia and hyaline membrane disease (newborn respiratory distress syndrome) - Both may result in preferential blood shunting away from the kidneys (ie, prerenal) to central circulation.

Causes of Intrinsic AKI include the following:

• ATN - Can occur in the setting of perinatal asphyxia; ATN also has been observed secondary to medications (eg, aminoglycosides, NSAIDs) given to the mother perinatally
• ACEIs - Can traverse the placenta, resulting in a hemodynamically mediated form of AKI
• Acute glomerulonephritis - Rare and most commonly the result of maternal-fetal transfer of antibodies against the neonate's glomeruli or transfer of chronic infections (syphilis, cytomegalovirus) associated with acute glomerulonephritis

Congenital malformations of urinary collecting systems should be suspected in cases of postrenal AKI.

Children

Prerenal AKI can be caused by the following:

• Gastroenteritis - The most common cause of hypovolemia in children
• Congenital and acquired heart diseases - Also important causes of decreased renal perfusion in this age group.

Intrinsic AKI

• Acute poststreptococcal glomerulonephritis - Should be considered in any child who presents with HTN, edema, hematuria, and renal failure.
• HUS - Often is cited as the most common cause of AKI in children.

The most common form of HUS is associated with a diarrheal prodrome caused by Escherichia coli O157:H7. These children usually present with microangiopathic anemia, thrombocytopenia, colitis, mental status changes, and renal failure.

Incidence in the United States

Approximately 1% of patients admitted to hospitals have acute kidney injury (AKI) at the time of admission. The estimated incidence rate of AKI is 2-5% during hospitalization.

AKI develops within 30 days postoperatively in approximately 1% of general surgery cases^[3] ; it develops in up to 67% of intensive care unit (ICU) patients.^[4] Approximately 95% of consultations with nephrologists are related to AKI.

Feest and colleagues calculated that the appropriate nephrologist referral rate is approximately 70 cases per million population.^[5]

Race predilection

No race predilection is recognized in AKI.

Sex predilection

Males and females are affected equally by AKI.

The prognosis for patients with AKI is directly related to the cause of renal failure and, to a great extent, to the duration of renal failure prior to therapeutic intervention.

On long-term follow-up (1-10 years), approximately 12.5% of survivors of AKI are dialysis dependent (rates range widely, from 1-64%, depending on the patient population) and 19-31% of them have chronic kidney disease.^[4]

A study from Canada showed a much higher incidence of AKI than in previous reports, 18.3% (7,856 of 43,008) in hospitalized patients.^[6] The incidence of AKI correlated inversely with estimated glomerular filtration rate (eGFR) and was associated with a higher mortality rate and a higher incidence of subsequent end-stage renal disease (ESRD) at each level of baseline eGFR; however, the greatest impact on mortality was seen in individuals with eGFR greater than 60 mL/min who developed AKI. Those with stage 3 AKI (AKIN criteria) had a mortality rate of 50% compared to individuals with eGFR greater than 60 mL/min who did not develop AKI (3%).

Conversely, individuals with eGFR less than 30 who did not develop AKI had a higher mortality rate (12.1%) than those with an eGFR of greater than 60 mL/min, but the mortality rate with stage 3 AKI in patients with advanced CKD was 40.7%, somewhat less than patients with eGFR greater than 60 mL/min. This study confirms the short- and the long-term mortality risk and ESRD risk associated with AKI and suggests that the condition may be a more common event than previously recognized.^[6]

Mortality rates and associated factors

If AKI is defined by a sudden increment of serum creatinine of 0.5-1 mg/dL and is associated with a mild to moderate rise in creatinine, the prognosis tends to be worse. (Increments of 0.3 mg/dL in serum creatinine have important prognostic significance.)

Even if renal failure is mild, however, the mortality rate for patients is 30-60%. If these patients need dialytic therapy, the mortality rate is 50-90%.

