# Superiority of Surgical Treatment in Stage 2 Acute Empyema: A Perspective on Lung Volume Improvement

## TL;DR

Early surgery for Stage 2 acute empyema improves lung recovery more than drainage alone, according to a study using CT scans to measure lung volume changes.

## Contribution

The study provides new evidence that surgery leads to better lung volume recovery in Stage 2 acute empyema compared to drainage.

## Key findings

- Surgery resulted in significantly better lung improvement (82% vs. 68%) compared to drainage.
- After propensity score matching, the surgery group still showed superior lung improvement (79% vs. 66%).
- A time-dependent improvement in total lung volume was observed in the surgery group.

## Abstract

Introduction: Early surgery for acute empyema can shorten hospitalization and reduce complications, especially in Stage 2 cases. Inflammation and fibrosis can impair long-term pulmonary function, but few studies have evaluated post-treatment lung recovery. We hypothesized that surgery promotes better lung re-expansion than drainage alone. To test this hypothesis, we analyzed lung volume changes on computed tomography (CT) scans before and after treatment.

Methods: This retrospective, single-center study included adult patients with Stage 2 acute empyema treated from 2012 to 2024 at Kofu Municipal Hospital, Kofu, Japan. Patients were included if they had CT scans before treatment and at least one month after discharge. CT-based lung volumes were analyzed using SYNAPSE VINCENT® (FUJIFILM Corporation, Tokyo, Japan) software. Since healthy-state CT scans are rarely available, the original volume of the diseased lung was estimated using the volume of the contralateral healthy lung, assuming a right-to-left volume ratio of 55:45. The primary outcome was the lung improvement rate on post-treatment CT. Secondary outcomes included hospital stay, drainage duration, and antibiotic use. Propensity score matching was used to adjust for baseline differences.

Results: Among 131 Stage 2 empyema cases, 25 met the inclusion criteria (10 surgery and 15 drainage). Surgery was performed after a median of seven days due to poor drainage. The surgery group showed significantly better lung improvement (82% vs. 68%, p < 0.01). Hospital stay and drainage duration were similar, but antibiotic use tended to be longer in the drainage group. After matching (nine patients per group), lung improvement remained superior in the surgery group (79% vs. 66%, p = 0.012). A statistically significant time-dependent improvement in total lung volume was observed in the surgery group following treatment (p = 0.04).

Discussion: Surgical intervention led to better lung volume recovery than drainage alone. However, selection bias may exist, as surgery was often delayed until after drainage failure. In three cases, limited decortication may have reduced recovery. This study only included patients with follow-up CT scans and good outcomes, potentially underestimating the full impact of treatment. Early surgical intervention may provide greater benefits by preventing disease progression and facilitating lung re-expansion.

Conclusion: Surgery for Stage 2 acute empyema significantly improves post-treatment lung volume recovery. Early surgical intervention should be considered in appropriate cases to optimize pulmonary outcomes.