🏥 Stations

🧠 Qbank

📖 Book

😃 More

💳 Pricing

🔒 Dashboard

📖 OSCE Learning

🔒 OSCE Stations

🔒 Qbank

🔐 Membership
Share your insights

Help us by sharing what content you've recieved in your exams


Oliguria

Medicine > Renal

Differential Diagnosis Schema 🧠

Prerenal Causes

  • Hypovolemia: Due to dehydration, hemorrhage, or excessive diuresis; presents with signs of volume depletion such as low blood pressure, tachycardia, and dry mucous membranes.
  • Heart Failure: Decreased cardiac output leads to reduced renal perfusion; presents with symptoms of heart failure such as shortness of breath, peripheral edema, and orthopnea.
  • Sepsis: Systemic vasodilation and hypotension reduce renal blood flow; look for signs of infection such as fever, altered mental status, and hypotension.
  • Renal Artery Stenosis: Narrowing of renal arteries reduces perfusion, often with a history of hypertension and evidence of atherosclerotic disease.

Renal Causes

  • Acute Tubular Necrosis (ATN): Most common cause of intrinsic renal failure; often due to ischemia or nephrotoxins, presenting with muddy brown casts in the urine and elevated creatinine.
  • Glomerulonephritis: Inflammation of the glomeruli, presenting with hematuria, proteinuria, and often associated with systemic diseases like lupus or vasculitis.
  • Acute Interstitial Nephritis: Typically drug-induced (e.g., NSAIDs, antibiotics), presents with fever, rash, eosinophilia, and sterile pyuria.
  • Vascular Disorders: Conditions like thrombotic microangiopathies (e.g., HUS, TTP) can cause renal ischemia and oliguria, often presenting with anemia and thrombocytopenia.
  • Tubulointerstitial Nephritis: Chronic inflammation and fibrosis of renal interstitium, leading to progressive renal impairment and oliguria.

Postrenal Causes

  • Urinary Tract Obstruction: Most common postrenal cause, can be due to benign prostatic hyperplasia, renal stones, tumors, or strictures; presents with lower abdominal pain, distended bladder, and anuria or oliguria.
  • Urethral Stricture: Narrowing of the urethra, often due to trauma, infection, or congenital conditions; presents with decreased urine stream, difficulty urinating, and possible urinary retention.
  • Neurogenic Bladder: Impaired bladder function due to neurological conditions like spinal cord injury or multiple sclerosis, leading to urinary retention and overflow incontinence.
  • Bilateral Ureteric Obstruction: Rare, usually due to malignancy or severe ureteric calculi; presents with severe flank pain and oliguria.

Key Points in History 🥼

Symptomatology

  • Onset and Duration: Acute onset suggests an obstructive or severe prerenal cause, whereas chronic oliguria may indicate progressive renal disease.
  • Associated Symptoms: Consider symptoms like hematuria, dysuria, fever, rash, or recent infections that may point towards specific etiologies.
  • Volume Status: Assess for signs of dehydration (e.g., dry mucous membranes, decreased skin turgor) or fluid overload (e.g., edema, pulmonary crackles).
  • Urine Output: Documenting the exact volume of urine output over 24 hours can help classify the severity of oliguria.
  • Pain: Flank pain may suggest a renal stone, whereas lower abdominal discomfort could indicate urinary retention.
  • Medication History: Review nephrotoxic medications (e.g., NSAIDs, ACE inhibitors, aminoglycosides) and recent changes in drug regimen.

Background

  • Past Medical History: Important to note any history of chronic kidney disease, hypertension, diabetes, or recurrent urinary tract infections.
  • Surgical History: Recent surgeries, especially abdominal or pelvic, can increase the risk of urinary retention or renal injury.
  • Family History: Consider family history of polycystic kidney disease, hereditary nephritis, or other genetic renal conditions.
  • Social History: Include lifestyle factors such as alcohol consumption, smoking, and occupation, which could influence kidney health or the risk of infections.
  • Recent Illnesses: Document any recent infections, systemic illnesses, or exposure to nephrotoxins.

Possible Investigations 🌡️

Laboratory Tests

  • Serum Creatinine and Urea: Essential for assessing renal function; elevated levels indicate renal impairment.
  • Electrolytes: Monitor for hyperkalemia, hyponatremia, and metabolic acidosis, which are common in renal dysfunction.
  • Urinalysis: Look for proteinuria, hematuria, casts, and specific gravity; these findings can help differentiate between prerenal, renal, and postrenal causes.
  • Full Blood Count: To assess for anemia, infection, or thrombotic microangiopathies.
  • Blood Cultures: Indicated if sepsis is suspected.
  • Autoimmune Screen: Consider if glomerulonephritis or vasculitis is suspected; includes ANA, ANCA, anti-GBM antibodies.
  • Creatine Kinase: Elevated in rhabdomyolysis, which can cause acute kidney injury and oliguria.

Imaging and Specialist Tests

  • Renal Ultrasound: First-line imaging to assess for obstruction, renal size, and the presence of hydronephrosis.
  • Bladder Scan: Useful for assessing bladder volume and diagnosing urinary retention.
  • CT Scan: Consider if there is suspicion of obstructive uropathy or renal masses not clearly visible on ultrasound.
  • Renal Biopsy: Indicated if glomerulonephritis or interstitial nephritis is suspected and the diagnosis is unclear from non-invasive tests.
  • Urodynamic Studies: May be necessary if a neurogenic bladder is suspected, particularly in patients with spinal cord injuries or multiple sclerosis.

No comments yet 😉

Leave a Reply

Renal