Urinary System

Abnormal Urine Output

Term Definition (mL/kg/h) Definition (mL/d)
Polyuria > 1.5 mL/kg/h > 2000 mL/d
Normal 0.5 ~ 1.5 mL/kg/h 800 ~ 2000 mL/d
Oliguria < 0.5 mL/kg/h < 500 mL/d
Anuria 0 mL/kg/h < 100 mL/d

Abnormal Urine Color

Color Diseases
Orange Rifampin
Black Alkaptonuria
Red Hematuria
Hemoglobinuria
Myoglobinuria
Brown Hyperbilirubinemia
Purple Porphyria

Abnormal Microscopic Findings in Urine

Finding Contents Conditions
RBC casts RBCs Glomerulonephritis
WBC casts WBCs UTI
Glomerulonephritis
Acute interstitial nephritis (AIN)
RTE cell casts RTE cells Acute tubular necrosis (ATN)
Hyaline casts Mucoprotein -
Granular casts Cellular debris Acute tubular necrosis (ATN)
Waxy casts Cellular debris Chronic kidney disease (CKD)
Fatty casts Lipids Nephrosis
Envelope crystals Calcium oxalate Ethylene glycol
Malabsorption
Coffin lid crystals Struvite Urease-positive pathogens
Rhomboid crystals Uric acid Hyperuricemia
Hexagonal crystals Cystine Cystinuria

Diuretics

Mechanism Mnemonic Medication Location K H Ca
Carbonic anhydrase inhibitors Abnormal Acetazolamide Proximal convoluted tubule (PCT) ↓ ↑ -
Na-K-2Cl sympoter blockers Loss Loop diuretics:
Furosemide
Bumetanide
Torsemide		 Ascending loop of Henle ↓ ↓ ↓
Na-Cl sympoter blockers Through Thiazides:
Hydrochlorothiazide
Chlorthalidone		 Distal convoluted tubule (DCT) ↓ ↓ ↑
Na channel blockers Kidney K-sparing diuretics:
Amiloride
Triamterene		 Collecting tubule (CT) ↑ ↑ -
Mineralocorticoid receptor antagonists (MRA) Kidney K-sparing diuretics:
Spironolactone
Eplerenone		 Collecting tubule (CT) ↑ ↑ -

Indications for Acute Dialysis {AEIOU}

  • Acidosis
  • Electrolyte disturbances
  • Intoxication
  • Overload of volume
  • Uremia

Mechanisms of Dialysis

Mechanism Dialysis Ultrafiltration
Transport Diffusion Convection
Drive Concentration gradient Pressure gradient
Removal Small molecules All molecules & Water
Fluids Dialysate Replacement fluid

Modes of Dialysis

  • Peritoneal dialysis (PD)
  • Intermittent hemodialysis (IHD)
  • Sustained low efficiency dialysis (SLED)
  • Continuous renal replacement therapy (CRRT)

Presentation of Uremia

  • Altered mental status (AMS)
  • Asterixis
  • Restlessness
  • Serositis
  • Nausea/Vomiting
  • Uremic frost
  • Bleeding

Classification of Acute Kidney Injury (AKI)

Variable Prerenal Renal Postrenal
Urine osmolality > 500 < 350 -
Urine Na < 20 > 40 -
FENa < 1% > 2% -
Serum BUN/Cr > 20 < 15 -

Staging of Acute Kidney Injury (AKI)

RIFLE

Stage Cr GFR Urine
Risk 1.5x ~ 2x 50 ~ 75% < 0.5 mL/kg/h for 6 ~ 12 hours
Injury 2x ~ 3x 25 ~ 50% < 0.5 mL/kg/h for 12 ~ 24 hours
Failure > 3x
↑ > 0.5 mg/dL to > 4.0 mg/dL		 < 25% < 0.3 mL/kg/h for > 24 hours
0 mL/kg/h for > 12 hours
Loss Failure > 4 weeks    
ESRD Failure > 3 months    

AKIN

Stage Cr Urine
1 1.5x ~ 2x
↑ > 0.3 mg/dL		 < 0.5 mL/kg/h for 6 ~ 12 hours
2 2x ~ 3x < 0.5 mL/kg/h for 12 ~ 24 hours
3 > 3x
↑ > 0.5 mg/dL to > 4.0 mg/dL		 < 0.3 mL/kg/h for > 24 hours
0 mL/kg/h for > 12 hours

Staging of Chronic Kidney Disease (CKD)

Stage GFR
1 > 90
2 60 ~ 90
3a 45 ~ 60
3b 30 ~ 45
4 15 ~ 30
5 < 15

Presentation of Glomerulopathy

Nephritis

  • Proteinuria < 3.5 g/d
  • Oliguria
  • Azotemia
  • Hypertension
  • Hematuria

Nephrosis

  • Proteinuria > 3.5 g/d
  • Hypoalbuminemia
  • Hypogammaglobulinemia
  • Hypercoagulability
  • Hyperlipidemia

