Chronic kidney disease

Chronic kidney disease (CKD), also known as chronic renal failure, describes abnormal kidney structure or function, typically represented by a progressive loss of glomerular function. It is present when the glomerular filtration rate (GFR) is less than 60 mL/min/1.73 m² for three consecutive months or greater than or equal to this value in patients with a kidney damage that is present for three or more months ¹.

Epidemiology

CKD is a prevalent disease, affecting between 10-15% of the adult population globally ⁴.

Clinical presentation

Clinical presentation varies depending on etiology, such as nephrotic or nephritic syndromes. Many cases present insidiously until complications ensue.

Complications

• oliguria and eventual anuria

• volume overload

• malnutrition and weight loss

• fatigue

• hypertension

• metabolic acidosis

• anemia

• mineral and bone disorder (renal osteodystrophy)

• vascular calcification

• calciphylaxis

• uremic syndrome (uremia), e.g. uremic encephalopathy, uremic pericarditis

Pathology

A variety of different diseases can affect and cause damage to the renal parenchyma, the most common are ²:

• diabetes mellitus (diabetic nephropathy) 

• hypertension

• glomerulonephritis

• polycystic kidney disease

• reflux nephropathy

• analgesic nephropathy

Classification

Chronic kidney disease can be classified in a variety of ways. One such classification, initially proposed in 2005 by KDIGO and revised in 2012, can be divided into stages based on the GFR (mL/min/1.73 m²) and albuminuria ^1,10.

GFR categories ^1,10:

• G1: >90: kidney damage with normal or elevated GFR

• G2: 60-89: kidney damage with mild reduction in GFR

• G3: 30-59: moderate reduction in GFR, this can be further sub divided as ⁵

  • G3a: 45-59

  • G3b: 30-44

• G4: 15-29: severe reduction in GFR

• G5: <15 (or dialysis): end-stage kidney disease (ESKD)

Albuminuria categories ¹⁰:

• A1: albumin/creatinine ratio <3 mg/mmol (<30 mg/g)

• A2: albumin/creatinine ratio 3-30 mg/mmol (30-300 mg/g)

• A3: albumin/creatinine ratio >30 mg/mmol (>300 mg/g)

Contrast agents

Iodinated contrast media

See the full article here: contrast-induced acute kidney injury.

Gadolinium contrast media

Gadolinium-based contrast agents (GBCAs) have been associated with nephrogenic systemic fibrosis (NSF) in the setting of chronic kidney disease ^8,9. The threshold that is a contraindication for administration of gadolinium contrast is institution dependent and also depends on the dose and type of contrast agent being used. Previous guidelines associated with Group I and III GBCAs consider a GFR of 20-30 mL/min a contraindication and a GFR of 30-60 mL/min usually requiring a smaller dose. Dialysis was a contraindication.

New joint consensus statements released by the American College of Radiology (ACR) and the National Kidney Foundation in November 2020 conclude that Group II GBCAs may be administered to high-risk patients without kidney function screening and without contact with the referring provider, although limited data is available for patients with stage 5 chronic kidney disease ⁹.

See the full article here: gadolinium-based contrast agents (GBCAs).

Radiographic features

There are no specific imaging features for CKD, and the diagnosis is based on clinical and laboratory findings. Radiological exams, especially ultrasound, are performed in most of the cases for etiological investigation (e.g. renal artery stenosis, polycystic kidney disease, hydronephrosis) and treatment follow-up.

Ultrasound

Ultrasound with Doppler examination of intrarenal vessels is usually performed in patients with CKD, and it is common to have a normal exam.

Typical B-mode findings of a long-standing severe CKD (especially stage 5) include ²:

• reduced renal cortical thickness <6 mm ⁶ 

  • more reliable than length ⁷

• reduced renal length

• increased renal cortical echogenicity 

• poor visibility of the renal pyramids and the renal sinus

• marginal irregularities

• papillary calcifications

• cysts (see also: acquired cystic kidney disease)

Abnormal Doppler findings in these patients include ²:

• reduced renal vascularity

• increased resistance index (RI) values (segmental and interlobular arteries)

Treatment and prognosis 

Stage 3 CKD patients are reported to be 20 times more likely to die of a cardiovascular event than to reach end-stage renal disease ³. Chronic vascular disease is a common CKD associated complication and deserves particular attention in regards to management ¹. One study found that treatment and prevention of coronary artery disease, congestive heart failure, diabetes mellitus, and anemia should be the targets of treatment to reduce the mortality of patients with CKD ³.