Diagnosis: Aspiration pneumonia (pulse identified)

Comment: Review of the history and discussion with the patient revealed a known 15-year history of gastroesophageal reflux disease (GERD) treated with omeprazole and elevation of the head of the bed. Although these measures decreased the frequency of heartburn and waking at night with gagging, hoarseness, and sore throat, he still has symptoms once or twice a month. He has a good gag reflex. Fundoplication is being considered.

In this case, a diagnosis of recurrent aspiration pneumonia was not considered in this AIDS patient with a prolonged history of GERD until the foreign material was identified in the lung biopsy taken at the time of a previous episode of pneumonia. In retrospect, the "tree-in-bud" image on the CT indicated a bronchiolitis due to aspiration. When a biopsy is performed in a patient with unsuspected aspiration, the pathologist plays a key role in making the diagnosis.

Aspiration Pneumonia

Introduction: Aspiration occurs in debilitated or sedated persons, persons with neurologic disorders that interfere with swallowing, those undergoing obstetric or urgent surgical procedures, and those with tracheoesophageal fistula or achalasia [1]. However, up to one third of people in the US have GERD, which may also lead to aspiration. GERD has been linked as an exacerbating factor to bronchitis, bronchiectasis, pulmonary fibrosis, and asthma. Recurrent pneumonia and cough are symptoms. When the diagnosis is suspected but not clinically evident, a 24-hr esophageal pH probe has high sensitivity and specificity for diagnosing reflux as a cause of pulmonary symptoms. In our patient, who had the onset of GERD at about the time he had the onset of asthma, reflux may be contributing to the asthma. Fundoplication is most likely to be useful in preventing symptoms in patients with recurrent, severe disease that does not respond to medical management [2]. In addition to a chemical pneumonia, infections (especially anerobic) or acute airway obstruction may result from aspiration of infected gastric material [3].

Biopsy diagnosis: When a diagnosis of aspiration pneumonia is unsuspected clinically, identification of foreign material in a biopsy may provide a diagnosis. Many types of food particles can be found in the lung, but few of them can be identified specifically. Besides meat fibers with preserved cross striations and lipoid substances, pulses are common and have a characteristic appearance. Pulse pneumonia, originally described as lentil pulse pneumonia, results from aspiration of gastric contents containing seeds of leguminous plants--beans, peas, lentils, peanuts--common constituents of the diet. In one study, pulse was found in 41 of 1500 (2.7%) of autopsies [1]. Besides the inflammation from the gastric acid and possible bacteria, there is an inflammatory reaction to the pulse itself.

Experimental pulse pneumonia: The course of the pneumonia was studied in experimental animals. The recognizable changes are transient. An acute bronchopneumonia occurs by 24 h after instillation of the pulse. By 10 days, epithelioid granulomas are formed. At 2 weeks the pulses become difficult to recognize, and the granulomas look like tuberculous or sarcoid granulomas. Later, they may become calcified. Only the cellulose shells and cotyledons produce a granulomatous reaction. The starch component is inert [1].

Other Clinical Settings of Aspiration Pneumonia

Childbirth: Acute aspiration of gastric contents may occur in women during childbirth (0.15% of deliveries) (Mendelson's syndrome) [4]. It usually develops abruptly within hours of delivery as ARDS (diffuse alveolar damage, histologically) with dyspnea, fever, wheeze, rales, and cough [5]. Prevention and support are the only effective measures. The mechanisms of acute inflammation in this situation include PMN recruitment and activation. In animals, some of the damage can be alleviated by anti-ICAM-1 and anti-CD11a antibodies, which interfere with PMN adhesion and activation [6].

Esophageal dysmotility of scleroderma: An uncontrolled study of 13 scleroderma patients using esophageal pH monitoring supported the hypothesis that GERD complicates the interstitial pneumonia associated with this disease [7].

Idiopathic pulmonary fibrosis: In a study of 17 consecutive patients with biopsy-proven IPF and 8 control patients with other interstitial lung diseases (e.g., sarcoidosis, Langerhans' cell histiocytosis, cryptogenic organizing pneumonia), esophageal acid exposure (24-hr pH probe) was significantly longer in the IPF patients, suggesting that aspiration occurs, even without symptoms typical of GERD [8].