Classification of Glomerulopathy {IAA-RAMD-MMF-DA}

Glomerulopathy Nephritis Nephrosis LM/IF/EM IC Shape IC Location C3 Associations
IgA nephropathy [Berger disease] + - Mesangial proliferation Mesangial Mesangial - HSP
Alport syndrome + - GBM thinning
GBM splitting
Basket-weave appearance		 - - - -
Anti-GBM disease [Goodpasture syndrome] + - Crescent shape Linear GBM - -
ANCA-associated vasculitis (AAV) + - Crescent shape - - - -
Rapidly progressive glomerulonephritis (RPGN) + - Crescent shape - - - Anti-GBM
ANCA
Acute proliferative glomerulonephritis (APGN) + - Lumpy-bumpy appearance
Starry sky appearance		 Granular Subepithelial ↓ GAS
Membranoproliferative glomerulonephritis (MPGN) + + Mesangial proliferation
GBM thickening
GBM splitting
Tram-track appearance		 Granular Subendothelial ↓ SLE
HBV
HCV
Diffuse proliferative glomerulonephritis (DPGN) + + Wire looping appearance Granular Subendothelial ↓ SLE
Membranous nephropathy - + GBM thickening
Spike-and-dome appearance		 Granular Subepithelial - Anti-PLA2R
SLE
HBV
HCV
Minimal change disease (MCD) - + Podocyte effacement - - - -
Focal segmental glomerulosclerosis (FSGS) - + Segmental sclerosis
Hyalinosis
Podocyte effacement		 - - - HIV
SCD
Diabetic nephropathy - + Nodular sclerosis
GBM thickening		 - - - -
Amyloid nephropathy - + Nodular sclerosis - - - -

Etiology of Acute Interstitial Nephritis (AIN)

  • Drugs
    • Analgesics :: NSAIDs
    • Antibiotics
    • Proton pump inhibitors (PPI)
  • Infections
    • Tuberculosis
    • Legionella
    • CMV
  • Autoimmune
    • SLE
    • Sjogren syndrome
    • Sarcoidosis

Etiology of Acute Tubular Necrosis (ATN)

  • Ischemia
  • Drug-induced nephrotoxicity
    • Analgesics :: NSAIDs
    • Antibiotics :: Vancomycin & Aminoglycosides & Amphotericin B
    • Antivirals :: DNA polymerase inhibitors
    • Antineoplastics :: Platinums [-Platins]
  • Contrast-induced nephropathy
  • Hematuria :: hemoglobinuria & myoglobinuria
  • Light chain deposition disease (LCDD)

Etiology of Renal Papillary Necrosis (RPN) {SAND}

  • Sickle cell nephropathy
  • Acute pyelonephritis
  • NSAIDs
  • Diabetic nephropathy

Renal Tubular Acidosis (RTA)

Type Synonym Defect Serum K Serum H
1 Distal H secretion ↓ ↑
2 Proximal HCO3 reabsorption ↓ ↑
3 Mixed - ↓ ↑
4 Hyperkalemic Aldosterone ↑ ↑

Etiology of Overactive Bladder (OAB)

  • Urinary tract infection (UTI)
  • Bladder stone
  • Urinary retention
  • Neurogenic bladder
  • Drug-induced

Etiology of Underactive Bladder (UAB)

  • Overdistension
  • Postoperative
  • Neurogenic bladder
  • Drug-induced

Urinary Incontinence

Type Urgency Nocturia Residual volume Etiology
Stress - - - Pelvic relaxation
Urge + + ↓ Overactive bladder (OAB)
Overflow - + ↑ Underactive bladder (UAB)

Etiology of Stress Incontinence

  • Urethral hypermobility
  • Intrinsic sphincteric deficiency
  • Pelvic organ prolapse (POP)

Etiology of Urinary Retention

  • Obstruction
  • Underactive bladder (UAB)

International Classification of Vesicoureteral Reflux (VUR)

Grade Description
1 Reflux to the ureter
2 Reflux to the pelvis
3 Dilatation of the ureter & pelvis & calyx
4 Blunting of the fornix
5 Loss of papillary impressions

Indications for Voiding Cystourethrogram (VCUG)

  • Boys with first UTI
  • Girls < 3 y/o with first UTI
  • Girls < 5 y/o with febrile UTI
  • Girls with recurrent UTIs

Pathogens of Urinary Tract Infection (UTI)

  • Staphylococcus saprophyticus
  • Serratia marcescens
  • Escherichia coli
  • Enterobacter cloacae
  • Klebsiella pneumoniae
  • Pseudomonas aeruginosa
  • Proteus mirabilis
  • Candida

Diagnosis of Urinary Tract Infection (UTI)

  • Voided urine > 105 CFU/mL
  • Catheterized urine > 5 × 104 CFU/mL
  • Suprapubic aspirate > 104 CFU/mL

Empirical Antibiotics for Urinary Tract Infection (UTI)

Patient Antibiotics
Outpatient Nitrofurantoin
TMP-SMX
Fosfomycin
Amoxicillin & Clavulanate
1° Cephalosporins
Outpatient & Complicated 3° Cephalosporins
Fluoroquinolones
Inpatient 3° Cephalosporins
Fluoroquinolones
Inpatient & Complicated Vancomycin & Carbapenems

Complicated Outpatients

  • Temperature > 38°C
  • Costovertebral angle tenderness
  • Pain :: pelvic / perineal

Management After Bladder Scan

Timing Volume (mL) Managment
PVR < 200 -
PVR 200 ~ 400 Intermittent catheterization
PVR > 400 Indwelling urinary catheter
Random < 400 Bladder scan Q2H
Random > 400 Indwelling urinary catheter
  • Post-voidal residual (PVR)