Step by Step
1
Normal urine characteristics
Pale yellow color (from urochrome, a pigment derived from bilirubin breakdown), specific gravity between 1.001 and 1.035, pH between 4.5 and 8.0, and composed of about 95% water plus urea, creatinine, and electrolytes.
2
Glucose and protein — two key abnormal findings
Glucosuria (glucose in urine) suggests blood glucose above 180 mg/dL (as in diabetes) or an SGLT2 transporter defect. Proteinuria (protein in urine) suggests kidney disease or glomerulonephritis — significant albumin leakage above 3.5 g/day defines nephrotic syndrome.
3
Blood, ketones, and bilirubin
Hematuria (blood in urine) suggests UTI, kidney stones, trauma, or cancer. Ketones suggest diabetic ketoacidosis or starvation. Bilirubin in urine suggests liver disease or hemolysis.
4
Casts and specific gravity — pinpointing the location of pathology
WBCs (pyuria) suggest a UTI. Urinary casts (cylindrical molds formed in the tubules) are especially diagnostic: RBC casts indicate glomerulonephritis, WBC casts indicate pyelonephritis, and granular casts indicate acute tubular necrosis (ATN). Specific gravity readings help distinguish concentrated urine (as in dehydration) from dilute urine (as in diabetes insipidus or overhydration).
Applied Walkthrough
1
A patient's urinalysis reveals glucose in their urine. This finding, combined with their history, suggests blood glucose has exceeded 180 mg/dL — consistent with diabetes.
2
A different patient's urinalysis shows significant protein loss, over 3.5 g/day — meeting the threshold for nephrotic syndrome, and pointing toward kidney disease or glomerulonephritis as the underlying cause.
3
A third patient's urine sample contains RBC casts specifically — since these cylindrical casts form in the kidney tubules themselves, their presence points specifically to glomerulonephritis, rather than a lower urinary tract problem like a simple bladder infection.
4
In contrast, if that same patient's sample instead showed WBC casts, this would point toward pyelonephritis (a kidney infection) rather than glomerulonephritis — illustrating how specific cast types help pinpoint exactly where in the urinary tract a problem is occurring.
Exam Application
Exams test whether you know the normal ranges for urinalysis findings, and specifically whether you can match abnormal findings (glucose, protein, blood, ketones, bilirubin, casts) to their most likely underlying clinical cause.
⚠ Common Trap
The most common trap is treating all urinary casts as equivalent — RBC casts, WBC casts, and granular casts each point to a distinctly different underlying condition (glomerulonephritis, pyelonephritis, and acute tubular necrosis, respectively), so identifying the specific cast type matters clinically.
✓ Quick Self-Check
1. What is the normal specific gravity range for urine?
1.001–1.035.
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2. What does glucosuria typically suggest?
Blood glucose above 180 mg/dL (as in diabetes) or an SGLT2 transporter defect.
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3. What defines nephrotic syndrome in terms of protein loss?
Significant albumin leakage above 3.5 g/day.
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4. What does an RBC cast in the urine suggest, versus a WBC cast?
RBC casts suggest glomerulonephritis; WBC casts suggest pyelonephritis.
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5. What does a granular cast suggest?
Acute tubular necrosis (ATN).
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