Diagnosis

Renal failure

Etiology

Cause of acute renal failure [eoz][6yt]

• Prerenal:

  • Hypovolemia: hemorrhage, severe burns, and gastrointestinal fluid losses such as diarrhea, vomiting, and high ostomy output.

  • Hypotension from decreased cardiac output: cardiogenic shock, massive pulmonary embolism, acute coronary syndrome.

  • Hypotension from systemic vasodilation: septic shock, anaphylaxis, anesthesia administration.

  • Renal vasoconstriction: NSAIDs, iodinated contrast, amphotericin B, calcineurin inhibitors, hepatorenal syndrome.

  • Glomerular efferent arteriolar vasodilation (causing intraglomerular hypotension): ACE inhibitors, angiotensin receptor blockers.

• Renal (hematuria or proteinuria):

  • Acute tubular necrosis (ATN): ischemia from prolonged prerenal injury, rhabdomyolysis; intravascular hemolysis (sickle cell), Hemolytic‐uremic syndrome

  • Acute interstitial nephritis (AIN): Infection, autoimmune conditions (systemic lupus erythematosus), hereditary AIN

  • Glomerulonephritis: anti-glomerular basement membrane disease, immune complex-mediated diseases (such as SLE, post-infectious glomerulonephritis, cryoglobulinemia, IgA nephropathy, IgA vasculitis), rapidly progressive glomerulonephritis, tubulointerstitial nephritis

  • Intratubular obstruction: monoclonal gammopathy (multiple myeloma), tumor lysis syndrome, hemolytic anemia, and toxins such as ethylene glycol. 

  • Systemic condictions: Trauma, sepsis, DIC, hepatorenal syndrome

  • Drugs: Aminoglycosides, Vancomycin, Penicillin, Amoxycillin, Ampicillin, Ciprofloxacin, Rifampicin, Sulphonamides, Co‐trimoxazole, Aciclovir, Phenytoin, Cimetidine, Omeprazole, Thiazide diuretics, Furosemide, Allopurinol, Mesalazine, Amphotericin B, Pentamidine, iodinated contrast, NSAIDs, proton pump inhibitors, 5-ASA

• Postrenal:

  • Renal/ureteral calculi, tumors, blood clots, neurogenic bladder, bladder cancer, urethral obstruction (BPH, prostate cancer, retroperitoneal fibrosis, pregnancy, fecal impaction, pelvic organ prolapse, pelvic masses/malignancy, phimosis)

Cause of chronic renal failure [4be]

• Type 2 diabetes (30%-50%)

• Type 1 diabetes (3.9%)

• Atherosclerotic hypertensive renal failure (27.2%)

• Primary glomerulonephritis (8.2%)

  Membranoproliferative, focal segmental, IgA nephropathy, minimal change, rapidly progressive, Goodpasture

• Chronic tubulointerstitial nephritis (3.6%)

• Hereditary or cystic diseases (3.1%)

• Secondary glomerulonephritis or vasculitis (2.1%)

• Plasma cell dyscrasias or neoplasm (2.1%)

• Sickle cell nephropathy

Pathophysiology [eoz][4be]

1. Kidney functions: EPO/vitamin D production, acid-base homeostasis, fluid/electrolyte regulation, and waste-product elimination

2. Glomerular filtration is based on pressure difference between the glomerulus and Bowman's space

3. Acute renal failure: Ischemia/toxins --> cellular insult --> cell death --> renal failure

   • Prerenal: Reduction in renal blood flow (under the direct control of the combined resistances of afferent and efferent vascular pathways)

   • Intrarenal: Intratubular obstruction (myoglobin, uric acid crystals in tumor lysis syndrome, immunoglobulin light chains), immune-mediated injury of the vasculature, immune complex deposition leading to glomerular and tubular damage

   • Postrenal: urinary reflux --> decreased renal perfusion, tubular atrophy, and interstitial inflammation

4. Chronic renal failure: sustained insults --> progressive nephropathy --> kidney fibrosis in the glomeruli (glomerulosclerosis), tubules and interstitium (tubulointerstitial fibrosis), and vessels (vascular sclerosis)

   • Prerenal: Decreased renal perfusion (chronic heart failure or cirrhosis)

   • Intrinsic renal:

     • Vascular: nephrosclerosis (chronic damage to blood vessels, glomeruli, and the tubulointerstitium), renal artery stenosis, fibromuscular dysplasia

     • Nephritic disease: abnormal urine microscopy due to post-infectious glomerulonephritis, infective endocarditis, IgA nephropathy, lupus nephritis, Goodpasture syndrome, and vasculitis

     • Nephrotic disease: proteinuria >3.5 g/24 h due to minimal change disease, focal segmental glomerulosclerosis, membranous glomerulonephritis, diabetic nephropathy, and amyloidosis