Bronchiolitis in the elderly: In a study of postmortem lungs with diffuse aspiration bronchiolitis (DAB); that is, granulomatous bronchiolitis with foreign particles limited to the airways, an incidence of 31/4880 (0.64%) was found. The average age of those affected was 81. Compared to 40 patients with aspiration pneumonia (mean age 82), the onset was more insidious, and in half, aspiration was unrecognized clinically. Neurologic disorders and dementia were common in both groups. Patients with DAB had bronchorrhea, bronchospasm, and dyspnea. Grossly, the lungs had scattered, millet-sized, yellowish nodules resembling the changes seen in diffuse panbronchiolitis. Histology showed chronic mural inflammation with a foreign body reaction. Thus, aspiration is a cause of wheeze in the elderly to be distinguished from the wheeze of asthma or panbronchiolitis [9].

Chronic lung disease in children: In a study of 74 children (<12 y old) with chronic respiratory tract disorders and documented GERD (by pH, Ba esophagram, esophagoscopy) and 41 with chronic respiratory tract disorders without GERD, lipid-laden alveolar macrophages were present in 85% of the first group and 19% of the second, suggesting that these cells are a marker of aspiration. Two oil-red-O-stained macrophages in at least one high-power field of a BAL fluid preparation were judged as positive [10]. Another study of infants has shown that a tracheal aspirate with more than 50 oil-red-O-positive macrophages has a sensitivity of 61% and a specificity of 97% for aspiration in patients with a diagnosis made by 24-h pH probe recordings, apnea and bradycardia with feedings, and/or response to head-up prone positioning or medication [11]. Aspiration of lipoid material also occurs in adults.

Foreign body aspiration as a cause of unresolved pneumonia: The etiology of unresolved pneumonia was studied in 30 patients, who had resections of nodules or masses suspected of being cancer. In 11, foreign material was found (7 in upper lobes; pulse in one) [12]. Similar lesions may be going under the name localized, organizing pneumonia (localized, idiopathic BOOP) if the foreign material is not found [13].

Radiographic changes after aspiration of liquid gastric contents: Radiographic manifestations of acute aspiration of gastric contents were studied in 60 patients. Most opacities were bilateral and multicentric, perihilar or basal; but localized or atypical densities also occurred. Radiographic changes often worsened for several days with improvement generally in the first week. Complications included bacterial pneumonia, ARDS, and pulmonary embolism [14].

Radiographic findings in patients with foreign body aspiration: In 60 adults (42 men/18 women) with non-asphyxiating foreign body aspiration, 25 had predisposing factors (neurologic disorders, loss of consciousness, sedative or alcohol use). Others were usually aware of aspiration. Aspirated items were food (24), dental or medical appliances (19), and other (17). Symptoms included cough, fever, hemoptysis, and dyspnea. Symptoms were present a median of 10 da before bronchoscopy. Radiographs helped to locate the foreign body and plan for removal. In only 3 patients was the foreign body so distal as to require thoracotomy. Foreign bodies were located in all lobar bronchi [15]. It has been emphasized that any segment can be involved and that the radiographic opacities may migrate. Further, the latent period between aspiration and diagnosis may be years [16].

Histopathology: Histologic diagnosis depends on recognizing the foreign material in the setting of a non-specific, acute or chronic inflammatory response--diffuse alveolar damage, abscesses, acute or chronic organizing pneumonia, or granulomatosis. Scanning the slide material completely with both polarized and normal light is mandatory, as foreign material may easily be missed, as in the present case. Endobronchial biopsies and lavage specimens should be examined in the same way: some bronchogenic "tumors" have turned out to be aspirated tablets with birefringent, crystalline fillers.

Conclusions: The suspicion of aspiration should be high in many types of lung disease, even in asymptomatic patients. Further, aspiration may exacerbate airway disease and interstitial pneumonias. Finally, when the clinical history fails to elicit the possibility of aspiration, histologic changes can be diagnostic if foreign bodies or lipoid material are recognized.


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Clinical summary

Comments: mw6825@itsa.ucsf.edu

Table of Contents

Last revised 7/9/99

Copyright 1999 by Martha L. Warnock. All rights reserved.