Urine Electrolytes

Urinary Sodium

Increased Urinary Sodium: Salt and water lost through kidneys

  • HYPOnatremia with hypovolaemia
    • Renal failure
    • ATN
    • Addison’s
    • Osmotic diuresis (Raised glucose and urea)
    • Diuretics (Thiazides)
    • Cerebral salt wasting
  • HYPOnatraemia with euvolaemia
    • Elevated urine osmolality (SIADH)
  • HYPOnatraemia with oedema
    • Renal failure
    • Hypertonic saline

Decreased Urinary Sodium: Increased interstitial salt attempted Na retention

  • HYPOnatraemia with oedema
    • Liver failure
    • Cirrhosis
    • CCF
    • Nephrotic syndrome
  • HYPOnatremia with dehydration (increased urine osmolality)
    • Burns, fistula, heat illness
    • Diarrhoea, sweat, vomiting

Urinary anion gap (UAG)

  • Differentiate renal or GIT cause of HYPERchloraemic metabolic disorders
  • or Normal anion gap metabolic acidosis (NAGMA)


  • Urine must maintain electrical neutrality
  • Urinary anion gap provides rough measure of urinary sodium excretion (Positively charged cation)
  • Low anion gap associated with increased NH4+ excretion

Urinary AG = (UA – UC) = [Na+] + [K+] – [Cl]

Hyperchloraemic metabolic acidosis associated with

  • neGUTive UAG
    • Loss of base by GIT (Diarrohea)
      • → hypovolemia and metabolic acidosis
      • → ↑ ­NH4+ excretion
      • → appropriate urine ↓Na but ‘inappropriate’ urine ­↑Cl
    • Loss of base by the kidney (RTA)
    • Impaired renal acidification and kidney unable to excrete enough NH4+
    • NOTE: However in the case of ‘gastric loss‘ the UAG is usually Positive
      • → hypovolemia and metabolic acidosis
      • → HCO3- excretion
      • → ‘inappropriate’ urine ­↑Na but appropriate urine ↓Cl

CCC Differential Diagnosis Series


Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision


Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement


Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction


Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage


Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency


Arthritis, Shoulder pain, Wasting of the small muscles of the hand


Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans


Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss




Floppy infant 


Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest


CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR,
Gas on abdominal X-ray, Kidney mass,
Intracranial calcification, Intracranial structures with contrastVentriculomegaly,
OTHER: Pseudofracture on X-Ray


LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia

HIGH: Bilirubin and Jaundice, HyperammonaemiaHypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia

ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis,

Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes


CCC 700 6

Critical Care


BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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