     • Tubular and interstitial disease: Polycystic kidney disease, nephrocalcinosis, sarcoidosis, Sjögren syndrome, and reflux nephropathy

   • Postrenal: prostatic disease, nephrolithiasis, abdominal/pelvic tumor, ureteropelvic or ureterovesical junction stenosis, retroperitoneal fibrosis or neurogenic bladder

5. Renal failure --> accumulation of water, sodium, and other metabolic products

6. Uremia (urine in the blood):

   • Fluid/electrolyte imbalance

   • Hormonal abnormalties

   • Accumulation of nitrogenous waste products (urea)

Complications [eoz][4be]

• Hyperkalemia --> arrhythmias

• Hyponatremia

• Hyperphosphatemia

• Metabolic acidosis

• Hypervolemia --> Pulmonary edema, heart failure

• Hypertension

• Anemia

• Metabolic acidosis

• CNS signs of uremia: lethargy, somnolence, cognitive impairment

Epidemiology

Incidence per 100.000 [ksr]

Approach

• Blood test: urea, electrolytes, hemoglobin, calcium, phosphate, PTH, albumin, kalium, lipid profile, albumin, ANA, C-ANCA, P-ANCA, anti-GBM, serum complement levels, hepatitis, HIV

• Urine-stix

• Urine microscopy/culture

• Electrocardiogram

• Isotope clearance

• Ultrasound kidney/bladder

• CT abdomen

• Biopsy

• Protein electrophoresis (serum and urine)

Acute vs Chronic renal failure

• Medical history: GP, family

• Anemia, hypocalcemia, and hyperphosphatemia

• Renal ultrasonography: size, cortical scarring and possibly cyst formation

Treatment

Acute renal failure: [6yt]

1. Treat life threatening features:

   • Hypotension/shock: IV fluid

   • Hypervolemia/pulmonary edema: IV furosemide during the oliguric phase of ATN

   • Hyperkalemia: Dietary restriction, Insulin, IV dextrose, beta-agonists, potassium-binding resins, calcium gluconate, dialysis

   • Acidosis: citrate or bicarbonate

   • Hyperphosphatemia: dietary ingestion or using phosphate binders

2. Treat cause of acute renal failure:

   • Prerenal/dehydration/hypovolumia: IV fluids, bowel obstruction, blood transfusion

   • Renal: Treat the underlying condition (avoid drugs, immunosuppression)

   • Postrenal: Relief of obstruction (double-J stent, lithotripsy, pyelostomi, surgery)

3. Renal Replacement Therapy (intermittent or continuous):

   • Severe hyperkalemia, unresponsive to medical therapy

   • Fluid overload with pulmonary edema

   • Uraemia (blood urea >30–50 mmol/l)

   • Complications of severe uraemia: encephalopathy, pericarditis, neuromyopathy

   • Severe acidosis (pH <7.1)

   • Drug overdose with a dialysable toxin

Chronic renal failure: [oqc]

1. Delaying the progression of CKD: Treatment of the underlying condition

   • Diabetes

   • Hypertension

   • Nephrotoxins: radiocontrast, NSAIDs, aminoglycosides, AR-blocker/ACE-inhibitor

   • Autoimmune kidney disease

2. Treating the pathologic manifestations of CKD:

   • Diet: Protein/salt/phosphate/potassium/volume restriction

   • Anemia: erythropoiesis-stimulating agents and iron

   • Hyperphosphatemia: phosphate binders and dietary phosphate restriction

   • Hypocalcemia: calcium supplements

   • Hyperparathyroidism: calcitriol or vitamin D analogues

   • Volume overload: fluid restriction, loop diuretics or ultrafiltration

   • Metabolic acidosis: oral alkali supplementation

   • Uremia --> renal replacement therapy (hemodialysis/peritoneal dialysis)

     • Severe metabolic acidosis

     • Hyperkalemia/hyponatremia/hypercalcemia/hypocalcemia/hyperphosphatemia

     • Pericarditis or pleuritis

     • Encephalopathy

     • Intractable volume overload

     • Hypertension not responsive to antihypertensive medications

     • Failure to thrive and malnutrition

     • Peripheral neuropathy

     • Intractable gastrointestinal symptoms

     • In asymptomatic patients: GFR of 5-9 mL/min/1.73 m²

3. Kidney transplantation

Differential diagnoses

Alport syndrome, Anemia, Benign prostatic hyperplasia, Diabetes mellitus, Essential hypertension, Gastrointestinal hemorrhage, Glomerulonephritis, Heart failure, Hyperchloremic acidosis, Hyperkalemia, Hypermagnesemia, Hyperparathyroidism, Hyperphosphatemia, Hypocalcemia, Hypothyroidism, Hypovolemia, Malignant hypertension, Multiple myeloma, Pericarditis, Prostate cancer, Renal artery stenosis, Subdural hematoma, Urinary retention, Urinary tract infection, Urolithiasis