[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Urinalysis [Biochemistry](https://durgical.com/en/biochemistry/) · Topic # Urinalysis Urinalysis combines appearance, dipstick and microscopy; it points to infection, kidney disease, diabetes and liver problems. Updated 2026-11-01 ## Key facts - Three parts: physical (colour, clarity, specific gravity), chemical by dipstick (pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, leukocyte esterase) and microscopic (cells, casts, crystals). - Nitrite + leukocyte esterase suggest urinary infection; nitrite needs nitrate-reducing bacteria (Enterobacterales) and urine held for some hours. - Glycosuria appears when blood glucose exceeds the renal reabsorption threshold (SGLT2) or when the tubule fails (Fanconi, SGLT2 inhibitors). - Dipstick positive for blood without red cells under the microscope: myoglobin (rhabdomyolysis) or free haemoglobin (haemolysis). - Casts: red cell = glomerulonephritis; white cell = pyelonephritis or interstitial nephritis; 'muddy brown' granular = acute tubular necrosis; waxy = chronic disease. ## In detail - Sample: clean-catch midstream urine, ideally the first morning void and analysed promptly, because cells and casts break down and bacteria multiply. - Specific gravity: reflects concentrating ability; fixed low (isosthenuria) in advanced kidney disease or diabetes insipidus; high in dehydration or after contrast. - Protein: the dipstick mainly detects albumin; it misses light chains (myeloma), which need other tests. The protein/creatinine or albumin/creatinine ratio quantifies. - Ketones: the dipstick detects acetoacetate (and acetone), not β-hydroxybutyrate, so it can underestimate ketoacidosis. - Urine bilirubin: only the conjugated (direct) form passes, so it appears in cholestasis and hepatitis, not in haemolysis; urobilinogen rises in haemolysis and liver disease and is absent in complete obstruction. - Crystals: calcium oxalate (stones, ethylene glycol), uric acid (acid urine, gout, tumour lysis), struvite (Proteus infection, alkaline urine), hexagonal cystine (cystinuria). - pH: alkaline with urea-splitting bacteria; acid in metabolic acidosis of non-renal cause and high-protein diets. **Also called** Urine test, Dipstick, Urine sediment, Urine microscopy ## Clinical notes - Asymptomatic bacteriuria is not treated except in pregnancy and before urological procedures. - A sediment with dysmorphic red cells and red cell casts points to glomerular disease and calls for assessment of kidney function. - High-dose vitamin C can give false negatives for glucose, blood and nitrite on the dipstick. ## Related conditions - [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/) - [Kidney stones (urolithiasis)](https://durgical.com/en/conditions/kidney-stones/) - [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/) - [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/) - [Acute pyelonephritis](https://durgical.com/en/conditions/acute-pyelonephritis/) - [Cystinuria](https://durgical.com/en/conditions/cystinuria/) ## Related - [Glucose](https://durgical.com/en/biochemistry/molecules/glucose/) - [Acetoacetate (acetoacetic acid)](https://durgical.com/en/biochemistry/molecules/acetoacetate/) - [Bilirubin](https://durgical.com/en/biochemistry/molecules/bilirubin/) - [Creatinine and estimated glomerular filtration rate (eGFR)](https://durgical.com/en/biochemistry/topics/creatinine-and-estimated-glomerular-filtration-rate/) - [Serum albumin as a lab test](https://durgical.com/en/biochemistry/topics/serum-albumin-as-a-lab-test/) ## Test yourself Think of the answer, then tap the question to see it. ## What does a dipstick positive for blood without red cells under the microscope suggest? Myoglobinuria (rhabdomyolysis) or haemoglobinuria (haemolysis), because the dipstick detects the peroxidase activity of haem. ## Why can the ketone dipstick underestimate ketoacidosis? It detects acetoacetate and acetone but not β-hydroxybutyrate, the ketone that predominates in severe ketoacidosis. ## Which bilirubin appears in urine, and why? Only the conjugated (direct) form, because it is water-soluble; unconjugated bilirubin travels on albumin and is not filtered. ## What do red cell casts indicate? Bleeding of glomerular origin, as in glomerulonephritis. ## Why does a negative nitrite not rule out urinary infection? Some bacteria (enterococci, staphylococci) do not reduce nitrate, and urine must stay hours in the bladder for nitrite to form. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/biochemistry/topics/urinalysis/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Urinalysis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003579.htm) (MedlinePlus, US National Library of Medicine, 2026); [Urinalysis: MedlinePlus](https://medlineplus.gov/urinalysis.html) (MedlinePlus, US National Library of Medicine, 2026); [Protein in Urine: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/protein-in-urine/) (MedlinePlus, US National Library of Medicine, 2026); [Glucose in Urine Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/glucose-in-urine-test/) (MedlinePlus, US National Library of Medicine, 2026); [Nitrites in Urine: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/nitrites-in-urine/) (MedlinePlus, US National Library of Medicine, 2026); [Leukocyte esterase urine test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003584.htm) (MedlinePlus, US National Library of Medicine, 2026); [Urine specific gravity test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003587.htm) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011). [← All of biochemistry](https://durgical.com/en/biochemistry/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/biochemistry/topics/urinalysis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/topics/urinalysis/