Urologic Laboratory Examination
The laboratory examination of urine, blood and genitourinary secretions is where most urologic workups begin — and where many of them end, because a well-performed urinalysis frequently establishes the diagnosis on its own.
The big picture
The laboratory examination of urine, blood and genitourinary secretions is where most urologic workups begin — and where many of them end, because a well-performed urinalysis frequently establishes the diagnosis on its own. The catch is that urinalysis is also one of the most abused tests in medicine: collected carelessly, left to stand, or never examined under the microscope, it gives misleading answers. The skill here is not memorising reference ranges; it is knowing how to collect and read a specimen properly, and what each abnormal finding actually means.
The framework: a complete urinalysis has three parts — the physical examination (colour, clarity, specific gravity), the chemical examination (the dipstick), and the microscopic examination of the sediment. Each adds something the others miss, which is why a dipstick alone is not a urinalysis.
Mechanism pathway
Tap any step to see why it happens.
Diagnostic algorithm
Each step answers one question. Tap to expand.
Board traps
A dipstick is not a urinalysis — its sensitivity for UTI is only ~44–77%; a negative strip does not exclude infection. Use microscopy and culture when it counts.
A delayed or standing specimen turns alkaline and destroys cells and casts — examine within an hour.
Cloudy urine is usually phosphates/urates, not pus.
Crystals are often normal; their presence alone is not disease (cystine is the exception — always abnormal).
PSA is prostate-specific, not cancer-specific — it rises with BPH, inflammation, and manipulation.
Casts localise disease to the kidney — red-cell casts mean glomerular bleeding.
No routine screening urinalysis in the asymptomatic patient.
On a 5-ARI, double the PSA to estimate the true value — and always ask about 5-ARI use (including for alopecia).
PSA density and free:total PSA refine a borderline value; faster PSA velocity is more suspicious.
Dysmorphic RBCs (± red-cell casts, proteinuria) → glomerular source → nephrology, don't scope.
Microscopic haematuria = ≥3 RBC/hpf, confirmed on microscopy (dipstick also reacts to haemoglobin/myoglobin).
Three-container collection localises the bleeding within the stream.