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- Renal insufficiency is deterioration of kidney function that is secondary to an acute kidney injury (AKI) or chronic kidney disease (CKD).
- It is defined by the rise in serum creatinine (Cr) in conjunction with or without decrease in glomerular filtration rate (GFR).
- Presence of albuminuria is sign of kidney damage.
- Decline in GFR is evidence of reduced renal function.
- Stages of AKI are based on serum Cr level or urine output (1).
- Stage 1: rise of serum Cr ≥0.3 mg/dL or 1.5 to 2 times the baseline, or <0.5 mL/kg/hr urine output in the last 6 hours
- Stage 2: rise of Cr 2 to 3 times from baseline, or <0.5 mg/kg/hr in the last 12 hours
- Stage 3: rise 3 times the baseline serum Cr or ≥4.0 mg/dL with a sudden increase of 0.5 mg/dL serum Cr or more
- Severity of CKD is staged based on GFR and presence of kidney damage (1).
- Stage 1: GFR is preserved (≥90 mL/min/1.73 m3) with presence of renal damage.
- Stage 2: renal damage with decrease in filtration rate (GFR 60 to 90 mL/min/1.73 m3)
- Stage 3: GFR 39 to 59 mL/min/1.73 m3
- Stage 4: severe disease with GFR 15 to 29 mL/min/1.73 m3
- Stage 5: kidney failure or end-stage renal disease with GFR <15 mL/min/1.73 m3 or need for renal replacement treatment
- Signs of kidney damage, required for stages 1 and 2, include elevated albumin-Cr ratio and can also include casts, hematuria, and abnormalities noted on imaging.
- 2 to 3 cases per 1,000 persons were diagnosed with AKI (2).
- Rise in incidence of AKI and CKD is due to increase in older patients and increase in prevalence of diabetes and hypertension (2).
- 11% of U.S. population suffers from CKD (3).
- Rates of AKI are between 1% and 26% due to variation in classification (1).
- Prevalence is high in patients admitted to the hospital and especially in critically ill patients with sepsis.
- In developing countries, AKI is common in patients with hypovolemia secondary to diarrhea. In the United States, open heart surgery patients are frequently at higher risk of AKI (4).
Etiology and Pathophysiology
- Factors that cause AKI can be divided into prerenal, intrinsic, or postrenal.
- Prerenal is often due to decreased perfusion to the kidney.
- Intrinsic causes can be found within the renal parenchyma.
- Postrenal etiologies are secondary to obstruction of urine from the distal portion of the kidney.
- CKD is most commonly caused by diabetes (5).
- Other causes of CKD can be divided into vascular (hypertension or renal ischemia), primary glomerular disease (vasculitis, lupus nephritis, IgA nephropathy, focal segmental glomerulosclerosis, membranous nephropathy, minimal change disease) and secondary conditions (infections, heroin use, malignancy, and amyloidosis), polycystic kidney disease, tubulointestinal disease (UTI, multiple myeloma, nephrolithiasis, obstruction, sarcoidosis, and drug toxicity) (5).
- CKD risk factors include diabetes mellitus, hypertension, autoimmune disease, family history of CKD, minority status (blacks, American Indians, Asian, Pacific Islanders), older age, sepsis, recovery from AKI, neoplasia, lower urinary tract obstruction, UTIs, nephrolithiasis, low birth weight, and low socioeconomic status (5).
- AKI risk factors are diabetes, history of CKD, older age, sepsis, hypovolemia/shock, cardiac surgery, infusion of contrast agents, chronic history of congestive heart failure and liver failure (2).
- Nephrotoxic drugs include radiocontrast agents, aminoglycosides, amphotericin, nonsteroidal anti-inflammatory drugs (NSAIDs), β-lactam antibiotics, sulphonamides, acyclovir, methotrexate, cisplatin, cyclosporine, tacrolimus, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs) (4).