Renal Failure and Acute Kidney Injury Overview

Renal Failure Overview

• Renal failure is characterized by decreased kidney filtration, leading to waste product retention and electrolyte imbalances.
• Consequences include accumulation of urea and creatinine, electrolyte disturbances like hyperkalemia and metabolic acidosis.

Acute Kidney Injury (AKI)

• AKI is a sudden decline in kidney function over hours to 7 days, marked by elevated creatinine and reduced urine output.
• Symptoms include oliguria, anuria, fluid overload, and electrolyte imbalances.
• Causes are categorized into pre-renal, renal (intrinsic).
• Pre-renal:
  • Hypovolemia from dehydration, blood loss, or diuretics.
  • Decreased cardiac output from heart failure or cardiogenic shock.
  • Vasodilation due to sepsis or anaphylaxis.
  • Renal artery stenosis.
  • Systemic hypotension.
• Renal (Intrinsic):
  • Acute tubular necrosis caused by ischemia or nephrotoxins.
  • Acute interstitial nephritis triggered by allergic reactions or infections.

Diagnostic Methods

• Blood tests: serum creatinine and BUN for kidney function; CBC for anemia; electrolyte panel for hyperkalemia and acidosis.
• Urinalysis: proteinuria and hematuria.
• Imaging studies: Ultrasound or CT scan for assessing kidney size, structure, and obstruction.
• GFR Calculation: Estimated using serum creatinine, age, sex, and race.

Treatment of AKI

• Address the underlying cause: Hydration for pre-renal AKI, cessation of nephrotoxins.
• Supportive care: Diuretics, electrolyte management.

Chronic Kidney Disease (CKD)

• CKD involves chronic kidney dysfunction lasting over 3 months, characterized by progressive decline in kidney function.
• Most common causes are diabetes mellitus and hypertension.
• Laboratory findings:
  • Elevated BUN (>20 mg/dL suggests kidney dysfunction).
  • Elevated creatinine (>1.2 mg/dL in women, >1.4 mg/dL in men, indicates kidney impairment).
  • Stages based on GFR:
    • Stage 1: GFR > 90 mL/min (normal kidney function).
    • Stage 2: GFR 60-89 mL/min (mild reduction).
    • Stage 3: GFR 30-59 mL/min (moderate reduction).
    • Stage 4: GFR 15-29 mL/min (severe reduction, approaching dialysis).
    • Stage 5: GFR <15 mL/min (end-stage renal disease).

Complications of CKD

• Anemia: Loss of EPO leading to normocytic anemia.
• Dyslipidemia: Increased triglycerides due to protein loss in urine and impaired clearance of chylomicrons and VLDL.

Treatment of CKD

• Manage underlying causes: Tight blood sugar control in diabetes, control of blood pressure using ACE inhibitors or ARBs.
• Supportive care: Dietary modifications (low protein, low potassium, low phosphorus), management of complications (e.g., erythropoietin-stimulating agents for anemia).
• Dialysis: Initiated when GFR falls below 15 mL/min or when symptoms like fluid overload or severe electrolyte imbalance arise.
• Kidney transplant: Considered for eligible patients with end-stage renal disease.

Dialysis

• Dialysis is a medical procedure that removes waste products and excess fluid from the blood when kidneys are not functioning adequately.
• Indications for dialysis (ΑΕΙΟU):
  • Acidemia: Metabolic acidosis not controlled by medications.
  • Electrolytes: Severe hyperkalemia posing a risk to cardiac function.
  • Intoxication: Poisoning or overdose from dialyzable substances.
  • Overload of fluid: Fluid overload leading to CHF or pulmonary edema.
  • Uremic Symptoms: Symptoms of uremia like nausea, vomiting, confusion, and pericarditis.
• Dialyzable substances include salicylates, lithium, isopropyl alcohol, magnesium laxatives, and ethylene glycol.

Renal Osteodystrophy

• Phosphate retention decreases calcium levels in plasma, causing hypocalcemia.
• Lack of active vitamin D reduces gut calcium absorption, also leading to hypocalcemia.
• Both pathways stimulate parathyroid hormone (PTH) secretion, resulting in secondary or tertiary hyperparathyroidism
• Symptoms/Manifestations: Bone pain, fractures, osteitis fibrosa cystica (bone disease due to high PTH), brown tumors.

Xanthogranulomatous Pyelonephritis

• A chronic kidney infection characterized by renal parenchyma destruction and the presence of lipid-laden macrophages (foam cells) within the kidney.
• Frequently confused with renal tumors due to its appearance.
• Common pathogens: Proteus mirabilis, other organisms can also be involved.
• Risk factors: Chronic urinary tract obstruction (stones or tumors), diabetes mellitus.
• Signs & Symptoms: Flank pain, fever, weight loss, hematuria, fluctuating renal function.
• Diagnostic methods:
  • CT scan: Shows a non-functioning kidney with enlargement, heterogeneous mass, and possible obstruction.
  • Ultrasound: May reveal a hydronephrotic kidney with changes suggestive of chronic infection.
• Treatment: Surgical intervention, nephrectomy is typically necessary due to significant renal destruction and complications.