Can hepatosplenomegaly occur in acute bacterial infections with leukocytosis (elevated white blood cell count) and left shift, and how is the Leukocyte Alkaline Phosphatase (LAP) test performed?

Hepatosplenomegaly in Acute Bacterial Infection and LAP Test Procedure

Yes, hepatosplenomegaly can occur in severe acute bacterial infections, especially when associated with markedly elevated white blood cell counts (75,000) with left shift and toxic granulations, as these findings suggest a significant systemic inflammatory response that can affect multiple organs including the liver and spleen.

Hepatosplenomegaly in Bacterial Infections

Severe bacterial infections can lead to hepatosplenomegaly through several mechanisms:

• Systemic inflammatory response causing increased blood flow to these organs
• Direct bacterial invasion of liver or spleen tissue
• Reactive hyperplasia of reticuloendothelial system in response to infection
• Cytokine-mediated effects on organ size and function 1

The extremely high leukocyte count (75,000) with left shift and toxic granulations strongly suggests a severe bacterial infection, possibly with sepsis or septic shock. According to guidelines, marked leukocytosis (>15,000/μL) with marked left shift (band neutrophils >20% of leukocytes) are criteria for severe sepsis 2.

Clinical Significance of Leukocytosis with Left Shift

The combination of elevated WBC count and left shift provides much stronger evidence for bacterial infection than either finding alone 1:

• WBC >14,000 cells/mm³: Likelihood ratio 3.7
• Band counts >1,500 cells/mm³: Likelihood ratio 14.5
• Neutrophils >90%: Likelihood ratio 7.5
• Band neutrophils >16%: Likelihood ratio 4.7

A WBC count as high as 75,000 with left shift is extremely concerning and suggests:

1. Severe bacterial infection
2. Possible leukemoid reaction
3. Need for urgent evaluation and treatment 3, 4

Leukocyte Alkaline Phosphatase (LAP) Test Procedure

The LAP test is important to differentiate between a leukemoid reaction (elevated LAP score) and leukemia (low LAP score). Here's how to perform it:

1. Specimen collection:

   • Collect fresh peripheral blood in EDTA tube
   • Prepare blood smears within 3 hours of collection

2. Staining procedure:

   • Fix air-dried blood smears in formalin-methanol solution for 30 seconds
   • Rinse in running tap water
   • Incubate slides in freshly prepared LAP substrate solution (containing naphthol AS-BI phosphate and fast blue RR salt in buffer) for 30-60 minutes at room temperature
   • Rinse thoroughly with distilled water
   • Counterstain with dilute hematoxylin for 5 minutes
   • Rinse again and air dry

3. Scoring:

   • Examine 100 neutrophils under oil immersion
   • Score each cell from 0-4 based on staining intensity:
     • 0: No granules visible
     • 1: Sparse, faint granules
     • 2: Moderate number of granules
     • 3: Numerous granules, intense staining
     • 4: Entire cytoplasm filled with intense staining
   • Calculate total score (0-400)

4. Interpretation:

   • Normal range: 40-100
   • Elevated in bacterial infections, leukemoid reactions
   • Decreased in chronic myeloid leukemia

Clinical Implications and Management

When encountering a patient with hepatosplenomegaly and extreme leukocytosis (75,000) with left shift:

1. Urgent evaluation:

   • Complete history and physical examination focusing on signs of infection
   • Blood cultures (at least two sets from separate sites)
   • Additional cultures based on suspected source
   • Imaging of liver and spleen to assess size and potential abscesses

2. Differential diagnosis:

   • Severe bacterial infection with sepsis
   • Leukemoid reaction
   • Hematologic malignancy
   • Chronic myeloproliferative disorders

3. Treatment considerations:

   • Empiric broad-spectrum antibiotics based on suspected source
   • Supportive care including fluid resuscitation if signs of sepsis
   • Monitor for organ dysfunction 2

Pitfalls and Caveats

• The pattern of WBC count and left shift changes throughout the course of bacterial infection. In early infection (0-10 hours), WBC may actually decrease before rising 3, 4
• Extremely high WBC counts (>50,000) should prompt consideration of hematologic disorders in addition to infection
• Hepatosplenomegaly may not be evident early in the course of infection but can develop as the inflammatory response progresses
• LAP scores must be interpreted in clinical context, as they can be elevated in various inflammatory conditions, not just infections

Remember that time-series data of left shift and WBC count provide more valuable information than a single measurement in evaluating the course of bacterial infection 4.