From the Guidelines
Diagnosing reactive pleural fluid in the setting of renal infection requires a thorough clinical evaluation and specific diagnostic tests, with a focus on pleural fluid analysis and imaging studies to guide treatment. The diagnosis involves obtaining a pleural fluid sample via thoracentesis and analyzing it for cell count, protein, LDH, glucose, pH, cytology, and cultures, as recommended by the BTS guidelines for the management of pleural infection 1. Reactive pleural effusions secondary to renal infection typically show exudative characteristics with predominant neutrophils, elevated protein and LDH levels, and possibly low glucose and pH if infection is present.
The connection between renal infection and pleural effusion occurs through direct extension, lymphatic spread, or hematogenous dissemination, particularly with conditions like perinephric abscess or xanthogranulomatous pyelonephritis. According to the ERS statement on benign pleural effusions in adults, the commonest aetiology for effusions described in the literature in this population is fluid overload, but not all patients will present with bilateral effusions or even transudates 1.
Key diagnostic steps include:
- Obtaining a pleural fluid sample via thoracentesis and analyzing it for cell count, protein, LDH, glucose, pH, cytology, and cultures
- Completing the workup with blood tests (CBC, renal function, inflammatory markers), urine analysis and culture, and imaging studies including chest X-ray, ultrasound of kidneys, and CT scan of chest and abdomen with contrast if not contraindicated
- Assessing pleural fluid pH, which is the most useful index predicting the need for chest tube drainage, with a pH of about 7.2 indicating the need for pleural drainage 1
Treatment should address both the primary renal infection with appropriate antibiotics and drainage of the pleural fluid if significant, with surgical intervention may be necessary for abscesses or complicated infections. The choice of pleural intervention is guided by patient choice and available treatment methods, but similar symptomatic relief has been achieved by repeat thoracocentesis alone when compared with IPCs in observational studies 1. The most recent and highest quality study recommends a pleural pH of about 7.2 as the best indicator for the need for pleural drainage 1.
From the Research
Diagnosis of Reactive Pleural Fluid in Pus in Renal
- The diagnosis of reactive pleural fluid in pus in renal disease can be challenging, as it may be related to disorders of the lung or pleura, or to a systemic disorder 2.
- Pyelonephritis, a type of renal disease, can cause pleural effusion, although it is a rare cause 3.
- The diagnostic evaluation of pleural effusion includes chemical and microbiological studies, as well as cytological analysis, which can provide further information about the etiology of the disease process 2.
- Laboratory testing helps to distinguish pleural fluid transudate from an exudate, which is essential for determining the underlying cause of the pleural effusion 2, 4.
- Thoracocentesis should be performed for new and unexplained pleural effusions to determine the etiology of the effusion 2.
- Immunohistochemistry provides increased diagnostic accuracy in the evaluation of pleural effusion 2.
- Pleural biopsy is recommended for evaluation and exclusion of various etiologies, such as tuberculosis or malignant disease 2.
Management of Pleural Infections
- The management of infected pleural effusion is complex and requires determining the appropriate antibiotic regimen, the need for pleural drainage, and the optimal drainage tube size 5.
- Empyemas need to be treated with appropriate antibiotics and intercostal drainage 2.
- Surgery may be needed in selected cases where drainage procedure fails to produce improvement or to restore lung function and for closure of bronchopleural fistula 2, 5.
- The proper treatment of pleural effusion can be determined only after meticulous differential diagnosis 4.