Urinalysis

OVERVIEW

• Visual inspection
• Dipstick
• Microscopy – cells, casts and crystals
• Electrolytes – Na, K, Ca
• Osmolality
• Urinary Cystatin C

VISUAL INSPECTION

• yellow: normal
• pale/clear: diuretics, diabetes insipidus
• milky: lipiduria, UTI
• pink/opalescent: haemoglobinuria
• pink/cloudy -> red: haematuria
• tea coloured: myoglobinuria, metronidazole, porphyria
• blue: methylene blue administration
• green: high dose propofol
• orange: rifampicin, conjugated bilirubin
• grey/black: homogentisic acid in alkaptonuria, melanogens in disseminated melanoma, Addisons disease

DIPSTICK

• specific gravity: normal 1.003-1.030, increased: hyperglycaemia, proteinuria, SIADH, intravascular dehydration, radiocontrast, deceased: DI, GN, pyelonephritis, renal failure
• pH: normal 4.5-8, < 6: acidosis and pre-renal failure, >7: alkalosis and alkalinising agents, RTA
• glucose: hyperglycaemia or renal glycosuria
• blood: positive in haematuria, haemoglobinuria, myoglobinuria
• protein: albuminuria (requires further investigation – GN, MM, malignancy, pyelo)
• BHCG: pregnancy status
• WCC: pyuria
• nitrites: bacterial infection (most convert nitrates to nitrite)
• ketones: starvation, diabetic or alcoholic ketoacidosis, carbohydrate free and high fat+protein diet
• bilirubin and urobilinogen: conjugated -> excess production or biliary obstruction, urobilinogen -> absent in biliary obstruction

MICROSCOPY

Cells

• RBC: renal disease (low specificity), dysmorphic cells -> GN
• WCC: infection (low specificity), renal calculi, interstitial nephritis, GN, vasculitis, infarction
• tubular cells: tubular disease
• eosinophils: interstitial nephritis

Casts

• hyaline: can be normal
• red cell casts: glomerular disease (GN), endocarditis
• white cell casts: pyelonephritis, interstitial nephritis, vasculitis, infarction
• granular: non-specific to many renal parenchymal disease
• fatty: diabetic nephropathy and nephrotic syndrome
• epithelial: recovery phase of ATN
• eosinophilia: interstitial nephritis and atheroembolism

Crystals

• oxalate crystals: ethylene glycol poisoning
• calculi: calcium, magnesium-ammonium-phosphate, urate, cysteine
• drugs: sulphonamides, methotrexate, acyclovir, radiocontrast

ELECTROLYTES

Sodium

• increased loss: hypoadrenalism, salt-losing nephropathy, ATN, excess salt loads, SIADH
• decreased loss: hyperaldosteronism, Cushing syndrome, intravascular dehydration, pre-renal failure, hepatorenal syndrome

Potassium

• helps clarify whether loss is renal or extra-renal
• increased loss: hypomagnesaemia, ATN, loop and thiazide diuretics, hyperaldosteronism, Cushing syndrome, amphotericin B

Chloride

• may help clarify the mechanism of metabolic alkalosis
• UrCl- <10mmol/L: intravascular volume depletion (diuretics, vomiting)
• UrCl- >10mmol/L: intravascular volume expansion + hypokalaemia (hyperaldosteronism)

Calcium

• may clarify deranged calcium homeostasis
• increased loss: loop diuretics, idiopathic hypercalcuria, hypoparathyroidism, vitamin D intoxication, renal failure, RTA, sarcoidosis
• decreased excretion: hyperparathyroidism, malabsorption syndromes, vitamin D deficiency, thiazide diuretics

OSMOLARITY

• like Na+ is a marker of hydration and concentration ability but also reflects excreted osmotically active substances (ie. mannitol, radiocontrast, glucose)

URINARY CYSTATIN C

• predictor of severity of acute tubular dysfunction in a range of renal pathologies.

References and Links

• Unusual urine – Clinical Cases
• CCC – Urinalysis
• CCC – Urine electrolytes – Urinary anion gap
• Urinalysis Overview Table
• Laboratory Urinalysis

CCC Differential Diagnosis Series
NEURO	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
RESP	Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement
CVS	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
GIT	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
GUT	Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency,
MSK	Arthritis, Shoulder pain, Wasting of the small muscles of the hand
DERM	Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans
ENDO	Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss
HAEM	Splenomegaly
PAEDS	Floppy infant
MISC	Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest
IMAGING	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, ABDO: Gas on abdominal X-ray, Kidney mass, BRAIN: Intracranial calcification, Intracranial structures with contrast, Ventriculomegaly, OTHER: Pseudofracture on X-Ray,
LABS	LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia,  HIGH: Bilirubin and Jaundice, Hyperammonaemia, Hypercalcaemia, 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

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