What does the presence of leukocytes and ketones in a urine sample indicate?

Leukocytes and Ketones in Urine: Clinical Significance and Management

The presence of leukocytes and ketones in a urine sample of a 67-year-old patient suggests a possible urinary tract infection combined with metabolic disturbance that requires prompt evaluation and management. 1, 2

Significance of Leukocytes in Urine

• Leukocytes (white blood cells) in urine strongly indicate inflammation in the urinary tract, most commonly due to a urinary tract infection (UTI) 2
• Leukocyte esterase is an enzyme released from white blood cells and serves as a reliable screening marker for pyuria with 100% sensitivity in detecting significant bacteriuria 3
• The presence of leukocytes alone has high sensitivity (95.8-100%) but moderate specificity for UTI diagnosis 2

Significance of Ketones in Urine

• Ketones in urine indicate that the body is breaking down fat for energy instead of using glucose 1
• While ketones are normally present in urine at concentrations below detectable levels, positive readings can occur in:
  • Fasting states
  • Poorly controlled diabetes
  • Acute illness or stress
  • Up to 30% of first morning urine specimens from pregnant women 4, 1
• Ketones may indicate impending or established ketoacidosis, which requires immediate medical attention, especially in diabetic patients 4

Clinical Approach to These Findings

Step 1: Assess for UTI

• Evaluate for UTI symptoms: dysuria, frequency, urgency, suprapubic pain
• Consider urine culture to confirm infection 2
• Microscopic examination can improve diagnostic accuracy:
  • Organism counts ≥10/μl have 94.4% specificity for UTI
  • Leukocyte counts ≥50/μl have 88.9% specificity for UTI 2

Step 2: Evaluate for Metabolic Disturbance

• Check blood glucose levels to rule out hyperglycemia
• Assess for symptoms of diabetic ketoacidosis (DKA): nausea, vomiting, abdominal pain, confusion 1, 5
• Consider blood ketone testing (β-hydroxybutyrate) which is more reliable than urine ketones for diagnosing ketoacidosis 1, 6
• Be aware that euglycemic DKA can occur (blood glucose <250 mg/dL with ketoacidosis), especially in patients taking SGLT2 inhibitors 1, 5

Step 3: Consider Other Causes

• False-positive ketone readings can occur with:
  • Sulfhydryl drugs (e.g., captopril)
  • Highly pigmented urine 4
• False-positive leukocyte readings can occur with:
  • Contaminated specimens
  • Certain medications
  • Highly concentrated urine 7

Management Recommendations

1. For suspected UTI: If symptomatic or high-risk patient (elderly), empiric antibiotic therapy is appropriate while awaiting culture results 2

2. For ketones:

   • If diabetic: Check blood glucose, assess hydration status, and consider insulin administration
   • If non-diabetic: Evaluate for fasting state, high-protein/low-carb diet, or other metabolic conditions
   • If ketones are significant with symptoms of acidosis: Urgent medical evaluation for possible DKA, regardless of glucose level 1

3. Follow-up testing:

   • Repeat urinalysis after treatment completion
   • Consider metabolic workup if ketones persist without clear explanation
   • HbA1c testing if diabetes is suspected 4

Important Caveats

• Urine ketone tests using nitroprusside reagents only detect acetoacetic acid and acetone, not β-hydroxybutyrate (the predominant ketone in DKA) 6
• The combination of leukocytes and ketones could indicate a serious condition in a diabetic patient, as infection can precipitate ketoacidosis 1
• In elderly patients, UTIs may present atypically without classic symptoms, making laboratory findings particularly important 2