The mortality rate is 31% in patients with normal urine sediment test results and is 74% in patients with abnormal urine sediment test results.

The survival rate is nearly 0% among patients with AKI who have an Acute Physiology and Chronic Health Evaluation II (APACHE II) score higher than 40; the survival rate is 40% in patients with APACHE II scores of 10-19.

The in-hospital mortality rate for AKI is 40-50%.

The mortality rate for patients in the ICU is higher in those who have AKI, especially when AKI is severe enough to require dialysis treatment; the mortality rate in patients in intensive care settings with AKI is 70-80%.

In addition, evidence suggests that the relative risk of death is 4.9 in patients in the ICU who have renal failure that is not severe enough to require dialysis. This reflects that the high mortality rate in patients with AKI who require dialysis may not be related to the dialysis procedure or accompanying comorbidities and that AKI alone may be an independent indicator of mortality.

In one published post hoc analysis of the Fluid and Catheter Treatment Trial (FACTT), which examined liberal versus conservative fluid management in intubated ICU patients, fluid balance and diuretic use were identified as prognostic factors for mortality in individuals with AKI. Specifically, greater cumulative fluid accumulation over an average of 6 days was associated with a higher mortality (10.2 L vs 3.7 L in the liberal vs conservative group), and higher furosemide use was associated with a lower mortality (cumulatively 562 mg vs 159 mg). Of note, more than one half of the individuals had Stage 1 AKI (AKIN criteria) CKD, so whether these results apply to more severe stages of AKI is not clear. One interpretation of this study is that patients who can be stabilized with less volume resuscitation fare better. From a practical standpoint, one conclusion is that aggressive prolonged volume resuscitation does not improve prognosis in AKI in the ICU setting.^[7]

Additional prognostic factors

Other prognostic factors include the following:

• Older age
• Multiorgan failure (ie, the more organs that fail, the worse the prognosis)
• Oliguria
• Hypotension
• Vasopressor support
• Number of transfusions
• Noncavitary surgery

Prerenal azotemia due to volume contraction is treated with volume expansion; if left untreated for a prolonged duration, tubular necrosis may result and may not be reversible.

Postrenal AKI, if left untreated for a long time, may result in irreversible renal damage. Procedures such as catheter placement, lithotripsy, prostatectomy, stent placement, and percutaneous nephrostomy can help to prevent permanent renal damage.

Timely identification of pyelonephritis, proper treatment, and further prevention using prophylactic antibiotics may improve the prognosis, especially in females. Early diagnosis of crescentic glomerulonephritis via renal biopsy and other appropriate tests may enhance early renal recovery, because appropriate therapy can be initiated promptly and aggressively. The number of crescents, the type of crescents (ie, cellular vs fibrous), and the serum creatinine level at the time of presentation may dictate prognosis for renal recovery in this subgroup of patients.

Approximately 20-60% of patients experiencing AKI require dialysis during their hospital stay. The majority of these patients recover, with only 25% requiring long-term renal replacement therapy.

A large cohort study demonstrated that proteinuria coupled with low baseline GFR is associated with a higher incidence of AKI and should be considered as an identifying factor for individuals at risk. An occurrence of AKI by itself also has significant negative prognostic implications.^[8]

One published study examining AKI after elective surgery in more than 200,000 patients older than 66 years suggested that patients taking statins had a lesser incidence and severity of AKI and lower mortality than individuals not on statins. Furthermore, the incidence and severity correlated with the potency of the statin as well. As the study was a retrospective review, the authors were not able to recommend routine preoperative administration of statins; however, the study certainly suggests that statins should not be routinely discontinued prior to elective surgery.^[9]

Educating patients about the nephrotoxic potential of common therapeutic agents is always helpful. A good example is NSAIDs; most patients are unaware of their nephrotoxicity, and their universal availability makes them a constant concern.

For patient education information, see the Diabetes Center, as well as Acute Kidney Failure.