Pathology Cheat Sheet
Read the Specimen First
Urinalysis and body fluids for NEET-PG: isosthenuria, urinary casts, CSF in meningitis, Light criteria, SAAG in ascites, and gout vs pseudogout crystals.
MedNext Academy | 3 min read
Read the Specimen First
Urinalysis and body fluids for NEET-PG: isosthenuria, urinary casts, CSF in meningitis, Light criteria, SAAG in ascites, and gout vs pseudogout crystals.
The interpretation of urinalysis and the analysis of cerebrospinal, pleural, peritoneal and synovial fluids.
High-yield lines
- Complete urinalysis integrates physical appearance, dipstick chemistry, and microscopy of the sediment.
- A fixed specific gravity near 1.010 (isosthenuria) indicates loss of tubular concentrating ability.
- Persistent foamy urine is a bedside clue to significant proteinuria.
- Red cell casts indicate glomerular bleeding as in glomerulonephritis.
- White cell casts indicate pyelonephritis or interstitial nephritis.
- Muddy brown granular casts indicate acute tubular necrosis.
- Cerebrospinal fluid in bacterial meningitis shows high neutrophils, high protein, and low glucose.
- Cerebrospinal fluid in viral meningitis shows lymphocytes, mildly raised protein, and normal glucose.
- Light criteria distinguish a pleural exudate from a transudate using fluid-to-serum protein and LDH ratios.
- The serum-ascites albumin gradient of 1.1 or more indicates portal hypertension as the cause of ascites.
- Synovial fluid with negatively birefringent needle crystals indicates gout, and positively birefringent rhomboid crystals indicate pseudogout.
- Turbid purulent synovial fluid with very high neutrophils indicates septic arthritis.
Mapped competency codes
- PA23.1
- PA23.2
Continue into the full chapter
This summary maps to PA23-clinical-pathology.
Frequently Asked Questions
What do red cell casts in urine indicate?
Glomerular bleeding, as in glomerulonephritis, because the casts form within the renal tubules from red cells that crossed the damaged glomerulus.
How does CSF differ in bacterial versus viral meningitis?
Bacterial meningitis shows a high neutrophil count, high protein, and low glucose, while viral meningitis shows lymphocytes, mildly raised protein, and normal glucose.
What do Light criteria distinguish?
They separate pleural exudates from transudates using the ratios of fluid to serum protein and LDH, guiding the differential diagnosis of an effusion.
How do gout and pseudogout crystals differ on synovial fluid analysis?
Gout shows negatively birefringent needle-shaped monosodium urate crystals, while pseudogout shows positively birefringent rhomboid calcium pyrophosphate crystals.
Continue reading
Cheat SheetsAll Pathology cheat sheets
Browse the complete authored set for this subject.
Open the complete revision pathway
Explore clinician-written learning resources, structured revision and practice across the MedNext platform.
Open in the MedNext appSee plans

