Renal Failure, Micturition & Bladder Disorders: An Overview

Posted on Nov 11, 2024 in Biology

Renal Failure: Kidney Function and Dysfunction

Acute Renal Failure (ARF)

Causes of ARF

  • Intrarenal: Acute tubular necrosis, nephrotoxins (drugs, chemicals), intratubular obstruction (hemoglobinuria, myoglobinuria).
  • Prerenal: Circulatory issues leading to decreased kidney perfusion (e.g., hypovolemia, heart failure).
  • Postrenal: Mechanical obstruction below the kidney (e.g., bilateral ureteral obstruction).

Phases of ARF

  • Onset/Initiating Phase: Decreased urine output, increased serum creatinine.
  • Maintenance Phase (Oliguric Phase): Marked decrease in GFR; complications include sodium and water overload, hyperkalemia, uremia, and metabolic acidosis.
  • Recovery Phase: Repair of renal tissue, gradual increase in urine output.

Pathophysiological Changes and Manifestations in ARF

  • Nephrotoxins: Swelling and necrosis of tubular cells leading to obstructed lumens and lower GFR.
  • Ischemia: Vasoconstriction leads to low blood flow, resulting in oliguria.
  • Manifestations: Oliguria, increased serum urea, hyperkalemia, edema, hypertension, and metabolic acidosis.

Chronic Renal Failure (CRF)

Causes of CRF

Chronic kidney disease, congenital polycystic kidney disease, systemic disorders, long-term exposure to nephrotoxins (e.g., hypertension, diabetes, glomerulonephritis).

Pathophysiology of CRF

  • Decreased Renal Reserve: Reduced GFR, higher serum creatinine without clinical symptoms.
  • Renal Insufficiency: GFR around 20% of normal, significant nitrogen waste retention, large volumes of dilute urine, decreased erythropoiesis.
  • End-Stage Renal Failure: Negligible GFR, fluid and electrolyte retention, azotemia, marked oliguria or anuria.

Manifestations and Treatment of CRF

  • Manifestations: Oliguria, peripheral neuropathy, encephalopathy, congestive heart failure, dysrhythmias, anemia, acidosis, uremic frost, and skin changes.
  • End-Stage Renal Failure: Diagnosis includes metabolic acidosis, azotemia, severe anemia, and electrolyte imbalances (e.g., hyponatremia, hyperkalemia). Treatment involves dialysis (hemodialysis or peritoneal dialysis), kidney transplantation, medications to stimulate erythropoiesis, and dietary restrictions.

Micturition and Urinary Disorders

Micturition: The Process of Urination

  • At Rest: Detrusor muscle is relaxed, internal and external sphincters are contracted.
  • During Micturition: Stretch receptors in the bladder signal the spinal cord, causing reflex actions. The detrusor muscle contracts, and sphincters relax to allow urine passage.
  • Neural Control: Centers in the brainstem and cerebral cortex can override the basic reflex, with parasympathetic control facilitating the micturition process.

Urinary Obstruction and Stasis

Causes and Stages

  • Causes: Benign prostatic hyperplasia (common in men over 80), bladder tumors or metastasis, congenital obstructions, fecal impaction, or constipation.
  • Early Stages: Bladder hypertrophy, hypersensitivity to stretch, increased urgency, and incontinence.
  • Late Stages: Thickened bladder wall, urine retention, incomplete emptying leading to frequency and urgency.

Neurogenic Bladder

Types, Symptoms, and Treatment Goals

  • Spastic Neurogenic Bladder: Caused by injury above T12 (e.g., stroke, multiple sclerosis); characterized by reflex bladder spasms and dys-synergia (synchronous contraction of detrusor and sphincter).
  • Flaccid Neurogenic Bladder: Caused by peripheral neuropathies (e.g., diabetes) or trauma; characterized by the inability to empty the bladder and possible overflow incontinence.
  • Symptoms: Involuntary voiding, incomplete voiding, urgency, and potential retention.
  • Treatment Goals: Prevent bladder overdistention, urinary tract infections, and renal damage. Mitigate social and psychological effects.

Urinary Incontinence

Types of Incontinence

  • Enuresis: Involuntary urination by a child over 4 years old.
  • Stress Incontinence: Involuntary loss of urine due to increased abdominal pressure.
  • Urge Incontinence: Overactive bladder with involuntary contractions during filling.
  • Overflow Incontinence: Inability to empty the bladder leads to leakage due to excessive intravesical pressure.

Bladder Cancer

Risk Factors, Symptoms, Diagnosis, and Treatment

  • Risk Factors: Chemicals, smoking, recurrent UTIs, heavy analgesic use.
  • Symptoms: Early signs include hematuria (blood in urine) and dysuria (painful urination).
  • Diagnosis: Urine cytology and biopsy.
  • Treatment: Surgical resection of the tumor, chemotherapy, radiation, and photoradiation therapy for early cases.
  • Localization: 10% dome, 70% posterior/lateral walls, 20% trigone/bladder neck.
  • Types: 80% papillary tumors (invasive), 3% carcinoma in situ (non-invasive).
  • Growth Patterns: Tumors invade the bladder wall and can metastasize to pelvic lymph nodes, liver, and bone.