Renal Function and Failure Overview

Anuria and Oliguria

• Anuria refers to the complete absence of urine production.
• Oliguria occurs when urine output is less than 300 ml per day.

Renal Blood Flow

• Kidney function and urine production hinge on oxygenated blood perfusion.
• Reduced renal blood flow or hypoxia can impair kidney function.

Types of Renal Failure

• Renal failure is classified into three categories:
  • Prerenal: Caused by factors affecting blood flow to the kidneys.
  • Renal: Caused by damage to the kidney itself.
  • Postrenal: Resulting from obstruction in the urinary tract.

Prerenal Causes

• Hypovolemia: Inadequate fluid intake or excessive water loss from dehydration, vomiting, diarrhea, burns, or sweating.
• Blood loss: Acute loss often due to trauma or surgery.
• Sepsis: Gram-negative septicemia can lead to shock and renal impairment, particularly in immunocompromised individuals.
• Cardiogenic shock: Can result from myocardial infarction-related dysarhythmia or pulmonary embolus, reducing cardiac output.
• Anesthesia: Hypotension can occur following epidural or spinal anesthesia.
• Hypoxia: Prolonged hypoxia from various causes may occasionally lead to renal impairment.

Renal Causes

• Nephrotoxic Drugs: Aminoglycosides, cephalosporins, diuretics, NSAIDs, and ACE inhibitors may lead to renal failure.
• Poisons: Certain toxins can harm renal function.
• Contrast Media: Can induce renal failure in dehydrated patients with pre-existing issues.
• Eclampsia: Early pre-eclampsia recognition prevents nephrotoxic effects.
• Myoglobinuria: Associated with crush syndrome post-trauma.
• Incompatible Blood Transfusion: May result in renal failure.
• Disseminated Intravascular Coagulation (DIC): Often follows major sepsis or blood transfusions.

Postrenal Causes

• Calculi: Common cause of acute obstruction leading to anuria; may accompany renal colic.
• Pelvic Malignancy: Tumors from bladder, prostate, cervix, ovary, or rectum may obstruct ureters.
• Surgery: Ureters may be accidentally damaged during pelvic surgeries.
• Retroperitoneal Fibrosis: May lead to ureteric obstruction.
• Bilharzia: Schistosomiasis can cause ureteric fibrosis and potentially lead to bladder cancer.
• Crystalluria: Rarely associated with sulphonamide medications; can occur in chemotherapy patients.

Clinical Assessment

• Determine if urine is produced through catheterization if necessary; assess urine specific gravity and appearance for casts or myoglobinuria.
• Identify potential prerenal causes through clinical examination and vital signs assessment.
• Check for ureteric obstruction via ultrasonography; plain abdominal radiographs for calculi.
• Review recent drug administration for potential nephrotoxic agents.
• Evaluate for chronic renal failure progression via ultrasound and clinical signs.

Management and Treatment Phases

• Acute tubular necrosis progresses through:
  • Oliguria Phase: Initial management focuses on restoring circulating volume and correcting tissue hypoxia.
  • Diuretic Phase: Typically occurs from the 8th to 10th day; glomerular filtration resumes first.
  • Recovery Phase: Not all patients will fully recover; some may require renal replacement therapy.

Supportive Care

• Nutritional Support: Administer parenteral nutrition cautiously to avoid overload.
• Infection Prevention: Increased infection risk necessitates routine cultures and use of non-nephrotoxic antibiotics.
• Fluid Balance Monitoring: Essential for patients; meticulous recording is crucial, especially for seriously ill patients.

Renal Replacement Therapies

• Peritoneal Dialysis: Performed if no recent abdominal surgery; involves using the peritoneum for dialysis.
• Hemodialysis: Life-saving if performed through a catheter placed in a large vein, but may cause fluid balance fluctuations.
• Hemofiltration: Similar to hemodialysis but with less cardiovascular instability.
• Obstructive Renal Failure Management: May require drainage via nephrostomy or stent placement if surgical intervention is not viable.

Surgical Interventions

• Percutaneous Nephrostomy: Involves catheter insertion for urinary drainage under ultrasound guidance.
• J-Stent Insertion: A procedure to drain urine into the bladder using fluoroscopic guidance.
• Open Surgery: Rare in the presence of advanced minimally invasive techniques.