Which criterion defines chronic kidney disease?

Which criterion defines chronic kidney disease?

• A. GFR < 60 mL/min/1.73 m2 for more than 3 months OR markers of kidney damage
• B. GFR < 90 for more than 6 months
• C. GFR < 60 for less than 1 month
• D. Blood urea nitrogen elevation alone

Answer: (A)

Chronic kidney disease is defined by kidney dysfunction or damage that persists for at least 3 months. The main criterion is a glomerular filtration rate below 60 mL/min/1.73 m² for more than 3 months, which shows a sustained decrease in filtration. Alternatively, evidence of kidney damage—such as persistent albuminuria (for example, an elevated urine albumin-to-creatinine ratio), abnormal kidney imaging, or specific histologic findings—also qualifies as CKD if present for more than 3 months. The 3-month duration is what separates chronic disease from an acute event, which can transiently lower GFR but isn’t CKD unless it lasts longer. Why this choice fits best: it captures both the functional decline (GFR <60) over a sustained period and the possibility of CKD being diagnosed through damage markers even if the GFR isn’t below 60, as long as the damage persists beyond 3 months. Why the other ideas don’t fit: a GFR below 60 for a short time points to acute kidney injury, not CKD. A GFR below 90 for a long time does not indicate CKD unless it falls below 60 or there are damage markers present; otherwise it can reflect mild, non-chronic changes. Elevation of BUN alone isn’t diagnostic of CKD, since BUN can rise for many non-kidney reasons and doesn’t by itself prove chronic damage or reduced GFR.

Chronic kidney disease is defined by kidney dysfunction or damage that persists for at least 3 months. The main criterion is a glomerular filtration rate below 60 mL/min/1.73 m² for more than 3 months, which shows a sustained decrease in filtration. Alternatively, evidence of kidney damage—such as persistent albuminuria (for example, an elevated urine albumin-to-creatinine ratio), abnormal kidney imaging, or specific histologic findings—also qualifies as CKD if present for more than 3 months. The 3-month duration is what separates chronic disease from an acute event, which can transiently lower GFR but isn’t CKD unless it lasts longer.

Why this choice fits best: it captures both the functional decline (GFR <60) over a sustained period and the possibility of CKD being diagnosed through damage markers even if the GFR isn’t below 60, as long as the damage persists beyond 3 months.

Why the other ideas don’t fit: a GFR below 60 for a short time points to acute kidney injury, not CKD. A GFR below 90 for a long time does not indicate CKD unless it falls below 60 or there are damage markers present; otherwise it can reflect mild, non-chronic changes. Elevation of BUN alone isn’t diagnostic of CKD, since BUN can rise for many non-kidney reasons and doesn’t by itself prove chronic damage or reduced GFR.