Reading a urinalysis

What it is

Urinalysis is a cheap, fast test with three parts. Inspection notes colour and clarity: dark urine may be concentrated or contain bilirubin, red or brown urine may contain blood, haemoglobin or myoglobin, and cloudiness may reflect cells, crystals or bacteria. The dipstick gives specific gravity, pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite and leukocyte esterase in a minute. Microscopy of the spun sediment counts red and white cells per high-power field and identifies casts, crystals, epithelial cells and organisms. Casts are moulds of the tubules and are the most specific finding: they place the problem inside the kidney. The best sample is a clean-catch midstream urine, examined within about two hours or refrigerated; many squamous cells mean contamination. The dipstick has well-known traps: the blood pad reacts to haemoglobin and myoglobin as well as red cells, the protein pad detects mainly albumin and misses light chains, and nitrite is only positive with bacteria that convert nitrate after urine has stayed in the bladder for some hours. Read the result in order and always with the patient: a positive test in someone with no symptoms (such as asymptomatic bacteriuria) often needs no treatment.

Reference values and concepts

• Specific gravity about 1.005–1.030; pH about 4.5–8.0 (ranges vary by laboratory and method).
• Normally negative: protein (trace may be normal in concentrated urine), glucose, ketones, blood, bilirubin, nitrite and leukocyte esterase; urobilinogen in small amounts.
• Glucose appears in urine when blood glucose exceeds the renal threshold of about 180 mg/dL, or with normal blood glucose in pregnancy, proximal tubule disease or with SGLT2 inhibitors.
• Microscopy: up to about 2–3 red cells and about 5 white cells per high-power field are usually accepted as normal; hyaline casts can be normal.
• Nephrotic-range proteinuria is above about 3.5 g/24 h in adults, with fatty casts and oval fat bodies in the sediment.
• Urine culture: about 10⁵ CFU/mL of a single organism is the classic threshold in a clean-catch sample; lower counts can matter with symptoms or catheters.

Reading it step by step

1. Check the sample type and time: clean catch, catheter or bag, and how old — contamination and delay change every result.
2. Look at colour and clarity — red, brown, dark or cloudy urine narrows the question before the strip is read.
3. Read specific gravity and pH — concentration changes how protein and cells are read, and pH helps with stones and infection.
4. Read protein, glucose and ketones — they point to kidney disease, diabetes or starvation and ketoacidosis.
5. Read blood, then confirm with microscopy — red cells versus haemoglobin or myoglobin changes the whole differential.
6. Read leukocyte esterase and nitrite with the symptoms — together they support infection; alone they are weak.
7. Read bilirubin and urobilinogen — bilirubin suggests cholestasis; high urobilinogen suggests haemolysis or liver disease.
8. Look at the sediment: cells, casts, crystals and squamous cells — casts place the problem inside the kidney.
9. Put it with the history, examination, creatinine and culture — a urinalysis supports a diagnosis rather than making it.

Patterns and likely causes

Patterns and common mistakes

• Uncomplicated cystitis: dysuria and frequency with positive leukocyte esterase and nitrite; culture is needed in men, pregnancy, children and recurrence.
• Sterile pyuria (white cells, negative culture): recent antibiotics, chlamydia or gonorrhoea, tuberculosis, interstitial nephritis or stones.
• Nephritic picture: haematuria with red cell casts, some proteinuria, high blood pressure and rising creatinine.
• Muddy brown granular casts suggest acute tubular necrosis; waxy casts suggest advanced chronic kidney disease.
• Crystals: calcium oxalate (envelope shapes; ethylene glycol poisoning), uric acid, struvite (coffin-lid shapes, urease-producing bacteria such as Proteus) and cystine (hexagons).
• Common mistakes: treating a positive dipstick in an asymptomatic or catheterised patient, ignoring many squamous cells, and not investigating painless visible haematuria in an older adult.

Next step

• Symptomatic infection with risk factors (pregnancy, male sex, fever, catheter, recurrence): send a culture before antibiotics, chosen by local guidance.
• Blood on the dipstick without red cells: check creatine kinase, potassium, creatinine and haemolysis tests the same day.
• Red cell casts, rising creatinine or high blood pressure: call a senior and nephrology urgently for suspected glomerulonephritis.
• Persistent proteinuria: quantify with a protein or albumin to creatinine ratio and repeat; refer if confirmed.
• Painless visible haematuria in an adult, especially a smoker over 40: refer for urology assessment for bladder or kidney cancer.
• Repeat a contaminated sample as a clean catch before drawing conclusions.

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Elsewhere in DurgiPedia

• Urinalysis
• Functional anatomy of the nephron
• Clinical syndromes of kidney disease
• Urinary symptoms: dysuria, frequency, oliguria and hematuria
• Nephrotic vs nephritic syndrome
• Urinary elimination: retention, incontinence and bladder scanning

Connections

← All clinical skills

Educational content; it does not replace supervised hands-on training, your institution's protocols or a prescriber's order. A procedure is learnt with a teacher and done only once you are trained to do it.

Sources: Urinalysis (StatPearls (NCBI Bookshelf), 2023).

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